Before installation, these instructions must be carefully read and understood�
ATTENTION
The safety of lives and property often depends on
the proper operation of the pressure relief valves.
Consequently, the valves should be kept clean and
should be tested and reconditioned periodically to
make sure they function properly.
WARNING
Suitability of the material and product for
the use contemplated by the buyer is the
sole responsibility of the buyer. Also storage,
installation and proper use and application
are the sole responsibility of the purchaser.
Emersondisclaims any and all liability arising out
of the same.
Any installation, maintenance, adjustment,
repair and testing performed on pressure
relief valves should be done in accordance with
the requirements of all applicable codes and
standards under which those performing such
work should maintain proper authorization
through appropriate governing authorities.
No repair, assembly and test work done by
TABLE OF CONTENTS
1 Introduction ��������������������������������������������������� 4
2 Storage and handling ������������������������������������ 4
3 Installation ����������������������������������������������������� 4
4 Hydrostatic pressure tests ��������������������������� 5
5 Setting, testing and adjustments ����������������� 6
6 Valve maintenance �������������������������������������� 10
7 Style variations �������������������������������������������� 21
8 Service records �������������������������������������������� 21
9 Spare parts �������������������������������������������������� 21
10 Trouble shooting pressure relief valves ���� 21
11 Emerson field servicesand
other than Emerson shall be covered by the
warranty extended by Emerson to its customers.
You assume full responsibility for your work. In
maintaining and repairing Crosby products you
should use only parts manufactured by Emerson.
Call your nearest Emerson regional sales office or
representative for a service engineer should you
wish assistance with your field needs.
3� Insurance spare parts: valve parts exposed to process or environmental wear
and/or corrosion and may require replacement as part of a major repair�
Emerson recommends that sufficient inventory of spare parts be maintained to
support process requirements� Always be sure to use genuine Emerson parts
to ensure continued product performance and warranty�
4� Contains complete set of gaskets for all style of valves�
When ordering spare parts, the valve size, style
and assembly number and/or serial number
should be given together with set pressure, part
name and reference number from page2� The
valve assembly number is shown on the valve
nameplate as, 'Shop Number'� Spare parts may
be ordered from any Emerson regional sales
office or representative�
Safety precautions
Proper handling, storage, installation,
maintenance and operation is essential to the
safe and reliable functioning of any pressure
relief product�
Precautionary statements in the form of
warnings, cautions and notes are used
throughout this instruction to emphasize
important and critical factors where applicable�
Examples:
WARNING
An operating procedure or practice which, if not
observed strictly, may result in injury to personnel
or loss of life.
CAUTION
An operating procedure or practice which, if not
observed strictly, may result in damage to or
destruction of equipment.
These precautionary statements are by no
means exhaustive�
Emerson cannot be expected to know, evaluate
and advise customers of all the possible
applications and operating conditions for
its products or of the possible hazardous
consequences which may result from the
misapplication or misuse of such products�
Consequently, the improper handling,
storage, installation, use or maintenance
of any Emerson product by a non Emerson
employee may void any Emerson guarantees or
warranties with respect to such product�
All personnel working with Emerson products
should be trained adequately and thoroughly
familiar with the contents of the appropriate
instruction manual(s)�
Emerson cannot evaluate all conditions in
which the products may be used�
However, Emerson offers the following general
safety suggestions:
• Never subject valves to sharp impact loads�
Rough handling (striking, bumping, dropping,
etc�) may alter the pressure setting, deform
valve parts and affect seat tightness and valve
performance adversely� Striking a valve which
is under pressure can cause premature
actuation�
• When moving a valve, never use the lifting
lever to lift the valve�
• Always lower the system pressure to the
pressure level specified in the instruction
before making any adjustment to the valve�
Furthermore, always install a proper test rod
to gag an installed valve before making any
ring adjustments on the valve�
• Ear and eye protection should be used when
working on a valve which has pressure�
• Never stand in front of the discharge
outlet of a pressure relief valve which is
under pressure�
• Always stand to the side of and at a safe
distance from the valve discharge and
use extreme care when observing a valve
for leakage�
The above precautions and suggestions are
by no means exhaustive and the user should
always approach and use any pressure relief
valve with great care�
Operation, Installation and Safety Instructions
are available at Emerson�com/FinalControl or
from your local Emerson regional sales office
or representative�
Crosby Style JOS-E/JBS-E Pressure Relief
Valves have been selected for installation
because of their performance features,
reliability and ease of maintenance�
Adherence to the installation and maintenance
procedures specified herein will provide the
utmost in safety, a minimum of maintenance,
and a long service life� Crosby Style JOS-E,
JBS-E and JLT-E Valves are manufactured
in accordance with the requirements of
Section VIII and Section XIII Pressure Vessels,
ASME Boiler and Pressure Vessel Code�
Style JOS-E is a conventional closed bonnet
valve� Style JBS-E has a balanced bellows for
minimizing the effect of back pressure�
Style JLT-E is a high performance valve
designed specifically for liquid service�
TheJLT-E features patented contoured liquid
trim in a standard JOS-E/JBS-E envelope�
2 STORAGE AND HANDLING
Valves are often on hand at the job site months
before they are installed� Unless stored
properly and protected, valve performance may
be affected adversely�
Rough handling and dirt may damage or
cause misalignment of the valve parts� It is
recommended that the valves be left in their
original shipping containers and that they be
stored in a warehouse or at a minimum on a
dry surface with a protective covering until they
are used�
3 INSTALLATION
3.1 Care in handling
Pressure relief valves must be handled
carefully and never subjected to sharp
impact loads� They should not be struck,
bumped or dropped� Rough handling may
alter the pressure setting, deform valve
parts and affect seat tightness and valve
performanceadversely�
When it is necessary to use a hoist, the chain
or sling should be placed around the valve body
and bonnet in a manner that will ensure that
the valve is in a vertical position to facilitate
installation� The valve should never be lifted or
handled using the lifting lever inlet and outlet
protectors should remain in place until the
valve is ready to be installed on the system�
3.2 Inspection
Pressure relief valves should be inspected
visually before they are installed to ensure that
no damage has occurred during shipment or
while in storage�
All protective material, sealing plugs and any
extraneous material inside the valve body or
nozzle must be removed�
The valve nameplate and other identifying tags
should be checked to ensure that the particular
valve is being installed at the location for which
it was intended�
The valve seals protecting the spring setting
