As an alternative to using a pressure pot in conjunction with spray painting, many manufacturers offer a range of double diaphragm pumps that basically perform the same task.
Although a double diaphragm pump has many more moving parts and is much more complex than a simple pressure pot there are several benefits which may make the additional cost of a double diaphragm pump viable in certain spray painting environments.
When using a paint pressure pot for spray painting, paint replenishment requires that air pressure to the pressure pot is turned off usually by way of the ball valve, air pressure in the pressure pot needs to be relieved with the air relief valve which is usually fitted somewhere on the lid of the pressure pot and then the pressure pot needs to be opened, paint needs to be poured into the pressure pot, or if the can of paint fits, placed inside the pressure pot, then the pressure pot lid replaced and the pressure tank re pressurised.
Using double diaphragm pumps as an alternative to a paint pressure pot negates the steps. Double diaphragm pumps typically have some type of suction pipe arrangement which may be flexible or rigid to draw paint directly from a container. This avoids the need for decanting paint from an original container into a pressure pot. Using double diaphragm pumps instead of pressure pots also avoids being forced to stop, de pressurise and open a paint pressure pot for refilling and subsequent re pressurisation.
One issue with double diaphragm pumps is the pumping action can introduce pulsation in the delivery of fluid to the spray gun unless a method of reducing paint pulsation is employed. Typically one of two methods are used on most double diaphragm pumps to reduce paint pulsation effect. One of the most economical options used on lower cost smaller double diaphragm pumps is an accumulator tank. An accumulator tank is usually designed with the bottom entry and set at the highest point of the double diaphragm pump paint outlet so air is trapped in the accumulator tank. The design principle is that trapped air in the accumulator tank will compress absorbing fluid pulsation to some extent. Another method of reducing pulsing as paint exits the spray gun when using double diaphragm pumps is to use a fluid regulator. A fluid regulator works in principle very similar to a air regulator and should generally be be more effective than an accumulator in removing pulsing. A negative with double diaphragm pumps and fluid pressure regulators is that where will occur which will accelerate rapidly when ever abrasive paints are used.
Paint pressure pots are a very simply constructed tool wear apart from regular cleaning the most common replacement part would be the lid gasket. Double diaphragm pumps are much more complex and over time will require many more replacement parts through normal wear and tear.
Double diaphragm pumps eliminate the need to lift and pour paint into pressure pots and downtime associated with the pressurising opening filling closing and re-pressurising paint pressure pots.
Image of a Wagner double diaphragm pump