Wisconsin Administrative Code › Department of Safety and Professional Services › SPS 301-399 - Safety, Buildings, and Environment › SPS 326-360 - General, Part II › Chapter SPS 341 - Boilers And Pressure Vessels › Appendix B - EXCERPTS FROM: ASME BOILER AND PRESSURE VESSEL CODE

Current through June 24, 2024
SECTION IV - HEATING BOILERS
2010 EDITION
INTRODUCTION
The rules of this Section of the Code cover minimum
					 construction requirements for the design, fabrication, installation, and
					 inspection of steam heating, hot water heating, hot water supply boilers that
					 are directly fired with oil, gas, electricity, coal, or other solid or liquid
					 fuels, and for operation at or below the pressure and temperature limits set
					 forth in this document. Similar rules for potable water heaters are also
					 included.
For Section IV application, the boiler proper or other
					 vessels terminate at the supply and return connections to the system or the
					 supply and feedwater connections of a hot water supply boiler. These
					 connections may be any of the following:
(a) the first circumferential joint for welding end
					 connections
(b) the face of the first flange in bolted flanged
					 connections
(c) the first threaded joint in that type of
					 connection
Included within the scope of the boiler are
					 pressure-retaining covers for inspection openings, such as manhole covers,
					 handhold covers, and plugs; and headers required to connect individual coils,
					 tubes, or cast sections within a boiler.
The rules are divided into four major Parts: Part HG,
					 applying to all materials of construction except as provided for in Part HLW;
					 Part HF, applying to assemblies fabricated of wrought material, except as
					 provided for in Part HLW; Part HC, applying to cast iron assemblies; Part HA,
					 applying to boilers constructed of cast aluminum; and Part HLW, applying to
					 potable water heaters. Part HF is further subdivided into Subpart HW,
					 containing rules for welded construction, and Subpart HB, containing rules for
					 brazed construction.
The Parts and Subparts of this Section are divided into
					 Articles. Each Article is given a number and a title, as for example, Part HG,
					 Article 3, Design. Articles are divided into paragraphs that are given a
					 three-digit number, the first of which corresponds to the Article number. Thus,
					 under Article 3 of Part HG, paragraph HG-307 will be found. Paragraphs are
					 further subdivided into subparagraphs. Major subdivisions of paragraphs are
					 designated by three- or four-digit numbers followed by a decimal point and a
					 digit or digits. Where necessary, further subdivisions are represented by
					 letters and then by numbers in parentheses. Minor subdivisions of the
					 paragraphs are also represented by letters. A reference to one of these
					 paragraphs in the text of the Section includes all of the applicable rules in
					 that paragraph. Thus, reference to HG-307 includes all the rules in HG-307.1
					 through HG-307.4.
This Section does not contain rules to cover all possible
					 details of design and construction. Where complete details are not given, it is
					 intended that the manufacturer, subject to the acceptance of the Authorized
					 Inspector, shall provide details of design and construction that will be as
					 safe as otherwise required by these rules.
When the strength of any part cannot be computed with a
					 satisfactory assurance of safety, these rules provide procedures for
					 establishing its maximum allowable working pressure.
ARTICLE 1
SCOPE AND SERVICE RESTRICTIONS
HG-100 SCOPE
(a) The rules of Part HG apply to steam heating boilers,
					 hot water heating boilers, hot water supply boilers, and to appurtenances
					 thereto. They shall be used in conjunction with the specific requirements in
					 Part HF, Boilers of Wrought Materials, Part HC, Cast Iron Boilers, and Part HA,
					 Cast Aluminum Boilers, whichever is applicable. The foreword provides the basis
					 for these rules. Part HG is not intended to apply to potable water heaters
					 except as provided for in Part HLW.
(b) This Part contains mandatory requirements, specific
					 prohibitions, and nonmandatory guidance for materials, designs, fabrication,
					 examination, inspection, testing, certification, and pressure relief.
(c) Laws or regulations issued by a municipality, state,
					 provincial, federal, or other enforcement or regulatory body having
					 jurisdiction at the location of an installation, establish the mandatory
					 applicability of these rules, in whole or in part.
HG-101 SERVICE RESTRICTIONS
HG-101.1 Service Restrictions.
The rules of
					 this Section are restricted to the following services:
(a) steam boilers for operation at pressures not exceeding
					 15 psi (100 kPa)
(b) hot water heating boilers and hot water supply boilers
					 for operating at pressures not exceeding 160 psi (1 100 kPa) and/or
					 temperatures not exceeding 250°F (120°C), at or near the boiler outlet,
					 except that when some of the wrought materials permitted by Part HF are used, a
					 lower temperature is specified
HG-101.2 Services in Excess of Those Covered by This
					 Section.
For services exceeding the limits specified in HG-101.l, the
					 rules of Section I shall apply.
HG-102 UNITS
Either U.S. Customary, SI, or any local customary units may
					 be used to demonstrate compliance with all requirements of this edition (e.g.,
					 materials, design, fabrication, examination, inspection, testing,
					 certification, and overpressure protection).
In general, it is expected that a single system of units
					 shall be used for all aspects of design except where unfeasible or impractical.
					 When components are manufactured at different locations where local customary
					 units are different than those used for the general design, the local units may
					 be used for the design and documentation of that component. Similarly, for
					 proprietary components or those uniquely associated with a system of units
					 different than that used for the general design, the alternate units may be
					 used for the design and documentation of that component.
For any single equation, all variables shall be expressed
					 in a single system of units. When separate equations are provided for U.S.
					 Customary and SI units, those equations must be executed using variables in the
					 units associated with the specific equation. Data expressed in other units
					 shall be converted to U.S. Customary or SI units for use in these equations.
					 The result obtained from execution of these equations may be converted to other
					 units.
Production, measurement and test equipment, drawings,
					 welding procedure specifications, welding procedure and performance
					 qualifications, and other fabrication documents may be in U.S. Customary, SI,
					 or local customary units in accordance with the fabricator's practice. When
					 values shown in calculations and analysis, fabrication documents, or
					 measurement and test equipment are in different units, any conversions
					 necessary for verification of Code compliance and to ensure that dimensional
					 consistency is maintained shall be in accordance with the following:
(a) Conversion factors shall be accurate to at least four
					 significant figures.
(b) The results of conversions of units shall be expressed
					 to a minimum of three significant figures.
Conversion of units, using the precision specified above
					 shall be performed to assure that dimensional consistency is maintained.
					 Conversion factors between U.S. Customary and SI units may be found in the
					 Nonmandatory Appendix M, Guidance for the Use of U.S. Customary and SI Units in
					 the ASME Boiler and Pressure Vessel Code. Whenever local customary units are
					 used the Manufacturer shall provide the source of the conversion factors, which
					 shall be subject to verification and acceptance by the Authorized
					 Inspector.
Material that has been manufactured and certified to either
					 the U.S. Customary or SI material specification (e.g., SA-516M) may be used
					 regardless of the unit system used in design. Standard fittings (e.g., flanges,
					 elbows, etc.) that have been certified to either U.S. Customary units or SI
					 units may be used regardless of the unit system used in design.
All entries on a Manufacturer's Data Report and data for
					 Code required nameplate marking shall be in units consistent with the
					 fabrication drawings for the component using U.S. Customary, SI, or local
					 customary units. It is acceptable to show alternate units parenthetically.
					 Users of this Code are cautioned that the receiving Jurisdiction should be
					 contacted to ensure the units are acceptable.
ARTICLE 2
MATERIAL REQUIREMENTS
HG-200 GENERAL MATERIAL REQUIREMENTS
HG-200.1 Materials Subject to Pressure Stress.
Material subject to stress due to pressure shall conform to one of the
					 specifications given in Section II and shall be limited to those that are
					 permitted in HF-200 for boilers of wrought materials and HC-200 for cast iron
					 boilers.
HG-200.2 Internal Parts Subject to
					 Deterioration.
Materials shall not be used for internal parts that are
					 liable to fail due to deterioration when subjected to saturated steam
					 temperatures at or below the maximum allowable working pressure.
HG-200.3 Materials Not Found in Section II.
Material not covered by specifications in Section II shall not be used unless
					 authorization to use the material is granted by the Boiler and Pressure Vessel
					 Committee on the basis of data submitted to the Committee in accordance with
					 Appendix A.
HG-200.4 Materials Use Not Limited by Specification
					 Title.
The title or scope paragraph of a material specification in
					 Section II with respect to product form or service shall not limit the use of a
					 material, provided the material is suitable for the application and its use is
					 permitted by the rules of this Section.
HG-200.5 Materials Use Not Limited by Method of
					 Production.
Materials covered by specifications in Section II are not
					 restricted as to the method of production unless so stated in the
					 Specification, and as long as the product complies with the requirements of the
					 Specification.
HG-200.6 Materials With Thicknesses Exceeding
					 Specification Limits.
Materials having thicknesses outside of the
					 limits given in the title or scope clause of a specification in Section II may
					 be used in construction, provided they comply with the other requirements of
					 the Specification and with all thickness requirements of this Code.
HG-200.7 Nonpressure Part Materials.