and ring adjustments should be intact� If seals
are not intact, the valve should be inspected,
tested and seals installed properly before use�
3.3 Inlet piping
Pressure relief valves should be mounted
vertically in an upright position either directly
on a nozzle from the pressure vessel or on a
short connecting fitting that provides direct and
unobstructed flow between the vessel and the
valve� Installing a pressure relief valve in other
than this recommended position might affect
its operation adversely� Where rounded or
beveled approaches cannot be provided ahead
of the valve it is recommended that one size
larger nozzle or fitting be used� Avalve should
never be installed on a fitting having a smaller
inside diameter than the inlet connection of
thevalve�
Inlet piping (nozzles) must be designed to
withstand the total resultant forces due
to the valve discharging at the maximum
accumulated pressure and the expected piping
loads� Themagnitudes of the bending moment
exerted on the inlet piping will depend on the
configuration and method of supporting the
outlet piping�
Many valves are damaged when first placed
in service because of failure to clean the
connections properly when installed� Both
the valve inlet and the vessel and/or line on
which the valve is mounted must be cleaned
thoroughly of all foreign material� The inlet
connection bolts or studs should be drawn
down evenly to avoid straining the valve body
with possible distortion of the nozzle flange
orbase�
Outlet piping should be simple and direct�
Where possible, for non-hazardous fluids, a
short discharge pipe or vertical riser connected
through a long radius elbow venting directly to
atmosphere is recommended� Such discharge
piping should be at least the same size as the
valve outlet�
All discharge piping should be run as direct as
is practicable to the point of final release for
disposal� Valve effluent must discharge to a
safe disposal area�
Where discharge piping is long, due
consideration shall be given to the use of long
radius elbows, and the reduction of excessive
line strains through the use of expansion joints
and proper means of support to minimize
line sway and vibration under operating
conditions� Adequate drainage is required
to prevent corrosive media from collecting
in the discharge side of the pressure relief
valve� When required, low point drains shall be
provided in the discharge pipe� Particular care
must be observed to ensure that the drains
are directed or piped to a safe disposal area�
In installations where the pressure relief valve
discharges into a closed system, care must be
taken to ensure that built up and superimposed
back pressure has been calculated properly,
specified and accounted for when sizing and
selecting the valve�
Where built up back pressure is expected to
exceed 10% of set pressure or if superimposed
back pressure is variable, a bellows valve
isrequired�
4 HYDROSTATIC PRESSURE TESTS
4.1 Hydrostatic test of vessel or system
When a pressure vessel or system is to be
hydrostatically tested, it is recommended
that the pressure relief valve be removed
and a blank flange be installed in its place�
This practice precludes the possibility of
any damage to the pressure relief valve�
Bent spindles and damaged valve seats are
problems that can be caused by improper
hydrostatic test procedures�
Blank flanges must be removed and the
pressure relief valve reinstalled before the
vessel is placed in service�
When the hydrostatic test must be performed
with the valve in place, a test gag may be used�
Crosby Style JOS-E/JBS-E Valves are designed
to accommodate test gags for use with each
type of cap� In the case of the Type C cap with
lifting lever, the lifting lever assembly must be
replaced with a hydrostatic test cap and test
rod prior to hydrostatic testing� When test rods
are used, care must be exercised to prevent
overtightening that could damage the valve
spindle and valve seats� Generally, a test rod
which is hand tight will provide sufficient force
to hold the valve closed�
After the hydrostatic test, the test rod (gag)
must be removed and replaced by either a cap
plug or a cap not fitted with a test rod�
4.2 Hydrostatic test of outlet system
When a hydrostatic test must be conducted
on the outlet piping system, with the valve in
place, special consideration must be given
not to exceed the design pressure limits of
the downstream side of the pressure relief
valve� The outlet side of a pressure relief valve
is known as the secondary pressure zone�
Thiszone is normally designed to a lower
pressure rating than the inlet and frequently is
designed to a lower pressure rating than the
outlet flange� This is true particularly in the
case of balanced bellows designs and in the
larger valve sizes�
Consult relevant product specifications
for the back pressure design limits of
the Style JOS-E/JBS-E or JLT-E Valves�
FIGURE 3 Recommended installation discharging to
atmosphere
Every new Crosby J Series Pressure Relief
Valve is tested fully and sealed prior to
shipment� The external adjustment points
of each valve are sealed to ensure that no
changes have been made to the valve after
shipment and that the valve has not been
disassembled or tampered with� The seals and
nameplates are your assurance that the valve
has been built and tested to the applicable
Codes and Standards and are the physical
evidence of our product warranty�
All new Crosby J Series Valves are tested fully
prior to shipment on the appropriate testing
medium, so there is no need to pre-test the
valve prior to installation� If pre-testing is
required, in order to maintain the product
warranty, a Crosby Valves authorized
service organization should be contacted to
perform the testing� Contact your local sales
representative or visit our website to locate
the authorized service organization closest
to your location� By choosing an authorized
service organization to perform testing you can
be assured that the correct testing procedure
is followed which will save time and cost by
avoiding possible valve damage caused by
improper testing methods�
In any event, if pre-testing is to be performed,
several important cautions should be observed�
First it is vital that the appropriate test fluid is
used to test any valve� See Section 5�5� This will
ensure accuracy of the test results as well as
avoid possible damage to the valve�
All Crosby J Series Valves are tested for seat
tightness after the final set point test and prior
to shipment from the factory� If further seat
tightness testing is required before installation,
it is recommended that the test be performed
prior to any set point verification testing�
Repeated pressure testing of a metal seated
valve can cause damage to the sealing surfaces
leading to seat leakage
Testing on a low volume test stand requires
specific testing techniques in order to ensure
accurate test results and to avoid damage to the
sealing surfaces of the valve� In many cases this
requires temporary adjustment of the nozzle
ring during the test as described in Section 5�8
and specifically in Section 5�8�1� For valves with
set points in excess of 500 psig (3447 kPa), it is
recommended that when testing on a low volume
test bench, the lift be restricted temporarily by
use of a gag or other suitable device�
However, it is good practice to inspect the valve
prior to installation�
This inspection determines any damage which
may have occurred due to rough handling in
transit or storage and initiates appropriate
service records�
5.2 Reconditioned valves
Valves which have not been in service for
extended periods due to plant shutdown or
long term storage, or valves which have been
repaired or reconditioned, also should be tested
before being put into operation�
CAUTION
Improper testing may cause valve damage and
seat leakage.
