Basics
for installing the device in a pipe
HON 5020 gas pressure regulator with HON 630 pilot
32
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.
