Material Preparation
Bar and forging stock arrives with a mill certificate. The grade is checked against the drawing before anything is cut, because a substitution found later means scrapping finished parts.
Turning and Milling
Blanks are turned and milled on CNC machines to the drawing with stock left on every face that will be ground later. How much stock to leave is a judgement based on how much the part will move in the furnace.
Heat Treatment
Carburising, quenching and tempering for case hardened parts, nitriding where the drawing calls for it. Hardness is measured on every batch after treatment and recorded on the batch card.
Grinding
Bores, spline seats, bearing seats and running faces are ground after heat treatment. This is where the distortion introduced by the furnace is taken out and the part reaches final size.
Lapping and Superfinishing
Valve plates, block faces and shoe faces are lapped. These are the pairs that have to seal against each other under full system pressure, and a ground finish is not good enough for that.
Inspection
Dimensions, hardness and surface finish are checked against the drawing on a sampling plan, with critical features measured on every piece.
Assembly and Matching
Rotary groups are assembled as matched sets. Vane cartridges are built and matched. Parts are not mixed between sets after matching.
Bench Test and Packing
Complete pumps are run in and tested for volumetric efficiency, external leakage and sound level. Everything is then oiled, vacuum sealed and boxed, and photographed before dispatch.
