Honeywell HON 5020 User And Maintenance Manual page 33

HON 5020 gas pressure regulator with HON 640a / HON 642a pilot
 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.
Basics for installing the device in a pipe
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