Catalog - Tri-State Technical Sales Corp.
Catalog - Tri-State Technical Sales Corp.
Catalog - Tri-State Technical Sales Corp.
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OPERATION<br />
System pr essur e is r outed fr om below the valve thr ough<br />
the pilot valve to the dome cavity of the main valve. This<br />
pr essur e, acting on a piston (dome) ar ea A d<br />
larger than<br />
the seat ar ea (A s<br />
), cr eates an ef fective downwar d for ce<br />
( F=Px( A d<br />
-A s<br />
)) holding the main valve piston down in<br />
the closed position.<br />
At the designated set pr essur e, the pilot valve<br />
r educes the dome pr essur e, pr oportional to demand<br />
if modulating (F300 or F500), or fully if snap-acting (F200),<br />
and allows the piston to go into lift. Once the system<br />
pr essur e is r elieved, the pilot valve closes at the pr eset<br />
blowdown, allowing the dome to r epr essurize and the<br />
main valve piston to close. When closed, dome pr essur e<br />
acting on a dif fer ential ar ea between the top and bottom<br />
of the piston assembly , cr eates a downwar d for ce on<br />
the seat pr oviding leak-tight shutof f.<br />
The F7000/8000 utilizes an elastomeric or plastic seat<br />
on the piston to achieve leak-tight seating. A dynamic<br />
piston seal pr events any leakage fr om the dome to the<br />
discharge. Wear rings on the piston eliminate metal-tometal<br />
contact with the liner and help to pr ovide smooth<br />
and consistent operation. Elastomeric/plastic seals seal<br />
the main valve and pilot valves.<br />
The F200 Snap-Acting pilot valve blowdown is set at<br />
5-7% of the set pr essur e and can be adjusted fr om 3%<br />
to 20% if so specified. The F300 and F500 modulating pilot<br />
valves pr ovide zer o blowdown, i.e. the main valve opens in<br />
pr oportion to demand and closes at the set pr essur e.<br />
The orifice size may be easily selected by choosing<br />
a full-bor e fixed inlet nozzle on the F7000, or by<br />
converting to a r educed size orifice (F8000) by<br />
attaching FLOW SAFE’ s unique annular-flow plug<br />
to the bottom of the piston assembly . This plug reduces<br />
the ef fective flow ar ea of the valve by directing the<br />
fluid between the plug O.D. and the nozzle I.D. This<br />
featur e in orifice selection allows the valve owner<br />
greater versatility in valve standar dization, utilization,<br />
and minimized inventor y.<br />
The F7000/8000 Series is particularly advantageous<br />
and cost-ef fective in installations wher e:<br />
Ther e may be size and weight limitations<br />
for the valve.<br />
A high cycling rate exists.<br />
A long service life is r equir ed.<br />
Minimal pr oduct loss is important .<br />
Reduced maintenance and installation<br />
time is desirable.<br />
3<br />
CLOSED<br />
OPEN<br />
OUTLET<br />
INLET<br />
F7000/8000 SERIES
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