Assembly of orifice chambers progressively reducing operating pressure for large gas flows

Disclosed is an improved assembly of orifice chambers for reducing pressure of large gas flows effective to reduce noise of the gas flows and wear on orifice chambers by progressive pressure drops in the gas flows through successive orifice plates which are releasably secured, preferably by fillet welding, in each of the orifice chambers, removal of one or more orifice plates in an orifice chamber providing manway access to the next succeeding orifice chamber for inspection, repairs, and replacement of the orifice plates thereby reducing the manway opening or access to only one orifice chamber and eliminating separate access manways or manholes for each of the orifice chamber necessary for maintenance of the orifice chambers. Preferably, an internal shell providing an annular space with the body to which the orifice plates are connected is connected to the body by an annular ring and brace by fillet welding in compressions.

FIELD OF THE INVENTION
 The field of the invention is an assembly of orifice chambers progressively
 reducing operating pressure of large gas flows having at least one orifice
 plate in each orifice chamber to take small progressive pressure drops
 across each orifice plate in lieu of one large pressure drop for reducing
 wear on each orifice plate and the overall noise.
 BACKGROUND OF THE INVENTION
 Present orifice chambers utilize an assembly of a number of orifice
 chambers having orifice plates to progressively reduce the operating
 pressure of large gas flows, typically flue gas operating from 20 to 40
 psig at temperatures ranging from 500 to 1500.degree. F., to atmospheric
 pressure. Each orifice chamber is equipped with one or more orifices or
 perforated plates, and typically the assembly has a minimum of two and a
 maximum of seven orifice chambers having orifice plates in order to
 progressively take small pressure drops across the orifice plates in each
 of the orifice chambers in lieu of one large pressure drop. The size of
 the orifice chambers ranges typically from 30 inches in diameter to 130
 inches in diameter. The flowing medium is typically flue gas from a
 catalytic cracking unit going to the stack outlet of a refinery. The flue
 gas is a result of the combustion process in a regenerator of a catalytic
 cracking unit.
 The orifice or perforated plates of the orifice chambers require periodic
 inspection and maintenance and therefore are equipped with a manway or
 manhole for access to each orifice chamber and the orifice plates or
 plates secured therein for inspection and maintenance such as repair or
 replacement, which requires opening and closing each manway or manhole, is
 time consuming and expensive.
 In the following prior art, U.S. Pat. No. 3,712,502 discloses a tanker
 having internal compartments formed by internal sections 2 which may be
 welded therein and having openings 10 therethrough; U.S. Pat. No.
 3,050,315 discloses a tank having spaced perforated surge plates 4 mounted
 therein; U.S. Pat. No. 4,611,724 discloses a fluid storage tank with
 internal welded baffles 20 and perforations to permit fluid to flow
 through the baffles; U.S. Pat. No. 5,346,092 discloses a tank having
 welded interior separators 13, 14 and one manhole 12 secured to an inner
 tank section; U.S. Pat. No. 2,092,490 discloses a welding of interior
 separating plate 22 within a tank.
 The following U.S. Pat. Nos. 710,405, 1,613,746, 1,952,867, 3,250,319,
 3,338,238, and 3,425,810 disclose various arrangements for mounting welded
 interior sections or providing perforations within the sections all within
 larger chambers.
 None of the foregoing prior art orifice chambers and patents disclose or
 suggest an assembly of orifice chambers for a gradual, progressive, and
 sequential reduction of operating gas pressures as it flows through a
 plurality of orifice chambers having removable orifice plates in the
 orifice chambers and a single access manway or manhole to a first orifice
 chamber, and access to successive chambers is provided by sequential
 removal of the orifice plates for maintenance, such as for inspection,
 repair, and replacement.
 It would be highly desirable to provide an improvement in the present
 assemblies of such orifice chambers which would require only one manway or
 manhole for the entire assembly for maintenance such as inspection,
 repair, and replacement of the orifice or perforated plates.
 SUMMARY OF THE INVENTION
 The present invention is directed to such an improved assembly of orifice
 chambers for progressive and gradual reduction of operating pressure of
 gas flow therethrough which requires only one manway or manhole for
 maintenance, such as inspection, repair, and replacement of the orifice or
 perforated plates.
