I've never used a PLD before. Where can I get some good info?
At 05:37 AM 9/20/2007, you wrote:
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
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Todd G. Williams, PE
Fire Protection Design/Consulting
Stonington, Connecticut
www.fpdc.com
860.535.2080
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