With 3 pumps, 2 needed and one backup the suction and discharge header should be sized for 2 pumps. 16" pipe would result in a suction velocity of less than 10 fps, I believe that is the recommended limit in NFPA 20. All common pipe subject to the full flow of two pumps should be sized accordingly. Ron F
-----Original Message----- From: Sprinklerforum [mailto:[email protected]] On Behalf Of Travis Mack Sent: Thursday, March 26, 2015 12:25 PM To: [email protected] Subject: Large pumping capacity I am working on a project where there is a fairly large demand. The EOR has determined there are to be (3) 3000 gpm pumps. These are all installed parallel. One of the pumps is to be a backup pump. The design has not been finalized, but the system demand (overhead sprinklers and grate foam nozzles) is somewhere around 6000 gpm. That is why we have two 3000 gpm pumps in parallel to create a 6000 gpm pumping capacity. There were some errors in the EOR pump room design that led to a few other questions. We are getting conflicting information from the EOR and the pump guys. The arrangement is that the pumps share a common suction header and a common discharge header. Per NFPA 20, a 3000 gpm pump needs a 12" discharge. The EOR showed 10" discharge piping and equipment, so this is what flagged some questions with the pump room design. The questions are now: 1 - Should the test header be sized to accommodate a 6000 gpm pump, or a 3000 gpm pump? The pump guy says that the common discharge header must be sized for the combined pumping capacity. The EOR states that it is only based on 1 pump flowing. I seem to agree with the pump guy, in that you need to test with both pumps flowing so you can test your water supply as well to show you can get the full 150% flow from the water supply. It is easy to size the piping so that the recommended velocities in NFPA 20 are not exceeded. It is just a question as to what is the basis. 2 - Should the common discharge header that the pumps tie in to be sized based on 3000 gpm pump or 6000 gpm pump? I believe that the common piping (after the pump discharge valve) only needs to be sized based on hydraulic calculations. 3 - These are diesel pumps. The individual relief valves are tied into a common discharge header. How should this be sized? Based on 3000 or 6000 gpm pumps? We are awaiting input from the authority having jurisdiction as well on this topic. The biggest issue is the pump test header and relief valve discharge piping. There are more issues of now trying to fit 12" valves/pipe/fittings on the discharge side of a pump in a room that was tight to begin with and was designed for 10" discharge equipment. Part of the issue is that NFPA 20 only goes to 5000 gpm tables for sizing pump room piping/equipment. The EOR is stating that the NICET tech is to correct anything in the pump room and provide it per NFPA 20. However, since we have a 6000 gpm total capacity, it is not possible to size things based on the summary table in NFPA 20 if it is to be based on 6000 gpm. I am just interested as to the thoughts of the guys on this forum. -- Travis Mack, SET MFP Design, LLC 2508 E Lodgepole Drive Gilbert, AZ 85298 480-505-9271 fax: 866-430-6107 email:[email protected] http://www.mfpdesign.com https://www.facebook.com/pages/MFP-Design-LLC/92218417692 Send large files to us via: https://www.hightail.com/u/MFPDesign _______________________________________________ Sprinklerforum mailing list [email protected] http://lists.firesprinkler.org/listinfo.cgi/sprinklerforum-firesprinkler.org _______________________________________________ Sprinklerforum mailing list [email protected] http://lists.firesprinkler.org/listinfo.cgi/sprinklerforum-firesprinkler.org
