Heat Exchanger Types of Online Repairs

Online repairs that can be made include:
1. Retorquing flanges

This usually involves tightening all of the bolts. Follow appropriate torquing procedures to prevent worsening the problem.

Belleville Spring Washers have sometimes been used to solve leakage problems caused by differential thermal expansion. It is usually necessary to replace the bolts one at a time when doing this. Appendix H discusses the use of Belleville Washers in more detail.

Note that torquing the bolts over their code allowable stress may stop a leak temporarily. However, this may cause permanent deformation of the flange such that, (1) the flange may leak on the next thermal cycle, and (2) the flange may need major repairs or replacement on the next shutdown.

2. Tapping the flange and pumping in sealant between the flange faces at high pressure.

3. Installing a ring around two flanges and pumping in sealant at high pressure.

Repairs 2 and 3 are only temporary fixes and can be very expensive. Permanent repairs must be made during the next turnaround. The work required to remove the leak sealing compound in order to repair the exchanger can also be time consuming and costly. The next section discusses these temporary repairs in more detail.

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