Parts washer
A parts washer is a piece of equipment used to remove contaminants or debris, such as dirt
Dirt is unclean matter, especially when in contact with a person's clothes, skin or possessions when they are said to become dirty. Common types of dirt include:* dust — a general powder of organic or mineral matter...

, grime, carbon
Carbon is the chemical element with symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds...

, oil
An oil is any substance that is liquid at ambient temperatures and does not mix with water but may mix with other oils and organic solvents. This general definition includes vegetable oils, volatile essential oils, petrochemical oils, and synthetic oils....

, grease
Petroleum or crude oil is a naturally occurring, flammable liquid consisting of a complex mixture of hydrocarbons of various molecular weights and other liquid organic compounds, that are found in geologic formations beneath the Earth's surface. Petroleum is recovered mostly through oil drilling...

, metal chips
Swarf, also known as turnings, chips, or filings, are shavings and chippings of metal — the debris or waste resulting from metalworking operations including milling and grinding. It can usually be recycled, and this is the preferred method of disposal due to the environmental concerns regarding...

, cutting fluid
Cutting fluid
Cutting fluid is a type of coolant and lubricant designed specifically for metalworking and machining processes. There are various kinds of cutting fluids, which include oils, oil-water emulsions, pastes, gels, aerosols , and air or other gases. They may be made from petroleum distillates, animal...

s, mold release agents, ink
Ink is a liquid or paste that contains pigments and/or dyes and is used to color a surface to produce an image, text, or design. Ink is used for drawing and/or writing with a pen, brush, or quill...

, paint
Paint is any liquid, liquefiable, or mastic composition which after application to a substrate in a thin layer is converted to an opaque solid film. One may also consider the digital mimicry thereof...

, and corrosion
Corrosion is the disintegration of an engineered material into its constituent atoms due to chemical reactions with its surroundings. In the most common use of the word, this means electrochemical oxidation of metals in reaction with an oxidant such as oxygen...

 from workpieces. Parts washers are one of the last steps in the parts manufacturing process; they are designed to clean, degrease and dry bulk loads of small or large parts in preparation for surface treatment, packaging and distribution. Newly machined, molded and fabricated products are coated in oils, chemicals, burrs, abrasive dust, paint and other residue left over from the fabrication process of metal, plastic and rubber components, and finishing coatings are not effective if they are applied on a dirty surface. Parts cleaners may be as simple as a stand-alone basket immersion washer, or they may be as complex as a five-step deburring, aqueous tumbling, rinsing, drying and paint coating machine. Parts washers are essential in maintenance, repair and remanufacturing operations as well, from cleaning fasteners, nuts, bolts and screws to engine parts and automotive assemblies.

A parts washer is distinctly different from a pressure washer
Pressure washer
A pressure washer is a high pressure mechanical sprayer that can be used to remove loose paint, mold, grime, dust, mud, and dirt from surfaces and objects such as buildings, vehicles, and concrete road surfaces. The volume of a pressure washer is expressed in Gallons Per Minute, which is designed...

 in that parts washers typically clean parts automatically in an enclosed cabinet, while pressure washers typically have a single spray jet mounted at the end of a manually-operated wand. Modern industrial technology makes it possible to combine many parts of the finishing process into one. As an integrated part of the manufacturing process, automatic parts washers are able to load, wash, rinse, dry and unload parts based on a preset computer-controlled program and the help of a conveyor belt
Conveyor belt
A conveyor belt consists of two or more pulleys, with a continuous loop of material - the conveyor belt - that rotates about them. One or both of the pulleys are powered, moving the belt and the material on the belt forward. The powered pulley is called the drive pulley while the unpowered pulley...

 to save time, money and man-power and ensure a quality product; innovations are being made to ensure parts washers are water and energy saving.

