corrosion prevention of non used equipments

[tarojm]

I would like to know how to prevent internal parts of equipments which are not in service for a long time from corrosion.In our plant some of equipments ( towers and coolers )are in two set and in pararel so at a time only one of them is in service and the other will be out of service for a long time ( more than two years).We have faced with severe internal corrosion which lead us to extra works and cost ( retubing ,...).We think to use nitrogen blanket but for some reasons it was not successfull.Any comments would be appreciated

 

[YLWEA]

There are several types of volile corrosion inhibitors specifically made for that purpose. Check out Cortec products as an example.

http://www.cortecvci.com

 

[0809]

Air with out vapor doesn’t cause corrosion. Wouldn’t be better using moisture absorbent to dry air?

 

[rmw]

Can you isolate it and put a nitrogen blanket on it. Requires regulators and a nitrogen supply, and maintenance of the system. This is often provided for large Hx's with Carbon steel tubes, but I have rarely seen them functioning.

Other than that Munters makes a dehumidifier that is used to keep large pieces of equipment such as boilers and turbines dry while out of service.

rmw

 

[metengr]

I agree with rmw on dehumdification. We had to lay-up two coal-fired fossil units for 2 years. We had leased dehumidification units for the turbine/condenser and the boiler firebox. We made sure to rotate the turbines once a month for 8 hours with oil conditioners on the lube oil system.

The boiler was flash drained to remove condensate from undrainable tube circuits, followed by a nitrogen blanket.
Dehumidification was used to keep the boiler firebox dry (the exit flue gas ductwork was sealed with heavy plastic tarps to avoid the ingress of moisture).

 

[YLWEA]

I agree that dehumidification can be effective...if it is properly maintained. VCI use is much less reliant upon maintenance of the systems that keep everything dry.

 

[PAN]

Preservation procedure for the idle equipment in refinery...
thread483-11534

 

[SMF1964]

Dehumidified air works if you can ensure the system is dry to begin with. We had problems with too many parallel circuits in our reheater and couldn't get air circulation in all of the tubes, so those tubes that started the lay-up dry remained dry, but those tubes that collected water did not lose any water over the 5 month lay-up. Consequently, our intermediate reheater was shot when we restarted.