"MAC" Jars feature the MacCorp Adjustable Collar providing external access to control jar settings. This feature allows the jar settings to be changed without special tools or removal from the tool string.
Mechanical jars trip to release stored energy in the wire or accelerator. Tension is applied to the wire to a point where the jar setting is exceeded. Once the jar setting is overcome, the jar releases and rapidly moves the free stroke distance. At the end of the stroke, the internal hammer and anvil make contact. This sudden interruption of the stroke creates the impact force.
Once the impact has been delivered, slacking off to relieve wire tension and tool string weight will cause the jar to recock. With mechanical jars, there is no time delay. Free pick up weight plus the jar setting must be exceeded for the jars to release. The jars can be cycled from impact to recock as quickly as the wire can be manipulated.
FEATURES
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External Adjustment Collar: No Special tools or removal of parts are required to adjust the jar setting. The tool does not need to be removed from the tool string for adjustment.
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Internally Splined: The E-Line model is internally splined to minimize failure due to debris accumulation within the tool.
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Specialized Trip Spring: The trip spring is designed for long service life and consistency. No belleville washers.
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Breather Ports: Screen filter breather ports permit fluid displacement and equalization yet prevent debris from fouling working parts.
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Compact design: Short make up lengths to minimize riser height and facilitate transport via helicopter.
The collar can also be rotated 90 degrees incrementally for more precise control over the jar setting. Each 90 degree (1/4 round) rotation will result in a 75 1b decrease or increase to the jar setting. Once the desired position of the collar is achieved, look through the set screw hole to make sure no threads are visible. If threads can be seen, rotate the collar in either direction to view a set screw groove. One direction will be closest to the desired collar position, choose the closest groove. The set screw will install flush or below the surface of the collar when properly aligned with the set screw groove. If unsure of the jars setting, rotate the collar toward the bottom of the tool until the collar stops against the shoulder. From this point the jar will be set at approximately 300 lb. Using the method described above, rotate the collar advancing upward to achieve the desired jar setting.