Tube Bundle Shop Hydro 1

[Krausen]

General question for the forum on shop hydro testing replacement tube bundles to be installed in an existing shell & channel (S&T HXs):

I work at a plant where it is unfortunately very common practice to replace existing tube bundles at end-of-life with new in-kind tube bundles, reutilizing the existing shell & channel with this new tube bundle. For hydrotesting the new tube bundle, shops are typically limited to leak tests at 150 psig max. This hydrotest pressure typically does not satisfy Section VIII pressure test requirements. How does forum typically handle this issue?

Are attempts made to code hydrotest new bundle in the field with the existing shell & channel that likely cannot handle the required bundle code hydro pressure in their existing corroded state? If hydro-ing new bundle in shop, are you requiring test heads to be fabbed by shop for both the channel side test & shell side test for new bundle? This would obviously add to cost of new bundle substantially.

 

[erkuts]

We have hydrostatic testing equipment or we make spare channels or shell for hydrostatic testing of new bundles in the shop.

Depending on which side, tube or shell side, is higher, only the higher side is hydrostatically tested in the shop.

In cases where we do not just make the shell for hydrostatic testing, we make the entire heat exchanger.

 

[r6155]

The best practice is to send the complete HX to the manufacturer.

Regards

 

[Krausen]

The best practice is to send the complete HX to the manufacturer.

I agree. I'm in process of changing this practice at my site. It will take some time to implement though.

 

[Krausen]

Depending on which side, tube or shell side, is higher, only the higher side is hydrostatically tested in the shop.

This makes sense in general. But is this also the case with new replacement tube bundles that have welded tube-to-tubesheet joints? Was wondering if typical practice was to code hydrotest these bundles on both the shellside & tubeside to test these welds from each side, regardless of which side is higher test pressure.

 

[erkuts]

Yes, remaining lower pressure side test is conducted on site after replacing new bundle inside of existing shell.

Higher side pressure test conducted in shop before coming new bundle to site eliminates risk of on site major problems.

 

[EdStainless]

While the tubes are rarely the controlling pressure boundary testing the tube-to-tubesheet joints is critical.
I will say that over the years I have rarely seen a bare bundle transported (no shell) that did not need field repair to T-t-T joints.
Putting them into the shell allows testing of both sides and offers support and protection in shipment.

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P.E. Metallurgy, consulting work welcomed

 

[Dhurjati Sen]

Why would you want to go for a shell test when the hx has failed due to tube side degradation?

Still, if you really want to go ahead....

Carry the shell side hydrotest at the operating pressure to satisfy yourself for any roll leaks. You must have the test ring, though.

Carry the tube side hydrotest at site as per code. You should not get any pressure drop.

DHURJATI SEN
Kolkata, India