Condensate storage tank material suggestions

[TimboGMO]

I posted this earlier in the mechanical engineering forum for boilers and pressure vessels. I thought perhaps it might be more suitable here.

Looking for condensate storage tank material suggestions. (carbon steel, lined carbon steel, duplex stainless, fiberglass, etc.) We are looking to purchase (2) several thousand gallon tanks to act as storage/surge tanks for condensate coming back from many buildings connected to our steam distribution system.

We currently have (2) storage tanks from the early 50's that have served us well, that were originally used as lime softening water tanks, I am not sure when they were switched over. These current tanks are fabricated out of carbon steel.

I would be very hesitant to use 304 or 316 SS due to the possibility of SCC, even though our chloride levels are normally low (6.4), there is a possiblilty they could spike if we had problems with water heaters in buildings on our steam distribution system if the water heaters had tube failures and sent raw water into our condensate return stream. A duplex stainless steel could be a possibility.

Below are our condensate conditions:

Chlorides: 6.4 mg/L
Conductivity: 2.8 uS (can be up to 70 temporarily if we have a large water heater failure on steam distribution system)
pH: 7.5-8.5
Temperature: 150-180 degF
hardness: 3-4

Thank you, -Tim

 

[EdStainless]

Since I am an alloy guy I'll start there. You might consider 439 or LDX2101 if you want metallic construction. Both will give you similar pitting resistance to 304 and no risk of CSCC. (they also cost less than 304)

My hunch is that composite tanks would be better. Less cost and good durability. Someone else will need to recommend a resin system for long term hot water exposure, but it is done all of the time.

= = = = = = = = = = = = = = = = = = = =
Rust never sleeps
Neither should your protection

http://www.trent-tube.com/contact/Tech_Assist.cfm

 

[strider6]

I've a question, why do you want to change material if the carbon steel serve well ? Did you have a failure on the Tank?

Strider

http://www.corrosionist.com

 

[TBP]

Carbon steel should work just fine - provided you don't add raw make-up water to the condensate tank. Cold make-up water holds a lot of dissolved oxygen, and when it hits the nice hot condensate in the tank, the corrosion rate (pitting) on carbon steel becomes very impressive. I've seen installations like this fail in 18 months. If the make-up water is added to the deaerator, the tanks should last like your old ones.