304L vs. 316L Economics
304L vs. 316L Economics
(OP)
I'm putting together a pump skid that will be used to circulate chemical cleaning solutions for boiler/HRSG chemical cleaning operations. Some of the chemistry is acidic (Citric, EDTA..) some is alkaline (Ammonia, Soda Ash...). Pumping pressures never exceed 150-160 psig and temps never exceed 180F. I'm going to use Sch10 stainless pipe with carbon steel slip-on flanges (so that wetted surface only is stainless). In selecting the stainless material, I was looking at 304L or 316L. I don't want corrosion problems around the weld areas, and I need to make an economical selection while selecting the properly suited material. Any thoughts.....? (gittings such as ells, tees, and reducers will also come into play).
Thanks,
CW3
Thanks,
CW3





RE: 304L vs. 316L Economics
I would go with 316L but I am not a metalurgist. You may want to ask the Corrosion Engineering people about that. As far as slip on flanges go, to get stainless on all wetted parts you have to get lap joint flanges. They are about three times the cost of just getting weld neck flanges. Sch 10 vs Sch 40. I would go with sch 40, you can price it out but the cost savings is not really there.
Hope this helps.
StoneCold
RE: 304L vs. 316L Economics
Another problem with CS on a multipurpose cleaning skid is that the whole works will become a rust ball after short time so if you can swing it weld neck flanges are the way to. Another point is that you should watch you pipe and supports if the unit is any size. A cleaning unit will see a lot of abuse. Use a totally enclosed motor for the pump if possible.
Watch the design as there is nothing more embarrassing that to breakdown on critical job.
RE: 304L vs. 316L Economics
You imply you seek the best economic solution. The answer will probably be 316 ss if stainless is a process requirement. (Of course, you’re the only one who can determine or decide what alloy is needed) Manufacturers have almost standardized on 316ss as a replacement for 304ss in order to eliminate having to deal with two similar alloys. Up to 5 years ago this had transpired in the valve market and in the heat exchanger tubing field. This fabrication move has made 316 more available and cheaper than the 304 alloy. This is a paradox where market demand once again determines the price and not the material or the properties of the alloy.
If your process requires stainless and your pressures are as low as you state, then 316ss, schedule 10s is the way to pipe it up. If you require flanges for maintenance, I always employ carbon steel backup flanges on van stone lap joints. This is done where the external carbon steel backup flange is not subject to external corrosion. The same criteria applies to the flange bolts and nuts. I would employ a minimum of welding on the piping. The excellent features and installation flexibility of the van stone flanges make them ideal for this application.
Art Montemayor
Spring, TX
RE: 304L vs. 316L Economics
RE: 304L vs. 316L Economics
Thanks again,
CW3
RE: 304L vs. 316L Economics