Traditionally, chemical solvents have been used to strip parts of grease and dirt during the cleaning process, but recent environmental concerns and regulations have encouraged the innovation of natural, non-chemically based solvents. Ultrasonic cleaning
Ultrasonic cleaning
thumb|300px|Ultrasonic cleaner showing the removable basket in place, and a closeup of the light and timerAn ultrasonic cleaner is a cleaning device that uses ultrasound and an appropriate cleaning solvent to clean delicate items...

 is the latest technology in environmentally safe precision surface cleaning.


Parts washers were originally developed for use in automotive transmission and engine
An engine or motor is a machine designed to convert energy into useful mechanical motion. Heat engines, including internal combustion engines and external combustion engines burn a fuel to create heat which is then used to create motion...

 repair shops as a way to improve the function of simple soak tanks. Soak tanks are vats filled with a mixture of water and detergent
A detergent is a surfactant or a mixture of surfactants with "cleaning properties in dilute solutions." In common usage, "detergent" refers to alkylbenzenesulfonates, a family of compounds that are similar to soap but are less affected by hard water...

, which take hours to "soften" the built-up road grime, fluids, tars and oils enough to be manually rinsed off prior to disassembly and repair.

Since the early 1970s, many methods of parts cleaning have been developed with improved levels of safety and lessened environmental impact. Stoddard solvent, gasoline
Gasoline , or petrol , is a toxic, translucent, petroleum-derived liquid that is primarily used as a fuel in internal combustion engines. It consists mostly of organic compounds obtained by the fractional distillation of petroleum, enhanced with a variety of additives. Some gasolines also contain...

, diesel fuel, and kerosene
Kerosene, sometimes spelled kerosine in scientific and industrial usage, also known as paraffin or paraffin oil in the United Kingdom, Hong Kong, Ireland and South Africa, is a combustible hydrocarbon liquid. The name is derived from Greek keros...

 were commonly used to clean and degrease parts. Then, chlorinated solvents in vapor degreasers became an industry standard. During the 1980s environmental and safety issues led to the banning of chlorinated solvents for parts cleaning. Aqueous-based cleaning systems took on new prominence that led to many improvements, in the systems and the processes. In 1971, Gary Minkin developed an aqueous based parts washer for degreasing automobile parts. The Minkin breakthrough used the force of hydraulic impact pressure to significantly improve the cleaning power of the aqueous parts washer.

Cleaning methods

Beside high mechanical energy, higher cleaning temperatures are one of the most effective methods of improving the cleaning results in a parts washer. In general, a 10 to 15 °F (5 to 8 °C) rise doubles the chemical reaction
Chemical reaction
A chemical reaction is a process that leads to the transformation of one set of chemical substances to another. Chemical reactions can be either spontaneous, requiring no input of energy, or non-spontaneous, typically following the input of some type of energy, such as heat, light or electricity...

 of the detergent. The increased chemical reaction between the greases and oils and the detergent delivers faster cleaning cycles and cleaner parts. Additionally, all greases and oils exhibit a lower viscosity
Viscosity is a measure of the resistance of a fluid which is being deformed by either shear or tensile stress. In everyday terms , viscosity is "thickness" or "internal friction". Thus, water is "thin", having a lower viscosity, while honey is "thick", having a higher viscosity...

 at higher temperatures. Cleaning solution temperatures of 170 °F (76.7 °C) and above softens or melts most oils and greases causing them to flow like water so they are easily removed resulting in faster cleaning, better results and cleaner parts. Many parts washers are not capable of maintaining this operating temperature due to the lack of amply heating systems. Additionally, careful design is required of the pumping system so it can pull in and deliver cleaning solution at temperatures that approach boiling in the parts washer. All centrifugal pump
Centrifugal pump
A centrifugal pump is a rotodynamic pump that uses a rotating impeller to create flow by the addition of energy to a fluid. Centrifugal pumps are commonly used to move liquids through piping...

s require a net positive suction head (NPSHr) in order to be able to pump solution. As the temperature of the solution approaches the NPSHr, the pump stops pumping because the cleaning solution flashes to steam in the pump intake. Careful design of the pump is required to minimize NPSHr and allow pumping of high temperature cleaning solution.

