New York Codes, Rules and Regulations › Title 1 - DEPARTMENT OF AGRICULTURE AND MARKETS › Appendices › Appendix 11

Current through Register Vol. 46, No. 28, July 10, 2024
EVAPORATING, DRYING AND DRY PRODUCT
EQUIPMENT CLEANING
(cf. Part 3)
I. Cleaning of Evaporators and Condensers
Some evaporators are designed to that the product is exposed to
				large surface areas for a long period of time at temperatures conducive to the
				growth of micro-organisms.
Pipelines and/or equipment designed for automated mechanical
				cleaning of evaporators should meet the following requirements:
1. A pH recording device should be installed in the return
				solution line to record the pH and time which the line or equipment is exposed
				during the cleaning and sanitizing operation.
2. These pH recording charts should be identified, dated, and
				retained for 3 months.
3. During each official inspection the regulatory agency should
				examine and initial the pH recording charts to verify the time of exposure to
				the cleaning solutions and their pH.
The following are suggested procedures for cleaning and
				sanitizing evaporators and condensers:
The surface area inside an evaporator is extremely large. Not
				only is there a large separator chamber and vapor lines but steam chests may
				also have as many as 500 heating tubes from 8 to 10 feet long. The total
				surface area may be 3000 to 4000 square feet which may require large volumes
				for recirculation. This surface area must be cleaned and sanitized carefully or
				it will contaminate the product. The operating temperatures in an evaporator
				are very close to the growing temperatures of thermoduric and certain
				mesophyllic types of bacteria. The first effect may operate at 140°F to
				170°F (60°C to 77°C) the second effect at 125°F to 145°F
				(52°C to 63°C), and the third effect at 100°F to 120°F
				(38°C to 49°C). The product being evaporated is often recirculated in
				the last effect several times until the right concentration is reached which
				may give bacteria ample time to grow. A clean evaporator operates more
				efficiently. It is necessary to clean the evaporators after long periods of
				operations because burned-on material reduces heat transfer and efficiency. A
				point is reached where it will be more economical to stop and clean up than to
				continue to operate. Evaporators need cleaning for sanitary reasons as well as
				for efficient operation. Tube chests and heating plates must be cleaned to get
				good heat transfer. If vapor lines are not cleaned, it is possible to get a
				back surge of vapor when the vacuum is released. This can carry soil back into
				the product thus lowering the quality. This soil may drop into the
				thermo-compression unit, block passage of vapors and actually prevent good
				operation. Compounds for cleaning are usually divided into two main
				groups:
1. The alkaline cleaners usually contain caustic with water
				conditioners, synthetic detergents and foam depressants added to enchance
				cleaning action. The purpose of the alkaline cleaner is to digest the bulk of
				the soil. The alkaline solutions are usually run first at concentrations
				ranging from 1 percent to 3 percent at temperatures of 180°F to 190°F
				(83°C to 88°C) for 30 to 60 minutes.
2. Acid cleaners are usually food grade with synthetic
				detergents and inhibitors to prevent attack on metal surfaces. The purpose of
				acid cleaners is to remove mineral films, alkali cleaner residues, and shine
				the inside surfaces. Acid solutions are usually used last at concentrations of
				0.2 percent to 0.5 percent at 140°F to 160°F (60°C to 71°C) In
				all cases cleaners and cleaning instructions should be followed as recommended
				by the manufacturer of cleaning compounds. It is also necessary to follow the
				recommendations and instructions of evaporator manufacturers. The evaporators
				operating with compressed ammonia require special cleaning precautions.
Cleaning Methods.
-There are three basic methods of
				cleaning evaporators: boil-out; circulation; spray cleaning; or a combination
				of the three methods. The boil-out method is the oldest but it is still very
				effective. It is accomplished by rolling or boiling the cleaning solution under
				partial vacuum. Heat is applied by the evaporator and just enough vacuum is
				used to roll the solution. Cleaning solutions are elevated to the dome and
				upper parts by opening and closing the vacuum breaker. Hand brushing of some
				areas is often necessary following boil-out because it is difficult to
				thoroughly clean the upper surfaces with this method.
