INSTALLATION, OPERATION & MAINTENANCE MANUAL (IOM)
MODEL BQ
BACK PRESSURE / RELIEF REG U LA TOR
SECTION I
I. DESCRIPTION AND SCOPE
The Model BQ is a back pressure relief regulator used to control upstream (inlet or P1) pressure. Side inlet and fl ow-thru
connections are 1/4", 3/8", and 1/2" NPT (DN8, DN10, DN15); outlet (bottom discharge) connection is always 1/2" NPT (DN15).
With proper trim utilization, the unit is suitable for liquid, gaseous, or steam service. Refer to Technical Bulletin BQ-TB for design
conditions and selection rec om men da tions.
CAUTION
This is not a safety device and must not be substituted for a code approved pressure safety relief valve or a rupture disc.
SECTION II
II. INSTALLATION
CAUTION
CAUTION
For welded installations, all internal trim parts, seals and
diaphragm(s) must be removed from reg u la tor body prior to
welding into pipeline. The heat of fusion welding will dam age non-metallic parts if not re moved. NOTE: This does
not apply to units equipped with extended pipe nip ples.
Installation of adequate overpressure pro tec tion is recommended to pro tect the reg u la tor from overpressure
and all down stream equip ment from damage in the event
of regulator failure.
IOM-BQ
12-13
1. An inlet block valve should always be installed.
2. If service application is continuous such that shutdown
is not readily accomplished, it is recommended that
an inlet block valve, outlet block valve, and a manual
bypass valve be installed.
3. Pipe unions should be installed to allow removal from
piping.
4. An inlet pressure gauge should be located ap prox i mate ly
ten pipe diameters upstream and within sight. An outlet
pressure gauge is optional.
5. All installations should include an upstream relief de vice
if the inlet pressure could exceed the pressure rating of
any equipment or the maximum inlet pres sure rating of
the unit.
WARNING
The maximum inlet pressure is equal to 1.5 times the larger
number of the stated range spring on the name plate, and is
the recommended “upper operative limit” for the sens ing
di a phragm. Higher pressures could damage the di a phragm.
(Field hy dro stat ic tests fre quent ly destroy di a phragms.
DO NOT HY DRO STAT IC TEST THRU AN IN STALLED UNIT;
ISOLATE FROM TEST.)
Recommended piping schematic for Back Pressure Regulator
6. Clean the piping of all foreign material including chips,
welding scale, oil, grease and dirt before installing the
regulator. Strainers are recommended.
7. In placing thread sealant on pipe ends prior to en gage ment, ensure that excess material is removed
and not allowed to enter the regulator upon startup.
8. Flow Direction: Install so the fl ow direction matches
the arrow cast on the body. Connect the inlet pressure
to the body side connection(s). Fluid will relieve out of
the bottom connection. The double inlet connections
are for in-line installation (plug one side connection if
in-line installation is not required).
9. Regulator may be installed in a vertical or horizontal
pipe. If it is a steam system, ensure the piping is properly
trapped and vented.
10a. Basic Regulator - (Refer to Figure 1): Regulator may
be rotated around the pipe axis 360°. Recommended
positions are with the spring chamber vertical upwards,
or horizontal. Orient such that the spring chamber vent
hole does not collect rainwater or debris.
10b. Cryogenic Regulator - Option -5 or -36 (Figure 2):
a. Recommended installation is with spring cham ber
hang ing directly below the body in a ver ti cal down wards orientation. Allow water to drain; i.e. melting
frost, rain water.
b. Recommend inert purge gas to spring cham ber
through vent hole and out drain hole.
10c. Differential Regulator - Option -1+6 (Refer to Figure 3).
SECTION III
III. PRINCIPLE OF OPERATION
1. Movement occurs as pressure variations register on
the diaphragm. The registering pressure is the inlet,
P
or upstream pressure. The range spring opposes
1
di a phragm movement. As inlet pressure drops, the range
SECTION IV
IV. STARTUP
* NOTE: Systems sequencing operations at startup, normal opera-
tion, failure mode(s), and shutdown must assure that the pressure
(P
) on the spring chamber does not exceed the pressure regis-
Load
tering on the wetted side of the diaphragm. Should this "pressure
reversal" occur, particularly to metal diaphragms, the diaphragm
may be permanently damaged and cause improper operation.
P
> P
1
Load
Pressure reversal is normally caused by the inlet pressure
to a regulator being interrupted (automatically or manually).
1. Ensure the proper range spring is indicated to be within
the regulator by inspection of the unit's name plate. Apply
setpoint pressures that are only within the stated range.
2. When stating direction of rotation of the adjustment screw,
the view is with respect to looking down towards the
adjusting screw or its normal location.
3. Start with the block valves closed. A bypass valve may be
used to maintain inlet pressure in the upstream system
without changing the following steps.
4. Remove closing cap, if installed. Relax the range spring
by turning the adjusting screw counterclockwise (CCW)
a minimum of three (3) full revolutions. This reduces the
inlet (upstream) pres sure setpoint.
5. If it is a “hot” piping system, and equipped with a bypass valve, slowly open the bypass valve to pre-heat
the system piping and to allow slow expansion of the
piping. Ensure proper steam trap operation if installed.
Closely monitor inlet (upstream) pressure, via gauge, to
ensure not over-pressurizing. NOTE: If no bypass valve
is installed, extra caution should be used in starting up
a cold system; i.e. do everything slowly.
6. Crack open the inlet (upstream) block valve.
a. Recommended installation is with the spring cham ber
directed upwards.
b. No corrosive fl uid should be utilized for spring cham-
ber loading.
c. System operation should ensure that loading pres-
sure (P
diaphragm damage may occur if this op er a tion al
) not exceed inlet pressure (P1); in ter nal
LOAD
mode occurs.
