sealless pumps

[rotaryguy]

as for acid service i have under procedure for quotation. for preliminarily budgeting issue any body have idea of materials alloy -20 (ASTM A 743) or Hastealloy C (ASTM A494) which one is more expansive one?

 

[JJPellin]

I assume you are asking which is more expensive, not expansive. Hastealloy would probably be much more expensive. The last set of sealless pumps I installed in acid (98% sulfuric) were Alloy 20 construction for the case, impeller, etc but had a Hastealloy can. These were replacing pumps purchased with 316 SS cases. The original project engineer used NACE tables and decided that 316 SS would only corrode 2 to 4 mils per year. Instead, the 3/4" thick housing corroded through in about 3 weeks. The concentration of the acid, the temperature of the acid and the velocity all play a strong role in the rate of corrosion. Make sure you are conservative about the highest temperature, lowest concentration and highest velocity you expect to see.

Johnny Pellin

 

[TenPenny]

A secret squirrel told me that you can estimate Hast C as double (2x) Alloy 20, which is in approx 1.2 x 316ss.
316ss = 1
A20 = 1.2
Hast C = 2.4

Very approximate, but good for a budget.

 

[rzrbk]

If both metallurgies are allowable, it would be worth showing both as allowable and letting the vendor quote his most economic.

 

[pumpking]

Have you looked at lined pump technology ? ETFE or PFA lining technology is often manufactured by us for such duties. It is far more resistant to 'changes' in service such as temperature rise, concentration fluctuation etc. It is easy to drastically increase the temperature in a pump just by somebody shutting a valve that they shouldnt, then you can have all kinds of corrosion problems.

Lining technology has improved drastically over recent years and is widely accepted in Industry - have a look at

http://www.cdrpumps.co.uk

for an idea of the technology behind the products.