Frequently Asked Questions

What is the actual pilot ratio of Sun's pilot to open check valves?

Good question. We have never published this data. If you compare the area of the pilot piston to the "as manufactured" area of the seat, the ratio of series 0 is a true 3:1, the series 1, 3, and 4 are 4:1 and the series 2 is 4.4:1.

In the beginning, the valve of choice was the Delrin seated valve and because of the compliance of the seat, the ratio went down as the pressure went higher and the poppet sank into the seat. Eventually the seat will take a set and the ratio will also be less at lower pressures. Everything lowers the ratio, even wear and tear on the steel seat. The springs in the valve lower the ratio by a large amount at low operating pressures (see the answer on piloting with air).

The effective pilot ratio is always less than the area ratio. Understating the pilot ratio of our pilot-to-open checks leads to more robust circuits.