Maintenance and cleaning of spray guns and pumps

One of the most commonly used methods of applying varnishes and paints is spraying. The method is used in both large factories and workshops and even by hobby woodworkers. For application, sophisticated equipment is used as well as simple spray guns, for which no special training is needed. If you want to keep using them for as long as possible and get good, consistent results, they must be maintained. Cleaning spray guns and spray pumps after each use and maintaining them on a regular basis can double the service life and eliminate half of the problems that occur during operation.

The other day I was talking to Gabriel Mănoiu from Falk Consulting, the Romanian distributor of pistols and pumps Sames Kremlin, who told me that, unfortunately, there was little discussion on the subject, as it was taken for granted. If you have a car, you will certainly think that without proper maintenance, without timely servicing, you can have problems. The same needs to be thought about with painting equipment. It is a way to protect your investment and at the same time get quality coatings.

What's involved in maintaining spray guns

After each use the gun must be cleaned. All routes through which the finishing materials flow are important, not just the nozzle. Lacquers and paints contain pigments, fillers, and fillers that can build up on the walls of the hoses and pump and gun passages, making them narrow. The equipment will work harder and harder and the results will also be poorer.

Even more dangerous is not cleaning equipment when using chemically hardening materials such as polyurethane varnishes, acrylic with curing, polyester. Paint or varnish residues will cure inside and the equipment will be totally compromised.

To avoid such situations, equipment should be washed after each use. Use the solvent with which the paint or lacquer has been thinned, as recommended by the manufacturer. Before putting thinner in the equipment, spray any remaining material inside in a separate container. It may be reused in another application, provided it is not a mixture with hardener that has passed its pot-life.

After removal of the varnish residues, solvent washing is started. Spray until clean solvent comes out of the gun, free of traces of varnish, paint or dye. Then unscrew the spray gun head and thoroughly clean the nozzle, filter and other components with the brush normally supplied with the spray gun. For better cleaning you can use special kits that are also available without the spray gun.

Reassemble the gun poi and leave thinner in it if it is to be used in the near future. If it is to be used periodically, thoroughly wipe the components, allow to soak, then reassemble the gun and store it in its original box.

In the case of pumps, the air supply must be turned off and the pressure relieved. Remove all filters and clean them thoroughly. They should be changed from time to time according to the manufacturer's recommendations. Check the gaskets and if they show the slightest sign of damage, replace them. A seal that does not seal very well is a danger of loss of material or pressure.

Washing thinners

There are such thinners, which are cheaper than those used in mixtures with finishing materials. The latter primarily ensure very good film quality. Washing thinners are more aggressive solvents or mixtures of solvents used to clean, to soften any debris trapped by equipment components.

One of the solvents used for washing is acetone. I asked the Falk Consulting representative if it isn't too aggressive and doesn't destroy the seals and components of the guns and pumps. It is indeed aggressive and can damage those very inexpensive guns made of less resistant materials. Guns sold by specialty firms have components made of stainless steel and seals made of Teflon, acetone resistant materials. Hence the differences in price, but also in the time of use.

Even if it is more expensive, it is recommended that the material is removed from the gun using its thinner. It is formulated to be compatible with all components of the paint or varnish. Finally, a washing thinner can be used to save money.

Equipment used for application water soluble products wash with water. Warm water or, if necessary, water as a specially formulated washing detergent shall be used for thorough cleaning. Clean water shall be used after the detergent water. Finally, do not leave water in the gun but a water compatible solvent such as technical alcohol. The alcohol also protects during the winter period when the water could freeze, damaging the trails and equipment components.

Switching from one type of material to another

In small workshops or factories different spray guns are not always used for solvent-based and water-based products. The small amount of finishing material used does not justify the investment. The gun provided will spray organic solvent-based and water-based products alternately. In this case washing must be done very carefully because contact with the wrong solvent can harden the paint or varnish inside the gun or in the pump paths, totally ruining the equipment.

Initially washing is done as above, removing the material from the gun using the specific thinner. Then use a wash diluent compatible with both organic solvents and water, such as acetone or technical spirit. After the trails have been thoroughly washed with the universal thinners, another wash is made, this time using the thinner for the material to be used. This last diluent is then drained off and the gun filled with the new material.

Although the process is more laborious it must be done. This is the only way to get a good quality film without crater and stings. Organic solvents and water do not get along, behaving like water and oil. If they come into contact, they tend to repel each other, dragging with them the paint or varnish they dilute. This creates holes in the film (craters) or small pinpricks.

The same defects can also occur if water-based products (and vice versa) are applied shortly afterwards in the room where the organic solvent-based varnish has been applied. Solvent vapors remaining in the atmosphere will damage the film. Therefore, if there is a spray booth, ventilate thoroughly by exchanging the air with the exhaust system before starting to work with the water-based product.

In conclusion

Good gun maintenance will be reflected in the quality of the film. The nozzle will not constrict, dry varnish particles will not be entrained by the new flow of material, the air will come out with constant pressure. The finished object will look good, the customer will be satisfied and you will be able to bet on new orders from him or from new customers where you will be recommended.

Plus you'll protect your investment by using your gun or pump for a long time without having to replace damaged parts or even buy new ones. And speaking of investment! Don't buy the cheapest spray guns thinking they are all the same. They are not the same and the price difference is justified by something. What's more, by buying from a specialized firm, you'll have somewhere to ask for advice and explanations in case you run into problems.

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