Material
					 for nonpressure parts, such as skirts, supports, baffles, lugs, clips, and
					 extended heat-transfer surfaces, need not conform to the specifications for the
					 material to which they are attached or to a material specification permitted in
					 HF-200 or HC-200; but, if welded, they shall be of weldable quality. The
					 allowable stress value shall not exceed 80% of the maximum allowable stress
					 permitted for similar material in Tables HF-300.1 and HF-300.2. Satisfactory
					 performance of a specimen in such service shall not make the material
					 acceptable for use in pressure parts of a vessel.
HG-201 SPECIFIC MATERIAL REQUIREMENTS
Specific material requirements for assemblies constructed
					 of wrought materials are given in Part HF, Article 2 and for assemblies
					 constructed of cast iron in Part HC, Article 2.
ARTICLE 4
PRESSURE RELIEVING DEVICES
HG-400 PRESSURE RELIEVING VALVE
					 REQUIREMENTS
Boiler HeatingSurface
FiretubeBoilers
WatertubeBoilers
Hand fired
5 (24)
6 (29)
Stoker fired
7 (34)
8 (39)
Oil, gas, or pul-verized fuel fired
8 (39)
10 (49)
Waterwall heating surface:
Hand fired
8 (39)
8 (39)
Stoker fired
10 (49)
12 (59)
Oil, gas, or pul-verized fuel fired
14 (68)
16 (78)
GENERAL NOTES:
(a) When a boiler is fired only by a gas having a heat
					 value not in excess of 200 Btu/ft 3 (7 400 kJ/m 3 ), the minimum safety valves
					 or safety relief valve relieving capacity may be based on the values given for
					 hand fired boilers above.
(b) The minimum safety valve or safety relief valve
					 relieving capacity for electric boilers shall be 3 ½ lb/hr/kW (1.6
					 kg/hr/kW) input.
(c) For heating surface determination, see HG-403.
(d) For extended heating surface, the minimum lb/hr/ sq/ft
					 may be determined by the Manufacturer [see HG-403 (d)].
HG-400.1 Safety Valve Requirements for Steam
					 Boilers
(a) Each steam boiler shall have one or more officially
					 rated safety valves that are identified with the V or HV Symbol of the spring
					 pop type adjusted and sealed to discharge at a pressure not to exceed 15 psi
					 (100 kPa).
(b) No safety valve for a steam boiler shall be smaller
					 than NPS ½ (DN 15) or larger than NPS 4 (DN 100). The inlet opening
					 shall have an inside diameter equal to, or greater than, the seat
					 diameter.
(c) The minimum relieving capacity of valve or valves shall
					 be governed by the capacity marking on the boiler called for in HG-530.
(d) The minimum valve capacity in pounds per hour shall be
					 the greater of that determined by dividing the maximum Btu output at the boiler
					 nozzle obtained by the firing of any fuel for which the unit is installed by
					 1,000, or shall be determined on the basis of the pounds (kg) of steam
					 generated per hour per square foot (m2) of boiler heating surface as given in
					 Table HG-400.1. For cast iron boilers constructed to the requirements of Part
					 HC, the minimum valve capacity shall be determined by the maximum output
					 method. In many cases a greater relieving capacity of valves will have to be
					 provided than the minimum specified by these rules. In every case, the
					 requirement of HG-400.l(e) shall be met.
(e) The safety valve capacity for each steam boiler shall
					 be such that with the fuel burning equipment installed, and operated at maximum
					 capacity, the pressure cannot rise more than 5 psi (35 Kpa) above the maximum
					 allowable working pressure.
(f) When operating conditions are changed, or additional
					 boiler heating surface is installed, the valve capacity shall be increased, if
					 necessary, to meet the new conditions and be in accordance with HG-400.l (e).
					 The additional valves required, on account of changed conditions, may be
					 installed on the outlet piping provided there is no intervening valve.
HG-400.2 Safety Relief Valve Requirements for Hot
					 Water Boilers
(a) Each hot water heating or supply boiler shall have at
					 least one officially rated safety relief valve, of the automatic reseating
					 type, identified with the V or HV Symbol, and set to relieve at or below the
					 maximum allowable working pressure of the boiler.
(b) Hot water heating or supply boilers limited to a water
					 temperature not in excess of 210°F (99°C) may have, in lieu of the
					 valve(s) specified in (a) above, one or more officially rated temperature and
					 pressure safety relief valves of the automatic reseating type identified with
					 the HV symbol, and set to relieve at or below the maximum allowable working
					 pressure of the boiler.
(c) When more than one safety relief valve is used on
					 either hot water heating or hot water supply boilers, the additional valves
					 shall be officially rated and may have a set pressure within a range not to
					 exceed 6 psi (40 kPa) above the maximum allowable working pressure of the
					 boiler up to and including 60 psi (400 kPa), and 5% for those having a maximum
					 allowable working pressure exceeding 60 psi (400 kPa).
(d) No safety relief valve shall be smaller than NPS
					 ¾ (DN 20) nor larger than NPS 4 (DN 100) except that boilers having a
					 heat input not greater than 15,000 Btu/hr (4.4 kW) may be equipped with a rated
					 safety relief valve of NPS ½ (DN 15).
(e) The required steam relieving capacity, in pounds per
					 hour (kg/h), of the pressure relieving device or devices on a boiler shall be
					 the greater of that determined by dividing the maximum output in Btu at the
					 boiler nozzle obtained by the firing of any fuel for which the unit is
					 installed by 1,000, or shall be determined on the basis of pounds (kg) of steam
					 generated per hour per square foot (m2) of boiler heating surface as given in
					 Table HG-400.1. For cast iron boilers constructed to the requirements of Part
					 HC, the minimum valve capacity shall be determined by the maximum output
					 method. In many cases a greater relieving capacity of valves will have to be
					 provided than the minimum specified by these rules. In every case, the
					 requirements of HG-400.2 (g) shall be met.
(f) When operating conditions are changed, or additional
					 boiler heating surface is installed, the valve capacity shall be increased, if
					 necessary, to meet the new conditions and shall be in accordance with
					 HG-400,2(g). The additional valves required, on account of changed conditions,
					 may be installed on the outlet piping provided there is no intervening
					 valve.
(g) Safety relief valve capacity for each boiler with a
					 single safety relief valve shall be such that, with the fuel burning equipment
					 installed and operated at maximum capacity, the pressure cannot rise more than
					 10% above the maximum allowable working pressure. When more than one safety
					 relief valve is used, the overpressure shall be limited to 10% above the set
					 pressure of the highest set valve allowed by HG-400.2 (c).
HG-400.3 Safety and Safety Relief Valves for Tanks
					 and Heat Exchangers
(a)
Steam to Hot Water Supply.
When a hot
					 water supply is heated indirectly by steam in a coil or pipe within the service
					 limitations set forth in HG-101, the pressure of the steam used shall not
					 exceed the safe working pressure of the hot water tank, and a safety relief
					 valve at least NPS 1 (DN 25), set to relieve at or below the maximum allowable
					 working pressure of the tank, shall be applied on the tank.
(b)
High Temperature Water to Water Heat
					 Exchanger.
1 When high temperature water is
					 circulated through the coils or tubes of a heat exchanger to warm water for
					 space heating or hot water supply, within the service limitations set forth in
					 HG-101, the heat exchanger shall be equipped with one or more officially rated
					 safety relief valves that are identified with the V or HV Symbol, set to
					 relieve at or below the maximum allowable working pressure of the heat
					 exchanger, and of sufficient rated capacity to prevent the heat exchanger
					 pressure from rising more than 10% above the maximum allowable working pressure
					 of the vessel.
(c)
High Temperature Water to Steam Heat
					 Exchanger.
1 When high temperature water is
					 circulated through the coils or tubes of a heat exchanger to generate low
					 pressure steam, within the service limitations set forth in HG-101, the heat
					 exchanger shall be equipped with one or more officially rated safety valves
					 that are identified with the V or HV Symbol, set to relieve at a pressure not
					 to exceed 15 psi (100 kPa), and of sufficient rated capacity to prevent the
					 heat exchanger pressure from rising more than 5 psi (35 kPa) above the maximum
					 allowable working pressure of the vessel. For heat exchangers requiring steam
					 pressures greater than 15 psi (100 kPa), refer to Section I or Section VIII,
					 Division 1. - See PDF for table
1 Suggested installation
					 practices for the secondary side of heat exchangers.
HG-401 MINIMUM REQUIREMENTS FOR SAFETY AND SAFETY
					 RELIEF VALVES
HG-401.1 Mechanical Requirements
(a) The inlet opening shall have an inside diameter
					 approximately equal to, or greater than, the seat diameter. In no case shall
					 the maximum opening through any part of the valve be less than ¼ in. (6
					 mm) in diameter or its equivalent area.
(b) Safety relief valves officially rated as to capacity
					 shall have pop action when tested by steam.
(c) O-rings or other packing devices when used on the stems
					 of safety relief valves shall be so arranged as not to affect their operation
					 or capacity.