A typical parts washer may be aqueous based or use a solvent.


Ben Palmer invented a solvent style parts washer in 1954. The parts washer was a success from the start, and he decided in the early 1960s not to sell his machine, but to lease it to the customer and service it by removing and replenishing the used solvent. Since the early 1990s there has been a significant shift towards aqueous based systems due to the environmental and safety hazards associated with solvent systems.

A solvent style parts washer is filled with several gallons of solvent that is stored in a settling pan at the bottom of the washer. A small flame-tight electric liquid pump is immersed in the solvent and skims clean solvent from near the top of the settling tank, and pumps it at low pressure through a stiff flexible nozzle onto a metal grating above the liquid where the metal components rest. Dirt and dissolved heavy greases fall into the bottom and settle to the bottom of the tank.

Originally, mixtures of oil distillates such as gasoline, diesel fuel, lacquer thinner
Lacquer thinner
Lacquer Thinner is usually a mixture of solvents able to dissolve a number of different resins or plastics used in modern Lacquer. Traditional Lacquerware is not based on solvent-dissolved resins at all.Shellac is a lacquer with an alcohol as solvent...

 or kerosene were used in solvent based manually-operated parts washers, but these are highly volatile and can ignite easily, potentially leading to an explosion and severe burns to the workers. For this reason, the solvent based "tub" washer typically has a large cover that is propped open by a lead
Lead is a main-group element in the carbon group with the symbol Pb and atomic number 82. Lead is a soft, malleable poor metal. It is also counted as one of the heavy metals. Metallic lead has a bluish-white color after being freshly cut, but it soon tarnishes to a dull grayish color when exposed...

 fusible link
Fusible link
Fusible links include mechanical and electrical devices.A mechanical fusible link is a device consisting of two strips of metal soldered together with a fusible alloy that is designed to melt at a specific temperature, thus allowing the two pieces to separate...

. In the event of a fire, the lead will melt and the cover will slam shut to snuff out the fire before it can cause further damage to the building.


An aqueous based parts washer is much like a large dish washer. It uses water and detergent combined with heat and mechanical energy
Mechanical energy
In physics, mechanical energy is the sum of potential energy and kinetic energy present in the components of a mechanical system. It is the energy associated with the motion and position of an object. The law of conservation of energy states that in an isolated system that is only subject to...

 to provide the cleaning action. There are two main process styles of aqueous parts washers, the jet spray process and the power wash process. In a cabinet parts washer, the parts are placed on a turntable and the door is closed. During the cleaning cycle hot solution is flooded or blasted on the parts as the turntable rotates. Many systems have a wash, rinse and dry cycle. When the cycle is complete the door is opened and the parts removed.

There are four primary factors that affect the cleaning results in an aqueous parts washer. These factors are mechanical energy, temperature, detergent and time. Adjusting any one of these factors in a cleaning cycle changes the cleaning results. A parts washer with large amounts of mechanical energy and a high temperature delivers shorter cleaning cycles and uses less cleaning detergent. Mechanical energy is provided by the pump drive system. Most aqueous parts washers use an electric motor to drive a centrifugal pump. The mechanical energy delivered to the wash load is what defines the mechanical energy for cleaning and not the horsepower of the pump. Efficient use of the pump motor energy through a well designed centrifugal pump and attention to details of piping design and nozzle types are critical to put the most mechanical energy into the cleaning process. Additionally, one must consider the work volume of the parts washer. In order to achieve similar results, from one size machine to another, the power density
Power density
Power density is the amount of power per unit volume....

 must be the same for a given work volume, This factor requires that substantially higher horsepower pumping systems be used as the work volume increases exponentially on larger diameter machines.

