Techniques for measuring pipeline surge/shock/hammer?

[seasar]

If someone is aware of any techniques used to analyze and measure pipeline shock / surge and guidelines for them, would you please pass them along to me?

The pipeline in question is a 5 mile long force main sewer line (peak pressure 120 psig). The discharge is open ended. The concern is that the line and pumps were designed for much higher sewer flow rates than currently exist. This has caused an issue with pumps cycling on and off as the minimum pump flow is greater than the average sewer flow. There is a surge tank at the suction side of the pumps but they do cycle on /off dozens of times/day. The concern is the sudden shock/surge the pipeline may be experiencing as the pumps start and overcome the checkvalves near them.

I've logged pressure readings during these times and I've only noticed a fluctuation of a few psi during cycling. The calculated pressure drop during full flow is 0.5 psi.
I've read that in order to see a pipeline "shock" or "surge" the instrument must we respond very fast and mine don't (1 second interval).

My gut feel is that this isn't a problem but if it is it would be much cheaper to replace the pumps than broken pipeline segments/vacuum breakers/air reliefs. It would still be upwards of $50K to replace the pumps though, rather not if there isn't any benefit.

Your advice would be greatly appreciated! Thanks!

 

[whammett]

Do you know the specs of the main sewer line?


"I came, I saw, I made it better."
-Ode to Industrial Engineers
Will ChevronTexaco Corp.

 

[IRstuff]

There are MEMS pressure transducers that could probably do the pressure and transient.

TTFN

FAQ731-376

 

[Bribyk]

...Or a piezoelectric sensor and charge amplifier. Look up ballistics or engine cylinder pressure sensors.

 

[BigInch]

If there are no other symptoms you can forget surge here. A few psi fluctuation does not indicate there is a problem with surge. A few psi is even very low for a pump start. If its severe surge, you should see (press gage), or feel, or hear (slamming and shaking pumps and pipe) initially and then another pressure wave about 15 to 20 seconds after pump start too. I would expect to see over a 10% of normal operating pressure increase as a bare minimum before starting to worry about surge conditions. The line is long enough to indicate surge pressure increases with a typical pressure gage.

Any pressure waves, shaking, things happening when you trip the pumps off?

What's the pump horsepower rating, the pipe diameter, pipe material, and flowrate/velocity now and at maximum design flowrate?

There are hydraulic analysis programs that can analyze these things for potential problems. Let me know if you have more interest.


**********************
"Pumping accounts for 20% of the world’s energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies)

http://virtualpipeline.spaces.live.com/

 

[stanier]

You may wish to go to

http://www.pipingdesign.com

and look at the papers there on surge. Also I attached a presentation I have given to ASME, Engineers Australia and IMechE.

 

[seasar]

Thanks for all the responses.

The pipe is 25" sched 20 ductile iron. No shaking or
otherwise violent/noticeable symptons after startup/shutdown.

 

[whammett]

I think you have nothing to worry about. As BigInch has previously stated, It would be a lot more noticable than a few psi change in a short interval.

"I came, I saw, I made it better."
-Ode to Industrial Engineers
Will ChevronTexaco Corp.

 

[cvg]

assuming your forcemain and pump system were designed for the pumps that are currently installed, it should have been analyzed and designed for the potential surge pressures. Just because the pumps are cycling more frequently does not increase the amount of surge in your line. If you are concerned that the designer did not do the proper surge analysis and design, than either ask them for the design report or do a surge analysis yourself. It will probably be quicker and cheaper and provide a better comfort level than installing complex, high speed pressure sensors.

 

[seasar]

Instead of doing it myself, with equipment and expertise I don't have, are their experts in this field that could be hired? Can someone point me in the right direction regarding them?

The original company that did the design did a surge analysis and it may still be fine. This company's resources/reputation have gone down a fair bit in the nearly ten years since the design was completed.

I'd like the defacto, industry expert, goto person/company for this kind of thing to have a look. Do they exist? I think high pressure sewer lines are a bit of a rarity but I imagine this kind of installation exists in the petroleum industry with much higher design requirements....can't have vacuum breakers/air reliefs spewing oil everytime there is a problem.

 

[dicksewerrat]

You should call the pump manufacturer with all the data you have on the pumps, hp , impeller size and number, etc. they may be able to get you a lower capacity impeller for your pump. That would be a cheaper fix. More like a maintenance operation. Have you seen any pipe breaks on this line?

Richard A. Cornelius, P.E.

http://WWW.amlinereast.com

 

[cvg]

before you spend any money installing sensors or modifying pumps, hire a consultant to do an analysis. It's not difficult and is done all the time. There are many experts out there at many companies. Unfortunately, limitations of this forum do not allow me to give you any names (see below, no promoting, selling or recruiting...) and besides it would depend on your location in the world - you should hire a local consultant to do it.