(d) The design shall incorporate guiding arrangements
					 necessary to insure consistent operation and tightness. Excessive lengths of
					 guiding surfaces should be avoided. Bottom guided designs are not permitted on
					 safety relief valves.
(e) Safety valves shall have a controlled blowdown of 2 psi
					 to 4 psi (15 kPa to 30 kPa) and this blowdown need not be adjustable.
(f)
Safety valves shall be spring loaded.
The spring shall be designed so that the full lift spring compression shall be
					 no greater than 80% of the nominal solid deflection. The permanent set of the
					 spring (defined as the difference between the free height and height measured
					 10 min after the spring has been compressed solid three additional times after
					 presetting at room temperature) shall not exceed 0.5% of the free
					 height.
(g) There shall be a lifting device and a mechanical
					 connection between the lifting device and the disk capable of lifting the disk
					 from the seat a distance of at least 1/16 in. (1.5 mm) with no pressure on the
					 boiler.
(h) A body drain below seat level shall be provided by the
					 Manufacturer for all safety valves and safety relief valves, except that the
					 body drain may be omitted when the valve seat is above the bottom of the inside
					 diameter of the discharge piping. For valves exceeding NPS 2½ (DN 65)
					 the drain hole or holes shall be tapped not less than NPS 3/8 (DN 10). For
					 valves NPS 2½ (DN 65) or smaller, the drain hole shall not be less than
					 ¼ in. (6 mm) in diameter. Body drain connections shall not be plugged
					 during or after field installation. In safety relief valves of the diaphragm
					 type, the space above the diaphragm shall be vented to prevent a buildup of
					 pressure above the diaphragm. Safety relief valves of the diaphragm type shall
					 be so designed that failure or deterioration of the diaphragm material will not
					 impair the ability of the valve to relieve at the rated capacity.
(i) In the design of the body of the valve consideration
					 shall be given to minimizing the effects of water deposits.
(j) Valves shall be provided with wrenching surfaces to
					 allow for normal installation without damaging operating parts.
(k) The set pressure tolerances, plus or minus, of safety
					 valves shall not exceed 2 psi (15 kPa), and for safety relief valves shall not
					 exceed 3 psi (20 kPa) for pressures up to and including 60 psig (400 kPa) and
					 5% for pressures above 60 psig (400 kPa).
(l) Safety valves shall be arranged so that they cannot be
					 reset to relieve at a higher pressure than the maximum allowable working
					 pressure of the boiler.
HG-401.2 Material Selection
(a) Cast iron seats and disks are not permitted.
(b) Adjacent sliding surfaces such as guides and disks
					 shall both be of corrosion resistant material.
(c) Springs of corrosion resistant material or having a
					 corrosion resistant coating are required.
(d) Material for seats and disks should be such as to
					 provide a reasonable degree of resistance to steam cutting.
(e) Material for valve bodies and bonnets or their
					 corresponding metallic pressure containing parts shall be listed in Section II,
					 except that in cases where a manufacturer desires to make use of materials
					 other than those listed in Section II, he shall establish and maintain
					 specifications requiring equivalent control of chemical and physical properties
					 and quality.
(f) Synthetic disk inserts of O-ring or other types if used
					 shall be compatible with the maximum design temperature established for the
					 valve.
(g) No materials liable to fail due to deterioration or
					 vulcanization when subjected to saturated steam temperature corresponding to
					 capacity test pressure shall be used.
HG-401.3 Manufacture and Inspection
(a) A Manufacturer shall demonstrate to the satisfaction of
					 an ASME designee that his manufacturing, production, and testing facilities and
					 quality control procedures will insure close agreement between the performance
					 of random production samples and the performance of those valves submitted for
					 capacity certification.
(b) Manufacturing, inspection, and test operations
					 including capacity are subject to inspections at any time by an ASME
					 designee.
(c) A Manufacturer may be granted permission to apply, the
					 HV Code Symbol to production pressure relief valves capacity certified in
					 accordance with HG-402.3 provided the following tests are successfully
					 completed. This permission shall expire on the sixth anniversary of the date it
					 is initially granted. The permission may be extended for 6 year periods if the
					 following tests are successfully repeated within the 6 month period before
					 expiration.
(1) Two sample production pressure relief valves of a size
					 and capacity within the capability of an ASME accepted laboratory shall be
					 selected by an ASME designee.
(2) Operational and capacity tests shall be conducted in
					 the presence of an ASME designee at an ASME accepted laboratory. The valve
					 Manufacturer shall be notified of the time of the test and may have
					 representatives present to witness the test.
(3) Should any valve fail to relieve at or above its
					 certified capacity or should it fail to meet performance requirements of this
					 Section, the test shall be repeated at the rate of two replacement valves,
					 selected in accordance with HG-401.3(c)(1), for each valve that failed.
(4) Failure of any of the replacement valves to meet the
					 capacity or the performance requirements of this Section shall be cause for
					 revocation within 60 days of the authorization to use the Code Symbol on that
					 particular type of valve. During this period, the Manufacturer shall
					 demonstrate the cause of such deficiency and the action taken to guard against
					 future occurrence, and the requirements of HG-401.3(c) above shall
					 apply.
(d) Safety valves shall be sealed in a manner to prevent
					 the valve from being taken apart without breaking the seal. Safety relief
					 valves shall be set and sealed so that they cannot be reset without breaking
					 the seal.
HG-401.4 Manufacturer's Testing
(a) Every safety valve shall be tested to demonstrate its
					 popping point, blowdown, and tightness. Every safety relief valve shall be
					 tested to demonstrate its opening point and tightness. Safety valves shall be
					 tested on steam or air and safety relief valves on water, steam, or air. When
					 the blowdown is nonadjustable, the blowdown test may be performed on a sampling
					 basis.
(b) A Manufacturer shall have a well-established program
					 for the application, calibration, and maintenance of test gages.
(c) Testing time on safety valves shall be sufficient,
					 depending on size and design, to insure that test results are repeatable and
					 representative of field performance.
(d) Test fixtures and test drums shall be of adequate size
					 and capacity to assure representative pop action and accuracy of blowdown
					 adjustment.
(e) A tightness test shall be conducted at maximum expected
					 operating pressure, but not at a pressure exceeding the reseating pressure of
					 the valve.
HG-401.5 Design Requirements.
At the time of
					 the submission of valves for capacity certification, or testing in accordance
					 with this Section, the ASME Designee has the authority to review the design for
					 conformity with the requirements of this Section, and to reject or require
					 modification of designs that do not conform, prior to capacity testing.
HG-402 DISCHARGE CAPACITIES OF SAFETY AND SAFETY
					 RELIEF VALVES
HG-402.1 Valve Markings.
Each safety or
					 safety-relief valve shall be plainly marked with the required data by the
					 Manufacturer in such a way that the markings will not be obliterated in
					 service. The markings shall be stamped, etched, impressed, or cast on the valve
					 or on a nameplate, which shall be securely fastened to the valve.
(a) The markings shall include the following:
(1) the name or an acceptable abbreviation of the
					 Manufacturer
(2) Manufacturer's design or type number
(3) NPS size _____ in. (DN) (the nominal pipe size of the
					 valve inlet)
(4) set pressure _____ psi
(5) capacity _____ lb/hr (kg/hr), or capacity _____ Btu/hr
					 in accordance with HG-402.7 (a)
(6) year built or, alternatively, a coding may be marked on
					 the valves such that the valve Manufacturer can identify the year the valve was
					 assembled and tested, and
(7) ASME Symbol as shown in Fig. HG-402
(b) Nameplates of safety or safety-relief valves may be
					 marked solely in metric units under the following conditions:
(1) The pressure-relief device will be installed in a
					 location where metric units are required or accepted by local authorities, if
					 any.
(2) Metric units shall be those required by the user when
					 not mandated by enforcement authorities.
(3) The Manufacturer's quality control system shall provide
					 for the conversion from U.S. customary units to the metric units that will be
					 marked on the nameplate.
HG-402.2 Authorization to Use ASME Stamp.
Each
					 safety valve to which the Code Symbol (Fig. HG-402) is to be applied shall be
					 produced by a Manufacturer and/or Assembler who is in possession of a valid
					 Certificate of Authorization. (See HG-540.) For all valves to be stamped with
					 the HV Symbol, a Certified Individual (CI) shall provide oversight to ensure
					 that the use of the "HV" Code symbol on a safety valve or safety relief valve
					 is in accordance with this Section and that the use of the "HV" Code symbol is
					 documented on a Certificate of Conformance Form, HV-1.
See PDF for
					 diagram
(a)
Requirements for the Certified Individual
					 (CI).
The CI shall
(1) be an employee of the Manufacturer.
(2) be qualified and certified by the Manufacturer.
					 Qualification shall include the following as a minimum:
(a) knowledge of the requirements of this Section for the
					 application of the "HV" Code Symbol
(b) knowledge of the Manufacturer's quality program
(c) training commensurate with the scope, complexity, or
					 special nature of the activities to which oversight is to be provided
(3) have a record, maintained and certified by the
					 Manufacturer, containing objective evidence of the qualifications of the CI and
					 the training program provided
(b)
Duties of the Certified Individual
					 (CI).
