Parr Instrument Pressure Relief Valves User Manual

Supplemental Protection
Although a safety rupture disc offers excellent protec­tion against overpressure, it may be desirable in some installations to supplement the rupture disc with a spring-loaded relief valve, pre-set to open at a pres­sure below the burst rating of the disk. Unlike rup­ture discs, relief valves can be slightly higher that the routine operating pressure and, since the valve will reseal once the pressure falls below the relief setting, valuable reactants will often be saved by this protec­tive feature. Also, adding a relief valve will provide positive protection for the pressure gage when using gages less than 1000 psi since small diameter rupture discs are not reliable at these lower pressures.
323M
Pressure Relief Valves
Operating Instructions
Two Different Styles
Parr spring-loaded relief valves are offered in two dif­ferent styles, both with 1/4” NPT mounting threads. They are commonly installed in the side port of the gage adapter or by adding a 155VB street tee below the pressure gage and attaching the relief valve to the side opening on the tee, but other arrangements can be used as well.
A140VB2 Values for Low Pressures
A140VB2 relief valves are offered in five ranges for use at low pressures up to 600 psi. Since small diam­eter rupture discs are not reliable at pressures below 1000 psi, adding a pre-set A140VB2 valve to a system will protect low range pressure gages from acciden­tal overpressure. The cracking pressure for A140VB2 valves is adjustable within the range prescribed for each valve. To adjust the spring tension on the valve, remove the green cap from the assembly. Remover the outer locking screw with 5/32” Allen wrench. Next, turn the inner 5/32” adjuster screw clockwise to increase the cracking pressure, or counterclockwise to lessen the cracking pressure. Replace the outer locking screw until it comes in contact with the inner screw. Place the green cap back onto the assembly.
Figure 1
A140VB2
Figure 2
A175VB
A175VB Valves for High Pressures
A175VB relief valves are offered in multiple ranges for pressures 50-5000 psi. When the upstream pres­sure overcomes the force exerted by the spring in these valves the poppet will open, allowing discharge through a 1/4” NPT female opening to which extension piping can be attached.
The cracking pressure in these valves is adjustable and can be set by the user. To increase the cracking pres­sure: release the lock nut under the adjustment cap clockwise to increase the compression on the spring.
Part No. Preset Psi Adj. Psi Bar
A140VB2PA 100 50-150 3.45-10.3
A140VB2P2 145 50-150 3.45-10.3
A140VB2P1 150 50-150 3.45-10.3
A140VB2PB 200 150-350 10.3-24.1
A140VB2PC 600 350-600 24.1-41.4
A140VB2PD 300 150-350 10.3-24.1
Parr Instrument Company www.parrinst.com
Part No. Adjustable Psi Bar
A175VB 750-1500 52-103
A175VB2 1500-2250 103-155
A175VB3 2250-3000 155-207
A175VB4 3000-4000 207-276
A175VB5 4000-5000 276-345
A175VB7 350-750 24-52
A175VB8 50-350 3.4-24.1
2X 827HC
O-RINGS
2683HC
COOLING SLEEVE
Pressure Relief Valves
1/4 NPT REF
1394HC3 COOLING BODY
2X 2714HC HOSE NIPPLES (SEE NOTE 1)
825HC
CLIP RING
1/4 NPT REF
Figure 3
A2599HC3
Cooling Body
The A2599HC3 cooling body assembly is provided when a Parr pressure apparatus is intended to be op­erated above 350 °C. Cooling is necessary to limit the temperature at the seals within the relief valve. To pre­vent overheating, a steady flow of cold water should be fed during all vessel operations at temperatures above 350 °C. Tubing connections for flowing water are provided on each sleeve, and a 10 foot length of tubing is furnished to connect to a water source.
154VB2 ELBOW 45
NOTE: (1) FOR USE WITH JP0025TB06 TUBING
Servicing the Cooling Sleeve
The cooling sleeve has two O-rings which seal the sleeve onto the cooling body. These O-rings will have to be replaced after extended periods of service or after excessive heating with no water flowing through the sleeve. To replace the O-rings, remove the cooling body from the elbow (see figure 3). After removing the cooling body, rotate and pull off the cooling sleeve. The O-rings can now be removed from the sleeve, be careful not to scratch or damage the O-ring grooves. Clean any accumulated lime deposits from the sleeve and insert new O-rings into the grooves; then moisten the O-rings and slide the cooling sleeve into place on the cooling body.
323M R04 12/10/14
P
arr Instrument Company
211 53rd Street • Moline, Illinois 61265 USA 1-309-762-7716 • 1-800-872-7720 • Fax: 1-309-762-9453
E-mail: parr@parrinst.com • http://www.parrinst.com
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