Basics for installing the device in a pipe
User manual for HON R100 gas pressure regulator with HON P095NG pilot
29
4.3
Operating and measuring lines
The lines must be arranged and sized in such a way that the devices’ intended function will be
ensured.
Measuring line
The measuring line transmits the pressure process value from the sensing
point to the measuring diaphragm of a controller or the pilot of a gas pressure
regulator or safety relief valve or to the measuring diaphragm of the moni‐
toring device of a slam‐shut device. It needs to be connected to the pipe
sideways or upwards separately for each device. In the case of safety equip‐
ment, the measuring line must be connected upstream of the first outlet‐side
shut‐off device in such a way that it cannot be shut off. If the measuring line is
additionally connected downstream of the first outlet‐side shut‐off device,
3‐way ball valves with negative overlap must be used for switching. These ball
valves do not have a valve position in which both measuring lines can be fully
closed at the same time.
Vent line
The vent line is used to connect a measuring diaphragm to the atmosphere. If
the measuring unit becomes damaged (e.g.,
diaphragm rupture), it can start
conveying gas. Under certain operating conditions, and following consultation
with the manufacturer, vent lines can be omitted if vent valves (HON
915) or
safety diaphragm configurations can be used instead.
Blowdown line
The blowdown line in a safety relief valve is used to divert gas (leaking gas,
for
example) into the atmosphere.
Grouping vent lines or blowdown lines (into a header) is permissible if it does not have a
negative impact on the individual devices’ operation. Within this context, it is recommended
to have the cross‐sectional area of the header be at least five times as large as the total of the
individual lines’ cross‐sectional areas.
For primary slam‐shut devices, it is recommended to route the slam‐shut devices’ vent lines
separately. Vent lines must not be grouped together with blowdown lines.
Discharging line
When using indirect acting (pilot‐operated) slam‐shut devices, the discharg‐
ing line is used to divert the exhaust gas from the pilot into the system’s out‐
let chamber. On certain devices, the discharging line will be grouped with the
feedback line.
Feedback line
When using indirect acting (pilot‐operated) slam‐shut devices, the feedback
line is used to return the outlet pressure to the actuator.
Connection lines between
device and gas regulating
line