Circulation cleaning is a newer method of cleaning. The
				cleaning solution actually follows the product path. The solution is circulated
				by returning it back to the starting point. Heat is applied by a pre-heater,
				tube chest, or steam jet, sometimes called a boil-out nozzle. This method is
				not adaptable to all types of evaporators and it is usually necessary to add
				spray cleaning devices to thoroughly clean separators and the bottom tube sheet
				in steam chests.
Spray cleaning is the newest method of cleaning evaporators.
				Cleaning solutions are pumped through spray devices and distributed over the
				surfaces which are contacted by the product. Heat is applied by pre-heater, a
				surge tank, or on the run with live steam. When properly designed and operated
				spray cleaning systems are used, cleaning problems are at a minimum. Spray
				cleaning offers many advantages over boil-out or circulation methods of
				cleaning. Less water and less cleaning solution is required. This not only
				results in a saving of water, heat and cleaners, but more concentrated cleaning
				solutions can be used giving faster, more effective cleaning. Heat for the
				rinse water and cleaning solutions is applied externally, preventing additional
				burn-on in tube chests. As the evaporator is not under vacuum, less heat is
				required to keep solution hot, resulting in a saving of fuel. Higher
				temperatures can be used to improve cleaning efficiency. There are some
				disadvantages to spray cleaning. Spray devices cost extra money because they
				are specifically designed for almost every operation. Spray devices must be
				properly placed and designed to cover the top of the dome in the separator, the
				tangential inlets, the vapor lines, sight glasses, and steam chest tubes. Spray
				cleaning may require additional stainless steel lines to convey the solution at
				the necessary volumes. Larger pumps are also required to pump the necessary
				volume of cleaning solution. Even with these disadvantages, the advantages of
				savings in heat, water, cleaning compound and time outweigh the disadvantages.
				Sometimes there are advantages in using combined systems of cleaning. It may be
				possible to boil out the steam chests and spray the separators. Sometimes it is
				possible to circulate the steam chests and spray clean the separators or other
				portions of the unit. Quite often the combined systems, especially the
				circulation in the spray system, will work best on certain types of
				evaporators.
One of the biggest factors affecting the method of cleaning
				used is the type of evaporator. In a falling film type, circulation cleaning
				can be used to clean the tube chests and spray cleaning can be utilized to
				clean the evaporator chambers. When using a plate-type, circulation cleaning is
				best. In an internal type tube chest, a boil-out system for the tubes and spray
				cleaning of the separator works very well. With an external cheat type, the
				entire unit can be spray cleaned. If it is a compressed ammonia operated
				evaporator, spray cleaning works well. Sanitizing should be done to eliminate
				any microorganisms which may have survived the cleaning regimen. Sanitizing can
				best be accomplished by using chemical sanitizers. Heat may be used if all
				surfaces are heated to 180°F (83°C) or higher. Since there is a
				tremendous investment in stainless steel evaporators, it is necessary to use a
				product which does not corrode stainless steel. Chemical sanitizers can be
				applied through the spray equipment or they can be applied with fogging
				guns.
II. High Pressure Pump and High Pressure
				Lines
The high pressure pump and high pressure line to the dryer
				nozzles may be cleaned as a separate circuit by connecting the line to the
				nozzle back to the drop tank and this tank connecting to the inlet of the high
				pressure pump. The regular product atomizing nozzles should be removed before
				cleaning is to be done.
Another method of cleaning the high pressure pump and lines is
				to include this pump and high pressure lines in the circuit when wet cleaning
				of some types of spray dryers. In either case a solution of 1 to 3 percent
				caustic heated to 160°F (72°C) should be circulated for at least 30
				minutes. A solution of inhibited acid should be pumped through the atomizing
				system as a daily procedure to remove the milkstone from the high pressure pump
				and high pressure line. The solution of inhibited acid should be recirculated a
				minimum of 10 to 15 minutes and followed by a rinse with potable water.