 The foregoing is accomplished by an assembly of orifice chambers for the
 progressive and gradual reduction of operating pressures of gas flow such
 as by flue gas from a catalytic cracking unit to the stack outlet of a
 refinery, which comprises a body having a flowway, inlet and outlet for
 the gas to flow through, a plurality of orifice plate supports secured to
 and extending partially into the flowway spaced from one another in a
 direction of the gas flow, orifice plates releasably secured to and
 supported by the support plates thereby forming the orifice chambers, the
 orifice plates being provided with one or more orifices or perforations
 effective to provide progressive gradual pressure drops in the gas flow,
 and a manhole or manway having a releasable closure in the body upstream
 from the first of the orifice plates so that upon removal of the first of
 the orifice plates access is provided to the next successive plate, and
 removal of the next orifice plate provides access to the next successive
 plate and so on for maintenance, such as inspection, repair, and
 replacement of each of the orifice plates in the assembly of orifice
 chambers. Preferably, the orifice plates are secured to an internal
 annular shell secured to the body by an annular ring providing an annular
 space between the internal shell and the body allowing for thermal
 expansion and contraction. Preferably, the orifice plates are releasably
 secured to the orifice plate supports by fillet welding and can be
 replaced by fillet welding. Sound dampening or thermal insulation or both
 can be utilized.
 Accordingly, it is an object of the present invention to provide an
 assembly of orifice chambers having a flowway therethrough for the
 progressive and gradual reduction of operating pressure of large gas flows
 through the flowway as previously described in which only a single access
 manway or manhole for maintenance, such as inspection, repair, and
 replacement of the orifice plates in the orifice chambers of the assembly
 is required.
 A further object of the invention is the provision of an improved assembly
 of orifice chambers for the progressive and gradual reduction of operating
 pressures of gas flow therethrough, each having a removable orifice plate
 which when removed provides a manway or manhole for access to the next
 orifice plate for maintenance, such as inspection, repairs, and
 replacement so that only one manway or manhole is necessary for access for
 maintenance of each of the orifice chambers of the assembly.
 It is a further object of the invention to provide such an improved
 assembly of orifice chambers which permits thermal expansion and
 contraction caused by gases flowing through its flowway.
 Other and further objects, features, and advantages of the present
 invention will be apparent from the following description of presently
 preferred embodiments of the invention taken in conjunction with the
 accompanying drawings in which the like reference numerals designate like
 parts throughout several views.

DETAILED DESCRIPTION OF THE INVENTION
 Referring now to FIG. 1 illustrating a prior art assembly of orifice
 chambers generally indicated by the reference numeral 10 which includes
 the body 12 having a flowway 14, entrance 16 and exit 18 for large gas
 flows therethrough, for example those operating from 20 to 40 psig and at
 temperatures ranging from 500 to 1500.degree. F. to atmospheric pressure.
 The flowing medium is typically flue gas from the outlet valve (not shown)
 of a catalytic cracking unit going to the stack outlet of a refinery (not
 shown). The flue gas is a result of the combustion process and the
 regenerator of the catalytic cracking process. The entrance 16 of the body
 is connected to a flow valve, and the exit 18 is connected to the stack
 outlet (both not shown). No further description is given or deemed
 necessary as large gas flows of this type from refineries are well known
 to those skilled in the art.
 As illustrated in FIG. 1, there are four orifice chambers 20, 22, 24, and
 26 formed by orifice plates 21, 23, 25, and 27 secured to the body 12
 having orifice or perforations 28 (not shown in orifice chamber 26 in this
 view because of staggering of positions of the orifices in the orifice
 plate 27) with respect to the other orifice plate. Typically a minimum of
 two and a maximum of seven orifice chambers are required in order to take
 progressively small, gradual pressure drops across each orifice plate in
 lieu of one large pressure drop to reduce wear on each orifice plate and
 to reduce the overall noise caused by the gas flow. Any number of orifice
 chambers can be used to accommodate the conditions of use.
 These orifice chambers require periodic inspection and maintenance, and
 therefore each are equipped with inspection manways or manholes 30 in
 between each of the plates 21, 23, 25, and 27. If any damage is present,
 then repairs to the orifice plates can only be made in place requiring
 separate manholes or manways for each orifice plate.
 Referring now to FIG. 2 which illustrates the improved assembly of orifice
 chambers 10a of the present invention and in which reference numerals with
 the letter "a" designate corresponding parts in FIG. 1, there is a body
 12a, having the flowway 14a, inlet 16a and outlet 18a for gas flow
 therethrough such as described in connection with FIG. 1. A series of
 support plates 29, 31, 33, and 35 are secured to the interior of the body
 12a by means of an internal shell 48 secured to the body 12a by the
 centering ring 50 and the braces or cone 34 which permit thermal expansion
 and contraction of the flowway 16a. Advantageously, the ring 50 and braces
 or cone 34 securing the internal shell 48 to the body 12a adjacent the
 inlet and outlet ends 16a and 18a, respectively, of the flowway 14a are
 secured by fillet welding which is in compressions rather than in tension
 contrary to prior art. These support plates extend partially into the
 flowway 14a which provide support for the orifice plates 20a, 22a, 24a,
 and 26a, respectively, which are removable as hereinafter described, and
 provide access manways or manholes 32, 34, 36, and 38 when the removable
 orifice plates 20a, 22a, 24a, and 26a are removed as hereinafter
 described. These orifice plates provide a series of orifice chambers 40,
 42, 44, and 46.
