Heat Exchanger Preservation

[RauMech]

Hi All..

I read the shipping and long term preservation requirement of exchangers in this forum. But I have a query re the requirements during or after installation - ie when installed on the site, and when piping start installing do we need to maintain the N2 purge..or after all piping is done do we need to put the N2 purger back in , as this exchanger will go into the precommissioning stage roughly after more than 12 or so months...the site location is in Alberta, Canada. and exchangers are CS..
I used to work in other part of the world where we dont maintain after installation, so if anybody have dealt with this appreciate an input.

Thanks for your help in advance,
Rahul

 

[EdStainless]

In general no, you don't need to maintain purge.
But you do need to keep them clean and dry.
If someone feels the need to hydro test or flow test the system then you need a way to drain and force dry the units. Simple protection is usually enough. Keep the rain and snow out.
We have all seen costly failures from HX left with residue of hydro test water in them.

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Plymouth Tube

 

[gr2vessels]

Rahul,
It all depends on the sensitivity of equipment operation, location, contaminants you might expect to come down from the connecting piping.
Nevertheless, if you expect more than 6 months of stagnant equipment, I would certainly blank off the exchanger nozzles and put back the N2 blanket, around 3-5 psi (I believe you referred to N2 blanket, not continuous purging). The exchanger is prone to 'breathing' due to thermal expansion/contraction and accordingly you will see condensate accumulating slowly inside the exchanger, together with dissolved O2, CO2 and other nasties. Just right receipe for corrosion, out of sight and out of control.
I do agree you need to keep the exchanger clean and dry, but without complete isolation and slight pressure with N2 I can't see how you'll achieve that.
Cheers,
gr2vessels

 

[RauMech]

Thank You gr2vessels - it cleared my double thinking.
Will leaving deseccant bag inside and tight closure of all nozzle openings will do good - as there are 100+ exchangers and still a construction phase, so leaving N2 blanket poses a safety concerns.
Rahul

 

[unclesyd]

As posted above very clean and dry are the key to dry storage. For dry storage we use a Vapor Phase Inhibitor with or without N2. For tube bundles we will bag them and use the VPI.

We have had to put some up wet where we add high chromates to the water in the exchanger. We are able add chromate as we have a waste water injection well.
Our biggest problem with this type storage is Microbiological Induced Corrosion (MIC). MIC can be problem with dry storage when the exchanger is returned to service when water is induced and the equipment sits.