CLIENT BACKGROUND

 A refinery had continuous nuisance leakage from a bank of high temperature heat exchangers with 3/4” bolts. Assessment of the joint integrity revealed that an extremely high assembly bolt load (90% of yield) was required to ensure good joint integrity.

CHALLENGES

Leakage of these joints was problematic for the refinery, requiring shutdown to retighten the joints and – on occasion – shutdown to replace the gaskets. The cost associated with these activities, and the risk to personnel were substantial.

PREVIOUS FIXES

Other load indicating bolts had been used in the past, but due to the small diameter of the bolts and the larger bore of the device, these devices prevented tightening to the high assembly bolt load. 

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SOLUTION

RT-Bolts were machined into a set of 3/4" diameter A193-B16 bolts, to facilitate accurate assembly of the joint to 90% of yield and allow ongoing monitoring of the residual bolt load using the ceramic high temperature RT-Bolt gauges.

CONCLUSION

The RT-Bolts worked well for assembly and the joints were brought online with no leakage issues. Online measurement of the bolt load indicated that some bolt relaxation or bolt yielding may have occurred, which will be investigated further once the joints are taken out of service.