5.3 Valves removed from service
Valves being removed from service should
be tested on a shop test bench before being
disassembled to determine the set pressure
and seat tightness� This is an important
phase of the maintenance routine and the test
results should be recorded for review and
determination of necessary corrective action�
The 'as received from service' condition
of a pressure relief valve is a most useful
tool in establishing the proper time interval
between inspections�
5.4 The test bench
The quality and condition of the shop test bench
is paramount to obtaining proper test results�
The test bench must be free of leaks and the
test fluid must be clean� Solids or other foreign
material in the test medium will damage the
seating surfaces of the pressure relief valve
being tested�
The test pressure gauge must be calibrated
and have a range proper to the pressure level
of the valve setting� Set pressure should fall
within the middle third of the dial range of the
test gauge� The test bench provides an accurate
and convenient facility for determining valve
set pressure and seat tightness� It does not
duplicate all of the field conditions to which
a pressure relief valve will be exposed while
in service� It is not practical to attempt to
measure relieving capacity or blowdown using
a test bench�
5.5 Test fluids - set pressure test
The test fluid should be air or nitrogen for
valves used on gas and vapor service and water
for valves used on liquid service� Valvesfor
steam service should be tested on steam�
Itmay be necessary to make a correction to
the adjusted set pressure to compensate for
the difference in temperature of the test fluids
(seeappropriate instruction)�
Crosby Style JOS-E/JBS-E Valves intended for
compressible fluid service and tested with air
or steam will open with a sharp clear popping
action at the set point� Valves for liquid service
tested with water are considered open when
there is a continuous unbroken stream of liquid
flowing from the valve�
5.7 Set pressure changes
Set pressure changes beyond the specified
spring range will necessitate a change in the
valve spring assembly consisting of the spring
and two fitted spring washers� The new spring
and washers must be obtained from Emerson
and the valve must be reset and the nameplate
restamped by an authorized valve repair facility�
5.8 Set pressure adjustment
Before making any adjustments, reduce the
pressure under the valve seat to at least 10%
below the stamped opening pressure� This will
prevent seat damage due to turning of the disk
on the nozzle seat and minimize the chance of
an inadvertent valve opening� A strong (high)
ring position is necessary to obtain a good clean
popping action of the valve on air or gas with
the limited volume available on the test bench�
5.8.1
(Not required for testing on liquid)� Remove
the nozzle ring set screw and raise the
nozzle ring until it touches the disk holder,
then back it down two (2) notches� Exercise
care in counting the number of notches
moved so that the ring can be returned to
its proper position following testing�
Moving the notches on the nozzle ring to
the left will lower the nozzle ring�
Replace the nozzle ring set screw before
each set pressure test� The set screw
must engage one of the ring notches,
being careful that it does not bear on the
top of a tooth�
5.8.2 Remove the cap or lifting lever following
the instruction for valve disassembly
(seeparagraph 6)�
5.8.3 Loosen the adjusting bolt nut and turn the
adjusting bolt clockwise to increase set
pressure or counterclockwise to reduce
set pressure�
5.8.4 Retighten the adjusting bolt nut following
each adjustment�
5.8.5 Two or three consecutive valve openings
at the same pressure are necessary to
verify the opening pressure accurately�
5.8.6 Opening pressure tolerance shall comply
with ASME Section XIII Table 3�6�3�1-2
for UV Designator as below or other
tolerance may be used so long as they
meet ASME requirement:
The set pressure tolerance for
pressure relief valves shall not exceed
±2 psi (15 kPa) for pressures up to and
including 70 psi (500 kPa) and ±3% for
pressures above 70 psi (500 kPa)
5.8.7 Once the set pressure has been
established, lower the nozzle ring to
the installed ring position as indicated
in Table 1 and replace the nozzle ring
set screw as described above� Seal wire
the adjusting bolt and adjusting ring set
screw with identifying seals�
5.9 Nozzle ring settings
The nozzle ring adjustment is made at the
factory and resetting in service is seldom
necessary� Should it be necessary to change
blowdown or reduce valve simmer, the nozzle
ring may be adjusted as follows: (see the next
paragraph for P, Q, R and T orifice Style JLT)�
CAUTION
Should any adjustments be made while the valve is
installed on a pressurized system, the valve should
be gagged while ring adjustments are made.
TABLE 1
ServiceOrifice sizeNozzle ring setting (below highest lock position)
Style JOS-E/JBS-E pressure relief valve recommended nozzle ring settings
Vapor and gases
Style JLT-E pressure relief valve recommended nozzle ring settings
Liquids and gases
NOTE
Minus sign indicates number of ring notches below starting position of nozzle ring which is the highest position
with the valve closed (contact with disk holder)�
D through J-5
K through N-10
P through T-15
D, E, and F-2
G, H, and J-3
K and L-5
M and N-10
P and Q (see Table 2)
R and T (see Table 2)
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
reducesimmer�
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�
5.9.5 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 disk insert� Assemble the disc
insert (8) and disc holder (5)� The disk
insert should snap into place using
hand force only�
C� Lower the disc holder and disk 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 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�
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 (689 kPa)
Constant back pressure 10 psi (69 kPa)
Cold differential test pressure 90 psi (621 kPa)
In all instances, the spring should be selected
based on the cold differential test pressure;
in the example above, 90 psi (621 kPa)� 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�
TABLE 2
JLT-E orifice sizeNozzle ring setting - Total revolutions below highest lock position
P and Q¾ Revolution
R and T1 Revolution
TABLE 4 - (JOS/JOS-E STYLE ONLY)
Orifice sizeSaturated steam set pressure (max), psig (kPa)
D, E, F, G, H, J, K, L1500 (10342)
M1100 (7584)
N, P1000 (6895)
Q600 (4137)
R, T, T2300 (2068)
TABLE 5 - SATURATED STEAM SERVICE
Air set pressure correction factors at ambienttemperature
Set pressure (psig)% Increase in spring set pressure
The cover plate should be
fitted with a suitable device to
relieve body pressure in case of
accidental popping of valve
5
/
16" O�D� x 0�035"wall
Tube
