O-Rings are our primary method of achieving a tight seal on our motors, and groves must be inserted in our parts, usually nozzle carriers and forward closures, to create a static seal.
To figure out which O-rings to use, and what gland sizes they need to be, consult the Parker O-Ring Guide (CLICK HERE), which is a standard in the industry and must be tightly toleranced. DO NOT try to calculate the grooves yourself. If you haven't used the guide before and are trying to find specifications for Static Male O-Rings (i.e. those found on forward closures, HEI's and other plugs), here is a brief intended to speed up the process and guarantee correctness.
To find the correct groove sizes, Look at design chart 4-2 "Industrial O-Ring Static Seal Glands", starting on page 89.