×
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

Fire Pumps and Overpressure

Fire Pumps and Overpressure

Fire Pumps and Overpressure

(OP)
  We have building with several double interlock preaction systems all served by one common riser.  This system is boosted by an electric fire pump complete with a pressure relief valve set at 170 psi.
  The problem we are having is to do with system overpressure at pump start up.  When the pump starts it provides a "bump" on the system raising the system pressure above the check valve to approx. 245 psi.  Conversations with relif valve manufacturers indicate that these valves do take a second or two to open.

  My question is:  How can we contain the initial bump without modifying the pump.  My initial thoughts are some type of retard chamber, however I am not familiar with these with such a pressure bump.  Any ideas?

RE: Fire Pumps and Overpressure

First, find the engineer who designed this and slap him for over-sizing the pump then quick-fixing it with a pressure relief valve. NFPA 20 is quite clear that this practice is not acceptable.

There are surge suppressers available for this type of application. I don't know of a mfg off hand, but I do have a picture of one and will be glad to send it to you. Let me know.

RE: Fire Pumps and Overpressure

(OP)
Pics would be nice and a great place to start, tks.

RE: Fire Pumps and Overpressure

what is your email address?

J. Scott Mitchell
Fire Protection Engineer

RE: Fire Pumps and Overpressure

A late post, but the two manufactures I know of are Greer and Young Engineering.  These companies have UL listed equipment.  They are very pricey.  Other companies make ASTM compliant tanks.

I agree with Scott, the original designer screwed up big time.  I recently worked on a project very similar.  The only solution other than replacing the pump that I know of is to add a pressure-reducing valve.  I personally think it is a poor solution but have seen other people use them.  Then in addition to the pressure-reducing valve they installed a couple surge tanks.

Good Luck.

RE: Fire Pumps and Overpressure

Hi everyone.

Is this a combined sprinkler and standpipe system? If so how about pressure reducing valves at sprinkler system connections?

RE: Fire Pumps and Overpressure

Hi,

I heard they sometimes solve this problem wit a jaw-way valve (don't know if I spell it correctly) . This is a valve with a quick response time, to relief the pressure in the system.

This bump could also be the result of water hammering. Check literature how to prevent this from hapening.

bye

RE: Fire Pumps and Overpressure

What pressures does the fire pump come on and what pressure does the jockey pump come on at? If the fire pump is coming on at a too low pressure, it will cause a water hammer. NFPA 20, 2003 sectionA14.2.7 indicated a 10 psi difference between the jockey start and fire pump. I see many pumps where the difference is sometimes 100 psi ( client does not want the fire pump to come on!). I have also have found pumps were the set point for the fire pump is below the incoming city pressure. This is not good either.

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