Emerson Fisher OS2 Instruction Manual page 3

BM1
TYPE OS2
E0564
MECHANISM BOX (BM1) WITH 1 MANOMETRIC SENSING DEVICE
(TYPE BMS1)
APPLICATION
Overpressure Shutoff (OPSO)
Underpressure Shutoff (UPSO)
Overpressure Shutoff (OPSO) and Underpressure Shutoff (UPSO)
Overpressure Shutoff (OPSO) and Underpressure Shutoff (UPSO)
Overpressure Shutoff (OPSO), Overpressure Shutoff (OPSO) and
Underpressure Shutoff (UPSO)
1. When using one manometric sensing device for both overpressure and underpressure shutoff, make sure that the difference between set pressures falls within the maximum range
shown in Table 2.
2. When using two manometric sensing devices (Types BMS1 and BMS2), the Type BMS1 can only be used for high trip.
protection (UPSO) or overpressure and underpressure
protection (OPSO/UPSO). When de-energized, the solenoid
valve allows the Type BMS manometric device to monitor
the controlled pressure as if the solenoid valve was not
present. When energized, the solenoid valve will be
repositioned to connect the Type BMS manometric device to
atmospheric pressure tripping the underpressure protection
slam-shut setting.
Principle of Operation (See Figure 3)
The Type OS2 slam-shut device used on Types OSE,
627-OSX, EZH-OSX, EZL-OSX and EZR-OSX provides
overpressure and/or underpressure protection by shutting off
the flow to the downstream system. The slam-shut valve is
typically installed upstream of a pressure reducing regulator
as shown in Figures 3 and 4.
Pressure is registered on one side of the diaphragm, piston
or bellows and is opposed by the setpoint control spring of
the manometric sensing device. The Type OS2 slam-shut
device tripping pressure is determined by the setting of the
control spring.
TYPE BMS1
TOP-MOUNTED (STAND-ALONE TYPE OSE VALVE)
Figure 2. Types of Installation
Table 1. Applications and Construction Guide (See Figure 2)
MECHANISM BOX REQUIRED
BM2
TYPE BMS2
(LEFT SIDE)
E0565
MECHANISM BOX (BM2) WITH 2 MANOMETRIC SENSING DEVICES
(TYPES BMS1 AND BMS2)
MANOMETRIC SENSING DEVICE REQUIRED
BM1
BM2
Overpressure: when the sensed pressure increases
above the setpoint, the pressure on top of the diaphragm
overcomes the spring setting and moves the manometric
device stem.
Underpressure: when the sensed pressure decreases
below the setpoint, the control spring pressure below the
diaphragm overcomes the downstream pressure and pushes
the diaphragm which moves the manometric device stem.
When the sensed pressure reaches the OPSO or UPSO
setpoint, the manometric device stem contacts Pin D1 or D2
and triggers the detection stage which activates the second
stage, releasing the slam-shut valve plug. A tight and total
shutoff is ensured by the plug seal O-ring closing on the
orifice and is helped by the "dash pot" effect between the
bonnet skirt and the valve plug. A "dash pot" effect occurs
when the valve plug closes by having both the closing spring
and the inlet pressure pushing on top of the valve plug.
This is accomplished by ports around the skirt of the bonnet
allowing inlet pressure above the valve plug.
Type OS2
TYPE BMS1
(RIGHT SIDE)
BMS1 - - - -
BMS1 - - - -
BMS1 - - - -
(1)
BMS1 BMS2
(2)
BMS1 BMS2
(2) (1)
3