Material Selection and Allowable Stress for a Threaded Rod

If the tank is <...corroding due to acidic reaction with the chemical inside the tank...> then there is a materials compatibility problem to address. The first thing is to ensure, as far as is reasonably practicable, that the new arrangement is a suitable wet-able material for the wetting agent. Only then does <...allowable stress...> enter the picture. The reason is that, if the tank were to continue to leak, no stress calculation will be of value if the fluid etches away the new bolts (been there, done it, secondhand T-shirt now on an popular internet auction site, etc.).

Talk to a local Process Engineer, first - after all, there is a <...we...> to be used to solve the problem.

Hi. Thank you very much for your response. Assuming I have looked into options to secure it from acid attack, how do I find what is the allowable stress of those threaded rods for such an application?

Oh, any number of sources, though it's really a fundamental question for Mechanical Engineering practitioners that ought to be written already on the inside of the cranium.

The word <...allowable...> infers consent from some source within the business or its insurers, and may be an inappropriate word to use in the current circumstances.

• The end Client may well have standards that cover it, or
• Kempe's Engineers Yearbook, any edition, comes to mind, or
• other machinery handbooks that may well be to hand

as preferred or required.

As this is a temporary fix, for which liability is apparently being taken by the Client and not its business loss prevention insurance provider, approaching that provider for technical support might prove fruitless.

One might also consider the prospect of draining and cleaning the tank, and applying such patching and lining in resistant materials as are needed onto its inside in order to stop the leak. Temporary arrangements with another tank may well be necessary during this event.

One might also consider having multiple tanks so that business is not interrupted by the temporary non-availability of one that is leaking. In providing alternative tanks, the incoming structures need to be selected from alternative wetted materials that will withstand the <...acid...reaction...> described. Many plastics are resistant to acidic fluids, for example, and widely used across many industries. Temperatures and pressures are fundamental to materials selection.

One might also look at process conditions to see whether there have been any changes since the tank was first specified and constructed that may be fundamental to its deterioration. It wouldn't be the first time that the change to a process fluid has had some serious implications that were not thought through at design stage and reviewed for significance at a formal HazOp Study before being invoked.

One might also look at the process to see whether the principle of intensification can be applied: "What you don't have can't leak" - with apologies to the late Dr. Trevor Kletz, a globally-recognised former process safety guru. The function of any tank is to allow the level to go up and down; if that facility is not needed, then get rid of the tank.

Corrosion charts are widely available though, for some reason, rarely used by Mechanical Engineering practitioners.

Thanks. Appreciate your detailed insight!!! :-)

Go to the Mechanical Engineer's Handbook (a very thick book), it has the best detailed analysis of stresses on nuts and bolts-thread stresses, etc.

Hi PAPADOC. Thanks for your reply. Any recommendations which handbook should I buy? I am a junior engineer but eager to learn mechanical concepts.

Get the big fat one. It's called "Mark's Mechanical Engineer's Handbook". I don't know what the cost, but I bet it's over a $100. Borrow one and copy the parts you need. However, there's a cheaper solution. The AISC Handbook has specifications that has a lot of bolt data-allowable loads, etc. It's a lot cheaper and easier. All structural engineers should have a copy of it. It may be on line. If you know a structural engineer, get him to help you.

First, are photos and/or sketches available?

Second, how wide, long, and tall, and of what material, is your rectangular tank made????

Third, what kind, size, etc., is the the joint?

Hi. The tank is 8 ft. deep by 14.5 ft. wide for the pressure calcs that I did. The length is 20 ft. but I did not consider that. The tank has a bolted joint but We are just clamping the tank from outside using threaded rods. It doe not come in contact with existing joint or tank except the tank edges where the rods are secured to the C-channels.

What are the lengths of the Channels?

Maybe this will help:

https://www.google.com/search?client=firefox-b-1-d&q=threaded+rod+tensile+strength+chart

I'm having trouble envisioning how to locate 3 rods for this, and how the C channels are to be positioned.

If the tank is corroding at the joints,it is an indication of much more severe weakness elsewhere.

What you propose is dangerous to say the least.

If an egg had a crack in it,would you clamp the ends back together?

Very similar to your scenario.

Interestingly, the details of the wetted material and the wetting agent have been withheld from the forum, as have fluid temperature and pressure.

Quite so. Good questions.