Measuring
for braided packing
(for pumps and valves)
from Joe Kelley
For those applications requiring a square braided packing for pumps and valves ie: a rotary pump with solid shaft (or pump sleeve) or plunger type of application such as the IHC M fuel pumps, one has to measure to get the correct size. This has always lead to some confusion about measuring, as packing is sold by fractional inch sizes and a lot of people get confused on how to measure for it. Here goes. There are 3 basic measurements we are concerned with. First the ID or the diameter of the plunger or the shaft (of the pump) or the stem (of the valve). For example say this measured 1/2". Next you have to measure the diameter of the bore, that is the space (often called the "stuffing box") that is taken up by the shaft or stem and the packing too. For example say this measures 1.0" Here is the hard part (G), We need to determine the packing size, that is, the cross section. Simply do a little subtraction of the OD (1.0") minus the ID (1/2") equals 1/2" then divide by 2 and you get the cross section which is the packing size which in this case would be 1/4". A lot of people forget to divide by 2 to get the cross section. That is the lesson for today! Hope this is of some help.... Joe Kelley |