Operating and Maintaining the Degreaser

An effective operator training program and a routine maintenance program are important to safe and efficient vapor degreasing. Proper education and maintenance practices can greatly extend working life with assurance of smooth production. Following the checklist provided below should aid in beginning an efficient degreasing operation.

Startup

• Be sure the degreaser operator is adequately trained and equipped with the appropriate safety equipment and clothing. For emergency situations, such as power failures, condenser coolant stoppages, and ventilation interruptions, have organic vapor respirators or air-line masks available for immediate use. Also, be sure the operator knows how to use personal protective equipment, understands first aid procedures, and is familiar with the hazards of the operation.

• Check proper operation of the vent system and leave it on.

• Turn on the condensing water. Observe the rate of flow and check for leaks. Leave the condenser water on. If the cooling water supply of the degreaser is equipped with an outlet water temperature control or a flow control safety shutoff, check these for proper operation. It is easier to do this with the degreaser heat on.

• Adjust the high temperature cutoff control for the boiling sump and the vapor safety thermostat control to the temperatures recommended for the particular degreasing solvent to be used. The high temperature cutoff control setting should be about the boiling point of a 25% mineral oil-in-solvent mixture (Table 6). The vapor safety control setting should be at least 6 °C (10 °F) lower than the boiling point of the solvent-water azeotrope (Table 6). Do not turn on a gas or electrically heated degreaser unless the heaters are covered by solvent. If the machine is steam heated, turn steam on and check for leaks and for proper settings and functioning of pressure gages, reducer valves, and traps. Turn off and cool before adding solvent.

• Add some solvent to the degreaser and check the operation of the liquid level control, if the machine is so equipped. Finish filling the degreaser by adding enough solvent to cover the heating elements by 75 to 150 mm (3 to 6 in.), or up to the bottom of the work rest if the machine is so equipped.

• Turn on the heat and, as the temperature rises, ensure proper operation of the various heat controls that may be in use.

• As condensation begins, observe the flow of condensate from the coil and jacket, through the trough and water separator, and the returning stream to the degreaser. Interrupt the flow of condensing water and observe for proper operation of the vapor safety control.

• Adjust the heat input and/or the condenser water flow so that the vapor zone rises only halfway up the condenser coils.

• Check the functioning of the degreaser auxiliary equipment, such as the sprayer, conveyor, still feed pump, and the still. Look at the solvent levels in each degreaser compartment and adjust to operating levels.

• Begin supplying work to the unit.

• Check the first parts through for satisfactory cleanness and for any signs of machine malfunction.

• Adjust the condenser discharge water temperature to about 8 to 11 °C (15 to 20 °F) above the dew point of the surrounding atmosphere, that is, about 32 to 46 °C (90 to 115 °F), for all the chlorinated solvents except methylene chloride. For methylene chloride or fluorocarbon 113, do not allow the discharge water temperature to go above about 29 °C (85 °F). Degreasers for these two solvents often employ refrigeration for vapor control.

Operation

• Check the upper level of the vapor zone. The vapor zone should not rise above the midpoint of the condenser.

• While the degreaser is operating, maintain a routine surveillance to see that the work is being cleaned properly and the various systems continue to function satisfactorily.

• Any time work is not being processed in the degreaser, the cover should be closed. Degreaser manufacturers supply covers for their degreasers. The cover should be relatively tight fitting but should allow the degreaser to breathe.

• Give some detailed attention to the arrangement of the work parts being cleaned. It may be necessary to reposition some of the parts to get proper cleaning and free draining. Cup-shape parts, for example, should be positioned as shown in Fig. 5.

• Observe the spraying operation. Be sure that the vapor-air interface is not being unnecessarily disturbed.

• Check to see that the amount of work being fed at one time is not so great that it causes vapor shock. The vapor level should not recede excessively. Be sure the rate of introduction of the work does not exceed 3.4 vertical m/min (11 vertical ft/min). A faster rate of entry increases vapor losses.

• Observe the vapor level as the work is being removed. The vapor level should not rise above the cooling coil or jacket. If the vapor level is rising too much, check the cross section of the work. This generally should not exceed 50% of the open area of the degreaser if the parts are traveling at a rate of about 3.4 vertical m/min (11 vertical ft/min). If the parts are larger than this, the rate of vertical movement should be reduced accordingly.

• Check to see that the parts are within the vapor zone long enough for condensation to cease before the parts are brought up into the freeboard area. Also, see that the parts are remaining in the freeboard area long enough for the solvent to evaporate completely.

