Emerson Fisher 627H - De-Icer System and Overpressure Protection; Type 627 M;627 HM De-Icer System Application; Overpressure Protection Mechanisms

627 Series
6
EQUALIZING LINE
NEEDLE
VALVE
HAND
VALVE
WORKING REGULATOR
CONTROL LINE
TYPE 627M SET LOWER
THAN WORKING REGULATOR
GRAVITY FEED
ALCOHOL DRIP POT
VENT VALVE
INLET
A3725
Perform steps 7 through 9 for Types 627M, 627HM,
and 627MR regulators only:
7. A Type 627M, 627HM, or 627MR regulator requires
a downstream control line. Install the control line
before putting the regulator into operation.
8. Ensure that the downstream control line piping
is at least 3/8 inch / 9.5 mm or larger outside
diameter tubing and connected to a straight
section of outlet piping 10 diameters downstream
of the regulator.
9. A hand valve should be installed in the control line.
This hand valve can be used to throttle down and
dampen outlet pulsations in control pressure which
may cause instability or cycling of the regulator.
Remote Vent Line Installation
All 627 Series regulators have a vent assembly
installed in the 3/4 NPT spring case vent opening.
The vent assembly can be removed to install a
remote vent line if necessary. Remote vent lines
must have the largest practical diameter. It should be
as short as possible with minimum number of bends
or elbows.
Protect the remote vent opening against entrance of
rain, snow, or any other foreign material that may plug
the vent or vent line and prevent proper operation of
the regulator. Periodically check the vent opening to
be sure it is not plugged with foreign debris.
Type 627M or 627HM Regulator
De-Icer System Application
For the Type 627M or 627HM regulator de-icer
system, refer to the application shown in Figure 3.
With a large pressure drop across the working
regulator, ice can form within this regulator. The
formation of ice decreases the size of the orice, so
the regulator is unable to supply enough ow to satisfy
the downstream demand. When the downstream
pressure falls below the outlet pressure setting of the
Type 627M or 627HM regulator, the disk assembly
of the Type 627M or 627HM regulator moves off its
orice, permitting alcohol to ow into the main gas
line. The alcohol carried to the main regulator by the
owstream prevents additional ice from forming on the
orice. When normal ow resumes, and as pressure
in the downstream system is restored, the Type 627M
or 627HM regulator shuts off.
Overpressure Protection
627 Series regulators have outlet pressure ratings that
are lower than their inlet pressure ratings. A pressure-
Figure 3. De-Icer System Operational Schematic