Melvelle Equipment manufactures three different sized Casing and Drill Rod Jacks.
Jacking is carried out by cycling the cylinders up and down. Each time the jaws alternatively grasp the drill pipe holding the pipe alternatively between the two bowls.
For releasing the jacking loads if the pipe does not come free from the hole, the jaws can be manually held open to allow the cylinders to retract and release the jaws to grab the pipe again when there is some travel left in the cylinders so they are able to re-grip the pipe
With the exception of the high pressure 174 series jack, all the other models are designed witha maximum system pressure of 3000psi which is availabl eon most drillin grigs.