The CI shall
(1) verify that each item to which the Code Symbol is
					 applied meets all applicable requirements of this Section and has a current
					 capacity certification for the "HV" symbol
(2) review documentation for each lot of items to be
					 stamped, to verify, for the lot, that the requirements of this Section have
					 been completed
(3) sign the Certificate of Conformance Form (HV-1) prior
					 to release of control of the item
(c)
Certificate of Conformance Form (HV-1
)
					 (see Appendix N)
(1) The Certificate of Conformance shall be filled out by
					 the Manufacturer and signed by the Certified Individual. Multiple duplicate
					 pressure relief devices may be recorded on a single entry provided the devices
					 are identical and produced in the same lot.
(2) The Manufacturer's written quality control program
					 shall include requirements for completion of Certificates of Conformance forms
					 and retention by the Manufacturer for a minimum of 5 years.
HG-402.3 Determination of Capacity to Be Stamped on
					 Valves.
The Manufacturer of the valves that are to be stamped with the
					 Code symbol shall submit valves for testing to a place where adequate equipment
					 and personnel are available to conduct pressure and relieving-capacity tests
					 which shall be made in the presence of and certified by an authorized observer.
					 The place, personnel, and authorized observer shall be approved by the Boiler
					 and Pressure Vessel Committee. The valves shall be tested in one of the
					 following three methods.
(a)
Coefficient Method.
Tests shall be
					 made to determine the lift, popping, and blowdown pressures, and the capacity
					 of at least three valves each of three representative sizes (a total of nine
					 valves). Each valve of a given size shall be set at a different pressure.
					 However, safety valves for steam boilers shall have all nine valves set at 15
					 psig (100 kPa). A coefficient shall be established for each test as
					 follows:
See PDF for
					 diagram
The average of the coefficients
KD
of the nine tests required shall be
					 multiplied by 0.90, and this product shall be taken as the coefficient
K
of that design. The stamped capacity for all sizes and
					 pressures shall not exceed the value determined from the following
					 formulas:
See PDF for
					 diagram
Note:
The maximum and minimum coefficient
					 determined by the tests of a valve design shall not vary more than
					 ±5%from the average. If one or more tests are outside the acceptable
					 limits, one valve of the Manufacturer's choice shall be replaced with another
					 valve of the same size and pressure setting or by a modification of the
					 original valve. Following this test a new average coefficient shall be
					 calculated, excluding the replaced valve test. If one or more tests are now
					 outside the acceptable limits, as determined by the new average coefficient, a
					 valve of the Manufacturer's choice must be replaced by two valves of the same
					 size and pressure as the rejected valve. A new average coefficient, including
					 the replacement valves, shall be calculated. If any valve, excluding the two
					 replaced valves, now falls outside the acceptable limits, the tests shall be
					 considered unsatisfactory.
(b)
Slope Method.
If a Manufacturer
					 wishes to apply the Code Symbol to a design of pressure relief valves, four
					 valves of each combination of pipe and orifice size shall be tested. These four
					 valves shall be set at pressures that cover the approximate range of pressures
					 for which the valve will be used, or that cover the range available at the
					 certified test facility that shall conduct the tests. The capacities shall be
					 based on these four tests as follows:
(1) The slope
(W/P)
of the actual measured
					 capacity versus the flow pressure for each test point shall be calculated and
					 averaged:
See PDF for
					 diagram
All values derived from the testing must fall within
					 ±5% of the average value:
minimum slope = 0.95 * average slope
maximum slope = 1.05 * average slope
If the values derived from the testing do not fall between
					 the minimum and maximum slope values, the Authorized Observer shall require
					 that additional valves be tested at the rate of two for each valve beyond the
					 maximum and minimum values with a limit of four additional valves.
(2) The relieving capacity to be stamped on the valve shall
					 not exceed 90% of the average slope times the absolute accumulation
					 pressure:
rated slope = 0.90 * average slope
stamped capacity = rated slope * (1.10 * set pressure +
					 14.7) psia or (1.10 * set pressure + 101) kPa for hot water applications
(c)
Three-Valve Method.
If a Manufacturer
					 wishes to apply the Code Symbol to steam safety valves or safety relief valves
					 of one or more sizes of a design set at one pressure, he shall submit three
					 valves of each size of each design set at one pressure for testing and the
					 stamped capacity of each size shall not exceed 90% of the average capacity of
					 the three valves tested.
Note:
The discharge capacity as determined by
					 the test of each valve tested shall not vary by more than ±5%of the
					 average capacity of the three valves tested. If one of the three valve tests
					 falls outside of the limits, it may be replaced by two valves and a new average
					 calculated based on all four valves, excluding the replaced valve.
ARTICLE 6
INSTRUMENTS, FITTINGS, AND CONTROLS
HG-600 GENERAL
All instruments, fittings, and controls described in this
					 Article shall be installed prior to operation.
HG-601 FOR STEAM HEATING BOILERS
HG-602 STEAM GAGES
(a) Each steam boiler shall have a steam gage or a compound
					 steam gage connected to its steam space or to its water column or to its steam
					 connection. The gage or piping to the gage shall contain a siphon or equivalent
					 device that will develop and maintain a water seal that will prevent steam from
					 entering the gage tube. The piping shall be so arranged that the gage cannot be
					 shut off from the boiler except by a cock placed in the pipe at the gage and
					 provided with a tee- or lever-handle arranged to be parallel to the pipe in
					 which it is located when the cock is open. The gage connection boiler tapping,
					 external siphon, or piping to the boiler shall not be less than NPS ¼
					 (DN 8). Where steel or wrought iron pipe or tubing is used, the boiler
					 connection and external siphon shall be not less than NPS ½ (DN 15).
					 Ferrous and nonferrous tubing having inside diameters at least equal to that of
					 standard pipe sizes listed above may be substituted for pipe.
(b) The scale on the dial of a steam boiler gage shall be
					 graduated to not less than 30 psi (200 kPa) nor more than 60 psi (414 kPa). The
					 travel of the pointer from 0 psi to 30 psi (0 kPa to 200 kPa) pressure shall be
					 at least 3 in. (75 mm).
HG-603 WATER GAGE GLASSES
(a) Each steam boiler shall have one or more water gage
					 glasses attached to the water column or boiler by means of valved fittings not
					 less than NPS ½ (DN 15), with the lower fitting provided with a drain
					 valve of a type having an unrestricted drain opening not less than ¼ in.
					 (6 mm) in diameter to facilitate cleaning. Gage glass replacement shall be
					 possible with the boiler under pressure. Water glass fittings may be attached
					 directly to a boiler.
Boilers having an internal vertical height of less than 10
					 in. (250 mm) may be equipped with a water level indicator of the Glass
					 Bull's-Eye type provided the indicator is of sufficient size to show the water
					 at both normal operating and low-water cutoff levels.
(b) The lowest visible part of the water gage glass shall
					 be at least 1 in. (25 mm) above the lowest permissible water level recommended
					 by the boiler Manufacturer. With the boiler operating at this lowest
					 permissible water level, there shall be no danger of overheating any part of
					 the boiler.
Each boiler shall be provided at the time of the
					 manufacture with a permanent marker indicating the lowest permissible water
					 level. The marker shall be stamped, etched, or cast in metal; or it shall be a
					 metallic plate attached by rivets, screws, or welding; or it shall consist of
					 material with documented tests showing its suitability as a permanent marking
					 for the application. This marker shall be visible at all times. Where the
					 boiler is shipped with a jacket, this marker may be located on the
					 jacket.
Note:
Transparent material other than glass
					 may be used for the water gage provided that the material will remain
					 transparent and has proved suitable for the pressure, temperature, and
					 corrosive conditions expected in service.
(c) In electric boilers of the submerged electrode type,
					 the water gage glass shall be so located to indicate the water levels both at
					 startup and under maximum steam load conditions as established by the
					 manufacturer.
(d) In electric boilers of the resistance element type, the
					 lowest visible part of the water gage shall be located at least 1 in. (25 mm)
					 above the lowest permissible water level specified by the Manufacturer. Each
					 electric boiler of this type shall also be equipped with an automatic low-water
					 cutoff on each boiler pressure vessel so located as to automatically cut off
					 the power supply to the heating elements before the surface of the water falls
					 below the visible part of the glass.
(e) Tubular water glasses on electric boilers having a
					 normal water content not exceeding 100 gal (300 l) shall be equipped with a
					 protective shield.
(f) A water level indicator using an indirect sensing
					 method may be used in lieu of an operating water gauge glass; however, a water
					 gauge glass must be installed and operable but may be shut off by valving. The
					 water level indicator must be attached to a water column or directly to the
					 boiler by means of valved fittings not less than NPS ½ (DN 15). The
					 device shall be provided with a drain valve of a type having an unrestricted
					 drain opening not less than ¼ in. (6 mm) in diameter to facilitate
					 cleaning. Service and replacement of internal parts and/or housing shall be
					 possible with the boiler under pressure.
