Encyclopedia of Anchoring (CA06114E)

High-Strength PISA® tooling has a longer socket on the Kelly bar adapter and locking dog assembly. This results in less wrench wobble during installation and reduces stress on bolts. Both products are thicker and heavier than 10,000 ft.-lb. rated units, so there’s greater strength. A thicker anchor-drive wrench gives added fatigue life and increased torque strength. If a single installing tool component fails, the tremendous torsional energy transmitted by the tooling can be released violently. This sudden energy release can cause personal injury or property damage. That’s why it is essential the proper anchor installing tools be used, including not interchanging the installing tools of different manufacturers. Whether you use installing trucks with more than 10,000 or 15,000 ft.-lb. of installing torque capability, do not exceed anchor or tool ratings. To do so can stress the wrench system beyond its designed safe limit. Installing anchors beyond the safety limit will subject the wrench system and the operators to a hazardous condition. CHANCE tools made of ductile material The selection of materials used in the manufacture of anchor tooling is very important. This is especially true for the drive wrench portion of the tool assembly. CHANCE wrench tube design is based on the accumulation of more than 30 years of experience. The steel used to make wrenches is processed to achieve the right balance of hardness, strength, and toughness to stand up to the demanding chore of installing anchors.

Anchor wrenches can fail by applying torque above their rating. The opportunity for this to occur increases if the wrench is subjected to bending, shock loading due to rocks, or anchor breakage. CHANCE wrench tubes are designed to fail in a ductile manner. In other words, if the tube fails, it will fail in a manner that helps protect workers. Generally, it will twist along its length under conditions of failure. Wrench tubes can be processed to make them harder and stronger in an attempt to increase their torque rating. However, limitations in wrench cross-section geometry make this a potentially dangerous situation because it can cause the wrench to fail in a non-ductile or brittle manner. Brittle failures are dangerous to workers because the wrench tube can actually fracture into pieces and fly outward from the tool string. CHANCE wrenches do not have this problem. They are processed to maintain ductility for a safe design. Over time, all wrench system components will wear due to continued use. This is normal and should be monitored to establish a tool component replacement schedule.

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Note the difference in size of the 15,000 ft.-lb. wrench tube on the left compared to the 10,000 ft.-lb. standard tube on the right.

The 15,000 ft.-lb. high-strength wrench assembly is on the left. The standard-strength 10,000 ft.-lb. wrench is on the right.

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