[7�9 mm O�D� x 0�89 mmwall]
Cover plate
Air receiver
5.11 Seat leakage tests
Ambiguous terms such as 'bubble-tight',
'drop tight', 'zero leakage' and 'commercial
tightness' sometimes are used to describe seat
tightness� However, these terms lack uniform
definition and true practical meaning�
• Test procedure
API standard 527 provides a standard for
'commercial' tightness and has been adopted
by industry and users in order to clarify
testing methods and tightness criteria� This
standard applies to flanged inlet nozzle type
pressure relief valves�
• Test apparatus
A typical test arrangement for determining
seat tightness for pressure relief valves
per API standard 527 is shown in Figure 4�
5
Leakage is measured using a
/
16 in� (7�9 mm)
OD tube with 0�035 in� (0�89 mm ) wall� The
tube end is cut square and smooth, is parallel
to and ½ in� (12�7 mm) below the surface of
the water� A snap-on type test clamp shown
in Figure 5 is available�
FIGURE 5
Seat leak apparatus for 150 and 300 lbs� (68 and 136 kg�) outlets 1” to 10” sizes
NOTE
The tube must be bent so that reservoir runs
parallel to face of coverplate
• Procedure
With the valve mounted vertically, the
leakage rate in bubbles per minute shall be
determined with pressure at the pressure
relief valve inlet raised up to and held at
90 percent of the set pressure (or cold
differential test pressure - CDTP) immediately
after popping� This applies except for valves
set at 50 psig (345 kPa) or below, in which
case the pressure shall be held at 5 psig
Soft seated valves
For soft seated valves there shall be no
leakage for one minute (zero bubbles for one
minute)�
• Crosby seat tightness standard-liquid service
valves (Style JLT-E)
Crosby liquid service pressure relief
valves are checked for seat tightness by a
quantitative seat leakage test�
(34 kPa) below the set pressure immediately
after popping� The test pressure shall be
applied for a minimum of one minute for
valves of inlet sizes through2"; two minutes
for sizes 2½", 3" and 4"; five minutes for sizes
6" and 8"� Air (or nitrogen) at approximately
ambient temperature shall be used as the
pressure medium�
• Tightness standard
Metal-to-metal seated valves
The leakage rate in bubbles per minute shall
be observed for at least one minute and shall
not exceed the values indicated in Table 6�
TABLE 6 - MAXIMUM SEAT LEAKAGE RATE - METAL SEATED PRESSURE RELIEF VALVES
Effective orifice sizes 0.307 In
Set pressure
psig (kPa)
15-1000 (103-6895)400�60�017200�300�0085
1500 (10,342)600�90�026300�450�0130
2000 (13,790)801�20�034400�600�0170
2500 (17,237)1001�50�043500�750�0210
3000 (20,684)1001�50�043600�900�0260
4000 (27,579)1001�50�043801�200�0340
5000 (34,474)1001�50�0431001�500�0430
6000 (41,369)1001�50�0431001�500�0430
Max. bubbles
per minute
Standard cubic feetStandard cubic metersStandard cubic feetStandard cubic meters
2
[198 mm2] and smaller D, E and FEffective orifice sizes larger than 0.307 In2 [198 mm2] G orifice and lager
All of the test fluid passing through an
assembled valve is collected and measured per
the following test procedure:
1� The inlet pressure is adjusted to a
test pressure which is 90% of the cold
differential test pressure� Valves set
below 50 psig (345 kPa) are tested at
5psig (34 kPa) below the cold differential
testpressure�
2� The test pressure is maintained for a period
of not less than ten minutes�
• Allowable leakage rate
The maximum allowableleakage rate should
not exceed 10 cubic centimeters per hour
per inch of diameter of nominal valve inlet
size� For nominal valve sizes of 1 inch or less,
the leakage rate shall not exceed 10 cubic
centimeters per hour� For soft seated valves
there shall be no leakage for one minute�
• Soft seated valves
For exceptional seat tightness, an O-ring soft
seat design is offered� Refer to Figure 15�
The Crosby soft seat design will provide a valve
that has no visible leakage at a test pressure
of 90 percent of the set pressure or cold
differential test pressure� Soft seated valves
are tested using the same test procedure used
for metal-to-metal seated valves�
6 VALVE MAINTENANCE
CAUTION
Valves in hazardous fluid service and any other
materials classified as dangerous must be
neutralized immediately after removal from service.
6.1 Visual inspection and neutralizing
A visual inspection shall be made when valves
are first removed from service� The presence
of deposits or corrosive products in the valve
and in the piping should be recorded and
valves should be cleaned to the extent possible
prior to disassembly� Check the condition
of external surfaces for any indication of
corrosive atmospheric attack or evidence of
mechanical damage�
6.2.2 Remove the nozzle ring set screw (4)
and set screw gasket (27)� Record
the position of the nozzle ring (3) with
respect to the disk holder (5) by counting
the number of notches required to raise
the ring until it just touches the disk
holder� This information will be needed
again when reassembling the valve�
(Measure the revolutions for P, Q, R and
T orifice Style JLT� See Table 2)�
6.2.3 Loosen the adjusting bolt nut (25)� Before
releasing the spring load, make note
of the depth of the adjusting bolt in the
bonnet and count the number of turns
required to remove the spring load� This
information will help when reassembling
t
he valve to its approximate original setting�
6.2.4 Release all of the spring load by
rotating the adjusting bolt (24) in a
counterclockwise direction�
6.2.5 Remove the bonnet stud nuts (22)�
6.2.6 Lift the bonnet (20) straight up to clear
the spindle (16) and valve spring (18)�
Exercise care when lifting the bonnet as
the spring and spindle will then be free
to fall aside�
6.2.7
The spring and spring washers (19) can
now be lifted off the spindle (16)� The spring
and spring washers are fitted together and
must be kept together as a subassembly�
Spring washers are not interchangeable
between ends of the spring�
FIGURE 6
Remove disk insert by pulling on bolt
Rectangular
bar bolt
Bolt
Remove disk insert by turning nut with wrench
FIGURE 7
Bolt
Washer
Nut
6.2 Disassembly
Crosby JOS-E/JBS-E Valves should be
disassembled as described below� Parts
identification may be found in Figure 1 on page2�
The parts from each valve should be marked
properly and segregated to keep them separate
from parts used in other valves�
6.2.1
Remove the cap (40) and cap gasket (41)�
If the valve has a lifting lever device
follow the instructions in Section 6�7�
6.2.8 Remove the spindle, guide (15), disk
holder and disc insert (8)� For balanced
bellows valves (Style JBS-E and
JLT-JBS-E) special care must be taken
not to damage the bellows subassembly
(6)� If parts are difficult to remove, due
to the presence of corrosive or foreign
materials, soaking in a suitable solvent
may be required�
6.2.9 Remove the spindle from the disc holder�
