ANSI Flange Pressure Ratings 7

[regular]

ANSI B16.5 furnishes information on Pressure / Temperature ratings of flanges. The pressures given are for NON-SHOCK values.
I have a pipe run (approx. 400 metres long) that occassionally experiences "hammering" due to rapid closing of a valve.
Would appreciate if anyone can tell how I can obtain / determine the maximum shock pressure values for the 150# A182 SUS 304 Slip On flanges operating at 40 deg.C

 

[arto]

How about put an accumulator on it, than you won't have water hammer?
[i.e.,

http://www.parker.com/frameless/def...&DivID=75&GID=0&Type=2&ID=75&TechID=&PSID=286

];-)

 

[uncleal52]

can you slow the valve down? its better to fix the source of the problem.

 

[jay165]

To echo the last post, I wouldn't subject a slip on flange to ANY kind of shock. It's bad enough for a WN, but much worse for a SO

 

[GenB]

I would not wery of the flange but the bolts, SO- if it was welded correctly it is nothing wrong with it if is within range(you do not give pipe size), some Codes prohibit/limit SO uses to certain sizes.
an accumulator will be the easiest fix.
ER

 

[uncleal52]

If the valve is pneumatic, an orifice would be easiest fix to slow the valve down. Just contact the vendor and see if what you can get. There are slow-acting actuators also if its an on/off solenoid valve...

Why add more equipment to the system with an accumulator?

 

[Montemayor]

I concur strongly with jay165's point. I know from experience that it is the underpinning of this pipe' "hammering" problem. Even with an outside & inside weld bead, the Slip On flange can't compete for strength with a full-penetration, butt-welded, welding neck flange. I don't see any justification to "accept" and live with the stress being imposed on this relatively weak Slip On flange. The source of the hammering should be resolved and cured; I would follow uncleal52's advice and try to ramp the valve stroke in order to dampen the hammering effect - if this is, in fact, the source. This also is the fastest and most expediant method to take most of the stress off this piping run. I suspect this is a "large" (>10") 150# pipe run and the shock force is rather large.

Art Montemayor
Spring, TX

 

[abeltio]

the weakest link is: the gaskets... but we cannot "vote them out of the team".
Dynamic loads will also affect the welds and bolts.
As all the previous postings suggested the proper way to deal with this issue is to solve the root cause, i.e. the hammering.

Also to consider is that as the standards provide values for non-shock pressures... liability and insurance start playing a rol because if anything happens the ruling would be that the equipment was operated outside the allowable range of operation... and may be construed as negligence.

HTH


saludos.
a.

 

[regular]

Guys,

Thanks for the comments and advice.
We are considering following steps viz.
1. Stop the pump at the same time the valve is to be shut.
The timing of stopping needs to be fine tuned as the
pipe run is rather long. This should prevent hammering.
2. The shut off valve is "air to open" and in the event
of air failure, the valve will shut automatically
with the accompanying hammering. To address this
"failure mode" a relief valve will be installed
near the shut off valve so that any surge pressure will
be relieved and this should "damp" down the hammering.
We were thinking of setting the relief pressure for the
relief valve to be as high as the system design allows;
hence this query about the non-shock maximum allowable
pressure for the flanges which is the structurally
weakest link. Leakage through the gaskets as "abeltio"
mentioned is another concern which has to be addressed.

The other alternative is to install an accumulator or pulsation damper as "arto" suggested.
Incidentally, the main pipe run is 12 inch. stepping down to 10 inch then 8 inch at the flow totaliser before going into ships vide a marine loading arm. Shut off valve is downstream of the totaliser (before the loading arm).

 

[MortenA]

A normal RV is not certain to solve your problems. You should also look at anti-surve valves. Try to look at:

http://www.mokveld.com/

for info.

The problem is that the RV maybe wont respond quickly enough.

Best regards

Morten

 

[regular]

Morten A - thanks. The relief valve would be a quick acting type.

 

[Montemayor]

regular:

Morten is absolutely correct. There is no such beast as a "quick acting type" of RV (relief valve). You'll still be waiting for the RV to actuate long after any hammering has leveled your long piping run.

I hope you never experience or witness the violent results of a shattered piping installation. I have, and it's a bitter price to pay. Good luck and safe operations.

Art Montemayor
Spring, TX

 

[bvi]

It depends upon the construction code for the piping system. For example, ASME B31.3 will permit you to go to 1.33 times the pressure rating (you would find in ASME B16.5) for events of short duration.