11. Regulators are not to be direct buried underground.
For insulated piping systems, recommendation is to
not insulate regulator.
12. Spring Chamber Vent Tap - Option -25: Pipe spring
chamber vent opening to remote location. Orient so as
not to take on rainwater.
spring pushes the diaphragm down, closing the port;
as inlet pressure increases, the di a phragm pushes up
and the port opens.
2. A com plete diaphragm failure will cause the outlet
process fl uid to mix with the loading fl uid.
7. Slowly open the outlet (downstream) block valve ob serv ing the inlet (upstream) pressure gauge. De ter mine if
the regulator is fl owing. If not, slowly rotate the regula-
tor adjusting screw counterclockwise (CCW) until fl ow
begins.
8. Continue to slowly open the outlet (downstream) block
valve until fully open.
9. Observing the inlet (upstream) pressure gauge, rotate
the adjusting screw clockwise (CW) slowly until the inlet
pressure begins to rise. Rotate CW until the desired
setpoint is reached.
10. Continue to slowly open the inlet (upstream) block valve.
If the inlet (upstream) pressure exceeds the desired
setpoint pressure, rotate the adjusting screw (CCW)
until the pressure decreases.
11. When fl ow is established steady enough that both the
outlet and inlet block valves are fully open, begin to
slowly close the bypass valve if installed.
12. Develop system fl ow to a level near its ex pect ed normal
rate, and reset the regulator setpoint by turning the
adjusting screw CW to increase inlet pressure, or CCW
to reduce inlet pressure.
13. Reduce system fl ow to a minimum level and observe
setpoint. Inlet pressure will rise from the setpoint of Step
9. (Ensure that this rise does not exceed the stated upper
limit of the range spring by greater than 50% i.e. 30-80
psig (2.07 - 5.52 Barg) range spring, at maximum fl ow
the inlet pressure should not exceed 1.5 x 80 (5.6 Barg)
or 120 psig (8.3 Barg). If it does, consult factory.)
14. Increase fl ow to maximum level if possible. Inlet (up-
stream or P
as necessary at the normal fl ow rate.
) pressure should rise. Readjust setpoint
1
IOM-BQ2
V. SHUTDOWN
1. On systems with a bypass valve, and where system
pressure is to be maintained as the regulator is shut
down, slowly open the bypass valve while closing the inlet
(upstream) block valve. Fully close the inlet (up stream)
block valve. When on bypass, the system pressure must
be con stant ly ob served and manually regulated. Close
the outlet (down stream) block valve.
CAUTION
SECTION V
CAUTION
Do not walk away and leave a bypassed reg u la tor un at tend ed!
2. If the regulator and system are both to be shutdown,
slowly close the inlet (upstream)block valve. Close the
outlet (downstream) valve only if regulator re mov al is
required.
SECTION VI
VI. MAINTENANCE
WARNING
SYSTEM UNDER PRESSURE. Prior to performing any
main te nance, isolate the regulator from the system and
relieve all pressure. Failure to do so could result in personal injury.
A. General:
1. Maintenance procedures hereinafter are based
upon removal of the regulator unit from the pipeline where installed.
2. Owner should refer to owner’s procedures for
removal, handling, cleaning and dis pos al of nonreuseable parts, i.e. gaskets, etc.
3. Refer to Figure 1 for basic construction, Figure 3 for
differential construction and Figure 2 for cryo gen ic
construction. For a blow-up of the com po si tion seat
trim, see Figure 4.
4. When counter clockwise (CCW) or clock wise (CW)
rotations are indicated, they are with respect to:
3. Draw or embed a match mark between body cast ing
(1) and spring chamber casting (2) along fl anged
area.
4. Remove all fl ange nuts (8) and fl ange bolts (7).
5. Remove spring chamber (2), range spring (11) and
spring button (12).
6. Remove the diaphragm subassembly con sist ing
of the piston cap screw (9), pres sure plate (10),
diaphragm(s) (4), piston (3.1) and piston gasket
(5). NOTE: Refer to the quantity of diaphragm(s)
(4) in cor po rat ed in the bill of ma te ri als listing.
De pend ing on inlet pres sure level, multiple met al
di a phragms may be “stacked”.
a. Spring Chamber - as viewed from above look-
ing down towards the closing cap or its normal
lo ca tion.
b. Body - as viewed looking into the body cavity
with the spring chamber removed.
B. Diaphragm Replacement:
1. Securely install the body (1) in a vise with the spring
chamber (2) directed upwards.
WARNING
SPRING UNDER COMPRESSION. Prior to removing fl ange
bolts, relieve spring compression by backing out the adjusting screw. Failure to do so may result in fl ying parts
that could cause personal injury.
2. Relax range spring (11) by turning adjusting screw
(13) CCW until removed from spring cham ber (2).
IOM-BQ
Diaphragm Sub as sem bly
7. To disassemble the diaphragm subassembly,
place piston (3.1) in a vise and rotate piston cap
screw (9) CCW. NOTE: Rec om mend using lead
jaws when placing the piston in a vise, so as not
to damage the piston grooves.
8. Separate all parts (3.1, 4, 5, 9 and 10) and clean
piston gasket (5) surface on piston (3.1) if piston is
to be reused. NOTE: No piston gasket (5) utilized
for composition diaphragm.
9. Inspect pressure plate (10) to ensure no de for ma tion due to over-pressurization. If de formed,
re place.
10. Remove diaphragm gasket (6) for metal di a phragm.
NOTE: No diaphragm gasket (6) utilized for com-
po si tion diaphragm.
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