6.2.10 Lift the guide off the disc holder�
6.2.11 Disk insert removal
Note: for removal of threaded inserts
supplied with JOS/JBS valves,
see IS-V3137A�
• Orifice sizes D through M (metal seats)
Screw a standard bolt into the tapped
hole (see Table 7) in the face of the disk
insert� Using hand force pull the bolt
straight out� The disk insert with the
retention clip (9) should come out with
moderate force� If the valve has been
in dirty service, it may be necessary to
use a suitable solvent to aid in removal�
If additional pullout force is required, a
bolt with a T handle may be used� The
method described below for orifice sizes
N through T may be used if necessary�
• Orifice sizes N through T (metal seats)
Safety precautions should be followed
whenever heavy parts are being lifted
or transported� Dropping disk holder
assembly may dislodge the insert� The
removal of the insert is accomplished by
the use of a tool as shown in Figure 6�
This tool consists of a rectangular steel
bar which spans the outside diameter
of the disk holder with a center hole
through which the standard bolt can be
inserted before screwing into the disk
insert� A nut and washer is also required
as shown� Tightening the nut with a
wrench will exert a pulling force on the
disc insert and cause it to be removed
from the disk holder�
• Orifice sizes D through K (O-ring seats)
The O-ring seat design for orifice sizes
D through K has a retaining screw in
the center of the disk insert� A drilled
and tapped hole (4-40 UNC) is provided
in the center of the retaining screw for
removal of the disk insert (Figure 7)�
Screw a standard bolt into the hole in the
retaining screw� Using hand force pull
the bolt straight out� The disk insert with
the retention spring should come out
with moderate force�
• Orifice sizes L through T (O-ring seats)
Safety precautions should be followed
whenever heavy parts are being lifted
or transported� Dropping the disk
holder may dislodge the insert� Remove
the three retaining screws from the
insert� Remove the retainer and O-ring
seat� Atapped hole (refer to Table 7) is
provided in the disk insert for insertion
of a removal bolt� Follow instructions for
metal seated insert removal�
6.2.12 For bellows valves only, place the disk
holder in a vise (the larger sizes may
require a 3-jaw vise) as shown in Figure8�
Using a suitable wrench
tailpiece and bellows from thediskholder�
6.2.13 Remove the nozzle ring (3) from
the nozzle (2)�
6.2.14 R
emove the nozzle (2) from the valve
body (1) if necessary� Unless the valve
seat on the nozzle has been damaged
mechanically or shows signs of corrosive
attack, it will not be necessary to remove
the nozzle� In most cases the nozzle can
be reconditioned without removal from
the valve body� To remove the nozzle,
turn the valve body over taking care not
to damage the bonnet studs (21)� Turn
the nozzle counterclockwise by using
the wrench flats on the nozzle flange or
a nozzle wrench designed to clamp onto
the nozzle flange�
6.3 Cleaning
External parts such as the valve body, bonnet
and cap should be cleaned by immersion in a
bath such as hot Oakite solution or equivalent�
These external parts may be cleaned by wire
brushing, provided the brushes used do not
damage nor contaminate the base metals�
Onlyclean stainless steel brushes should be
used on stainless steel components�
The internal parts such as the guide, disk
holder, disk insert, nozzle ring and spindle
should be cleaned by immersion in a
commercial high alkaline detergent�
Guiding surfaces on the disc holder and guide
may be polished using a fine emery cloth�
Thebellows and other metal parts may be
cleaned using acetone or alcohol, then rinsed
with clean tap water and dried�
Check all valve parts for wear and corrosion�
The valve seats on both the nozzle and disk
insert must be examined to determine if they
have been damaged� Most often, lapping the
valve seats is all that is necessary to restore
them to their original condition�
If the inspection shows that the valve seats are
damaged badly, remachining will be necessary
or it may be advisable to replace these parts�
When the time element is a factor, it may be
advantageous to replace damaged parts from
spare parts stock, thereby permitting the
replaced part to be checked and reworked at
leisure� (See Figure 10 and Table 8 for critical
dimensions)� The valve spring (18) should be
inspected for evidence of cracking, pitting or
deformation� Thebellows (6B) in a Style JBS-E
and JLT-JBS-E valve should be inspected for
evidence of cracking, pitting or deformation that
might develop into a leak�The bearing surfaces
on the guide and disk holder should be checked
for residual product build up and any evidence
of scoring� Inspection of valve components is
important to ensure proper valve performance�
Damaged valve parts must be repaired
orreplaced�
Spindle assemblies should be checked for
excessive runout� For D to K orifice the total
runout between the spindle point to top of the
spindle rod should be less than 0�015 in�
(0�38 mm)� ForL orifice and larger it should be
less than 0�030 in� (0�80 mm)�
Check and inspect all gaskets for evidence of
damage (creases, gouges, cuts) or corrosion�
Metal gaskets may be re-used if found to be
undamaged� All organic fiber or soft gaskets
should be replaced�
6.5 Reconditioning of valve seats
The tightness of a valve and its proper
operation depend directly on the condition of
the seats� Many pressure relief valve problems
are due to eroded or damaged seats�
The standard Crosby Style JOS-E/JBS-E/JLT-E
Valve is constructed with a flat metal-to-metal
seat� It is important that seating surfaces
be refurbished properly by lapping with a
flat cast iron lap coated with the correct
lapping compound�
6.5.1 Lapping procedures
Unless the seats have been damaged
badly by dirt or scale, lapping the seating
surfaces should restore them to their
original condition� Never lap the disk
insert against the nozzle� Lap each part
separately against a cast-iron lapping
block of the proper size� These blocks hold
the lapping compound in their surface
pores and must be recharged frequently�
Lap the block against the seat� Never
rotate the block continuously, but use an
oscillating motion� Extreme care should
be taken throughout to make certain
that the seats are kept perfectly flat�
Ifconsiderable lapping is required, spread
a thin coat of medium coarse lapping
compound on the block� After lapping with
the medium coarse compound, lap again
with a medium grade compound� Unless
much lapping is called for, the first step
can be omitted� Next, lap again using a
fine grade compound� When all nicks
and marks have disappeared, remove all
the compound from the block and seat�
Applypolish compound to another block
and lap the seat�
As the lapping nears completion, only the
