Maintenance - Emerson Fisher OS2 Instruction Manual

6. Verify that the trip pressure is equal to the desired
pressure setting by increasing pressure to the
Type BMS2, resetting the detection stage and then
reducing pressure to the Type BMS2 until the detection
stage trips. Adjust trip pressure setting if necessary.
resetting the Trip Mechanism
Resetting of the Type OS2 slam-shut device is done
manually and, for NPS 8 and 10 / DN 200 and 250 body
sizes, with the bypass valve open. After the Type OS2 has
closed, it must be manually reset before it can be placed
back in service. Before resetting the Type OS2, check for
and correct the reason for the overpressure/underpressure
condition. For the following procedures, see Figures 7 and 8.
To reset the detection stage, the pressure
in the manometric sensing device must
be below the overpressure trip point and/
or above the underpressure trip point.
Otherwise the detection stage cannot
be reset.
Because the Type OS2 mounted on the
Type EZHOSX, EZrOSX or EZLOSX is turned
180°, the following directions apply to the
Type OSE only, however, the reset procedure
for the Type EZHOSX, EZrOSX or EZLOSX is
the same. When a specific direction is given
(i.e. top left), the Type EZHOSX, EZrOSX
or EZLOSX direction will be reversed
(i.e. bottom right).
To reset the Type OS2, close the upstream block valve.
Open the front cover of the mechanism box.
Detection Stage (First Stage)
The reset pin with white dot is at the top center location of
the mechanism box, see Figure 8. Push this pin up and to
the right (Type OSE only, see note above). This action will
lock in the detection stage (see step A in Figure 7).
Power Stage (Second Stage)
The reset tool is keyed and will only fit on
the second stage releasing shaft in one
orientation. Be sure the tool securely fits
onto the shaft before turning.
To reset the power stage, use the square reset tool located
on the lower left corner of the mechanism box. Place the
square end of the tool on the second stage releasing shaft at
the center of the box and slowly rotate clockwise (see step B
in Figure 7).
*For further instructions on Types EZR, EZH and EZL, refer to the corresponding instruction manual of these products.
note
note
note
When movement is started on the stem, the internal bypass
in sizes from NPS 1 through 6 / DN 25 through 150 will open
and equalize the pressure on each side of the valve plug
before the valve plug can be moved off the seat. For NPS 8
and 10 / DN 200 and 250, external bypass valve should be
opened. Continue turning the reset tool.
CaUTiOn
Wait for the pressure on each side of the
valve plug to equalize before proceeding to
the following steps. never use an extension
with the reset tool when resetting the
second stage. Failure to do so may result in
equipment damage.
This action will raise the valve plug, compress the closing
spring and latch the second stage (power stage) mechanism.
Replace the reset tool on its holder and replace the cover.
Slowly open the upstream block valve.
Shutdown*
Warning
!
To avoid personal injury or property damage
due to explosion or damage to shutoff
device, regulator or downstream components
during shutdown, release downstream
pressure to prevent an overpressure
condition on the regulator diaphragm.
Installation arrangements may vary, but in any installation it
is important that the valves be opened or closed slowly. The
steps below apply to the typical installation.
1. Slowly close the downstream shutoff valve.
2. Slowly close the upstream shutoff valve.
3. Slowly open the vent valves downstream of the
slam-shut valve.
4. Slowly open the vent valves upstream of the
slam-shut valve.

Maintenance

Instructions are given for complete disassembly and
assembly. Key numbers are referenced in Figure 14 for
NPS 1 through 6 / DN 25 through 150 body sizes and
Figure 15 for NPS 8 and 10 / DN 200 and 250 body sizes
unless otherwise noted.
Type OS2
11