HG-604 WATER COLUMN AND WATER LEVEL CONTROL
					 PIPES
(a) The minimum size of ferrous or nonferrous pipes
					 connecting a water column to a steam boiler shall be NPS 1 (DN 25). No outlet
					 connections, except for damper regulator, feedwater regulator, steam gages, or
					 apparatus that does not permit the escape of any steam or water except for
					 manually operated blowdowns, shall be attached to a water column or the piping
					 connecting a water column to a boiler (see HG-705 for introduction of feedwater
					 into a boiler). If the water column, gage glass, low-water fuel cutoff, or
					 other water level control device is connected to the boiler by pipe and
					 fittings, no shutoff valves of any type shall be placed in such pipe, and a
					 cross or equivalent fitting to which a drain valve and piping may be attached
					 shall be placed in the water piping connection at every right angle turn to
					 facilitate cleaning. The water column drain pipe and valve shall be not less
					 than NPS ¾ (DN 20).
(b) The steam connections to the water column of a
					 horizontal firetube wrought boiler shall be taken from the top of the shell or
					 the upper part of the head, and the water connection shall be taken from a
					 point not above the center line of the shell. For a cast iron boiler, the steam
					 connection to the water column shall be taken from the top of an end section or
					 the top of the steam header, and the water connection shall be made on an end
					 section not less than 6 in. (150 mm) below the bottom connection to the water
					 gage glass.
HG-605 PRESSURE CONTROL
Each automatically fired steam boiler shall be protected
					 from overpressure by two pressure-operated controls.
(a) Each individual automatically fired steam boiler shall
					 have a safety limit control that will cut off the fuel supply to prevent steam
					 pressure from exceeding the 15 psi (100 kPa) maximum allowable working pressure
					 of the boiler. Each control shall be constructed to prevent a pressure setting
					 above 15 psi (100 kPa).
(b) Each individual steam boiler shall have a control that
					 will cut off the fuel supply when the pressure reaches an operating limit,
					 which shall be less than the maximum allowable pressure.
(c) Shutoff valves of any type shall not be placed in the
					 steam pressure connection between the boiler and the controls described in (a)
					 and (b) above. These controls shall be protected with a siphon or equivalent
					 means of maintaining a water seal that will prevent steam from entering the
					 control. The control connection boiler tapping, external siphon, or piping to
					 the boiler shall not be less than NPS ¼ (DN 8), but where steel or
					 wrought iron pipe or tubing is used, they shall not be less than NPS ½
					 (DN 15). The minimum size of an external siphon shall be NPS ¼ (DN 8) or
					 3/8 in. (10 mm) O.D. nonferrous tubing.
HG-606 AUTOMATIC LOW-WATER FUEL CUTOFF AND/OR WATER
					 FEEDING DEVICE
(a) Each automatically fired steam or vapor-system boiler
					 shall have an automatic low-water fuel cutoff so located as to automatically
					 cut off the fuel supply before the surface of the water falls below the lowest
					 visible part of the water gage glass. If a water feeding device is installed,
					 it shall be so constructed that the water inlet valve cannot feed water into
					 the boiler through the float chamber and so located as to supply requisite
					 feedwater.
(b) Such a fuel cutoff or water feeding device may be
					 attached directly to a boiler. A fuel cutoff or water feeding device may also
					 be installed in the tapped openings available for attaching a water glass
					 direct to a boiler, provided the connections are made to the boiler with
					 nonferrous tees or Y's not less than NPS ½ (DN 15) between the boiler
					 and the water glass so that the water glass is attached directly and as close
					 as possible to the boiler; the run of the tee or Y shall take the water glass
					 fittings, and the side outlet or branch of the tee or Y shall take the fuel
					 cutoff or water feeding device. The ends of all nipples shall be reamed to
					 full-size diameter.
(c) Fuel cutoffs and water feeding devices embodying a
					 separate chamber shall have a vertical drain pipe and a blowoff valve not less
					 than NPS ¾ (DN 20), located at the lowest point in the water equalizing
					 pipe connections so that the chamber and the equalizing pipe can be flushed and
					 the device tested.
HG-607 MODULAR STEAM HEATING BOILERS
(a) Each module of a modular steam heating boiler shall be
					 equipped with
(1) steam gage, see HG-602
(2) water gage glass, see HG-603
(3) a pressure control that will cut off the fuel supply
					 when the pressure reaches an operating limit, which shall be less than the
					 maximum allowable pressure
(4) low water cutoff, see HG-606
(b)The assembled modular steam boiler shall also be
					 equipped with a safety limit control that will cut off the fuel supply to
					 prevent steam pressure from exceeding the 15 psi (100 kPa) maximum allowable
					 working pressure of the boiler. The control shall be constructed to prevent
					 pressure setting above 15 psi (100 kPa).
HG-610 FOR HOT WATER HEATING OR HOT WATER SUPPLY
					 BOILERS
HG-611 PRESSURE OR ALTITUDE GAGES
(a) Each hot water heating or hot water supply boiler shall
					 have a pressure or altitude gage connected to it or to its flow connection in
					 such a manner that it cannot be shut off from the boiler except by a cock with
					 tee or lever handle, placed on the pipe near the gage. The handle of the cock
					 shall be parallel to the pipe in which it is located when the cock is
					 open.
(b) Mechanical Gages (Analog). The scale on the dial of the
					 pressure or altitude gage shall be graduated to not less than 1½ nor
					 more than 3½ times the pressure at which the safety relief valve is
					 set.
(c) Electronic gages used in lieu of mechanical gages shall
					 meet the following requirements:
(1) Gage shall be powered from the boiler power supply and
					 it shall have a display that remains on at all times. The gage shall have a
					 backup power supply.
(2) The full scale range of the transducer must be a
					 minimum of 1½ times the pressure at which the safety relief valve is
					 set. It shall be accurate to within ±2% of full scale.
(3) The transducer shall have a media compatibility of both
					 liquids and gases and be temperature compensated.
(4) The gage shall have an operating temperature range of
					 32°F to 250°F (O°C to 120°C) unless otherwise required by the
					 application.
(d) Piping or tubing for pressure- or altitude-gage
					 connections shall be of nonferrous metal when smaller than NPS 1 (DN
					 25).
HG-612 THERMOMETERS/TEMPERATURE SENSORS
Each hot water heating or hot water supply boiler shall
					 have a thermometer or temperature sensor with display so located and connected
					 that it shall be easily readable. The thermometer or sensor shall be so located
					 that it shall at all times indicate the temperature of the water in the boiler
					 at or near the outlet.
(a) Thermometer shall have a minimum full scale range of
					 5O°F to 250°F (10°C to 120°C).
(b) Electronic temperature sensor used in lieu of a
					 thermometer shall meet the following requirements:
(1) The sensor shall be powered from the boiler power
					 supply and it shall have a display that remains on at all times. The gage shall
					 have a backup power supply.
(2) The full scale of the sensor and display must be a
					 minimum of 250°F (120°C). It shall be accurate to within: ±1
					 deg.
(3) The sensor shall have a minimum operating temperature
					 range of 32°F to 300°F (0°C to 150°C).
(4) The display shall have an ambient operating temperature
					 range of 32°F to 120°F (0°C to 50°C) unless otherwise required
					 by the application.
HG-613 TEMPERATURE CONTROL
Each automatically fired hot water heating or hot water
					 supply boiler shall be protected from over-temperature by two
					 temperature-operated controls.
(a) Each individual automatically fired hot water heating
					 or hot water supply boiler shall have a high temperature limit control that
					 will cut off the fuel supply to prevent water temperature from exceeding its
					 marked maximum water temperature at the boiler outlet. This control shall be
					 constructed to prevent a temperature setting above the maximum.
(b) Each individual hot water heating or hot water supply
					 boiler shall have a control that will cut off the fuel supply when the system
					 water temperature reaches a preset operating temperature, which shall be less
					 than the maximum water temperature.
HG-614 LOW-WATER FUEL CUTOFF
(a) Each automatically fired hot water boiler with heat
					 input greater than 400,000 Btu/hr (117 kW) shall have an automatic low-water
					 fuel cutoff that has been designed for hot water service, and it shall be so
					 located as to automatically cut off the fuel supply when the surface of the
					 water falls to the level established in (b) below (see Fig. HG-703.2).
(b) As there is no normal waterline to be maintained in a
					 hot water boiler, any location of the low-water fuel cutoff above the lowest
					 safe permissible water level established by the boiler manufacturer is
					 satisfactory.
(c) A coil-type boiler or a watertube boiler with heat
					 input greater than 400,000 Btu/hr (117 kW) requiring forced circulation to
					 prevent overheating of the coils or tubes shall have a flow-sensing device
					 installed in lieu of the low-water fuel cutoff required in (a) above to
					 automatically cut off the fuel supply when the circulating flow is
					 interrupted.
(d) A means shall be provided for testing the operation of
					 the external low-water fuel cutoff without resorting to draining the entire
					 system. Such means shall not render the device inoperable except as described
					 as follows. If the means temporarily isolates the device from the boiler during
					 this testing, it shall automatically return to its normal position. The
					 connection may be so arranged that the device cannot be shut off from the
					 boiler except by a cock placed at the device and provided with a tee or
					 lever-handle arranged to be parallel to the pipe in which it is located when
					 the cock is open.
