The control is not too complex- imagine the pilot operator of a cla val prv, instead of adjusting the diaphragm of the PRV it adjusts the driver rpm. Yes, it would be nice to have a 2-stage start, first to the managable rpm , then continuing after a few seconds- like a reduced voltage elec?
I guess this "unnecessarily" complicated something that needs to remain simple. It could also, in a design requiring immediate full pressure such as those with critical water delivery requirements, rob you off the needed oomph to get your water thru the feed main ASAP. The Quell systems we're feeding with the twin 2,000 @ 150's need to have the heads up to operating pressure in 25 seconds from first head activation, and that's PDQ- every second counts. Must have remote start off detection, for example, you can't lose 5 seconds for pressure drop and diesel startup. And I don't want to think how much the 2-stage start would complicate FDT calculations (sorry Mike M!). This situation only arose due to concerns on the UG, on other installations the grid relief valves around an ESFR warehouse bleed off the excess. Once you get past the first couple calls from the customer that the grid PRVs are dripping, and they understand that's normal, we've not had a problem except one clogged 1/2" PRV. We didn't want to install cla-val 55L's on each riser ($) if we didn't need to, that's a couple grand on even a small warehouse (this one is 400k SF) vrs $250 for 10 of the little Watts (we use the higher pressure ones). Tom, we're amongst the few that wake up to Jay Leno instead of falling asleep to him:) Go Penn State! glc -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Tom Duross Sent: Thursday, September 20, 2007 6:00 AM To: [email protected] Subject: RE: PLD and PRV I would blast-out Clarke if it was me, why can't it start at a manageable RPM and ramp up after? It's all in the controls. I guess they're not so magic after all. Can you imagine putting a Cla-Val after? Talk about embarrassing! This is my only morning to sleep in G, 4 AM test yesterday and tomorrow and Saturday. I don't usually wake up as early as you do George. Todd, check out Clarke's website and then talk to George (both of them, MA George and also PA George). GRS I'd considered a surge bladder for this, but do't have any field experience with them. May have to wait for the 8-5'ers to get to the office.....I've only used bladderes on AF loops. Did talk to Clarke, they thought either would work (bladder or PRV). I think the main criteria may be operating speed, in which the bladder would win. Have asked CLA Val and OCV about reaction speed. Ps- TD- are ready to go out or are you coming back in from an early test? glc I thought these were out-coded for oversized diesels, constant speed or variable. I'd go back to Clarke. How about a surge/bladder tank? Tom Fire only, manufacturing/warehouse occupancies. :) next to two 2,000 GPM pumps, I thought 2.5" WAS small ! I want to make sure it doesn't get clogged, but DUH, pilot lines aren't 2.5" or ", are they. Will look at 2", smallest without switching styles down to a 3/4". glc Since your only using it to restore the lower operation pressure in the mains why use a 2.5" device? The smaller a device the lower the impact if it fails open. Also if the only usage on this system is for fire, you'll have a small spike at start up, but a very low volume to deal with to return it to 155 / 160 Psi. If the system feeds domestic / industrial uses wouldn't that relieve the excess? Thom McMahon > > We've noticed the PLD's we've installed allow brief surge of > overpressurization while the diesel starts up, builds pressure, and > for the time it takes the PLD to react, there's an inrush of some of > the churn pressure until the governor kicks in and backs it down. Guy > at Clarke confirmed this. > > We have a project with what is possibly fragile UG in many sections of > the facility. We're trying to keep it, and the related interior > systems, from creeping up to high pressure (isn't that why we have the > PLD?). This particular site is getting twin 2,000 @ 150 diesel > vertical turbines, which feed a large looped yard system, in turn > feeding -oh, couple dozen risers scattered around. > > We're thinking a small (2.5"?) Relief valve located past the pump > discharge valve, just before it drops into the yard system, PRV > discharge piped back to the reservoir, set point 5 PSI above the PLD, > set adjustment on reaction time to ASAP setting, so it will bleed off > the excess pressure as soon as possible. We think the size of the yard > loop- complete with sectionals, hydrants, etc.- will absorb the shock > with only a small amount of it getting into the interior systems. If > some does, 1/2" relief valves on the grid will take care of anything > > 175. But we want to be able to have the UG drop back to the 155~160 > range as soon as possible. > > Since the twin pumps go into one yard system, the small PRV only has > to be installed on one of these. Since its relatively small, even if > it failed OPEN the loss wouldn't de-rail the train, we have 150 @ > 4,000 when combined, and demand is about 150 @3,000. Assuming the 2.5" > PRV stuck open wouldn't flow more than 1,000 GPM, it could drop the > water back in the hole to be re-pumped all day long. > > Both pumps will start remotely from elec detection systems on these > large demand systems, and on pressure drop for the conventional wets. > > Yes, the owner has authorized high pressure testing of the UG, still > doesn't mean we can slam the heck out of it or let it sit at 175+ and > not see a main break in a couple yrs. > > Any other thoughts from those with some PLD experience? > > glc _______________________________________________ Sprinklerforum mailing list [email protected] http://lists.firesprinkler.org/mailman/listinfo/sprinklerforum To Unsubscribe, send an email to:[EMAIL PROTECTED] (Put the word unsubscribe in the subject field) _______________________________________________ Sprinklerforum mailing list [email protected] http://lists.firesprinkler.org/mailman/listinfo/sprinklerforum To Unsubscribe, send an email to:[EMAIL PROTECTED] (Put the word unsubscribe in the subject field)