• After the degreasing operation has continued for several hours, observe the water separator to see that any water entering the degreaser is being withdrawn efficiently by the separator. A cloudy ghost vapor in the vapor zone of the degreaser is a warning sign that water is not being properly removed. If water is allowed to accumulate in the degreaser, the boiling point of the solvent may drop due to the formation of the solvent-water azeotrope. The direct results are poor cleaning, greater solvent losses, water spotting, and more odor complaints.

• As the solvent level in the degreaser drops due to evaporation and leakage losses, fresh makeup solvent should be added to maintain a solvent level of about 150 mm (6 in.) above the heating elements. Particular care should be exercised that the solvent level in the boil chamber never drops lower than 25 mm (1 in.) above the heating elements. Makeup solvent should be added to the degreaser before startup, that is, while cold.

• On a periodic basis, perhaps every few days during initial operation, the acid acceptance inhibitor level of the solvent should be checked. The acid acceptance value should stabilize at no less than 40% of the original value. Should the inhibitor level show an unexpected drop, the trouble should be traced and eliminated. The problem might be excessive water in the degreaser, introduction of acid soils, soil buildup on, or exposure of, the heating surfaces, or accumulation of excessive amounts of metal fines or soluble soils.

• Based on the total soil load and type, and taking into account work scheduling, regular periodic degreaser cleanouts should be performed. The frequency of cleanout can sometimes be extended by removal of particulate soils from the degreasing solvent by use of an external filtration system. Nevertheless, at intervals varying from a few days to a few months, it is necessary to shut down the degreaser and clean it out. The oily soil level of the degreaser should not be allowed to go higher than 25 vol%.

Shutdown

• A scheduled shutdown should be planned so that work is not inconveniently backlogged. The degreaser, of course, should be shut down only after the last parts in process have cleared the machine.

• Turn off the heat supply to the degreaser. Wait for solvent condensation on the cooling surfaces to cease and the vapor zone to collapse.

• Turn off the cooling water and any unneeded pump.

• If the degreaser is being used to partially distill the solvent, the solvent condensate from the water separator should be directed to storage rather than returned to the degreaser. Heating should be stopped when the boiling chamber solvent level approaches 25 mm (1 in.).

• Additional information is available in the Manual on Vapor Degreasing published by ASTM.

Maintenance

• Routine cleanout operations can and should be conducted from outside the equipment. Workers entering vapor degreasing equipment or associated pits should follow the confined-space-entry procedures outlined in the next section.

• For a routine cleanout, allow the machine to cool completely and then drain the soil-laden solvent. Ventilate the interior to outside the plant to remove solvent vapors and dry any remaining solvent.

• Remove any auxiliary equipment from the degreaser that may interfere with the cleaning or might be damaged in the process.

• Clean out the trough, water separator, spray pump sump, and associated piping.

• Scrape and brush out the metal fines and other particulate soils. Pay particular attention to corners and recesses where residues tend to collect.

• Clean off excess rust and corrosion, paying particular attention to the heating elements. Consider replacing mild steel piping with stainless steel if heavy rust is noted.

• Inspect and repair any defective auxiliary equipment. Lubricate pumps and conveyor drives.

• Install a new cleanout door gasket, using as a sealant either plain or litharge-thickened glycerol or ethylene glycol. Reinstall all auxiliary equipment items removed during cleanout.

• If the degreaser has experienced an acid condition, the cleaning procedure should be augmented by charging the compartment with water containing 30 g/L (4 oz/gal) sodium carbonate (soda ash), to a depth of about 300 mm (12 in.). The solution should be boiled for about 15 min, and the compartment should be rinsed and thoroughly dried. The degreasing unit is then ready for recharging with clean solvent. If acid conditions persist, contact the solvent supplier or degreaser manufacturer for detailed procedures to cope with the condition and prevent its recurrence.

Table 6 Applications of vapor degreasing by vapor-spray-vapor systems

Note: Degreasing by vapor only is applicable to the cleaning of flat parts with light soils and little contamination. Anything that can be cleaned by vapor degreasing usually can be cleaned better by liquid-vapor systems

Table 6 Applications of vapor degreasing by vapor-spray-vapor systems

Note: Degreasing by vapor only is applicable to the cleaning of flat parts with light soils and little contamination. Anything that can be cleaned by vapor degreasing usually can be cleaned better by liquid-vapor systems

Parts

Metal

Production rate

Soil removed

Subsequent, operation

Notes on processing

kg/h

lb/h

Spark plugs

Steel

270

600

Machining oil

Special fixture and conveyor

Kitchen utensils

Aluminum

450

1000

Buffing compound

Inspection

Special fixture and conveyor

Valves (automotive)