HG-615 MODULAR HOT WATER HEATING
					 BOILERS
(a) Each module of a modular hot water heating boiler shall
					 be equipped with
(1) pressure/altitude gage, see HG-611
(2) thermometer, see HG-612
(3) temperature control that will cut off the fuel supply
					 when the temperature reaches an operating limit, which shall be less than the
					 maximum allowable temperature
(b) The assembled modular hot water heating boiler shall
					 also be equipped with
(1) a safety limit control that will cut off the fuel
					 supply to prevent the water temperature from exceeding the maximum allowable
					 temperature at the boiler outlet. The control shall be constructed to prevent a
					 temperature setting above the maximum. This control shall be located within
					 3ft. (1.0 m) of the fitting connecting the last module to the heating supply
					 piping.
(2) low water fuel cutoff, see HG-614.
HG-620 FOR ALL BOILERS
HG-621 INSTRUMENTS, FITTINGS, AND CONTROLS MOUNTED
					 INSIDE BOILER JACKETS
Any or all instruments, fittings, and controls required by
					 these rules may be installed inside of boiler jackets provided the water gage
					 on a steam boiler is accessible without the use of tools and provided the water
					 gage and pressure gage on a steam boiler or the thermometer and pressure gage
					 on a water boiler are visible through an opening or openings at all
					 times.
HG-630 ELECTRIC WIRING
HG-631 ELECTRICAL CODE COMPLIANCE
All field wiring for controls, heat generating apparatus,
					 and other appurtenances necessary for the operation of the boiler or boilers
					 should be installed in accordance with the provisions of the National Electric
					 Code and/or should comply with the applicable local electrical codes. All
					 boilers supplied with factory mounted and wired controls, heat generating
					 apparatus, and other appurtenances necessary for the operation of the boilers
					 should be installed in accordance with the provisions of the nationally
					 recognized standards such as listed in footnote 2 [17]of HG-640.
HG-632 TYPE CIRCUITRY TO BE USED
Whether field or factory wired, the control circuitry shall
					 be positively grounded and shall operate at 150 V or less. One of the two
					 following systems may be employed to provide the control circuit.
(a)
Two-Wire Nominal 120 V System With Separate
					 Equipment Ground Conductor
(1) This system shall consist of the line, neutral, and
					 equipment ground conductors. The control panel frame and associated control
					 circuitry metallic enclosures shall be electrically continuous and be bonded to
					 the equipment ground conductor.
(2) The equipment ground conductor and the neutral
					 conductor shall be bonded together at their origin in the electrical system as
					 required by the NEC.1 - See PDF for table
1 See Appendix H.
(3) The line side of the control circuit shall be provided
					 with a time delay fuse sized as small as practicable.
(b)
Two-Wire Nominal 120 V System Obtained By Using
					 an Isolation Transformer
(1) The two-wire control circuit shall be obtained from the
					 secondary side of an isolation transformer. One wire from the secondary of this
					 transformer shall be electrically continuous and shall be bonded to a
					 convenient cold water pipe. All metallic enclosures of control components shall
					 be securely bonded to this ground control circuit wire. The primary side of the
					 isolation transformer will normally be a two-wire source with a potential of
					 230 V or 208 V or 440 V.
(2) Both sides of the two-wire primary circuit shall be
					 fused. The hot leg on the load side of the isolation transformer shall be fused
					 as small as practicable and in no case fused above the rating of the isolation
					 transformer.
HG-633 LIMIT CONTROLS
Limit controls shall be wired on the hot or line side of
					 the control circuit.
HG-634 SHUTDOWN SWITCHES AND CIRCUIT
					 BREAKERS
A manually operated remote heating plant shutdown switch or
					 circuit breaker should be located just outside the boiler room door and marked
					 for easy identification. Consideration should also be given to the type and
					 location of the switch to safeguard against tampering. If the boiler room door
					 is on the building exterior the switch should be located just inside the door.
					 If there is more than one door to the boiler room, there should be a switch
					 located at each door.
(a) For atmospheric-gas burners, and oil burners where a
					 fan is on a common shaft with the oil pump, the complete burner and controls
					 should be shut off.
(b) For power burners with detached auxiliaries, only the
					 fuel input supply to the firebox need be shut off.
HG-640 CONTROLS AND HEAT GENERATING
					 APPARATUS
(a) Oil and gas-fired and electrically heated boilers
					 should be equipped with suitable primary (flame safeguard) safety controls,
					 safety limit switches, and burners or electric elements as required by a
					 nationally recognized standard.2
2 Examples of these nationally
					 recognized standards are:
American National Standard/CSA Standard Z21.13lCSA 4.9 for
					 Gas-Fired Low Pressure Steam and Hot Water Boilers.
American National Standard/CSA Standard Z21.171CSA 2.7 for
					 Domestic Gas Conversion Burners.
Underwriters Laboratories, Inc., UL 296, Standards for
					 Safety, Oil Burners.
Underwriters Laboratories, Inc., UL 726, Standards for
					 Safety, Oil Fired Boiler Assemblies.
Underwriters Laboratories, Inc., UL 795, Standards for
					 Safety, Commercial-Industrial Gas-Heating Equipment.
Underwriters Laboratories, Inc., UL 834, Electric Heating,
					 Water Supply and Power Boilers.
(b) The symbol of the certifying organization3 that has
					 investigated such equipment as having complied with a nationally recognized
					 standard shall be affixed to the equipment and shall be considered as evidence
					 that the unit was manufactured in accordance with that standard. - See PDF for
					 table
3 A certifying organization is
					 one that provides uniform testing, examination, and listing procedures under
					 established, nationally recognized standards and that is acceptable to the
					 authorities having jurisdiction.
ARTICLE 7
INSTALLATION REQUIREMENTS
HG-700 INSTALLATION REQUIREMENTS, ALL
					 BOILERS
HG-701 MOUNTING SAFETY AND SAFETY RELIEF
					 VALVES
HG-701.1 Permissible Mounting.
Safety valves
					 and safety relief valves shall be located in the top or side1 of the boiler.
					 They shall be connected directly to a tapped or flanged opening in the boiler,
					 to a fitting connected to the boiler by a short nipple, to a Y-base, or to a
					 valveless header connecting steam or water outlets on the same boiler. Coil or
					 header type boilers shall have the safety valve or safety relief valve located
					 on the steam or hot water outlet end. Safety valves and safety relief valves
					 shall be installed with their spindles vertical. The opening or connection
					 between the boiler and any safety valve or safety relief valve shall have at
					 least the area of the valve inlet. - See PDF for table
1 The top or side of the boiler
					 shall mean the highest practicable part of the boiler proper but in no case
					 shall the safety valve be located below the normal operating level and in no
					 case shall the safety relief valve be located below the lowest permissible
					 water level.
HG-701.2 Requirements for Common Connections for Two
					 or More Valves
(a) When a boiler is fitted with two or more safety valves
					 on one connection, this connection shall have a cross-sectional area not less
					 than the combined areas of inlet connections of all the safety valves with
					 which it connects.
(b) When a Y-base is used, the inlet area shall be not less
					 than the combined outlet areas. When the size of the boiler requires a safety
					 valve or safety relief valve larger than 4½ in. (115 mm) in diameter,
					 two or more valves having the required combined capacity shall be used. When
					 two or more valves are used on a boiler, they may be single, directly attached,
					 or mounted on a Y-base.
HG-701.3 Threaded Connections.
A threaded
					 connection may be used for attaching a valve.
HG-701.4 Prohibited Mountings.
Safety and
					 safety relief valves shall not be connected to an internal pipe in the
					 boiler.
HG-701.5 Use of Shutoff Valves Prohibited.
No
					 shutoff of any description shall be placed between the safety or safety relief
					 valve and the boiler, or on discharge pipes between such valves and the
					 atmosphere.
HG-701.6 Safety and Safety Relief Valve Discharge
					 Piping
(a) A discharge pipe shall be used. Its internal
					 cross-sectional area shall be not less than the full area of the valve outlet
					 or of the total of the valve outlets discharging thereinto and shall be as
					 short and straight as possible and so arranged as to avoid undue stress on the
					 valve or valves. A union may be installed in the discharge piping close to the
					 valve outlet. When an elbow is placed on a safety or safety relief valve
					 discharge pipe, it shall be located close to the valve outlet downstream of the
					 union.
(b) The discharge from safety or safety relief valves shall
					 be so arranged that there will be no danger of scalding attendants. The safety
					 or safety relief valve discharge shall be piped away from the boiler to the
					 point of discharge, and there shall be provisions made for properly draining
					 the piping. The size and arrangement of discharge piping shall be independent
					 of other discharge piping and shall be such that any pressure that may exist or
					 develop will not reduce the relieving capacity of the relieving devices below
					 that required to protect the boiler.
HG-701.7 Temperature and Pressure Safety Relief
					 Valves.
