DIY air manifold for fill station

[phantomrfa]

Hello,I was hoping that someone could help with a little problem i have?.I have been looking on the internet and found lots of usefull parts but they are mostly NTP threads((U.S)) standard .To make my life easy i need BSP .I have found the part i like but itis ntp so i am think of getting it made here in the U.K. the grade of metal is the problem what to use , is this grade going to work at 4500 psi 6082 T6 (HE30)

 

[fppf]

Why go through all that work, just use a few Tee's and some check valves.
Or just get some adapter fittings?

Most of the manafold blocks have check valves internal, do you have all the parts and dimensions to duplicate those?

Without knowing the exact material and heat treat you would need to do an FEA on the part. This would include all wall thinkness, threads, and fatiuge stresses.

 

[Jimmer]

I agree, it would likely be much easier to order the manifold block and NPT to BSP adaptors.

 

[pescador775]

6061-T6 will work. HE30 is kind of old hat. I don't see any problem machining a simple job like that but ask the supplier to verify that the metal is actually 6061-T6. That should be easy as it is such a common alloy. Add some check valves somewhere if you like. Some people are paranoid about back flow and other issues like CO. IMO, the CO detector or heart rate monitor make for bragging rights but probably useless to a small operation. However, if cousin Verne has access to the machine the check valve might be a good idea. The check valve is a ball bearing and spring. Drill the outlet ports deeper than normal (past the thread) and drop in the parts. Use a hollow type steel British fitting and part of the spring can just slide inside the fitting. BTW, a check valve on the coalescer is another thing. It can prevent simultaneous draining of the final filter. Not a bad idea.

You really ought to join that Yahoo group. Every time you post here somebody is going to say "don't do that". Over there, if you hear that you know to just stop what you are doing. Chances are they will be able to describe a better way.

 

[iain/hsm]

In the UK, BSP (taper) and BSPP (parallel) threads are normally used in low pressure compressors and in hydraulic fittings, however unless they are marked with a makers name etc you cant tell them apart. They are cheap. Typically low pressure 150psi (10barg) fittings are in brass and high pressure 3000psi (207barg) in plated steel. Fittings in steel are used typically for hydraulic applications and have a 3:1 safety factor.

NPT on the other hand is also quite common in the UK, but is used more in offshore diving applications and in high pressure gas and high pressure pipe line work.
Typical NPT thread fittings from the likes of Parker or Swagelok etc have a 4:1 safety factor and are typically supplied in stainless steel. They are also marked with a name, batch codes and part numbers for true traceability of a pressure assured fitting.

IMHO I would also not fit steel male fittings to an aluminium part, when the plating wears off, corrosion will ruin your aluminium threads. Stainless fittings would be better.

In UK a 5 port manifold block (1/4NPT female outlets) 5000 psi (350 barg rated) as your photo the retail cost is £50 plus £2.80 p&p.

 

[pescador775]

Plated steel should be as strong or stronger than stainless. However, some BSP fittings are maleable iron. I've never had a problem with stuck pipe fittings but it is a good idea to use teflon paste on the smaller pipe threads for obvious reasons(to me). This is especially true with stainless fittings which will gall and jam in some materials. The paste takes care of that and also silicone grease. I would get the 3000 psi pipe nipples/tube fittings because the male body is likely to be hollow. I discussed the reasons already but the idea would have to be tested.

These folks sell BSP stuff. Interesting:
British Standard Pipe, Parallel (BSPP) Hydraulic Fittings

 

[fppf]

All fittings in an air system should be stainless. Air before filtering will be soaked with water. Hydraulic fittings are made to handle oil, not water. Rust can lead to contamination issues and in the long term possible failers.

Gulling of threads is due to like material strengths. Most people don't reliaze that 300 series stainless's and 6000 series aluminums have simular strength. This should be taken into account when designing thread interfaces.

I would really suggest staying away from custom high pressure parts unless you have knowledge in high pressure design. You also need to properly test items made for material and machining defects. Its not as easy as buying a block of material and hogging it out.

 

[pescador775]

fppf, you don't know what you are talking about. 304 stainless is quite a bit stronger (tensile) and harder than aluminum, especially 6061 T6. I already mentioned that plated fittings are fine for compressed air. All major compressor manufacturers use the stuff without problems. Carbon steel is no good for fabricating coalescers but plated fittings are OK. After many years, steel fittings will show a little rust but so what? You actually think that something would get clogged up? Maybe you are forgetting that the fittings that Jimmer plans to install come after the final filter. I have nothing against stainless, in fact I like it, but let's not exaggerate the advantages and downplay the disadvantages, like cost, galvanic corrosion and galling of pipe threads. "Staying away" from custom HP parts is a ridiculous and condescending remark. Prepostrous to say that to Jimmer, a degreed engineer.

 

[fppf]

Humm, well I work in aerospace with spacecraft engine control valves, aircraft acutators, and a lot of other stuff. I work with real high pressure systems, like 100,000 PSI hydrualics and 20,000 PSI gas systems. But yeah I don't have a clue, no problem.

And yes, if you read the whole post, someone without background and knowledge should not in anyway design, build, and test custom high pressure stuff. It can kill you before you blink an eye.

Oh and to quote Jimmer in this thread I beleive he agreed with my first post....
"I agree, it would likely be much easier to order the manifold block and NPT to BSP adaptors."

 

[Jimmer]

Well to clarify my position here. Yes I do agree with Pesky, that a manifold block is hardly the most difficult engineering challenge on the planet to sort out. Having said that I still feel that in the OP's case, as a lighting engineer, who (I presume) lacks the background in materials and design, buying a commercially available unit, and the associated adaptors would be the easier option. Even if he did go ahead and have one machined out of 6061-T6, I still think the other inconveniences such as getting certified material and not some scrap taking up space in the machine shop, anodizing or some other form of surface finish for the bare machined aluminum, is a bit more of a PITA than I feel necessary for something that can I solved easily with the use of the correct adaptors.