ESDV Closure Times to Prevent Surge
ESDV Closure Times to Prevent Surge
(OP)
Hello all,
I'm currently completing a study whereby I'm looking to rule out the possibility of surge occurring in certain systems. The valves in question are ESDVs on large bore lines (24") and I have the data sheets which specify achieved closure times of 25s. The pressure originates from a set of high pressure pumps upstream which are designed to stop on high pressure.
To me this looks like a no brainer as I can't imagine a pumped system being at risk of surge with valve closure times of 25s, however, I am looking for a rule of thumb to use in my explanation. Are there any rules of thumb for screening for surge issues based maybe on closure time, flowrate and line size/valve trim size for instance? It is not necessary for this work to do any Joukowski or other such surge calculations all I require is a quick rule of thumb.
Thanks in Advance
I'm currently completing a study whereby I'm looking to rule out the possibility of surge occurring in certain systems. The valves in question are ESDVs on large bore lines (24") and I have the data sheets which specify achieved closure times of 25s. The pressure originates from a set of high pressure pumps upstream which are designed to stop on high pressure.
To me this looks like a no brainer as I can't imagine a pumped system being at risk of surge with valve closure times of 25s, however, I am looking for a rule of thumb to use in my explanation. Are there any rules of thumb for screening for surge issues based maybe on closure time, flowrate and line size/valve trim size for instance? It is not necessary for this work to do any Joukowski or other such surge calculations all I require is a quick rule of thumb.
Thanks in Advance





RE: ESDV Closure Times to Prevent Surge
Richard A. Cornelius, P.E.
WWW.amlinereast.com
RE: ESDV Closure Times to Prevent Surge
The other key factor is length of pipeline between the valves and the pumps - "upstream" could be 10m or 100km. Again anything much past about 20km is often far enough to attenuate any surge, but it is difficult to judge with no real information.
Pump run down time, how much pressure you have between pump shut off head and design pressure, the fluid being pumped, it's bulk modulus all have an impact on surge pressures.
given that most ESd valves are ball valves and that most of the closure effect is in the last 20% (5 seconds) I can easily imagine a very significant surge from this, but with no data provided it's impossible to comment further.
My motto: Learn something new every day
Also: There's usually a good reason why everyone does it that way
RE: ESDV Closure Times to Prevent Surge
you must get smarter than the software you're using.
RE: ESDV Closure Times to Prevent Surge
A rule of thumb is normally used and in most cases will lead to an acceptable rersult is: "one second per one inch valve size"; then with lack of adequate info and as a quick estimation if the valve size is same as the line, 25 seconds closing time for a 24" valve size could be reasonable...
RE: ESDV Closure Times to Prevent Surge
you must get smarter than the software you're using.
RE: ESDV Closure Times to Prevent Surge
Best Regards,
PR
RE: ESDV Closure Times to Prevent Surge
RE: ESDV Closure Times to Prevent Surge
Unfortunately your idea that you can find "I just need a reference to back up what I say" is not going to be easy as each system needs to be looked at on its own and the consequences of getting it wrong are too high for anyone to say in general this isn't a problem. How your pumps start stop and how your system is configured and designed all has an impact. If the pumps keep running or take a long time to slow down then you could easily get surge issues, whether form high pressure or having the LPG vaporise on you then collapse again - Now that can generate some big spiking pressures...
BTW do you mean ANSI class 900 or 900 psi rated? This appears to have no relationship to the discharge pressure of the pumps.
Can you describe a bit more what this study is for "screening exercise for vibrational fatigue due to surge using the EI guideline" I have difficulty believing that surge events contribute any significant part of a vibration study.
My motto: Learn something new every day
Also: There's usually a good reason why everyone does it that way
RE: ESDV Closure Times to Prevent Surge
you must get smarter than the software you're using.
RE: ESDV Closure Times to Prevent Surge
As for the rule of thumb, I would think that if you keep the closure time somewhat longer than the time it takes a pressure wave to travel through the fluid twice the length of the pipe involved, the closure is no longer "rapid" and the surge or hammer is quantifiable but often tolerable.
RE: ESDV Closure Times to Prevent Surge
BigInch, thank you, I'll have a read of those sources, much appreciated as always.
RE: ESDV Closure Times to Prevent Surge
a) drip feeding information,
b) making errors,
c) accusing people of not knowing what they're talking about without any information
d) clearly looking for free information to complete a paid for task
e) Not reading posts properly or answering perfectly reasonable questions
My point, not that you seem to recognise it, was that if you're worried about vibrational analysis from what should be a very rare event (ESD trips are not normal) then it seemed unlikely to contribute to what is normally a long term issue, but instead of trying to address the point you simply dismiss the notion as not worth replying to or providing any further information.
If your ESD trip is guaranteed to stop the pumps and I mean stop rotating, before the valves have got even half way closed you might be correct, but without looking at the whole of the system and not simply a 20 m section of pipe from pumps to the valves I don't believe it is possible to simply rule out the possibility of surge without doing at least some basic transient runs. That's my opinion - take it or leave it, but please don't insult my knowledge or experience or anyone else who bothers to reply - it won't get you many friends on this site.
My motto: Learn something new every day
Also: There's usually a good reason why everyone does it that way
RE: ESDV Closure Times to Prevent Surge
Closure time on a pipeline of any appreciable length is almost always shorter than the 2x sonic travel time down a pipeline to the initiating valve, although sometimes you do find remote controlled, relatively fast acting valves at intermediate locations. Lesser reflections are also bounced back from reducers, bends, control valves, orifices and other incomplete flow obstructions (which are proportional to the reduction of flow area). As well as the worst problem typically comes on surges created between pump and the ESD of a discharge isolation valve. Those distances are extremely short (at sonic velocities) so there are usually 4 or 5 wave reflections generated in quick sequence before most of the energy is dissipated. When a valve closes there is a positive pressure generated on the upstream side and a simultaneous negative pressure wave initiated on the downstream side. Each reflection is (very roughly) 1/2 the energy of the previous wave in most engineering systems, but it does depend on energy dissipation due to pipe friction effects at the surge velocities.
you must get smarter than the software you're using.
RE: ESDV Closure Times to Prevent Surge