Steel

540

1200

Machining oil

Nitriding

Automatic conveyor

Valves (aircraft)

Steel

590

1300

Machining oil

Aluminum coating

Automatic conveyor

Parts

Metal

Production rate

Soil removed

Subsequent, operation

Notes on processing

kg/h

lb/h

Small-bore tubing

Aluminum

680

1500

Wax extrusion lubricant

Annealing

Hoist-operated unit

Builders' hardware

Brass

2270

5000

Buffing compound; rouge

Lacquer spray

Racked work on continuous monorail

Acoustic ceiling tile

Steel

2720

6000

Light oil (stamping lubricant)

Painting

Monorail conveyor

Gas meters

Terneplate

4540

10,000

Light oil

Painting

Monorail conveyor

Continuous strip, 0.25-4.1 mm (0.010-0.160 in.)

Cold rolled and stainless steels; titanium

13,600

30,000

Oil emulsion (steels); palm oil (titanium)

Annealing

Continuous processing at up to 0.6 m/s (120 ft/min)

Automatic transmission components

Steel

18,100

40,000

Machining oil; light chips; shop dirt

Assembly

Double monorail conveyor

Degreasing by warm liquid-vapor system

Aircraft castings

Magnesium

230

500

Polyester resin (from impregnating)

Curing

Solvent: methylene chloride

Speedometer shafts and gears

Steel; brass

340

750

Machining oil; chips

Inspection; assembly

Rotating baskets (drainage and chip-removal)

Screws

Steel; brass

680

1500

Machining oil; chips

Painting; finishing

Flat and rotating baskets; conveyorized

Automotive die castings

Zinc-base

910

2000

Light oils, grease; tapping lubricants; chips

Assembly

Flat and rotating baskets; conveyorized

Electron-tube components

Steel

910

2000

Light oils

Dry hydrogen fire

Conveyorized unit

Tractor gears and shafts

Steel

910

2000

Machining oil; chips; quenching oil

Nitriding

Elevator-type conveyor handling of work in heat treating trays

Flexible hose connectors

Steel; brass

1250

2750

Machining oil; chips

Assembly

Conveyorized unit

Parts

Metal

Production rate

Soil removed

Subsequent, operation

Notes on processing

kg/h

lb/h

Wire, 0.8-3.2 mm (0.0300.125 in.) diam

Aluminum

1810

4000

Drawing lubricants; light oil

Shipment

Processed at 3 m/s (500 ft/min)

Hand power-tool components

Cast iron; aluminum

2270

5000

Machining oil; chips; polishing; buffing compounds

Painting or plating;

assembly

Rotating and flat baskets on conveyorized machine

in.) diam; 762-1270 mm (30-50 in.) long

Aluminum

5670

12,500

Drawing lubricants

Annealing

Hoist-operated 1134 kg (2500 lb) loads

Degreasing by boiling liquid-warm liquid-vapor system

Transistors

Gold and tin plated

25

50

Silicone oil; light oil

Painting; branding

Manual; mesh basket

Electron-tube components

Stainless steel

90

200

Light oil

Dry hydrogen oil

Manual; mesh basket

Calculating-machine components

Steel

450

1000

Stamping oil

Painting

Manual operation

Valves (automotive, aircraft)

Steel

450

1000

Machining oil

Welding

Manual operation

Knife blades

Steel

820

1800

Oil; emery

Buffing

Manual operation

Carbide-tip tool holders

Steel

910

2000

Lubricant; chips

Recess milling

Conveyorized unit

Tubing, 60 cm (2 ft) long

Aluminum

910

2000

Drawing lubricants; quench oil

Satin finishing

Conveyorized; tube handled vertically

Calculating-machine components

Steel

1360

3000

Stamping oil

Plating

Conveyorized unit

Hand-tool housings, die-cast

Zinc-base

1360

3000

Tapping oil; chips

Assembly

Automatic conveyor; racks

Screw machine products

Steel; brass

1360

3000

Cutting lubricants; chips

Assembly

Flat and rotating basket; conveyor

Parts

Metal

Production rate

Soil removed

Subsequent, operation

Notes on processing

kg/h

lb/h

Cable fittings

Steel

1810

4000

Light oils

Inspection

Conveyorized

Stampings (miscellaneous)

Steel

2270

5000

Light oil; chips

Furnace brazing

Small stampings nested in baskets

Wafers

Silicon

Sealing wax; paraffin

Acid etch; diffusing

Manual, in beakers;

fixtured

Fig. 5 Positioning of cup-shape parts to drain solvent. (a) Incorrect positioning. (b) Correct positioning
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