It is also recommended that the high pressure pump head be
				disassembled as a daily procedure immediately following the final rinse and the
				parts be placed on a table or rack for air drying. When the pump is
				disassembled the parts are to be checked to see if they are clean, and to see
				if any maintenance is required to remove pits; seats are also checked at this
				time. Since a high pressure pump is subjected daily to extreme heavy duty, the
				valves and seats are recommended to be ground periodically to maintain uniform
				pressure on the atomizing nozzles. Prior to use, the entire system should be
				sanitized.
III. Wet Cleaning of Dryers
There are several methods of wet cleaning dryers. The first
				method is hand brushing. The operators get into the dryer with buckets of
				cleaning solution and brush all surfaces of the dryer. The unit is then rinsed
				with a hose. Cleaning can also be done with hand operated spray guns. These
				spray guns are pressure pumps which operate at high pressures in low volumes;
				in many cases, box type dryers can be completely cleaned with the addition of a
				seven-foot extension on these pressure guns. By using high pressure spray guns
				and cleaning compounds with a high synthetic detergent content, it is possible
				to remove very difficult soil. The third method of wet cleaning is by spray
				cleaning with various types of stationary or rotating spray devices. They
				usually operate at a high volume of low pressure in the range of 10 to 20 psi.
				Constant spray coverage can be obtained when spray devices are properly
				designed. Usually several spray devices are required because of the many
				chambers, collectors, and down pipes within these units. Less time is required
				to do a complete job with spray cleaning. The systems are installed so that
				cleaning lines are easily connected to the spray devices and an effective
				return system. Spray cleaning time is much shorter than hand cleaning time,
				especially in large units. Spray cleaning eliminates the entry of men into the
				drying units. Silo or vertical type dryers are often 20 to 50 feet high and it
				is difficult and dangerous to clean by hand or by hand operated units. Spray
				cleaning eliminates the flavor contamination when switching to other products.
				If an ungraded product is run through the dryer, it is necessary to thoroughly
				clean before running a product like Grade A nonfat powder. There are
				disadvantages to spray cleaning. The spray devices must be properly placed and
				designed to do the complete cleaning job. They must be removable so as not to
				affect the air currents during operation. However, the advantages of safety
				plus cleaning time and consistently complete cleaning outweigh the
				disadvantages. A typical spray cleaning cycle might operate as follows:
The various spray heads are placed in the dryer and securely
				fastened into place. The rinse water is pumped through the spray device and
				allowed to run down the side walls of the drying units. Cleaning compounds
				which are mild alkalis or chlorinated cleaned-in-place cleaners are prepared at
				0.3 to 1 percent concentration heated to 160 to 180F (71 to 83C), and
				circulated for 45 minutes to 1 hour. The unit is given a final rinse and is
				thoroughly dried. Occasionally acid type cleaners are used to control mineral
				films. Sanitizing with chemical sanitizers is a controversial subject.
				Sanitizing can be done with heat but it may be difficult to heat all surfaces
				to 180°F (83°C). Heating to 180°F (83°C) for 10 minutes does
				not kill spore formers. However, they are killed with many chemical sanitizers.
				Even if heat is used, it is recommended that chemical sanitizers be
				occasionally used. By pumping the sanitizer solution to the high pressure pump
				or by fogging with high pressure, it is possible to completely cover the
				product-contact surface. Actually, the unit must be thoroughly dried before
				operation. Chlorine sanitizers may cause corrosion. Obviously, these compounds
				should be used with care. If chlorine is left on the dryer and heat is applied,
				the chlorine droplets will become hot and concentrate and cause pitting. When
				chlorinated cleaners are used, a dryer surface can be effectively cleaned and
				at least partially sanitized and the solution can be completely rinsed.