Hot water heating or supply boilers limited to a water
					 temperature of 210°F (99°C) may have one or more officially rated
					 temperature and pressure safety relief valves installed. The requirements of
					 HG-701.1 through HG-701.6 shall be met, except as follows:
(a) AY-type fitting shall not be used.
(b) If additional valves are used they shall be temperature
					 and pressure safety relief valves.
(c) When the temperature and pressure safety relief valve
					 is mounted directly on the boiler with no more than 4 in. (100 mm) maximum
					 interconnecting piping, the valve may be installed in the horizontal position
					 with the outlet pointed down.
HG-703
					 PIPING2
2 Guidance for the design of
					 piping systems may be found in ASME B31.9, Building Services Piping.
HG-703.1 Provisions for Expansion and
					 Contraction.
Provisions shall be made for the expansion and contraction
					 of steam and hot water mains connected to boilers by providing substantial
					 anchorage at suitable points and by providing swing joints when boilers are
					 installed in batteries, so there will be no undue strain transmitted to the
					 boilers. See Figs. HG-703.1(a), HG-703.1(b), and HG-703.2 for typical schematic
					 arrangements of piping incorporating strain absorbing joints for steam and hot
					 water heating boilers.
HG-703.2 Return Pipe Connections
(a) The return pipe connections of each boiler supplying a
					 gravity return steam heating system shall be so arranged as to form a loop
					 substantially as shown in Fig. HG-703.l(b) so that the water in each boiler
					 cannot be forced out below the safe water level.
(b) For hand-fired boilers with a normal grate line, the
					 recommended pipe sizes detailed as "A" in Fig.HG-703.1 are NPS 1½ (DN
					 40) for 4 ft2 (0.37 m2) or less firebox area at the normal grate line, NPS
					 2½ (DN 65) for areas more than 4 ft2 (0.37 m2) up to 14.9 ft2 (1.4 m2),
					 and NPS 4 (DN 100) for 15 ft2 (1.4 m2) or more.
(c) For automatically fired boilers that do not have a
					 normal grate line, the recommended pipe sizes detailed as "A" in Fig. HG-703.1
					 are NPS 1½ (DN 40) for boilers with minimum safety valve relieving
					 capacity 250 lb/hr (113 kg/hr) or less, NPS 2½ (DN 65) for boilers with
					 minimum safety valve relieving capacity from 251 lb/hr (114 kg/hr) to 2,000
					 lb/hr (900 kg/hr), inclusive, and NPS 4 (DN 100) for boilers with more than
					 2,000 lb/hr (900 kg/hr) minimum safety valve relieving capacity.
(d) Provision shall be made for cleaning the interior of
					 the return piping at or close to the boiler. Washout openings may be used for
					 return pipe connections and the washout plug placed in a tee or a cross so that
					 the plug is directly opposite and as close as possible to the opening in the
					 boiler.
See PDF for
					 diagram
See PDF for
					 diagram
See PDF for
					 diagram
HG-705 FEEDWATER AND MAKEUP WATER
					 CONNECTIONS
(a)
Steam Boilers.
Feedwater or water
					 treatment shall be introduced into a boiler through the return piping system.
					 Alternatively, feedwater or water treatment may be introduced through an
					 independent connection. The water flow from the independent connection shall
					 not discharge directly against parts of the boiler exposed to direct radiant
					 heat from the fire. Feedwater or water treatment shall not be introduced
					 through openings or connections provided for inspection or cleaning, safety
					 valve, water column, water gage glass, or pressure gage. The feedwater pipe
					 shall be provided with a check valve or a backflow preventer containing a check
					 valve3 near the boiler and a stop valve or cock between the check valve and the
					 boiler or between the check valve and the return pipe system.
(b)
Hot Water Boilers.
Makeup water may be
					 introduced into a boiler through the piping system or through an independent
					 connection. The water flow from the independent connection shall not discharge
					 directly against parts of the boiler exposed to direct radiant heat from the
					 fire. Makeup water shall not be introduced through openings or connections
					 provided exclusively for inspection or cleaning, safety relief valve, pressure
					 gage, or temperature gage. The makeup water pipe shall be provided with a check
					 valve or a backflow preventer containing a check valve3 near the boiler and a
					 stop valve or cock between the check valve and the boiler or between the check
					 valve and the piping system. - See PDF for table
3 Plumbing codes may require the
					 installation of a reduced pressure principle backflow preventer on a boiler
					 when the makeup water source is from a potable water supply.
HG-707 OIL HEATERS
(a) A heater for oil or other liquid harmful to boiler
					 operation shall not be installed directly in the steam or water space within a
					 boiler.
(b) Where an external type heater for such service is used,
					 means shall be provided to prevent the introduction into the boiler of oil or
					 other liquid harmful to boiler operation.
HG-708 STORAGE TANKS FOR HOT WATER SUPPLY
					 SYSTEMS
If a system is to utilize a storage tank that exceeds the
					 capacity exception of HLW-101.2 (c), the tank shall be constructed in
					 accordance with the rules of Part HLW; Section VIII, Division 1; or Section X.
					 For tanks constructed to Section X, the maximum allowable temperature marked on
					 the tank shall equal or exceed the maximum water temperature marked on the
					 boiler.
HG-709 PROVISIONS FOR THERMAL EXPANSION IN HOT WATER
					 SYSTEMS
All hot water heating systems incorporating hot water tanks
					 or fluid relief columns shall be so installed as to prevent freezing under
					 normal operating conditions.
HG-709.1 Heating Systems With Open Expansion
					 Tank.
An indoor overflow from the upper portion of the expansion tank
					 shall be provided in addition to an open vent, the indoor overflow to be
					 carried within the building to a suitable plumbing fixture or the
					 basement.
HG-709.2 Closed Heating Systems.
An expansion
					 tank shall be installed that will be consistent with the volume and capacity of
					 the system. If the system is designed for a working pressure of 30 psi (200
					 kPa) or less, the tank shall be suitably designed for a minimum hydrostatic
					 test pressure of 75 psi (520 kPa). Expansion tanks for systems designed to
					 operate above 30 psi (200 kPa) shall be constructed in accordance with Section
					 VIII, Division 1. Alternatively, a tank built to Section X requirements may be
					 used if the pressure and temperature ratings of the tank are equal to or
					 greater than the pressure and temperature ratings of the system. Provisions
					 shall be made for draining the tank without emptying the system, except for
					 prepressurized tanks.
The minimum capacity of the closed type expansion tank may
					 be determined from Table HG-709.2 or from the following formula where the
					 necessary information is available:
(U.S. Customary Units)
Vt = [(0.00041T - 0.0466)Vs ]/[(P
					 a/Pf) - (Pa/Po)]
(SI
Units)
Vt = [(0.18155T -
					 8.236)Vs
					 ]/[(Pa/Pf) -
					 (Pa/P o)]
where
Pa = atmospheric pressure
Pf = fill pressure
Po = maximum operating
					 pressure
T
= average operating temperature
Vs = volume of system, not including
					 tanks
Vt = minimum volume of tanks
TABLE HG-709.2
EXP ANSION T ANK CAP ACITIES FOR FORCED
HOT W A TER SYSTEMS
[Based on average operating water temperature 195 ° F
					 (90 ° C), fill pressure 12 psig (83 kPa), and maximum operating pressure 30
					 psig (200 kPa)]
Tank Capacities, gal
								  (m3)
System Volume,gal
								  (m3)
Prepressurized
Diaphragm
Type
NonpressurizedType
100 (0.38)
9 (0.034)
15 (0.057)
200 (0.76)
17 (0.064)
30 (0.114)
300 (1.14)
25 (0.095)
45 (0.170)
400 (1.51)
33 (0.125)
60 (0.227)
500 (1.89)
42 (0.159)
75 (0.284)
1,000 (3.79)
83 (0.314)
150 (0.568)
2,000 (7.57)
165 (0.625)
300 (1.136)
HG-709.3 Hot Water Supply Systems.
If a system
					 is equipped with a check valve or pressure reducing valve in the cold water
					 inlet line, consideration should be given to the installation of an airtight
					 expansion tank or other suitable air cushion. Otherwise, due to the thermal
					 expansion of the water, the safety relief valve may lift periodically. If an
					 expansion tank is provided, it shall be constructed in accordance with Section
					 VIII, Division 1 or Section X. Except for prepressurized tanks, which should be
					 installed on the cold water side, provisions shall be made for draining the
					 tank without emptying the system. See Fig. HLW-809.1 for a typical acceptable
					 installation.
HG-710 STOP VALVES
HG-710.1 For Single Steam Boilers.
When a stop
					 valve is used in the supply pipe connection of a single steam boiler, there
					 shall be one used in the return pipe connection.
HG-710.2 For Single Hot Water Heating
					 Boilers
(a) Stop valves shall be located at an accessible point in
					 the supply and return pipe connections as near the boiler nozzle as is
					 convenient and practicable, of a single hot water heating boiler installation
					 to permit draining the boiler without emptying the system.
(b) When the boiler is located above the system and can be
					 drained without draining the system, stop valves may be eliminated.
HG-710.3 For Multiple Boiler Installations.
