What Causes Gas Lock?


Gas lock occurs when the pressure built up in the compression chamber on the down stroke is not sufficient to open the traveling ball and seat. The graph below is a result of data gathered from compression testing 2" bore RW standing cages from different manufacturers.

The tests were done by stroking a one foot long plunger inside a 2" bore RW barrel tube with the bottom of the traveling cage coming within 2-1/4"; 1-1/4"; and 1/4" of the top of the standing cage.

The traveling cage used was of API design with a blank disc in place of the seat to simulate hydrostatic load on the traveling ball which would keep the ball on the seat during the downstroke of the plunger.

The standard API seat plug and the recessed seat plug were both used to illustrate the importance of close valve spacing.

The tests were done using a 24" plunger stroke.

All values shown in the table below are in PSIG.

2-14" CAGE COMPRESSION ANALYSIS
CONTINENTAL
AXELSON
EMSCO
INSERT
INSERT
FLOW
HIVAC
GUIDED
GUIDED
MORE
STANDARD SEAT PLUG WITH 2-1/4" CAGE SPACING
84
68
64
54
STANDARD SEAT PLUG WITH 1-1/4" CAGE SPACING
99
78
74
62
STANDARD SEAT PLUG WITH 1/4" CAGE SPACING
121
93
88
70
RECESSED SEAT PLUG WITH 1/4" CAGE SPACING
148
101
97
76


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It is evident from the above information, that it is the proximity of the balls and seats that determines compression, not the proximity of the cages.


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