				Acid-synthetic detergent type sanitizers have been developed which are
				effective on spore formers. These compounds are germicidal, effective in hard
				water and stable in hot or cold solutions. They have an advantage in that they
				are noncorrosive to dairy metal. It is not necessary to wet clean dryers on a
				daily basis. However, a schedule should be set up so cleaning is done
				periodically. As long as a dryer is operating continuously, it is not necessary
				to clean it from an efficiency standpoint. Some types of dryers require very
				little cleaning, maybe once each month; others require dry cleaning on a more
				frequent basis. It is necessary to clean and sanitize dryers if they are going
				to remain idle any appreciable length of time. Bacteria may grow in dryers
				which remain idle. Dryers must be spray cleaned if they are improperly
				operated, causing burn-on in the drying chamber. Whenever fires develop inside
				the drying unit or when burn-on occurs, it is necessary to thoroughly clean at
				least the drying chambers. Quality is the key to the dry milk industry. There
				should be a program of cleaning and sanitizing of both evaporators and dryers.
				Better quality products are produced in evaporators and dryers when thoroughly
				cleaned and sanitized on a regular basis.
IV. Dry Cleaning
It is very difficult to discuss proper cleaning procedures
				without also discussing proper operating procedures, especially the start up
				and shutdown of the dryer. Assuming the dryer has been properly started and
				operated throughout the run or drying cycle, the first step in a successful
				cleaning operation is shutting the dryer down properly. The type of energy
				supplying heat to the dryer chamber, i.e., steam or gas, alters the proper
				shutdown technique. The correct procedure in shutting down a steam heated dryer
				is as follows:
1. Shut off the main steam valve at the proper time.
2. Maintain proper dryer outlet temperature for drying by
				gradually reducing the output of the high pressure pump until the residual heat
				of the steam coil is dissipated to a point where it does not maintain proper
				temperature or until the product being pumped by the high pressure pump does
				not maintain a satisfactory spray pattern.
3. Keep product removal system and conveying system in
				operation.
4. Keep air intake and exhaust fans on dryer in operation until
				main chamber is sufficiently cooled to provide a comfortable atmosphere for the
				cleanup crew.
On a gas-fired spray dryer, the burner assembly has very little
				or no residual heat capacity. Therefore, the shutdown is more rapid. The
				correct procedure for shutting down a gas-fired dryer is as follows:
1. Shut off gas supply to burner.
2. Immediately shut off high pressure pump.
3. Same procedure as steam heated dryer.
4. Same procedure as steam heated dryer.
After the above procedures have been accomplished, shut down
				the intake fan. Let exhaust fan and vibrators or shakers continue to operate,
				also product removal system. The exhaust fan should be severely dampered so
				that it induces only a small air flow. A small auxiliary fan is sometimes used
				in lieu of the dampered exhaust fan. The use of either fan serves a twofold
				purpose: first, it is helpful to put the drying system under a slight negative
				pressure to reduce the tendency for product to drift out of the system into the
				plant through open doors, etc. Secondly, it is vital to prevent thermal
				currents from creating a reverse air flow through the drying system, which
				tends to deposit product on the heating surfaces and plenum duct. Product
				deposits on steam coils reduce their heating ability, create sediment and
				conceivably bacterial problem areas. If the dryer is gas fired, there is a
				further hazard of fire. It is important, therefore, that the closure or covers
				supplied by the manufacturer be placed on the inlet air duct system
				simultaneously with the shutdown of the fan. After any prime product has been
				removed from the drying system and the sifter operator notified, the system is
				ready for cleaning. The cleanup crew should be supplied each day with a freshly
				laundered set of coveralls, white cap, white face mask, and clean rubbers or
				boot covers (canvas, or single-service plastic). Prior to donning the above
				uniform, the procedure is to remove the spray nozzles and pipes as these are
				normally cleaned with the liquid dryer feed equipment. With clean uniforms,
				proper brushes and preferably vacuum cleaning equipment, they enter the main
				desiccator chamber and start the cleaning process as far upstream as possible
				from the powder removal or pneumatic conveyor system.
1. The first portion cleaned is the collector system. This is
				done by inserting a brush into the cloth tubes and brushing the length of the
				tube. Again, this can be done more satisfactorily by utilizing the special
				vacuum tools designed and available for this service.
2. Remove dustcovers and brush or vacuum out nozzle
				ports.
3. Manually brush or vacuum ceiling and walls of drying
				chamber.
4. Sweep or vacuum clean floor of the dryer, placing product in
				a container.