Aqueous based parts washers use alkaline detergents mixed with water to clean parts. This solution is safer than solvent based systems because the risk of the cleaning solution catching fire is eliminated. The detergent for an aqueous parts washer may be in the form of a powder or a liquid. Each form has its advantages and the particular parts cleaning application will determine the best form. In general, powder detergents are the more aggressive and typically used in maintenance and rebuilding operations while liquids are more commonly found in lighter cleaning applications that were once commonly the domain of vapor degreasers.

Jet spray vs. power wash processes

A jet spray washer cleans by flooding the parts with hot chemical solution depending on the heat and high chemical concentration to clean the parts. In the power wash process the parts are blasted with hot chemical solution utilizing the hydraulic impact force of the cleaning solution as the primary cleaning mechanism. A parts washer utilizing the power washer process operates at a very low concentration of cleaning detergent. The lower concentration causes the cleaning solution to last longer before it becomes supersaturated and requires disposal. Additionally, a low concentration of cleaning chemicals allows for easier rinsing of the detergent from the parts thereby minimizing rinse cycle requirements thus saving water and cycle time. A final factor used in the power wash process is an oscillating manifold system that is non-synchronous to the rotation of the turntable. This system assures that the blasted solution reaches all areas of the parts load that are otherwise blinded by the stationary manifolds used in the jet spray process. All things considered the power wash process is superior to the jet spray process for faster more through parts cleaning cycles while minimizes detergent use and waste generation. The power wash process is generally effective for difficult soil removal applications such as burnt hydrocarbons, paint, scale
-Length:* Architect's scale, a ruler-like device which facilitates the production of technical drawings* Engineer's scale, a ruler-like device similar to the Architect's scale, they are helpful when drawing rooms...

, varnish
Varnish is a transparent, hard, protective finish or film primarily used in wood finishing but also for other materials. Varnish is traditionally a combination of a drying oil, a resin, and a thinner or solvent. Varnish finishes are usually glossy but may be designed to produce satin or semi-gloss...

, carbon, mastic
Pistacia lentiscus is a dioecious evergreen shrub or small tree of the Pistacio genus growing up to tall which is cultivated for its aromatic resin, mainly on the Greek island of Chios.- Description :...

, or rubber
Natural rubber, also called India rubber or caoutchouc, is an elastomer that was originally derived from latex, a milky colloid produced by some plants. The plants would be ‘tapped’, that is, an incision made into the bark of the tree and the sticky, milk colored latex sap collected and refined...

. Additional power wash types of applications generally include cleaning diesel engines, aerospace components, aluminum automobile engine parts and rolling mill equipment.

There are some considerations when using the "power wash" process in that comparatively high horsepower, thus high-current motors requiring an adequate power source, are utilized with correspondingly high washing pressures that require the parts to be adequately secured to the turntable. The "jet spray" process is found to be adequate for many cleaning applications that do not involve removal of difficult soils but in general the power wash process is the superior cleaning process.

Power density

A parts washer can be characterized by its power density. The power density is calculated by dividing the total horsepower of all the pump systems providing the wash function by the total work volume for that washing function. Typical units are horsepower per cubic foot. The results of this calculation offer a beginning point in comparing various parts washing systems. The power density number is also useful when it is desired to achieve the same cleaning standard and throughput in a different work volume. Note that the power density calculation does not take into account the pump system efficiency and assumes that all of the energy delivered to the pump is delivered to the wash load. A more accurate power density would consider the pump system efficiency as efficiencies varying greatly even from an identical pump as the efficiency is highly dependent on the pump operating point, the piping design and the friction losses in the system.

External links

  • A Gasoline Sprayer for Cleaning Engine Parts, Popular Science
    Popular Science
    Popular Science is an American monthly magazine founded in 1872 carrying articles for the general reader on science and technology subjects. Popular Science has won over 58 awards, including the ASME awards for its journalistic excellence in both 2003 and 2004...

    monthly, February 1919, page 127, Scanned by Google Books:
  • Chemical Training for Parts Washers
The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.