Certification of Full Pressure Ram

The rules say,

"Custom made components, or parts operating above the suppliers maximum working pressure, must beindependently tested and certified at 120% of the maximum system pressure available at that point."

Please can someone tell me of a person/organisation who can provide this service. I have a full CO₂ pressure ram that needs certifying. I also need to know the pressure to which it needs testing. As I will have a 1000psig bursting disc, this would seem to be a sensible test pressure. It is also about 120% of the likely maximum system pressure. I am happy to be guided by others.

Is it the steel 100*140 you got a few years back?

Wow! You've got a good memory. It was made for me by Mario deJongh about 10 years ago.

That ram was build to cope with 105 bar/4500psi hydraulic, static pressure.

Thanks for that information. I guess that I need a piece of paper to say that. I really don't know what proof is required of me by those inspecting my robot.

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Originally Posted by JeremyCuss

Wow! You've got a good memory. It was made for me by Mario deJongh about 10 years ago.

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You're talking to Mario (maddox) :rofl: As for certification, I don't know if anybody certifies custom components....for sure it will be difficult to find someone who would risk testing an unknown component and giving it a certificate unless they are really confident the component is well made etc...

I guessed that it must be Mario. No-one else would know the dimensions of my ram. There must be other roboteers running full-pressure rams. Perhaps they could tell me whether they had any problems or need for certification.

My certification capability evaporated with the change of job earlier this year.

HPAC (http://hpac-armourlite.co.uk) might be able to help you with pressure certifications. They're running a little slow at the moment because Trev's in hospital, but they've certified some of my old pressure components to 300 bar before.

Thank you Robert. That is an excellent solution to my problem. I have rung them. They will test it next week and can do it while I wait. They will provide a certificate. What is more they only charge £40 and obviously have done quite a few rams for Robot Wars in the past!

Quote:

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Originally Posted by JeremyCuss

Thank you Robert. That is an excellent solution to my problem. I have rung them. They will test it next week and can do it while I wait. They will provide a certificate. What is more they only charge £40 and obviously have done quite a few rams for Robot Wars in the past!

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Great to hear! Yes, HPAC have been around for a while. Very nice bunch of guys - if Trev's there, ask him about his lawnmower tank! (I know him from tournament paintball)

Hi Jeremy, did your ram get certified in the end? Trev mentioned Robot Wars parts but I didn't catch him before he went off again

No, the ram didn't get certified. The valves were pressure tested successfully up to 90 bar, but the ram leaked very badly around the seal. I am planning to replace the seal, but I haven't done so yet, because of a series of problems, which I am overcoming one at a time. I will then bring it back to HPAC for testing.

That's a shame. O ring sealing is never fun, and rarely right on the first or second try.

What pressure are you trying to seal? I'm alright with reciprocating O Ring glands

I'm trying to seal full CO2 pressure - maybe 60barg. I'm interested in the reciprocating O ring glands that you mention. They sound like the sort of O rings used in my old 16 barg Norgren pneumatic cylinder. They were made with very soft elastomer and appeared to have a lip to seal the pressure. This old cylinder had two seals, but I only need one, as the pressure is at one side of the ram only. I have no idea where to get such seals, nor what the best material of construction would be. Any help would be appreciated.

That ram was made back in 2004.... I can imagine the oring on the piston not being all that happy with 13 years of idleness.

Does the rod/piston move smoothly?

Quite so, Mario. There is no criticism from me of your work. I need to replace the O ring because it is old and does not allow the ram to be pressurised. I may look at other designs of O ring, which may make a better seal.

The ram doesn't move smoothly. The problem is not the O ring seal, but the piston catching on the plastic (nylon?) seal which is inserted in the top plate of the ram. I have sanded and smoothed the ram and the plastic seal to improve the movement and will do some more to allow the ram to move freely.

The only reasons I can imagine why the nylon bushing would case "tightness" are the 2% moisture retainment and swelling it can cause or disalignment.

In the worst case, send it back, and I'll rebuild it.
But I cannot certify it anymore. That capacity went when I changed jobs earlier this year.

Jeremy, it sounds like you have yourself an excellent solution.

However, if you're still interested, this here is the O Ring Bible: https://www.parker.com/literature/OR...g_Handbook.pdf

Ingest all of that and you'll have an ok understanding of all the seals involved. Personally, I tend to run a bit more stretch on the O rings I use (a more shallow groove), but that's because I come from paintball pneumatics, where you're on the edge of a good seal and really low friction. For 60+ bar use, stick to the handbook and you shouldn't go too wrong.

I have now got a new O ring for the ram which is 5.3mm instead of 5mm diameter. The O ring fits the piston beautifully and the ram fits into the cylinder OK. It is of course much more rubbery than the old O ring. We will see how it seals. The advice the I received from the hydraulics supplier was that an O ring will probably seal better that a U ring as the ring slot in the piston was not designed for that type of seal. I will take their word for it.
I have also sanded enough from the nylon bushing to allow the ram to travel freely. I am making progress.

Today the ram with the new seal has been tested and certified at 90barg. Hurrah! There was a small leak of water past the O ring, but nothing of any consequence. I have now got a ram which meets FRA and Robot Wars rules for custom-built components when used with full-pressure CO2. I ended up going to a local firm, Hebble Hydraulics, for the pressure test on the ram. This was a lot easier than going back to the West Midlands. The cost of £40 was the same as I was charged by HPAC.

Good to hear. After 13 years of idleness that ram finaly can fullfill its destiny.