Note.--Do not remove this product by way of product removal
				system.
5. Inspect dryer for any inadvertent wet spraying or nozzle
				drippings that may have occurred during the drying cycle. Should either of
				these have occurred, the application of a minimum amount of water and effort
				will be required to remove the clinging material. Any moisture introduced must
				be removed before operation because of its effect upon smooth product flow and
				because it would establish a more favorable environment for bacterial growth if
				it were allowed to remain.
6. Check collector for loose or torn bags and any other
				mechanical checks necessary before leaving the dryer.
7. Close dryer securely and check switches to make sure they
				are in the proper starting positions. At frequent intervals, not over a
				two-week period, the operator should clean and inspect the heated air intakes
				of the dryer, assuming that the dryer is properly operated during this time.
				However, should a malfunction occur where the dryer operator does not follow
				the procedures outlined for proper shutdown, it may require inspection and
				cleaning at closer intervals. Frequent inspection will eliminate a source of
				sediment contamination.
8. On startup after dry cleaning of the cloth collector dryer,
				the first two bags of product shall be discarded. This will allow for the
				removal of any product remaining in the tubes and system after shutdown.
V. Auxiliary Dry Product Equipment
Part A. Sifters
In general, there are two types of dry product sifters in
				use by the dry milk manufacturing industry. These are the shaker type and the
				rotary or gyrating type. Both are designed to operate at various capacities
				either manually bagging or packaging from their outlet or designed for
				automatic packaging equipment.
For the general guidance of sifter manufacturers and the dry
				milk industry, the following screen size openings may be considered as
				recommended openings to result in satisfactory screening of the listed dry
				products:
TABLE 3
Sieve
							 designation
Maximum sieve
							 opening
Product
(from ASTM
							 223.1)
(approx.)
mm.
inch
Nonfat dry milk .......
#25
0.707
0.027
Dry whole and dry buttermilk .......
#16
1.19
0.045
It is recognized that larger screen size openings may be
				necessary for sifting certain special dry products (such as "instant" products)
				and for classification of products into different particle sizes.
Openings referred to above are based on general experience as
				to what constitutes satisfactory screening to remove product lumps or potential
				product contamination, and also on ability of most currently used sifters to
				successfully sift dry products through such size openings without excessive
				loss of fine product into the "reject material" outlet. (Other factors also
				affect loss, such as: percent of "open area" in screen used; uneven flow rates
				to the sifter; ratio of screening surface to dryer capacity; amount and kind of
				mechanical energy applied to the screening surface; sifter design and
				construction; and nature of dry product being sifted.)
Screen opening dimensions may be obtained by any desired
				combination of wire thickness and number of wires per inch. For instance, if
				the screening surface is made of stainless steel woven wire, the 0.027 inch
				opening might be obtained by using 24 X 24 mesh market grade screen cloth made
				of wire 0.014 inch thick (about 45 percent open area) or by using 30 X 30
				bolting cloth screen made of wire 0.0065 inch (about 65 percent open area) or
				by many other mesh-wire thickness combinations. These combinations allow a wide
				choice to obtain desired balance between screen strength and percent open area.
				If materials other than stainless steel are used to construct the screening
				surface, similar combinations may be employed to achieve desired opening
				size.
Recommendations for Cleaning Dry Product
				Sifters
1. Dry cleaning program.
-The procedures set forth
				below should be followed.
a. Completely dismantle and thoroughly vacuum or dry brush
				clean all product-contact surfaces of the dry milk sifter. Reassemble as soon
				as finished and make every effort to keep all parts dry.
b. Check sifter screen(s) for broken or displaced wires
				(threads) and for other openings around the frame of the screen, which might
				permit the passage of unsifted product. Other parts of the sifter, including
				ball trays and balls, if used, should also be inspected for condition. Any
				necessary repair or replacement should be made as soon as possible.
c. Flexible rubber or cloth connectors at the inlet and outlets
				of the sifter should be thoroughly cleaned daily following the procedures as
				recommended for the sifter. At this time, connectors should be closely examined
				for holes, cracks, or other damage. (To facilitate removal for cleaning, use of
				easily removable fastening devices are recommended.)
d. Thoroughly vacuum or dry-brush clean all external parts of
				the sifter, including the sifter frame and drive mechanism.
