Mche: I'm going to assume you are a Chemical Engineer. As such, then, I also presume you are talking about Process design - as opposed to mechanical design. This is important to distinguish because H2 makes a big differnce in the mechanical design and very little difference in the process design.
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For Process Design, you basically design a Hydrogen pipeline just as you would any other gas. The fundamental and basic guideline to all gas lines is the allowable (or design) pressure drop.
Normally that is the key (& oftentimes) the optimum design level to base your calculations on. If you were questioned for basis, state your scope of work - which you should have generated before any attempts to resolve the problem(s). Use the recognized velocities as they obviously will drop out when you design around the allowable pressure drop.
You have to stay sub-sonic in velocity, so that gives you an automatic ceiling value to design from. Always resort to recognized, acceptable standards such as the NORSOK process standards. Norsok recommends that in lines where pressure drop is not crtical, gas velocity should not exceed limits that may create noise or vibration problems. A rule-of-thumb velocity is given as: V = 175 (1/Den)^0.43 where, V = Max velocity to avoid noise, m/s Den = gas density, kg/m^3 Norsok also lists recommended velocities if you lack these. To download their complete process design standards, go to: I hope this helps. Art Montemayor Spring, TX RE: Hydrogen service lines (Chemical). Montemayor, You guessed it correctly, I needed answer from Process Design point of view which I got from above.
Pirates 2 Stagnettis Revenge Movie Free Online. However I am curious about impact of hydrogen on mechanical design also. Is there anything additional, that Process Engineer can do than mentioning presence of Hydrogen and its concentration in the service? (for material selection and fabrication procedure control?) Could you please suggest some readings as to know why 'H2 makes a big differnce in the mechanical design' and are there any guidelines, when it should be higlighted to Mechanical design?
Preferably on internet or Codes. Thanks RE: Hydrogen service lines (Chemical) 13 Apr 04 23:58. Mche: As we both know, Hydrogen is the smallest molecule in the Cosmos. It will literally permeate through anything, if given enough time to do so. It goes through steel pipe walls and if you have ever operated and maintained a Hydrogen system, you will have experienced the fact that when you D&R (Demolish & Remove) old carbon steel Hydrogen piping, you cannot go in and burn out the pipe without first allowing the H2 soaked into the walls to evaporate out.
Introduction To Mythology Thury Ebook Readers here. If you don't, the pipe seems to 'catch fire' when the cutting torch heats it up. Hydrogen also has a negative effect on steel that is titled 'embrittlement' - a process that weakens the parent metal to the point of failure.
The higher the temperature and pressure of the H2, the more pronounced are the negative effects. I don't have my materials library here handy at the moment but I recall that we were using a chrome-steel alloy on piping for H2 service back in 1970. There may be other aspects to H2 materials of construction that you should bear in mind, but those two particularly come to mind. I personally have always butt-welded all my H2 piping, reducing the quantity of flanges or possible leaks down to zero - if possible. If you have ever seen (it would have to be at night) a self-ignited H2 leak through a flange gasket, you will wind up doing the same.
Hydrogen will always leak -to begin with- and what's worse is that the stuff has a negative Joule-Thomson value: it heats up when it expands. It also self-ignites with the expansion friction created and the leak catches fire. The way we found most H2 leaks in Steam Reformer units and Hydrogenation plants was to walk out at night and keep an eye out for the bright, whitish flame that H2 gives. You can't see it in the daytime and, in fact, we had an operator severly burned by walking on a catwalk besides a Hydrogen line where there was a leaking flange. He never saw the flame as he walked by and had his arm burned just as if it had been a cutting torch.