Carbon steel heat exchanger passivation beneficial?
Carbon steel heat exchanger passivation beneficial?
(OP)
I'd like some opinions on the benefits/pitfalls of passivating new carbon steel heat exchangers. I'm concerned, since they're not stainless steel, that this is not really beneficial, but a waste of time. Most water treatment specialists have promoted this. But won't the chemical just form a layer of rust with the steel?





RE: Carbon steel heat exchanger passivation beneficial?
If you don't passivate prior to placing the heat exchanger into service, iron oxide (rust) will form and dissolve into your feed water system. This could create corrosion problems elsewhere in your system.
RE: Carbon steel heat exchanger passivation beneficial?
The issue of getting the unit clean is a big one. Often various parts of the unit will have different surface conditions and this can aggivate corrosion.
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Corrosion never sleeps, but it can be managed.
http://www.trenttube.com/Trent/tech_form.htm
RE: Carbon steel heat exchanger passivation beneficial?
Your water treatment supplier is correct in recommending you to flush and hold the equipment with an inhibitor, typically 3X the normal dose during operation before putting it into service. In some cases, particularly high pressure BFW exchangers, acid cleaning is needed, to prevent minute amounts of iron from reaching the boilers, which is usually followed by a neutralizing and passivating step.
In the case of new carbon steel boilers, an alkaline boil out is performed. This removes oils & grease from rolling tubes in place and to promote a dense protective oxide film.
All of the above are for short term periods prior to putting the equipment into service. If you plan to keep the equipment in standby for weeks or months, then you need to devise a long term standby program such as nitrogen capping, a suitable wet method, cryogenic or dehumidified air. Keep in mind environmental conditions such as rain, humidtiy and deposit composition for instance when you have the fire side of a boiler in standby. All will need frequent monitoring and inspection.
RE: Carbon steel heat exchanger passivation beneficial?
I have also seem a multitude of CS tubed exchangers being retubed or replaced with stainless.
If the plant doesn't use the protections that the engineers provide, then they are worthless. It gives CS as a tubing choice a bad rap.
rmw
RE: Carbon steel heat exchanger passivation beneficial?
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