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Why would you do Hot Bolting on Bolts that are in Good Condition?

At SRJ Technologies, we have come across this scenario quite frequently. A client contacts us to purchase BoltEx® so they can change out bolts on flanges with little or no corrosion.


“Why would this be?” you may ask. The short answer is that the installed bolts are the wrong type of good bolts!

Bolted flange with galvanic corrosion.

When assets are restarted after shutdowns or commissioned as brand-new plants, there are sometimes aspects of the mechanical completion that, although safe, are not as designed. A critical area we see is using the wrong bolt material to secure a flange (e.g. using carbon steel bolts on stainless steel flanges and vice versa), which, if left, will cause galvanic corrosion due to dissimilar materials.

In other cases, the bolt material is correct per the piping design. However, the insulating kits for the bolts were not inserted as they were unavailable in the time-pressured environment of asset start-up.

Bolts with dissimilar materials to flange body.

In both scenarios, a sub-optimal situation can be recovered without impacting operations and production by exchanging the bolts on pressurised piping using hot bolting.


Traditionally, these scenarios would be left to the next shutdown, which may be many months or years away. During this time, the accelerated corrosion would be allowed to take hold and affect the integrity of the flange faces and the connecting bolts. A more serious situation has been created, which takes more resources and precious shutdown time to rectify as the flange now needs replacement.

Bolted flange with galvanic corrosion.

There is another way. Proactively changing out these dissimilar material bolts or fitting the insulation kits can be done online during normal operations using BoltEx® before galvanic corrosion takes hold.


Do you have dissimilar materials inadvertently installed on the bolted flange connections on your plant? If you do, then please get in touch with us to see how we can help you.

BoltEx being used for hot bolting.

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