Oily Seawater separator - Material? 1

[misterd]

We need to build a wastewater unit for separating oily water genereted by a naval test establishment. Water is heavily contaminated with solids, cleaning chemicals, emulsied oil and synthetic seawater.

From the collection tank, the wastewater will be treated through an ultrafiltration unit. The temperature during treatment might vary between 2-60 C. Depending on the location, piping will vary between 25-150 mm (1-6").

What material is best suited for this application? Plastic is not an option.

Thanks in advance.

 

[mcguire]

Use 2507 duplex stainless or a 6Mo grade such as AL6XN. Titanium is also an option.

 

[misterd]

Thanks for the reply. If those metals are unavailable, what about SS 2205 or hastalloy? My charts are really vague ont the subject...

 

[mcguire]

2205 will pit in ambient seawater. I have a paper by STATOIL that says that 6MO grades are required on North Sea platform seawater systems implying that the less alloyed 2205 is not acceptable. It goes onto say that alloy(2205) is used in seawater only with cathodic protection.
If you can't get 2507, then you may be stuck with hastalloy.

 

[Elvie]

Hastelloy C22/C276 are by far more reliable than all other alternatives(except Titanium)especially in stagnant waters and higher temperatures.

 

[mshimko]

I concur with Elvie - Hastalloy C22 or C276 would almost certainly work well, if your budget can handle the cost, that is. Some of the inconels should also be considered and may be slightly less expensive.

However, what's wrong with carbon steel - painted or unpainted? This is what's typically used for OWS shells on marine vessels. If you're concerned about corrosion, you can paint the inside with a chemical resistant edge-retentive epoxy such as Sigma Edgeguard of Sherwin-Williams Novaplate.