IT has obviously gained legitimacy through longevity in their eyes. IT NEVER was a good idea to really on a mechanic device instead of properly sizing the pump and/or using the appropriate components. That's like having a car engine staying rev'd up and engaged and relying on the brake to overcome it. Who would do that - intentionally anyways?
The argument that 20 never previously said you could not do it is a weak basis. The standards seldom say DON"T DO A BAD PRACTICE. The exception is when something starts becoming too prevalent. The standard never said over design then rely on a relief valve. Saying use a relief valve if the pressure is too high is not the same as saying use a relief valve to offset poor design. JUst because many casually did it does not make it a sound design but old habits are hard to kick especially bad habits. The primary reasons that comes to mind have been expressed in other messages. Good suggestion by George to review the ROP/ROC which are available for the last several cycles on the NFPA website. If it is older than what is available their library can send you the info. Roland On Apr 5, 2010, at 12:36 PM, Frans Stoop wrote: > Roland, > > The technicians that I have to communicate with don't take "it's a > very bad thing" for an answer. > They like to know why it is so bad. They even don't take the wording > "shall not be used" as it is in the current NFPA 20 edition as a > sufficient reason not to do it. > > Regarding the past: there was no reference in the 1996 edition of > NFPA 20 about not using the pressure relief valve to limit the > maximum pressure. > Even the Fire Pump Handbook (1998) makes no reference to this issue > in its commentary text. > > The first appearance that I found is in the Appendix of the 1999 > edition where it is called "poor design practice". > > In today's edition the wording "shall not be used" is in the main > text. > My reasoning is that somewhere between 1999 and today the committee > must have had good reasons to decide to change the wording and forbid > the use of the pressure relief valve to limit the pressure. I'm > curious what that reasons could be. > > Regarding dumping the water in the parking lot: The cases I refer to > are mainly industrial plants. The fire water is usually taken from a > large suction tank. The discharge of the pressure relief valve is > piped back to the top of that tank. So nobody is troubled by the > discharge and the water is not wasted. > > The high pressure in the point of operation happens when there are > one or more design areas on a high elevated places (like happens e.g. > in power plants). At the same time there are components on ground > level that are only available in 175 psi design (like dry pendents > and ESFR sprinklers). > There are quite a lot of watersupplies overhere that use the pressure > relief valve for this purpose if a high operating pressure is > required. And what worries me more: even in new installations it > seems still a popular way to limit the pressure. > > However, thank you for sharing your point of view. > > Frans Stoop > TOS architecture & fire protection > Netherlands <[email protected]> > Tel. +31-24-324 0112 > > At 09:42 2-4-2010 -0700, you wrote: _______________________________________________ Sprinklerforum mailing list [email protected] http://fireball.firesprinkler.org/mailman/listinfo/sprinklerforum For Technical Assistance, send an email to: [email protected] To Unsubscribe, send an email to:[email protected] (Put the word unsubscribe in the subject field)