 A manway or manhole 30a is provided for access into the first orifice
 chamber 40, removal of the removable orifice plate 20a provides an access
 manway or manhole from orifice chamber 40 into the orifice chamber 42,
 removal of orifice plate 22a provides manway access into the orifice
 chamber 44, and removal of orifice plate 24a provides manway access into
 orifice chamber 46. Thus, manway access is provided into each of the
 orifice chambers as described for maintenance, such as inspection and
 repair or replacement of the orifice plates 20a, 22a, 24a, and 26a with
 only one access manhole or manway 30a being required therefor.
 FIG. 3 illustrates the construction of a preferred removable orifice plate,
 an example of which is the orifice plate 20a in chamber 40 which includes
 a support ring 21 having a cross member 19, which support ring 21
 preferably is secured by welding 15 to the interior wall 17 of the body
 12a. The orifice plate 20a is releasably secured to the orifice support
 plate 21, preferably by fillet welding 15 so that the orifice plates 20a
 may be removed by cutting the fillet weld 15. This permits access through
 the manway opening 32 to provide access into the orifice chamber 42.
 The remaining plate support members and removable orifice plates are the
 same as described and can be sequentially removed to provide access into
 each of the following orifice chambers 44 and 46. Thus, the orifice plates
 can be accessed for inspection, repair, and replacement simply by
 utilization of a single manway or manhole and removal of the orifice
 plates as described. The manway or manhole 30a has a releasable closure
 (as do those in FIG. 1) which is removed and replaced for such access. The
 releasable closures are conventional, and no further description thereof
 is deemed necessary or given.
 Any type of suitable material for noise or thermal insulation can be used.
 For example, any refractory material having sufficient strength can be
 used for the liner, which materials are available from a number of
 suppliers including Harbison Walker (Pittsburgh, Pa.), National
 Refractories (Oakland, Calif.), Norton Co. (Worchester, Mass.), The
 Carborundum Co. (Niagara Falls, N.Y.), Resco Products, Inc. (Morristown,
 Pa.) Plibrico (Chicago, Ill.), and A. P. Green (Mexico, Mo.).
 For noise dampening ceramic fibrous materials such as Kaowhool from Thermal
 Ceramics of Augusta, Ga., or other suitable materials can be used.
 Accordingly, no further description is deemed necessary or given as noise
 dampening and thermal insulation materials are readily available on the
 open market.
 For reducing the operating pressure of large gas flows in the range of from
 20 to 40 psig at temperatures ranging from 500 to 1500.degree. F. to
 atmospheric pressure, typically a minimum of two and a maximum of seven
 orifice chambers are satisfactory in order to take progressive small
 pressure drops across each orifice plate in lieu of one large pressure
 drop. For these gas flows, the size of the orifice chambers ranges
 typically from 30 inches diameter to 130 inches diameter. Preferably, the
 openings or perforations in the plate are staggered with respect to one
 another in the direction of flow through the successive orifice chambers.
 The orifices or perforations in the orifice plates may vary from plate to
 plate.
 The following is an example of satisfactory low areas calculation for flue
 gas valve and orifice chambers utilizing four orifice chambers.
 EXAMPLE 1

Flow Gas Valve with Orifice Chambers
 FLOW P1 DIFF. P TEMP. DISCH. OPEN AREA VALVE OR
 #/HR M.W. PSIG PSI DEG. F. COEFF. % IN2 HEAD #
 250000 29 35 10.2 1350 .9 50 301 FG VALVE
 250000 29 24.8 8.14 1340 .75 100 226 1 Orifice
 chamber
 250000 29 16.67 6.45 1330 .75 100 284 2 Orifice
 chambers
 250000 29 10.22 5.15 1320 .75 100 356 3 Orifice
 chambers
 250000 29 5.07 4.07 1310 .75 100 448 4 Orifice
 chambers
 From the above Example 1, the sequential pressure drop through the four
 orifice chambers indicated in the columns entitled "PI PSIG" and "DIFF.P
 PSI" dropped from 35 and 10.2 psig to 5.07 and 4.07 psig which
 substantially reduced the noise and wear on the orifice plates to the
 sequential incremental pressure drops indicated.
 The improved orifice chambers can be utilized with a wide range of gas
 pressures, temperatures, and flow rates modified as to size, number, and
 arrangement to accommodate the circumstances of use.
 The present invention, therefore, is well suited and adapted to attain the
 objects and the ends and has the advantages and features mentioned as well
 as others inherent therein.
 While presently preferred embodiments of the invention have been given for
 the purpose of disclosure, changes may be made which are within the spirit
 of the invention as defined by the scope of the appended claims.