8
0 - 150 (-18-65°C) -
151 - 600 (66-315°C) 1%
601 - 800 (316-430°C) 2%
801 - 1000 (431-540°C) 3%
15-400 3%
401-1000 4%
1001-1500 5%
D, E, F, G, H, J, K, L 1500
M 1100
N, P 1000
Q 600
R, T, T2 300
CROSBY STYLE JOS-E, JBS-E, JLT*-JBS-E, JLT*-JOS-E VALVES
InstallatIon and MaIntenance InstructIons
TABLE 2
JLT-E orifice size Nozzle ring setting - Total revolutions below highest lock position
P and Q ¾ Revolution
R and T 1 Revolution
5.9.1
Remove the nozzle ring set screw and insert
a screwdriver to engage the ring notches.
5.9.2 Turning the ring to the right raises the
ring, thereby increasing blowdown.
Turning the ring to the left lowers the
ring, thereby decreasing the blowdown.
5.9.3 Do not lower the nozzle ring to the point
where the valve begins to have excessive
simmer. Raising of the ring will reduce
simmer.
5.9.4 The nozzle ring should not be moved
more than two notches before retesting.
When making adjustments, always keep
count of the number of notches and
the direction in which the nozzle ring is
moved. This will permit returning to the
original setting in case of error.
5.10 Cold differential test pressure
adjustments
When a pressure relief valve is on a test
bench at room temperature and atmospheric
pressure, and is to be installed on a system
operating at a higher temperature and/
or a higher back pressure, a compensating
adjustment is necessary. The test pressure
required to have the valve open at the desired
set pressure under actual service conditions is
known as the cold differential test pressure.
5.10.1
Temperature correction
When a Crosby Style JOS-E/JBS-E or
JLT-E valve is set on air or water at
room temperature and then used at a
higher service temperature, the test
pressure shall be corrected to exceed
the set pressure using the temperature
correction shown in Table 3.
Note: this table is not applicable to
steam service valves.
TABLE 3
Operating temperature (°F)
% Excess pressure
TABLE 4 - (JOS/JOS-E Style only)
Orifice size Saturated steam set pressure (max) (psig)
TABLE 5 - Saturated steam service
Air set pressure correction factors at ambienttemperature
Set pressure (psig) % Increase in spring set pressure
5.9.5 Style JLT
The Style JLT in the P, Q, R and T orifice
sizes is preset at the factory and cannot
be adjusted externally in the field, since
the special contoured skirt on the disc
holder prevents engagement of the set
screw with the nozzle ring. As a result the
nozzle ring is not slotted and is held in
place by three set screws. The position of
the nozzle ring must be set prior to valve
assembly as follows:
A. S
crew the nozzle ring (3) on to the
nozzle. The top of the nozzle ring should
be below the nozzle seating surface.
B. Install the disc insert retention clip (9)
onto the disc insert. Assemble the disc
insert (8) and disc holder (5). The disc
insert should snap into place using
hand force only.
C. Lower the disc holder and disc insert
carefully onto the nozzle.
D. Reach through the valve body outlet
and turn the nozzle ring until it touches
the disc holder lightly. This is the
highest lock position.
E. Carefully remove the disc holder and
disc insert from the valve.
F. Lower the nozzle ring (turn to the left)
the total number of revolutions shown
in Table 2.
G. Carefully tighten each of the set
screws on the nozzle ring to hold the
ring in position.
5.10.2
Back pressure correction
Conventional valves without balancing
bellows set with atmospheric pressure
at the outlet and intended for use
under elevated constant back pressure
conditions shall be adjusted so that the
test pressure is equal to the set pressure
minus the expected back pressure.
Seeexample below:
Set pressure 100 psi
Constant back pressure 10 psi
Cold differential test pressure 90 psi
In all instances, the spring should be selected
based on the cold differential test pressure;
in the example above, 90 psi. See sample
nameplate on page 3 which shows how
temperature and back pressure are indicated.
5.10.3 Saturated steam correction factors
Crosby Style JOS and JOS-E pressure
relief valves that are used for saturated
steam service and are within the
set pressure limits established in
Table 4 may be set on air at ambient
temperature, provided the correction
factors in Table 5 are applied to the valve
set pressure.
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