A
					 stop valve shall be used in each supply and return pipe connection of two or
					 more boilers connected to a common system. See Figs. HG-703.1 and
					 HG-703.2.
HG-710.4 Type of Stop Valve(s)
(a) All valves or cocks shall conform with the applicable
					 portions of HF-203 and may be ferrous or nonferrous.
(b) The minimum pressure rating of all valves or cocks
					 shall be at least equal to the pressure stamped upon the boiler, and the
					 temperature rating of such valves or cocks, including all internal components,
					 shall be not less than 250°F (120°C).
(c) Valves or cocks shall be flanged, threaded, or have
					 ends suitable for welding or brazing.
(d) All valves or cocks with stems or spindles shall have
					 adjustable pressure type packing glands and, in addition, all plug type cocks
					 shall be equipped with a guard or gland. The plug or other operating mechanism
					 shall be distinctly marked in line with the passage to indicate whether it is
					 opened or closed.
(e) All valves or cocks shall have tight closure when under
					 boiler hydrostatic test pressure.
HG-710.5 Identification of Stop Valves by Tags.
When stop valves are used, they shall be properly designated
					 substantially as follows by tags of metal or other durable material fastened to
					 them:
Supply Valve - Number ( )
Do Not Close Without Also Closing Return Valve - Number (
					 )
Return Valve - Number ( )
Do Not Close Without Also Closing Supply Valve - Number (
					 )
HG-715 BOTTOM BLOWOFF AND DRAIN VALVE
S
(a)
Bottom Blowoff Valve.
Each steam
					 boiler shall have a bottom blowoff connection fitted with a valve or cock
					 connected to the lowest water space practicable with a minimum size as shown in
					 Table HG-715. The discharge piping shall be full size to the point of
					 discharge.
TABLE HG-715
SIZE OF BOTT OM BLOWOFF PIPING, VAL VES, AND
					 COCKS
Minimum Required SafetyValve
Capacity, lb (kg) of steam/hr[Note (1)]
Blowoff Piping,Valves, and CocksMin. Size NPS
								  (DN)
Up to 500 (225)
¾ (20)
501 to 1,250 (225 to 550)
1 (25)
1,251 to 2,500 (550 to 1 200)
1¼ (32)
2,501 to 6,000 (1 200 to 2700)
1½ (40)
6,001 (2 700) and larger
2 (50)
NOTE:
(1) T o determine the dischar ge
					 capacity of safety relief valves in terms of Btu, the relieving capacity in lb
					 of steam/hr is multi - plied by 1,000.
(b) Boilers having a capacity of 25 gal (95 l) or less are
					 exempt from the above requirements, except that they must have an NPS ¾
					 (DN 20) minimum drain valve.
(c)
Drain Valve.
Each steam or hot water
					 boiler shall have one or more drain connections, fitted with valves or cocks.
					 These shall be connected at the lowest practicable point on the boiler, or to
					 the lowest point on piping connected to the boiler, at the lowest practicable
					 point on the boiler. The minimum size of the drain piping, valves, and cocks
					 shall be NPS ¾ (DN 20). The discharge piping shall be full size to the
					 point of discharge. When the blowoff connection is located at the lowest water
					 containing space, a separate drain connection is not required.
(d)
Minimum Pressure Rating.
The minimum
					 pressure rating of valves and cocks used for blowoff or drain purposes shall be
					 at least equal to the pressure stamped on the boiler but in no case less than
					 30 psi (200 kPa). The temperature rating of such valves and cocks shall not be
					 less than 250°F (120°C).
HG-716 MODULAR BOILERS
(a)
Individual Modules
(1) The individual modules shall comply with all the
					 requirements of Part HG, except as specified in HG-607, HG-615, and this
					 paragraph. The individual modules shall be limited to a maximum input of
					 400,000 Btuh (gas), 3 gal/hr (1 l/hr) (oil), or 115 kW (electricity).
(2) Each module of a steam heating boiler shall be equipped
					 with
(a) safety valve, see HG-701
(b) blowoff valve, see HG-715 (a)
(c) drain valve, see HG-715 (c)
(3) Each module of a modular hot water heating boiler shall
					 be equipped with
(a) safety relief valve, see HG-701
(b) drain valve, see HG-715 (c)
(b)
Assembled Modular Boilers
(1) The individual modules shall be manifolded together at
					 the job-site without any intervening valves. The header or manifold piping is
					 field piping and is exempt from Article 2, Part HG, HF, HB, or HC.
(2) The assembled modular steam heating boiler shall also
					 be equipped with
(a) feedwater connection, see HG-705 (a)
(b) return pipe connection, see HG-703.2
(3) The assembled modular hot water heating boiler shall
					 also be equipped with
(a) makeup water connection, see HG-705 (b)
(b) provision for thermal expansion, see HG-709
(c) stop valves, see HG-710.2
HG-720 SETTING
Boilers of wrought materials of the wet-bottom type having
					 an external width of over 36 in. (900 mm) shall have not less than 12 in. (300
					 mm) between the bottom of the boiler and the floorline, with access for
					 inspection. When the width is 36 in. (900 mm) or less, the distance between the
					 bottom of the boiler and the floorline shall be not less than 6 in. (150 mm),
					 except that, when any part of the wet bottom is not farther from an outer edge
					 than 12 in. (300 mm), this distance shall be not less than 4 in. (100
					 mm).
HG-725 METHODS OF SUPPORT
HG-725.1 Loadings
(a) The design and attachment of lugs, hangers, saddles,
					 and other supports shall take into account the stresses due to hydrostatic head
					 in determining the minimum thicknesses required. Additional stresses imposed by
					 effects other than working pressure or static head, which increase the average
					 stress by more than 10% of the allowable working stress, shall also be taken
					 into account. These effects include the weight of the component and its
					 contents, and the method of support.
(b) In applying the requirements of (a) above, localized
					 stresses due to concentrated support loads, temperature changes, and restraint
					 against dilation of the boiler due to pressure shall be provided for. Lugs,
					 hangers, brackets, saddles, and pads shall conform satisfactorily to the shape
					 of the shell or surface to which they are attached or are in contact.
HG-725.2
Boilers Over 72 in. (1 800 mm)
					 in Diameter.
A horizontal-return tubular boiler over 72 in. (1 800 mm)
					 in diameter shall be supported from steel hangers by the outside-suspension
					 type of setting, independent of the furnace wall. The hangers shall be so
					 designed that the load is properly distributed.
HG-725.3 Boilers Over 54 in. (1 400 mm) up to 72 in.
					 (1 800 mm) in Diameter.
A horizontal-return tubular boiler over 54 in.
					 (1 400 mm) and up to and including 72 in. (1 800 mm) in diameter shall be
					 supported by the outside-suspension type of setting, or at four points by not
					 less than eight steel brackets set in pairs, the brackets of each pair to be
					 spaced not over 2 in. (50 mm) apart and the load to be equalized between them.
					 [See Fig. HG-725(a).]
HG-725.4
Boilers up to 54 in. (1 400 mm)
					 in Diameter.
A horizontal-return tubular boiler up to and including 54
					 in. (1 400 mm) in diameter shall be supported by the outside-suspension type of
					 setting, or by not less than two steel brackets on each side.
HG-725.5 Supporting Members.
If the boiler is
					 supported by structural steel work, the steel supporting members shall be so
					 located or insulated that the heat from the furnace can not impair their
					 strength.
HG-725.6 Lugs or Hangers.
Lugs, hangers, or
					 brackets made of materials in accordance with the Code requirements may be
					 attached by fusion welding provided they are attached by fillet welds along the
					 entire periphery or contact edges. Figure HG-725(b) illustrates an acceptable
					 design of hanger bracket with the additional requirement that the center pin be
					 located at the vertical center line over the center of the welded contact
					 surface. The bracket plates shall be spaced at least 2½ in. (64 mm)
					 apart, but this dimension shall be increased if necessary to permit access for
					 the welding operation. The stresses computed by dividing the total load on each
					 lug, hanger, or bracket, by the minimum cross-sectional area of the weld shall
					 not exceed 2800 psi (19 MPa). Where it is impractical to attach lugs, hangers,
					 or brackets by welding, studs with not less than 10 threads/in. (approx. 4
					 threads/cm) may be used. In computing the shearing stresses, the root area at
					 the bottom of the thread shall be used. The shearing and crushing stresses on
					 studs shall not exceed 8% of the strength given in Table HF-300.1 for bolting
					 materials.
HG-725.7
Settings.
Boilers of
					 wrought materials of the wet-bottom type having an external width of over 36
					 in. (900 mm) shall be supported so as to have a minimum clearance of 12 in.
					 (300 mm), between the bottom of the boiler and the floor, to facilitate
					 inspection. When the width is 36 in. (900 mm) or less, the clearance between
					 the bottom of the boiler and the floorline shall be not less than 6 in. (150
					 mm), except when any part of the wet bottom is not farther from the outer edge
					 than 12 in. (300 mm). This clearance shall be not less than 4 in. (100 mm).
					 Boiler insulation, saddles, or other supports shall be arranged so that
					 inspection openings are readily accessible.
See PDF for
					 diagram