Different components in a piston pump can be configured to give various desired results. Most commonly the difference between the diameter of the air & fluid pistons dictates what is know as the pump ratio. This ratio number is a multiplier of the supply air pressure to the fluid output pressure. For example, a common pump ratio is 3:1, therefore a 100 psi air input pressure would create a fluid output pressure of approximately 300 psi.

Another premise related to ratios is that the higher the ratio the lower the amount of product per stroke. This trade off is commonly used to an advantage for applications where long piping runs are required or when thick or high viscosity fluids are dictated. Some common ratios are 1:1, 3:1, 5:1, & 50:1. The lower ratio pumps, 1:1 for example are best suited to transfer applications.

An example of this might be where a fluid is being transferred from a large bulk drum to a smaller container in a very short distance. The advantage to using a lower ratio pump for this type of application is that the pump delivers a relatively large amount of fluid per stroke, which increases the life of the pump. The trade off is that it does not have the ability to deliver the product at high pressure. This low pressure trade off can be acceptable for short distances because the pump is not having to overcome significant line loss, or the mechanical flow resistance of the fluid flowing through the piping system to the dispense point.

The 3:1 & 5:1 ratio pumps will be better suited to moving a fluid to more distant dispense points. A typical application for this ratio range would in an automotive quick lube facility were the fluids might need to be pumped from a below ground bulk storage tank up into the ceiling height piping network to multiple dispense points.

The 50:1 ratio pumps are most commonly used to convey higher viscosity fluids such as grease. This high ratio allows this thick product to be pumped great distances & still maintain a relatively high pressure at the dispense point. The trade off for this end of the ratio spectrum is that the product delivery rate is relatively low, but in this application is perfectly acceptable.