Material specifying for high pressure

[C4nn1b4L]

I have been looking into some material problem we have in our pumps. We have a few specifications of material possibly for a part we use that can have up to 1500 PSI on it.

The current part is cast c90300 bronze. We have had cracking issues in this part.
We have looked into a competitor part and the material they use is C67300 brass or CS33500, and possibly UNS 34000.

I'm looking into the basics and I'm trying to keep it as simple as possible, what do you look into to know what makes it stronger for high pressure applications. I found that the C90300 has a much lower Tensile and Yield strength rating compared to the two other materials I specified. Is is this something I can use to deterime a new material?

I'm just one of the drafter / designers here at this company and we do not have a engineer at the time for this type of work right now and I'm looking to you guys for help the first time. I have tried to search these fourms and I hope I found the proper location for this.

Some things I've noted on these types of material and found, C67300 is a typically forged type of material or bar round. I could assume that forging could be a big help for strength in the area we have the cracking issues at high pressure. And, is there possibly a casting material that is of course brass / bronze that is strong enough comparable to C67300?

 

[EdStainless]

Do you know what specification you call out for your castings? (ASTM?)
Then look at the spec and see what similar alloys there are and what the strength levels are.
However this is more complicated, you need to also consider:
machinability
wear resistance
corrosion resistance
castability
availability

I would seriously question if strength is your problem. It is more likely to be related to design (wall thickness) or manufacturing (uniform casting properties or defects).

You need a real failure analysis and an engineer to study the situation. (where are you in the world?)

= = = = = = = = = = = = = = = = = = = =
Plymouth Tube

 

[micalbrch]

If the pumpo was rated for 1500 psi and you had cracking issues at it, I wonder what the pump manufacturer says. It sounds as if it was not the pump casing which broke but an internal part of the pump. The cracking has most probably nothing to do with the pressure if the pump is designed for it.

 

[metengr]

If this part is internal to the pump, which it implies in the OP, you need to have a proper failure analysis performed on the existing part material. After this task is completed, you can develop a plan to either change material or design of the part. Right now there is little information to go on.

 

[C4nn1b4L]

Right now I'm assuming the material we are using currently isn't the proper material. The same part, exactly the same(in shape and machine form) but from another manufacture, has a different material specification. I'm only assuming now the reason it is not cracking is because of the different material. I'm trying to find what I can look at in the material composition to compare them with to justify that. This gets me to the one question I asked already:

I'm looking into the basics and I'm trying to keep it as simple as possible, what do you look into to know what makes it stronger for high pressure applications. I found that the C90300 has a much lower Tensile and Yield strength rating compared to the two other materials I specified.

I'm just trying to be able to justify or mention to the managers here we have a problem because of the material call out.

So what would you say about the 3 materials I specified:
c90300 bronze
C67300 brass
uns c33500

I found on the internet that c67300 is more of a bar round material so we would have to possibly forge the part

 

[metengr]

What do you want to be said about the three candidate materials? You are in over your head trying to guess the failure of your original material callout and trying to substitute materials indiscriminately to avoid future failure will get you into trouble fast. First, you need to determine what is needed to be specified, not guess, and not compare. You mentioned you have a part from another pump manufacturer that is identical to your pump and has not had a problem, take a look at it and decide if you can reverse engineer it.

 

[stanweld]

C4nn1b4l,
There is no way to answer your question without knowing the service conditions. Materials selection by pump manufacturer must address total fabricated cost + service condition. Pressure can readily be addressed with thickness calculations. Obviously thicker materials may add to costs; however, those costs can readily be mitigated due to increased fabrication costs if parts are heavily machined from bar stock or forgings.

You do not state whether the cracking problem is service related or manufacturing related. That is why others have recommended a proper failure analysis be performed. If you have recently had problems with cast parts provided by a particular casting supplier, it is highly conceivable that the manufacturer's casting practices are suspect, assuming that similar parts did not experience the same degree of failures or similar parts from other suppliers did not experience premature failures.

 

[redpicker]

I am not familar with the copper alloys. From what I could see from google, the C67300 and C33500 are both generally machined while the C90300 is a casting.

Changing a part from a cast part to a machined part can affect cost.

Material choice can be complicated. You may not know all of the factors that went into the current material choice.

Trying to correct a problem (cracking issues) without knowing the cause is difficult. Is it a corrosion issue? A hardness/tensile strength issue? A ductility issue? A manufacturing issue? Each of these issues will have a different solution, and any of them can have a solution that does not involve changing material.

I understand that you may not be albe to authorize a failure analysis to find the correct answery, but you do have options.

If I was in your position, I would consider taking the failed part to the vendor who supplied the material, and see if they have any suggestions.

rp

 

[IRstuff]

"I'm just trying to be able to justify or mention to the managers here we have a problem because of the material call out. "

How are you to justify this without ANY analysis or failure report? You may find that going to a different material, and burning a bunch of NRE will still result in the same failures because you made unwarranted assumptions.

TTFN
faq731-376

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[MintJulep]

I'm looking into the basics and I'm trying to keep it as simple as possible

Parts fail when the stresses exceed the strength.

The strength of a part is determined by the part geometry and the material properties.

To make a part stronger use a stronger material or use more of the original material.

That's about as simple as things can be kept.

 

[mrfailure]

MintJulep, I wish failure analysis was that simple. Of course, it is the interaction of many factors beyond applied stress that really require a proper failure analysis to determine root cause as recommended above.

 

[C4nn1b4L]

I'm just trying to find out what you would look at in material to determine if it's stronger comparing it to another in regards to high pressure applications.

We have tested our parts and their parts, ours crack sooner then theirs prematurely. This lead to testing the material of theirs, and finding the difference in material they used compared to ours. I more of less want to know the science in material in comparing the strength. Is is the yield/tensile strength together? Can I compare the numbers of one material to the other and say they are stronger and should help reduce the chance of cracking?

I'm just trying to learn the basics in material choices and see if its just simple as that, or does it go down to something else in composition.

Like some of the materials that we inspected seem to have high lead content, does that effect strength? I just don't know and google isn't getting me anyplace.

Thanks

 

[MintJulep]

You are trying to simplify something that is not necessarily simple.

There are many factors to consider when selecting a material for any application. Strength, ductility, corrosion resistance, susceptibility to attack from process chemicals or environment, abrasion resistance, galvanic compatibility with other materials just to name a few.

If your company is interested in doing this right they need to hire an engineer with the appropriate skill set. Providing a full course in materials science is beyond reasonable expectations for a web forum.