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Im interested in your advice. I have pressure relief valves being installed in My Glycol reconcentrators. These vessels have a working temp. of 375* f @ atmos pressure. the relief valves they are sending me have a set pressure of 2 lbs. But no design temp is stamped on the tags. As most relief valves are set at either 72*f or 100*f. I am wondering how the 375*f bath temp. will effect the relief valve setting.
Thanks
Terry
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Pressure Relief Valve Settings
Started by Guest_Terry_*, Jan 17 2005 07:08 PM
4 replies to this topic
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#2
gvdlans
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Posted 18 January 2005 - 05:25 AM
Terry,
I assume that the holding temperature (=spring temperature) of the relief valve is the same as the operating temperature of the vessel (=375°F). I have a table that gives the relation between the holding temperature (=spring temperature) and the pressure multiplier which translate the set pressure to the spring pressure (except for steam services).
t=300°F, multiplier is 1.006
t=350°F, multiplier is 1.009
t=400°F, multiplier is 1.013
t=450°F, multiplier is 1.016
So for t=375°F, mulitiplier is 1.011. If this table is applicable for your relief valves (to be confirmed by the relief valve supplier), this means that the actual set pressure is 2/1.011 = 1.98 psig. This does not look very disturbing to me...
I assume that the holding temperature (=spring temperature) of the relief valve is the same as the operating temperature of the vessel (=375°F). I have a table that gives the relation between the holding temperature (=spring temperature) and the pressure multiplier which translate the set pressure to the spring pressure (except for steam services).
t=300°F, multiplier is 1.006
t=350°F, multiplier is 1.009
t=400°F, multiplier is 1.013
t=450°F, multiplier is 1.016
So for t=375°F, mulitiplier is 1.011. If this table is applicable for your relief valves (to be confirmed by the relief valve supplier), this means that the actual set pressure is 2/1.011 = 1.98 psig. This does not look very disturbing to me...
#3
Guest_Terry_*
Guest_Terry_*
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- guestGuests
Posted 19 January 2005 - 06:23 PM
I guess I should have been clearer in My question.Sorry about that. The unit indeed has a blanket of steam across it. The vapor is made up of water & BTEX.
I do greatly appreciate your help the multiplier chart will help me alot.
Thanks
I do greatly appreciate your help the multiplier chart will help me alot.
Thanks
#4
Guest_Barwani_*
Guest_Barwani_*
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- guestGuests
Posted 30 January 2005 - 01:48 AM
QUOTE (Terry @ Jan 17 2005, 07:08 PM)
Im interested in your advice. I have pressure relief valves being installed in My Glycol reconcentrators. These vessels have a working temp. of 375* f @ atmos pressure. the relief valves they are sending me have a set pressure of 2 lbs. But no design temp is stamped on the tags. As most relief valves are set at either 72*f or 100*f. I am wondering how the 375*f bath temp. will effect the relief valve setting.
Thanks
Terry
Thanks
Terry
Terry,
the relief valve will be tested little higher on the TEST BENCH due to the factor of temp. because temp. is softening the characteristic of the spring.
Thanks,
barwani Arafat
#5
Guest_Vivian Rodrigues_*
Guest_Vivian Rodrigues_*
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- guestGuests
Posted 02 February 2005 - 05:43 AM
Relife Valves are tested on the production test stand taking into consideration the operating temperature. That is why operating temperature is a factor while sizing a pressure relief valve.
An increase in temperaure causes a reduction of valve set pressure as a result of the direct effect of temperature on the spring and expansion of body and bonnet which reduces spring loading . Since pressure relief valves are invariably tested at atmospheric temperature , it is customery to adjust the set pressure at ambient conditions to compensate for higher operating temperaures as follows.
OPERATING TEMP %INCRESE IN SET PRESSURE AT ATMOSP.
TEMP.
-450*F TO 300*F NONE
301*F TO 600*F 1%
601*F TO 900*F 2%
901*F TO 1200*F 3%
Steam service valves are tested on steam by the manufacturer and require no additional temperature compensation. Where the set pressure is above the production steam test facility limits , Section VIII steam valves may be tested on air. When steam valves are tested on air , the compensation shown in the table above should be used.
An increase in temperaure causes a reduction of valve set pressure as a result of the direct effect of temperature on the spring and expansion of body and bonnet which reduces spring loading . Since pressure relief valves are invariably tested at atmospheric temperature , it is customery to adjust the set pressure at ambient conditions to compensate for higher operating temperaures as follows.
OPERATING TEMP %INCRESE IN SET PRESSURE AT ATMOSP.
TEMP.
-450*F TO 300*F NONE
301*F TO 600*F 1%
601*F TO 900*F 2%
901*F TO 1200*F 3%
Steam service valves are tested on steam by the manufacturer and require no additional temperature compensation. Where the set pressure is above the production steam test facility limits , Section VIII steam valves may be tested on air. When steam valves are tested on air , the compensation shown in the table above should be used.
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