×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Water Hammer
5

Water Hammer

Water Hammer

(OP)
We have a sludge piping system that vibrates and moves  due to what appears to be water hammer (in this case sludge). As a structural engineer the first thing I can think of is to restrain the piping at all changes of direction.

1. Does any one see any problems with this approach?
2. Is there any literature available?
    
Thank you

RE: Water Hammer

While your approach is logical, it treats the symptoms, while doing nothing for the disease.  Additionally, every guide, restraint or anchor you add to the pipe potentially increases the stresses in the pipe.  Flexibility is the key to low pipe stresses, but that obviously would do little for the movement you have observed.

Controlling hydraulic surges is best initially approached by slowing down the changes in velocity of the fluids within the pipe.  Slow down either the maximum fluid velocity or at least try slowing down any valve opening and closing times.

A surge analysis can be done on your piping system to determine the optimum method to reduce surging if the above does not work.  Surge tanks or some other relief type system might be in order, but that is still a bit premature to say.  Try the above first.

BigInchworm-born in the trenches.
http://virtualpipeline.spaces.msn.com

RE: Water Hammer

I was just curious what are the flow velocities, material type(s)/joints, and support system of the piping involved?  

RE: Water Hammer

There are a couple of other fixes  besides stiffening at elbows, including:
a) dampers, similar to those used in seismic restraint, allow thermal growth or differential settlement while restraining surges.
b)the pump rotor can be replaced with one that has more vanes - we this problem with a 3 vane rotor, and are now replacing it with a 5 vane rotor.
c) air or N2 filled bladder installed near the pump discharge in a tee fitting- dampens pressure surges, which may dampen slurry momentum surges.

RE: Water Hammer

(OP)
Sludge is pumpoed at relative low velocities, DI pipe, Flamged & Victaulic Mixed, Standard Support System

RE: Water Hammer

Is the sludge pumped with a positive displacement pump?  Is it a single piston, duplex, or triplex?  If yes to any of the above, let me know and I can post a link that describes the problem mathematically.  Davefitz’s item “c” may be the solution provided the accumulator is sized properly.  

RE: Water Hammer

(OP)
Yes it is. Single Piston

RE: Water Hammer

If the observed movements are not caused by pump starts, shutdowns or valve openings and closings, are continuous at some multiple of pump rpm, its not "surge", but rather pulsation coming from the pump.  Chose your solution accordingly.

BigInchworm-born in the trenches.
http://virtualpipeline.spaces.msn.com

RE: Water Hammer

I would suspect all-flanged joints would likely be some more rigid/stiff than grooved joints in general, and perhaps also "rigid" grooving detail for the latter type joints is probably (you guessed it) at least some more "rigid" than flexible grooving detail for grooved joints.  If there are not supports there now, I wonder if the addition of some more supports or tie-downs particularly very near any unsupported grooved joints might minimize whatever it is you are experiencing?  Are there pumps also adjacent this piping, and if so could how are they connected be a factor as well?  

RE: Water Hammer

Is inproper, type, sizing and reaction time of check valves ruled out as cause of the vibration? If check valves are installed in the system this may well be the cause for violent vibrations by start up and closing.

Types of valves, sizes, layout and flow conditions needed for further advice.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources