A customer brought to our attention that for a Lufkin Conventional unit (C-912D-365-192) the stroke lengths shown in the latest Lufkin catalog of 192, 170, 147 and 124” did not agree with what RODSTAR was showing (192, 165, 139, 113) for this unit.
I contacted Lufkin and found out that starting in May 1990, Lufkin changed crank pin radii for the crank used on some Conventional units. This change affected the following pumping units:
We have since updated our pumping unit data base with the new pumping unit dimensions. Because some of our users may have some of the older units that were built before May 1990, we decided to keep both sets of pumping units dimensions in our database.
The way to distinguish between them is to look in the Other information field on the pumping unit input window after you select a unit. For the units above, you will see either Made before May 1990 or Made after May 1990. Also, you can tell which unit you have by the stroke lengths listed in the software vs the ones measured.