The jack never slips down Prior to dispatch, each jack is load tested at 1.5 times its rated capacity On customer request, the load test can be witnessed by a Third Party Inspection agency like Bureau Veritas, SGS or the like. Each jack has two pairs of case hardened grip jaws made of special grade of steel. At any given point of time, either one of the pairs is engaged or locked. During lifting both the pairs are in "locked"position. In this position, the jack can move only upwards. During lifting of a tank using jacks, an oil cushion is formed since all jacks are connected to each other hydraulically. This implies that no single jack will be subject to excessive load.