Upper Collar Type B ( Data Sheet DS 830 )

This nut is in two parts. A plain bore load cell and a collar nut. The collar nut is threaded internally and externally, and is fitted with a load retaining, locking collar. A gap is created between the load cell body and the locking collar when the load cell is pressurised. Again the gap is a combination of the compression of the bolted joint and gasket, if fitted, plus the elongation of the bolt.

In use the load cell is pressurised until the hydraulic jack develops more than the desired pre-load. The locking collar is tightened. The pressure is released and the pre load is transferred onto the locking collar threads. Due to settling of the collar threads some of the pre load is lost. This is more critical in short bolt applications where the bolt elongation may be small. The pre-load loss on transfer to the collar becomes less significant on long grip length bolts.

Because the load cell has a plain bore the hydraulic connection can be located in the best position. The load cell can be fastened to the joint face and left in place. Similarly the hoses or rigid steel pipe-work may be permanently connected and left in place.