Correct material selection 3

[Martin001]

We are working with Sulphuric Acid 0-98% (0-100 degrees celcius) and Hydrochloric Acid (Ambient temperature +- 40 degrees celcius). I am having trouble allocating a proper Polymere (Plastic pipes, valves and tanks)to handle these products. We have now been looking at different supplier acid resistance charts and to be honoust, I am now getting confused. Some indicates that PVDF can do the job while other say PP. I am looking for a handbook that have the correct Acid and Polymere comparitive matrix charts. I bought a book "Material Selection Handbook" but that one is not really helping with the comparitive selection process. I understand that Hastelloy B will be appropriate but want to look at the correct polymere type material.

 

[dogtop]

Take a look at:

Chemical Resistance Guide for Plastics
ISBN: 1-889712-03-5
Compass Publications
P. O. Box 1275
La Jolla, CA 92038-1275
Phone: 858-551-9240

HIH, dog

 

[Martin001]

Thanks Dog, I really appreciate it. I will purchase this book and give you a further update

 

[moltenmetal]

Using 98% sulphuric acid at 0 C will be tough (it freezes at ~ 3 C). And at 100 C, I wouldn't want any strong acid in a plain PP tank or pipeline. You can get away with PP up to 100- 105 C for water or weak solutions, but forget about pushing it beyond this temperature. Even a PVDF tank should have FRP over-wrapping for reinforcement if it's going to handle hot acid for long periods, because otherwise it will creep over time.

If you're using these acids at more modest temperatures (i.e. 40- 60 C tops), look at what they're shipped in: HDPE drums. If you're not designing for 20+ year durability and your application is of modest size, there's much you can get away with.

Chemline has one of the best chemical resistance charts I've found for thermoplastics (

http://www.chemline.com),

indicating both temperature and concentration for most potential corrodents.

 

[Martin001]

Thank you Moltenmetal. I had a look at it and for the range of Sulphuric Acid from 0-98% (0 degrees celcius to 100 degrees celcius)it seems that for our operation PVDF is sufficient but Teflon will be a appropriate solution.
Thanks for the reply

 

[JJPellin]

I would use some caution when setting the range of conditions for a selection such as this. The widest possible range of concentrations at the widest possible range of temperatures could produce strange results. We need to be conservative, but also need to be realistic. I come across this often on projects involving tanks. If we use the lowest possible tank level at the highest possible temperature with the lightest possible specific gravity I could be forced into a very poor selection for pump design. In certain other elements of hazard analysis, we warn that we don't need to protect against double jepardy scenarios unless there is a real chance of both events occuring at the same time. If the product is supposed to be 40 to 80 percent strength and 20 to 70 °C, then 98% acid at 100 °C might be a once in 100 year event (or more rare than that). As an alternative, could you consider a system to protect against these deviations such as a high temperature alarm or a periodic sampling program with action ties to force action if the concentration gets too strong?