compound left in the pores of the block
should be present� This should give a very
smooth finish� If scratches appear, the
cause is probably dirty lapping compound�
These scratches should be removedby
using compound free from foreignmaterial�
Disk inserts should be lapped in the
same way as nozzles� The disk insert
must be removed from the holder before
lapping� Before the disk insert is placed
back in the holder all foreign material
should b
e removed from both parts�
The insert must be free when in the
holder� If the disk insert is damaged too
badly to be reconditioned by lapping, it
should be replaced�
Remachining the insert will change critical
dimensions, affect the action of the valve
and is not recommended�
• Lapping blocks
Lapping blocks are made of a special
grade of annealed cast iron� There is a
block foreach orifice size� Each block
has two perfectly flat working sides and
it is essential that they retain this high
degree of flatness to produce a truly flat
seating surface on either the disc insert
or the nozzle� Before a lapping block is
used, it should be checked for flatness and
reconditioned after use on a lapping plate�
The block should be lapped in a figure
eight motion, applying uniform pressure
while rotating the lapping block against
the plate as shown in Figure 9�
• Lapping compounds
Experience has proven that medium
coarse, medium fine and polish lapping
compounds will condition any damaged
pressure relief valve seat properly except
where the damage requires remachining�
The following lapping compounds, or their
commercial equivalents are suggested:
other major repairs are necessary, it is
recommended that the valve be returned
to a Emerson facility for repair� All
parts must be machined accurately per
Emerson specifications�
No pressure relief valve will be tight,
nor will it operate properly unless all
parts are machined correctly� The most
satisfactory way to machine a nozzle is to
remove it from the valve body� However,
it may also be machined while assembled
within the valve body� In any event, it is
vitally important that the seating surfaces
run absolutely true before machining�
FGHJKLMNPQRT
in. mm in. mm in. mm in. mm in. mm in. mm in. mm in. mm in. mm in. mm in. mm in. mm
Machining dimensions for Crosby Style
JOS-E/JBS-E Valves with metal-to-metal
FIGURE 10
Nozzle seat critical dimensions
nozzle seats are shown in Figure 10
and Table 8� Remove only enough metal
to restore the surface to its original
condition� Turning to the smoothest
possible finish will facilitate lapping�
The nozzle must be replaced when
minimum face to seat dimension is
Minimum
face to
seat dim,
refer to
Table 8
reached� This critical dimension is shown
in Table 8�
6.5.3 Machining of disk insert seats
When the damage to the disk insert seat
is too severe to be removed by lapping,
the disk insert may be machined and
lapped provided that minimum seat height
is maintained (Figure 11 and Table 9)�
Seat
15°
0�004 after lapping
Related
surfaces
45°
Raised seal face
0�010-0�014
machined
0�008 min after
lapping
FIGURE 11
Disk insert minimum seat height (Table 9)
All components should be clean� Before
assembling the following parts, lubricate with
pure nickel 'Never-Seez'�
• Nozzle and body threads
• Nozzle and body sealing surface
• All studs and nut threads
• Spindle and threads
• Set screw threads
• Spring washer bevels
• Adjusting bolt and bonnet threads
• Bonnet pipe plug
• Cap threads
• All metal gaskets
• Dog shaft bearing threads
• Disk holder threads (bellows valves only)
Lubricate the spindle point thrust bearing and
disc insert bearing with pure nickel 'NeverSeez'� Special attention should be given to
the guiding surfaces, bearing surfaces and
gasket surfaces to ensure that they are clean,
undamaged and ready for assembly (Figure 12)�
For parts identification, refer to Figure 1�
6.6.1 Before installing the nozzle (2) apply
lubricant to the flange surface in contact
with the valve body (1) and on the body
to nozzle threads� Screw the nozzle (2)
into the valve body (1) and tighten with a
nozzle wrench�
6.6.2
Screw the nozzle ring (3) onto the nozzle (2)�
Note: the top of the nozzle ring should be
above the nozzle seating surface� For P,
Q, R and T orifice Style JLT, position the
nozzle ring per Table 2�
6.6.3 For bellows valves only, place the disk
holder in a vise (larger sizes may require
a 3 jaw vise) as shown in Figure 8�
Installthe tailpiece gasket (29)�
Screw the bellows assembly onto
the disc holder� Tighten with a
suitable wrench�
6.6.4 Assemble the disk insert (8) and the disc
holder (5)�
seat assembly)�
Install the disk insert retention clip (9)
onto the disk insert�
Install the disk insert into the disk
holder� The disk insert should snap into
place using handforce only�
Safety precautions should be followed
whenever heavy parts are being lifted
or transported�
Dropping the disk holder assembly may
dislodge the insert�
6.6.5
Assemble the disk holder (5) and guide (15)
by sliding the guide over the disk holder�
Note: The guide for D and E orifice valves
protrudes up into the valve bonnet�
6.6.6 Install the two guide gaskets (28),
oneabove and one below the guide�
Note: When assembling bellows valves,
the bellows flange eliminates the need
for a bottom guide gasket�
(See Figure 14 for O-ring soft
6.6.7
While holding the top of the disk holder,
install the guide into the body� Align the
hole of the guide with the body outlet� Once
the guide is seated, the disk holder and
disk insert can be lowered onto the nozzle�
Note: Lower the nozzle ring below the
seats so that it moves freely�
6.6.8 Place the spring (18) and washers (19)
onto the spindle (16) and assemble the
spindle to the disk holder (5) with the
spindle cotter pins�
Note: No cotter pins are required in D
through K orifice sizes; all other orifice
sizes use two cotter pins�
6.6.9
Lower the bonnet (20) over the spindle
and spring assembly onto the bonnet
studs (21) in the body� Position the bonnet
counter bore on the O�D� of the guide and
lower the bonnet onto the guide�
6.6.10 Screw the bonnet nuts (22) onto the
bonnet studs and tighten down evenly
to prevent unnecessary strain and
possible misalignment�
6.6.11 Screw the adjusting bolt (24) and
nut (25) into the top of the bonnet to
apply force on the spring� (The original
set pressure can be approximated by
screwing the adjusting bolt down to the
predetermined measurement)�
6.6.12 Move the nozzle ring up until it touches
the disk holder, then lower it two
notches� This is a test stand setting only�
6.6.13 Place the set screw gasket (27) onto
the set screw (4) and screw the set
screw into the body engaging the nozzle
ring� The nozzle ring should move back
and forth slightly after the set screw
is tightened�
6.6.14 The valve is now ready for testing�
After testing, the following measures
should be taken:
• Be sure that adjusting bolt nut (25) is
locked�
• Return the nozzle ring to either the
original recorded position or to the
recommended position shown in Table 1�
• Install the cap or lifting device�
SeeFigure 14 for lifting lever assembly�
• Seal the cap or lifting lever device
and nozzle ring set screw to
prevent tampering�
Crosby JOS-E and JLT-JOS- E Pressure Relief
Valves are available in a restricted lift version�
All J series variations including JBS and all
service medias may be supplied in a restricted
lift version� The purpose of a restricted lift valve
is to more closely match the required capacity
of the protected vessel or pipe with the actual
and rated capacities of the relief valve providing
over-pressure protection�
Restricted lift (RL) versions of the J series may
be built by a certified Emerson manufacturing
facility or by an ASME certified Assembler with
the required certification specific to the RL
version (National Board certificates 01045 and
01382)� Any ASME marked RL valve may be VR
repaired by a repair organization certified under
the National Board VR repair program� Existing
non- restricted lift versions of the J series may
be converted to the restricted lift version by
VR certificate holders� In addition existing RL
versions may have their lift modified using the
same procedures�
NOTE
Restricted lift valves may be identified by the restricted
lift nameplate by model number with “-RL"�
6.7.1
Restricted lift valves have a limit spacer
that prevents the disc and disc holder
from lifting its limits� These valves may be
restricted to a minimum lift of 30% of the
full rated capacity or �080 in� (2�03 mm)�It
is important to check lift on all restricted
lift valves to ensure accuracy of the
capacity on the nameplate� For production
purposes the spacers are precut for 10%
increments� 5% increments can be added
for K orifice and larger�
6.7.2 Determining the correct limit spacer height
• T
• The required lift should also
• Select the limit spacer(s) to the
he nameplate capacity should
be as specified on the nameplate
or determined by calculation
(See example on page 18)�
be specified on the nameplate
or determined by calculation
(See example on page 18)�
required limit spacer height
(See Table 10 and 11)�
6.7.3 Measure the valve lift.
• Install the limit spacer (see Figure 13)
with the chamfer down and reassemble
the valve as described in Steps 6�6�1
through 6�6�10�
Note: install bellows to disc holder for
JBS F orifice valve, then install spacer�
•
Measure the lift of the valve and
compare it with the required lift as given
on the restricted lift nameplate with
tolerance (-0�020 in�, +0�020 in�
[-0�50 mm, +0�50 mm])�
• Based on the results, if the lift is not in
the tolera
If the actual lift is less than required, machine
the limit spacer as necessary to obtain the
required lift� (Machine chamfer, deburr and
polish before installation into the valve�)
If the actual lift is greater than required, obtain
a new next taller limit spacer, disassemble
the valve and return to section 6�7�3� (Machine
chamfer, deburr and polish before installation
into valve�)
• Once correct lift is obtained,
disassemble the valve�
•
Ensure the limit spacer has been
chamfered to fit over the radius of the
disc holder� The limit spacer must be
installed so that the chamfered end is
mating to the back face of disc holder,
and not sitting on the disc holder radius�
• Prior assembly, verify the lift for
each
CAUTION
Do not interchange internal parts or use a
different nozzle after a set of parts has been
custom-fit.
valve�
nce:
6.7.4 Assembly
Valves need to be assembled as per
section 6�6�
6.7.5 Restricted Lift Nameplate
For new restricted lift version valves, use
the restricted lift nameplate (See Figure 2�)
I
f a non-restricted lift J series PRV is
converted to the RL version, or if the
restricted lift is changed on an existing
RL version valve the following procedure
regarding nameplates should be followed�
• The information on the original ASME
nameplate which is changed by the
conversion, such as model number,
capacity and restricted lift should be
lightly etched out�
• Information changed by conversion of
the valve or change to the restricted
lift shall be included on the repair
nameplate to serve as a record of
the conversion and its effect on the
performance of the PRV�
Styles JOS-E, JBS-E and JLT-E Pressure Relief
Valves are furnished with several different
caps and lifting lever devices� The following
describes assembly of the available types of
cap construction�
(Disassembly is the reverse of assembly)�
Forpart identification refer to Figure 14�
• Type A and J
Install the cap gasket and screw the cap onto
the top of the bonnet� Tighten the cap with a
strap wrench�
• Type B and K
Install the cap gasket and screw the cap onto
the top of the bonnet� Tighten the cap with
a strap wrench� Install the cap plug gasket
and screw cap plug into the cap� The test rod
is installed only during system hydrostatic
testing� Never install the test rod unless
performing system hydrostatic testing�
• Type C
Screw the spindle nut onto the spindle�
Place the cap on the bonnet� Install the forked
lever and forked lever pin� Attach the lever to
the cap using the lever pin and secure with
the lever pin cotter�
Adjust the spindle nut until the forked
lever rests on the lever and there is a
1
/
16 in� (1�58mm) minimum of play between
the forked lever and the spindle nut� The
spindle nut may be adjusted by removing the
forked lever pin, forked lever and cap� When
the spindle nut is in proper adjustment, install
the spindle nut cotter pin� Replace the cap
and forked lever and install the forked lever
pin and forked lever pin cotter�
Position the lever opposite the valve outlet
and install the four (4) cap set screws and
tighten them against the groove in the top of
the bonnet�
• Type D
Install the cap gasket on the bonnet� Screw
the spindle nut onto the spindle� Place the
dog in the cap and install the dog shaft so
that the dog is horizontal and the square
on the end of the dog shaft has a corner on
top� With the dog shaft in the position above,
scribe a horizontal line on the end of the dog
shaft� This line must be horizontal when the
lifting gear is finally installed on the valve�
Installthedog shaft O-ring in the dog shaft
bearing and place the dog shaft bearing
gasket on the dog shaft bearing�
Screw the dog shaft bearing into the cap�
Rotate the dog shaft so that the dog is
pointing down and install the cap assembly
onto the bonnet� Rotate the dog shaft so that
the dog contacts the spindle nut� With the
scribed line horizontal, remove the assembly
and adjust the position of the spindle nut�
Repeat the operation until the scribed line is
horizontal when the dog contacts the spindle�
Remove the assembly and install the spindle
nut cotter pin�
Install the lifting gear assembly onto the
bonnet and secure it with cap studs and nuts�
For Type D lifting levers that have two part
caps (cap and cap top) the above procedure
is accomplished more easily� After the cap is
screwed to the bonnet, the positioning of the
dog shaft is the same as above except that the
positioning of the spindle nut is performed
last through the open end of the cap�
With the dog in the horizontal position,
screw the spindle nut onto the spindle until
it contacts the dog� Install the spindle nut
cotter, cap top gasket and screw the cap top
into the cap�
• Type E
Assembly of Type E lifting lever is identical
to Type D with the addition of the cap plug
gasket and cap plug� The test rod is installed
only during system hydrostatic testing�
Neverinstall the test rod unless performing
system hydrostatic test�
• Type G and L
Install the cap studs to the bonnet top�
Placethe cap gasket onto the bonnet and the
cap onto the cap studs� Install and tighten cap
stud nuts�
• Type H and M
Assembly of Type H and M is identical to
Type G and L with the addition of the cap plug
gasket and cap plug� The test rod is installed
only during system hydrostatic testing� Never
install the test rod unless performing system
hydrostatic test�
6.9 Soft seat construction
Coat O-ring with 'Parker Super O-Lube'
and place a small amount of Loctite 242
(orequivalent removable thread lock) onto
retainer screw before assembly� Tighten
retainer screw(s) securely�
seated pressure relief valves may be
converted to an O-ring soft seat by replacing
the standard disc insert and nozzle with those
parts designed to house the O-ring soft seat
or vice versa�
The Crosby Style JOS-E Pressure Relief
Valve was designed with flexibility and
interchangeability in mind� Retrofitting
from conventional to balanced bellows high
performance liquid trim or soft seat design
is accomplished with a minimum number
of new parts� These style retrofits can be
accomplished at lowest possible cost�
• Balanced bellows
A Crosby JOS-E Conventional Non-bellows
Pressure Relief Valve may be converted
to a Style JBS-E balanced bellows valve
simply by adding the bellows assembly and
tailpiecegasket�
• JLT liquid trim
Crosby Style JOS-E/JBS-E Pressure
Relief Valves in D to N orifice sizes may be
converted to high performance JLT liquid
service design simply by replacing the
standard disk holder with a JLT disc holder,
or vice versa� For P to T orifice sizes, a new
nozzle ring is alsorequired�
Relief Valves in all orifice sizes may be
converted from the standard metal-tometal seats to an exceptionally tight soft
seat design� This style conversion can be
accomplished by replacing the standard
disc insert and nozzle with parts adapted to
accommodate the soft seat design�
The soft seat design uses standard size
O-rings and is capable of handling pressures
to 1480 psig (10,204 kPa)� Standard O-ring
materials include NBR, EPR, FKM, Kalrez
®
,
Silicone and PTFE (see Figure 15 and Table 12)�
8 SERVICE RECORDS
Service records should be completed before
a valve is returned to service� These records
are important and will provide guidance on
establishing time intervals between repairs as
well as providing the historical record of repairs
and service conditions� Well kept records will
be useful in predicting when to retire a valve
and which spare parts should be maintained in
inventory to ensure uninterrupted plant operation�
9 SPARE PARTS
When ordering spare parts, the valve shop
number, assembly number or serial number
should be given together with set pressure, part
name and item number, valve size and style�
On the valve nameplate, the valve assembly
number is shown as shop number�
Spare parts may be ordered from any Emerson
regional sales office or representative�
10 TROUBLE SHOOTING PRESSURE
RELIEF VALVES
Troubles encountered with pressure relief
valves can affect the life and performance of
the valve vitally and must be corrected at the
first possible opportunity�
Failure of a pressure relief valve to function
properly could result in the rupture of a line or
vessel jeopardizing the safety of personnel and
causing damage to property and equipment�
Some of the most common troubles and
the recommended correction measures are
discussed in the following paragraphs�
10.1 Seat leakage
Of all the problems encountered with pressure
relief valves, seat leakage is the most common
and the most detrimental� A leaking valve
allows fluids to circulate into the secondary
pressure zone of the valve where it can cause
corrosion of the guide and valve spring�
When a leaking valve problem is not addressed
immediately, the leakage itself will further
contribute to seat damage through erosion
(wire-drawing)�
10.1.1 Seats damaged by foreign matter
Seating surfaces may be damaged
when hard foreign particles such as mill
scale, welding spatter, coke and dirt are
trapped between the seats� While this
type of damage usually occurs while the
valve is in service, it may also happen in
the maintenance shop� Every precaution
should be taken to clean the process
system before installing a pressure relief
valve and to test the valve using only
clean fluids�
Generally, damaged seating surfaces
are reconditioned by lapping� Most often
small pits and scratches may be removed
by lapping alone� More extensive damage
will also require remachining prior
tolapping�
In some instances, valve construction can
be changed to reduce the effects of seat
leakage� The use of an O-ring soft seat
when applicable will minimize leakage
and thus eliminate the associated
corrosion and erosion problems� If it is
not possible to use a soft seated valve, or
if the corrosive media is present in the
exhaust system, conversion to a Style
JBS bellows seated valve will isolate and
protect the guides and valve spring from
any corrosive fluids�
excessive piping loads causing seat
leakage� Both inlet and discharge
piping must be supported properly and
anchored so that high bending loads are
not transmitted to the valve body�
10.1.3 Operating pressure too close to
set pressure
A carefully lapped metal-to-metal
seated valve will be commercially tight
at a pressure approximately ten percent
under the set pressure or 5 psi (34 kPa),
whichever is greater� Consequently, this
minimum pressure differential should be
maintained between set and operating
pressure to avoid seat leakage problems�
10.1.4 Chatter
Oversized valves, excessive pressure drop
in the inlet lines, restrictions in the inlet
line, too great a build up of back pressure
or pulsating inlet pressure will cause
instability to the pressure relief valve� In
such installations, the pressure under the
valve disc may be great enough to cause
the valve to open but, as soon as flow is
established, the pressure drops allowing
the valve to close immediately� This cycle
of opening and closing sometimes occurs
at very high frequency causing severe
seat damage, sometimes beyond repair�
Proper valve selection and installation
techniques are paramount to reliable
valve performance�
10.1.5 Incorrectly adjusting lifting gear
1
A space of
/
16 in� (1�58 mm) minimum
should always be provided between the
lifting device and the spindle lift nut�
Failure to provide sufficient clearance
may result in inadvertent contact causing
a slight shift in the opening pressure�
10.1.6 Other causes of seat leakage
I
mproper alignment of the spindle, too
much clearance between the valve spring
and the spring washers, or improper
bearing contact between the adjusting
bolt and the spring washers, spindle
and disc holder or spindle and lower
spring washer may cause seat leakage
problems� Spindles should be checked
for straightness and springs and spring
washers should be fitted properly and
kept together as a spring assembly�
10.1.7 Corrosion
Corrosion may result in pitting of valve
parts, failure of various valve parts, build
up of corrosive products and general
deterioration of the valve materials�
Generally, corrosive attack is controlled
through selection of suitable materials
or by employing a bellows seal to isolate
the valve spring, adjusting bolt, spindle
and guiding surfaces from the corrosive
attack of the process fluid�
Environmental corrosion attacks all
exposed surfaces, including studs and
nuts� In general, the materials required
for a particular service are dictated
by the temperature, pressure and the
degree of corrosion resistance required�
11 EMERSON FIELD SERVICE AND REPAIR
PROGRAMS
Emerson field service
provides on-site, in line
testing and repair capability for all types of
pressure relief devices�
11.1 Parts
Emerson will help you establish the right mix of
on-site spares with Emerson’s own distribution
and manufacturing support�
11.2 Training
Emerson offers intensive factory or onsite seminars to improve maintenance and
application skills�
11.3 Testing
Emerson has the capability to evaluate
pressure relief valve operability either in the
field or at various Emerson facilities� Special
qualifications programs may also be conducted
in our laboratories�
11.4 Contract management
Emerson will combine a group of services to
satisfy your special maintenance needs�
WARNING
The product is a safety related component
intended for use in critical applications.
Theimproper application, installation or
maintenance of the product or the use of parts or
components not manufactured by Emerson may
result in failure of the product. The advice of a
qualified engineer should be sought prior to any
use of the product.
Any installation, maintenance, adjustment,
repair or test performed on the product must be
done in accordance with the requirements of all
applicable codes and standards.
The information, specifications and technical data
(the 'Specifications') contained in this document
are subject to change without notice. Emerson
does not warrant that the specifications are
current and assumes no responsibility for the use
or misuse thereof.
The purchaser should verify that there have been
no changes to the specifications prior to use.
The contents of this publication are presented for informational purposes only, and while every effort has been made to ensure their accuracy, they are not to be construed
as warranties or guarantees, express or implied, regarding the products or services described herein or their use or applicability� All sales are governed by our terms and
conditions, which are available upon request� We reserve the right to modify or improve the designs or specifications of such products at any time without notice�
Emerson Electric Co� does not assume responsibility for the selection, use or maintenance of any product� Responsibility for proper selection, use and maintenance of any
Emerson Electric Co� product remains solely with the purchaser�
Emerson�com
22
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