Can I Replace SS 304 With Another Material?

How big are these tanks? Homes in the UK use a spun copper cylinder to approx 0.1m3 insulated when new with expanded foam, sometimes fitted with heating devices such as an electrical element rated at 3kW or a coil of copper tube often connected to the central heating system circuit. They are usually rated at 0.5Barg. These can be had new for a few tens of pounds Sterling. Is this equivalent?

Most plastics tend to lose stiffness as temperatures increase. Glass-reinforced polyester [GRP] might do the job for the larger, loose-lid, tank depending on the size of the tank and its pressure rating. Moulds/molds can be designed to provide appropriate stiffening for the larger panel.

Another option is to use a plastic or rubber lining over a substrate of material having a lower value than 304 SS.

Along with the materials of construction, the design will need to allow for the secure attachment of insulation, partly for thermal economy, partly for personnel protection.

'Horses for courses.'

if you want many --- and high capacity say 2000 litres-- Your best bet is

:Mild steel with optimum thickness at bottom and nominal on top-with a manhole.

;And paint whole Internal with Epoxy

Maybe paint outside - after Priming with AntirustZinc Chromate- Aluminium Enamel

Traditionally that has been the case and copper cylinders are still used today for basic H W cylinders.

There have been problems in the industry with copper corroding this has resulted in anodes being fitted to the bottom of copper cylinders.

Also the price of copper has gone through the roof and it is no longer a cheap option.

Most manufacturers offer a stainless steel option to the copper for H W cylinders and most gas condensing boiler heat exchangers now made of stainless steel.

They use aluminum in aircraft but the design is way different.

You can also consider carbon steel or casting steel with plating zinc,chrome.

This is another question without enough facts such as pressure, end usage etc. 85 is very hot for domestic purposes and one has to ask why the tanks were initially specified as 304 if a cheaper material would do?

Exactly!

Offering advice on the web without knowing the full situation isn't engineering, its long distance point and shoot russian roulette.

Presumption is that the 304 stainless is for the tank body, may or may not be true.

Presumption that water may be potable may or may not be true.

We do not know how the heat is being applied to the water- via tank, via element, via what means???

We do not know the application of the water, the scale of the project, the servviceability (Could home owners easily replace sacrificial anodes in situ at 85 degrees, I'm not so sure...)

We do no one any good by prescribing remedies before we truly understand their needs.

fire, ready, aim is not engineering.

Engineering is 1)Hear the question, 2)Understand the requirements , 3)Conceive solutions, 4) Consider solutions in light of situation, 5)Offer potential solutions.

Going straight from 1 to 5 may be excercise (jumping to conclusions) but it ain't engineering.

Nutwood, Thanks for pointing out the error of folks rushing in before the facts are at hand. To get good answers, ask good questions. In the absence of sufficient facts, ask clarifying questions, rather than rush to give half a$$*d answers.

The last thing this forum needs is misfeasant or nonfeasant advice because we didn't understand the application before prescribing advice.

milo " protect the customer is first priority"

Thanks Milo. I was beginning to think I was the only one developing a bee in my bonnet about questions with no facts. There seems to be a plethora of questions from Mr Guest. Interesting enough questions, but with no details and what's worse, Mr Guest never re-posts to update the initial lack of detail.

My view of the ideal query is one that gives the salient facts briefly up front. If others can help there should be a follow up giving further details as required. Ideally this should then be followed up with feedback as to the success or otherwise of the applied solution. Not to mention of course, a thank you to all the people who expend mental energy and key board time attempting to help.

This question is simple enough on the face of it but from previous observations there could be a host of little details that we are not being given that makes any suggestions a potential minefield. Someone below suggests (actually states) that they think that these are solar hot water tanks. Reasonable suggestion but I can't see where the OP states that, or have I missed something?

You are not the only one.

Imagine going to the Dr. and being told to take pennicillin.

Its a good solution.

Except that you have a viral infection and carpal tunnel syndrome.

Lot of good the penicillin will do.

I have come to expect lousy questions, but I am annoyed at Miracle answers that do not have enough facts to have much chance at being relevant. Engineering is not about magical prescriptions. Its about understanding first, then arriving at a solution. Practice of magick should be on another forum.

But quantity of answers rather than quality of answers provided seems to be the focus here.

milo

Oops, not logged in on that computer. sorry.

milo

This appears to be for solar water heater & if it is so, any replacement material should also take care of contamination etc., including long term effects.

Thanks

Ashok Toshniwal

What kind of life for the tank do you require? You could use carbon steel and protect it with a magnesium anode.

You may want to discuss your application with www.techlinecoatings.com . The contact is Leonard Warren out in CA. They are manufactures of high temp coatings, however they have a coating called Peek, which has unique properties similiar to stainless steel.

Howard

I just received a Power Point presentation on the use of 201 instead of 304. I quote:

•" 201 is suitable for food contact surfaces and food service, the same as 304. 201 is approved for use by ANSI/NSF International Standard for Food Equipment 51."

Basically the material selection is based on the fluid property, its pressure and temperature conditions and the duty,for which it is being used.

Therefore if the duty allows, you may go for material suitable for that pressure and temperatutre conditions. You may go for chrome or zink plated Carbon steel

However plastic may not be suitable as the plastic loss its stifness as temperature increases.

While I am sure the design maximum temperature might be 85 deg C, you would have to assume that a malfunction in the thermostat might allow water to boil. That is why there are always pressure relief valves. As said, hot water often causes a softening of plastics, I would assume that a build up in pressure before the pressure relief valve opens may cause a distortion in the tank possibly leading to rupture.

It you are looking for any metal substitution the metal directory is a good place to start http://www.key-to-metals.com/

Depending on the service these thanks are for, you can use carbon steel (lot cheaper), fiberglass, concrete etc... but the choice of the coating will make big difference.

Please provide more details so we can make more specific recommendations.

For example if it for a pharmaceutical needs like demineralize water or distilled; any regular epoxy won't do the job especially at 85oC. I have some epoxy coatings able to stand 121oc for demineralized water up to a certain pressure.

If it's for potable water your choice is limited to coating approved under NSF-61.

How big those tanks are? in what kind of environment ( ex: submarine, nuclear power plant, hospital etc)? How long the water stays in the tank? Any mixing or special configuration? Is there any kind of additive or treatment added to the hot water?

Answering these questions will help you out to choose the right material and internal linings.

Don't forget if you go with lining do what we call a Holiday test (ASTM 5162): any pinholes or defects in the coatings/lining and your tank won't last a year!