Cold Tight systems

The SKF Cold Tight systems offer considerable benefits. The SKF CT reduces downtime by several days each time a steam turbine is opened and closed. Long cool-down periods are not needed. The system also helps in planning the outage more efficiently.

The Cold Tight bolts sharply reduce accident risks and personal safety is increased since no heat is required to stretch the bolts. The necessary force is provided using clean and safe oil.

Every CT bolt can be tightened individually or as a group. Up to half of all bolts on a casing can be preloaded at the same time and all bolts are tightened using a uniform method. The entire design is fitted within the available area on the spot face of the casing. All tools are operated as an integrated unit with an tapered thread adapter that leaves no threads extending from the nuts.

By preloading bolts individually or simultaneously and by relating the pressure in the pump to the effective pressure area of the tensioner, the required bolt preload and an exact load distribution on the casing can be obtained. This ensures a safe, reliable closing and sealing of the horizontal joint with reliable, repeatable results.

The SKF CT is based on the SKF oil injection method developed in the early 1940s. Since then, the technology have been carried even further.

The tensioner assembly is fitted to the bolt by the tapered adapter thread. A safety rod is then fitted through the adapter and the tensioner assembly is completed.

The tensioner is operated by a pneumatic pump unit that deliver an oil pressure of 150 MPa for the preloading.

When closing/opening a turbine casing, the tensioners are mounted on up to 50% of the casing bolts.

The tensioners are connected in series and pressurized by a pump unit. At a specified oil pressure the pump is stopped and the nuts are tightened manually. The pressure is released and the pistons are retracted. The tools are removed and the tension is verified. The process is reversed for dismounting.