Contaminants and aqueous parts washing

Contaminants and Aqueous Parts Washing

Last Updated Nov 30, 2020Thierry Moutier

CONTAMINANTS AND HOW TO ADDRESS THEM IN PARTS CLEANING

It is important to know what types of soils are present on the parts as well as the composition of the component to be cleaned. This will determine the cleaning process needed to remove the soils. In addition, maintaining the cleaning process will require systems to remove the soils from the washer.

METALWORKING FLUIDS

Metalworking fluids encompass a wide range of products used to lubricate and cool tools during the manufacturing process. These fluids leave a thin film over the parts that must be removed before subsequent manufacturing processes or as a final cleaning step.

These oils and coolants are easily removed with an automatic parts washer using a mild alkaline cleaner, a moderate wash pressure of 60 psi, and a temperature ranging from 120–140°F. After washing, the part is rinsed to remove excess washing solution. In the case of iron/steel parts, the rinse includes a rust inhibitor. The final step in the process is a blow-off to remove the solution from the part surface. Any remaining droplets flash dry at the end of the process as long as the parts are hot.

In order to maintain the washing effectiveness of the industrial parts washer, oil skimmers or coalescers may be used to remove free oils. In the case of emulsified oils, an ultrafiltration system is more effective.

GREASE

Grease such as that found on bearings must be removed using a combination of a moderately alkaline wash chemical, high heat, high pressure, and high flow. The high temperature helps soften the grease and the powerful spraying action from the pump helps blast the grease off of the bearings. The alkaline detergent sequesters the grease so that it does not redeposit on the cleaned parts.

Large amounts of grease in the wash solution must be removed to reduce the possibility of foaming. A sludge conveyor and grease skimmer help extend the wash solution life, reduce chemical usage, and limit downtime required for cleaning out the tank.

CHIPS

Chips are generated during the manufacturing process. The bulk of the chips are removed in the machining centers, yet some adhere to the parts and must be removed before subsequent manufacturing processes or as a final cleaning step.

Typically, wash temperatures of 120°F and a moderate pump pressure of 30–60 psi are used to chase chips off machined components. The pump flow must be high enough to flush away contaminants. Custom spray nozzle configurations may be required to address specific areas on parts with complex geometry.

Proper filtration removes chips from the solution that has been sprayed on the parts. This is especially important in automotive parts washers where gravimetric and particulate size limitations need to be met.

CARBON

Cleaning carbonaceous deposits and heat scale from engine heads and exhaust manifolds represents a cleaning challenge. These cooked-on deposits adhere to the part surface and must be removed as part of the maintenance and overhaul of engine components.

Parts can be cleaned in a dip tank, which will help soften soils, yet this is a time-consuming process. The preferred method of cleaning is in a spray washer. Parts need to be washed with a highly alkaline solution at a temperature of 175–185°F and a pressure of at least 200 psi. This combination effectively blasts the carbon deposits off of the parts. At the end of the wash cycle, the parts will be hot, which will help in flash drying.

Over time, carbon accumulates in the wash tank and renders the cleaning chemical ineffective. At that point, the solution needs to be replaced.

CARBON DUST

Carbon dust is found on the field coils and armatures of locomotive traction motors. It must be removed from the parts prior to overhaul. Poor cleaning and rinsing of the coils and armatures leads to false diagnostic test readings.

The standard process uses a low concentration of the alkaline chemical, sprayed at a pressure low enough to not cause damage to the insulation, yet high enough to lift the carbon dust off of the windings. The wash stage is followed by a recirculating rinse stage with water to remove detergent residue, and a final rinse stage with water and rust-inhibitor to provide rust-prevention on the parts.

To prolong solution life, a bed filter can be used to remove carbon dust as well as other contaminants from the solution in the wash tank. This system prolongs the cleaning effectiveness of the wash tank.

METAL SWARF

Swarf is generated in grinding and machining operations. Machining of cast iron blocks results in excessive swarf that must be removed from the block prior to final assembly.

Swarf is easily removed using a general-purpose aqueous cleaner and moderate wash pressures. Some of the removed swarf sinks to the bottom of the wash tank while the finer particles remain in suspension in the wash solution and must be removed by means of a magnetic filter. If it is not removed, swarf will quickly clog up the wash tank filters. Adequate filtration must be used to avoid depositing swarf on parts that have been cleaned.

DRAWING LUBRICANTS

Drawing lubricants accumulate on the surface of rolling dies and tooling. Under tremendous pressure and heat, the lubricants bond onto the surface of the dies and become very hard to remove.

A combination of heavy-duty alkaline chemical and heat softens the lubricants. The high pressure and high flow from the pump blasts the soils from the surface of the dies and tooling. For effective cleaning, the spray nozzles must be placed in proximity to the surface to be cleaned so as to ensure the maximum impact of the cleaning jets.

To prolong solution life, a sludge conveyor removes the sludge that settles at the bottom of the wash tank.

SAND AND HARDENED CLAY

Sand and hardened clay found on earth-moving equipment drive components must be removed as part of an overhaul process. Over time, these deposits form a hard shell that is particularly hard to remove.

A powerful pump and an extended exposure time softens and removes sandy clay. Afterward, the contaminants accumulate in the wash tank and must be removed as these abrasives cause excess wear on pumps and spray nozzles.

A sludge conveyor is used to remove deposits that have settled at the bottom of the wash tank.

CONCLUSION

Whatever the part size and soils to be removed, PROCECO's team of engineers will work with you to provide an industrial parts washer to meet any process requirements.

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Thierry Moutier (Author)

Thierry Moutier has been employed at PROCECO since 1991 and is currently the Sales Agency Business Development Manager. Part of his responsibilities involves training agents and employees on PROCECO’s cleaning technologies. In his spare time, he enjoys touring and mountain biking with his wife and children.

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