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pipespec for methylamines

pipespec for methylamines

pipespec for methylamines

(OP)
There are many professionals out there, does anybody know anything about methylamines?
I work since a few months with a company that produces methylamines (monomethylamine, dimethylamine, trimethylamine etc.)and I don't thrust their pipespecs.
des. temp. 230 deg C, des. press. 20 barg.
What valves and what material should be used.
What pipesched., what connections?

greetings, a guy from Europe

RE: pipespec for methylamines

20 barg is not too serious a pressure concern, provided you there is a little bit of wall thickness there.  Flange ratings will generally amount to a topped out ANSI#300 or a very under-designed ANSI#600 Flange rating.

http://virtualpipeline.spaces.msn.com

RE: pipespec for methylamines

(OP)
Big Inch,
That´s not my concern, but the fluid/gas seems to be very volatile and smells a lot.
The spec is ss316L, I think that´s good.
But they use buttweld bellowsealed globevalves as a first choice, they couldn´t explain why.
What should it be?
Everywhere are leakrepairs on the valves and the seats are wearing very fast.
I suggested flanged bellowsealed gatevalves but they won´t listen to me.
Am I wrong?
(i´m just a contractor)

Thanks for your reply

RE: pipespec for methylamines

Well yes, amines stink like hell... so much that it is difficult to avoid the smell, even with very good valves.  I wouldn't use flanges, given a choice, anywhere that leaks are critical, but it does make change out and repair easier.

It sounds like the globe valves are not holding up, perhaps due to improper seat material, or is it from high velocity?  Are they control valves or on/off?  If for control purposes, that may explain why they use globes and why substituting gates or balls would probably not be a good idea.  If that is the case, other material, antiflash trim, or simply larger valves may be the solution.

Too many unknowns to suggest a solution, but perhaps it could be possible to use weld-end top entry valves, if they are in on/off service.



http://virtualpipeline.spaces.msn.com

RE: pipespec for methylamines


Hello europipe,

What are your actual pipe and valvesizes?
Seat and stem sealing material (seat metal to metal or other)? How does the fluid behave when colder (sticking, gluing, abrasive), and does a colder temperature occur sometimes during process or at regular stops? Are the pipelines cleaned out and washed (CIP) with other fluids/temperatures and pressures?

Disregarding answer to above, if smaller size valves are used, then y-type globevalves sometimes have a longer and better protected and sealed stem than normal globe - valves, less force 90 degree on stem (?), and more often stem scraper incerts protecting part of stem to enter stem sealing area.

If abrasive or gluing, sticking  and drying fluid anywhere (or when) in the process, globe valves would in general be the best choice, preferably with metal to metal seat.

If high maintenance cost and often occuring leakage, you could even for on/off duty check if a regulating type of globevalve could give a better economy over lifetime.

I am thinking about a construction for instance with globe part slotted, open ended cylinder form and protected (innerside of cylinder) metal seat, or similar constructions.

RE: pipespec for methylamines

(OP)
Globe valves are their only valve choice in the specs
in 95% of the cases on/off usage.
They are wearing very fast (also the hardseat type), most likely because of the high velocity.
Why should you use valves with such a low Cv-value?
Uhhm...I´m contractor of piping eng. work.

RE: pipespec for methylamines

(OP)
Gerhard,

pipesizes up to approx 4"
not sticky stuff, volatile medium, boiling point average 0 degC, saets metal to metal(des temp 230degC)
not very cold temps no flashing.
there are also y-type valves but they wear even fast
washing out by water and dried by nitrogen.
Why should you use globevalves?

greetings

RE: pipespec for methylamines

If no control is required other than on/off, I can't see from here why it is necessary to use globes at all.  Use of full port valves wherever possible (on/off service) would probably reduce velocities to accepatble levels ... at least if the velocities are suitable to the 4" piping at this time.



http://virtualpipeline.spaces.msn.com

RE: pipespec for methylamines



europipe,

OK! So this seems to give no other cause for the wear than high velocity? If so, I agree with full port solution.

But what are the high velocity - typical at nominal pipe-size?

RE: pipespec for methylamines

(OP)
Gerhard,
I´m really not a process engineer but I think the max velocity is about 3 m/s, that is I think normal for a pipe,
but in a globe valve with it´s constuction?
I think the valves also causes the pump startup problems they have, is that possible?

RE: pipespec for methylamines

Pump startup problems? As shutterings or noises and waterhammer-behaviour of the pipeline?

3 m/s is normal both for pipe and for any valve, including a globe-valve, if else adapted for the temperature, pressure class and medium, (and fluid viscosity - and non abrasive fluids or particles at any time, including cleaning) and should in itself not cause wearing problems.

If yes for the latter, the problem could be caused by the former.

Only speculating but: If hammering /shutterings problems could be lay-out of pipeline and/or oversized or type of check valves. What about two-phase (gas and fluid phase) in pipeline, or (perhaps most probably?) nitrogen residues giving 'non evacuated air pillows - compressible' acting as 'springs' when you start pumping fluids (???)

Cleaning with water at what pipeline and water temerature (chock -chilling)?. No particles (non-abrasive) when cleaning and drying?

RE: pipespec for methylamines

(OP)
When the velocity is 3 in the pipe, isn´t the velocity in the valve higher?

Different pumpproblems: some pumps are turning backwards,
isn´t that funny.
It´s a great company for a laugh here.

RE: pipespec for methylamines

(OP)
Thanks guys,

I was not sure but you confirmed what I thought

Greetings & Nice holidays

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