Technical Specification: According to API 10D specification, The purpose of Centralizer is to maintain the Centering of Running Casing in the Well bore upto the desired Depth. Centralizer should have low Starting Force and High Restoring Force; Staring Force is the Max Force required pushing the Centralizer into previous running Casing. The Starting Force should be less then the weight of 40 feet medium weight casing. The Restoring Force is the Minimum Force exerted by Bow Spring against the wall of Well Bore to keep the Casing away from the wall and to maintain the centering of casing. As per API 10D specification, Centralizer has to achieve a minimum Stand Off ratio of 67%, while under Minimum load. SledgeHammer standard Centralizer generally achieve a Stand Off Ratio more then 75%, instead of 67% for a minimum Restoring Force. In SledgeHammer regular performance tests insure that products always achieve the highest standard as per API specification. SledgeHammer testing Procedure as per API 10D specification.
1. Hardness Testing & 12 Time compression test. Hardness testing of each Bow springs done at various stages. To ensure that Bow Spring have uniform hardness this test is done at least twice on each bow, For 12 times compression test Each Bow Spring mounted on fixed plate under Hydraulic Press and load is applied from top and compressed the horizontal placed Bow Spring for at least 12 times. This test helps to detect spring loss and hidden fracture in bow.
2. Starting Force and Running Force. A new assembled Centralizer installed vertically on the inner pipe. The test assembly held with in 5 degree of the vertical with the Centralizer resting on the edge of Outer pipe. Load is applied from the Top of the Centralizer and the reading of Force is recorded from time of the first load was applied, until the Centralizer completely moved inside the Outer pipe. Starting Force equals the maximum force required to start the Centralizer inside the outer pipe. The Starting Force should be less than the weight of 40 feet (12.2 meter) of medium weight casing. Next, continuation of load applied on the Centralizer inside the outer pipe, which slides out the Centralizer from outer pipe. The maximum Force recorded while sliding out is count as the Running Force of the Centralizer.