2. Wet cleaning program.
-The procedures set forth
				below should be followed.
a. Completely dismantle as in 1. above, remove all loose dry
				product; then rinse all parts with clear water; and follow by a thorough hand
				brushing of all parts using a general purpose dairy cleaner. Rinse thoroughly
				to remove all evidence of cleaning solution or soil. It is recommended that hot
				water (170°F (77°C) or above) be used for rinsing in order to sanitize
				the equipment and to aid the subsequent drying.
b. Allow all parts to air dry completely prior to
				reassembly.
c. The wet wash should be done as frequently as necessary and
				should be done after each use if the sifter is not being used on a daily
				basis.
d. After cleaning, drying, and reassembly, the product outlet
				should be protected against recontamination.
3. General recommendations.
-a. Vacuum cleaning is
				preferred to brush cleaning or cleaning with air under pressure as it decreases
				the dust drift problem to other areas of the plant.
b. Brushes or vacuum cleaner fittings used for cleaning
				product-contact surfaces should not be used for cleaning nonproduct-contact
				surfaces or for other uses which might result in contamination. Such brushes
				and special fitting should be stored in an enclosed cabinet when not in use.
				For protection and housekeeping considerations, such cabinets preferably should
				be of non-wood construction and should have open mesh metal shelving.
Note.-For additional details see
3-A Sanitary Standards
				for Sifters for Dry Milk and Dry Milk Products,
Serial 26-01.
Part B. Storage Bins
The use of portable bins is becoming increasingly popular with
				the dry milk industry. These tote, or portable, storage bins when used shall
				comply with the construction requirements of Item 11p and the cleaning and
				sanitizing requirements of Item 12p (sections
				3.19 and
				3.20).
If interior bracing and ladders are used in plant storage bins
				they shall be constructed of smooth rounded metal, and be installed
				sufficiently far from the walls to prevent harborages. Product entrance and
				discharge openings connected to the attending conveying equipment shall be
				dust-tight and shall be easily accessible for cleaning. Vents to the exterior
				shall be equipped with readily removable air filters of adequate capacity or
				readily removable covers. If air is to be introduced into the product zone,
				only filtered air shall be used, and it shall comply with the applicable
				standards of Appendix 7. Auxiliary agitators or any other interior devices, if
				used, shall be designed to be smooth, crevice-free, and readily cleanable. The
				exterior surface of the bin should be smooth, hard finished, and readily
				cleanable. Hinges on covers, if used, shall be the take-apart type. Covers or
				doors shall be provided to enclose the product zone when product is not being
				dumped. These shall be so constructed that dirt or dust on top will not slide
				or fall into the bin when the cover is open. Access openings shall be provided
				on all in-plant bins. Such openings should not be less than 18 inches in their
				smallest dimension. Covers shall be constructed without raised internal
				reinforcements and should be hinged and equipped with a quick opening device.
				The gaskets for such openings shall be made of material which is nontoxic,
				nonabsorbent, smooth, and unaffected by the product. Storage bins in continuous
				use either in the plant or in transporting dry products from one plant to
				another should be cleaned according to manufacturer's recommendations when
				necessary. They may be cleaned by either approved dry cleaning methods or wet
				cleaned.
Part C. Packaging and Packages
Packaging equipment for dry milk, dry milk products and dry
				whey will vary greatly as to their design depending upon whether the packages
				being filled are drums, bins, or bags. Whatever equipment is used should be
				designed so as to protect the product from contamination from outside sources
				and from air during the packaging operation. All connections of conveying
				equipment to packaging devices should have dust-tight connections. All
				conveyors, ducts, belts, and screws used in connection with packaging equipment
				should be provided with a dust collector system capable of eliminating any
				visible dust, All product hoppers, when used, should be provided with covers to
				properly protect the product from contamination. Hand filling should not be
				permitted except for periods of adjustment of automatic weighing
				devices.