These instructions provide information for installation, electrical connection, process
®
connection and calibration of SOR
Series 20 Differential Principle Basic construction is a Static “O” Ring diaphragm and
piston pressure sensor. Process pressure acts on the diaphragm to produce force Fh
against the piston. Fh is counteracted by two forces: Fl, which comes from the Lo side
Pressure port through the electrical housing, and Fs which comes from the adjustable
range spring. Since the Lo side process media pressurizes the electrical housing, Lo side
process media is limited to clean, dry air or inert gas.
NOTE: If you suspect that a product is defective, contact the factory or the SOR Representative
in your area for a return authorization number (RMA). This product should only be installed by
trained and competent personnel.
When Fh exceeds the combination of Fl and Fs, the piston (and piston shaft)
moves to actuate the electrical switching element.
There are only three wetted parts on
the Hi side process connection:
pressure port, diaphragm and o-ring.
F
I
NC
NO
C
The force-balance system
F
virtually eliminates friction
and resultant wear while
yielding excellent repeatability.
F
h
d
F
s
Series 20 Differential Pressure
Switches are well suited for a variety
A
of process applications. They are not intended for high-pressure fluid power (hydraulic)
applications where high-shock pressures and high-cycle rates are expected.
Installation
This type of differential pressure switch can be mounted in any position. Install low range
models in the same orientation that they are calibrated.
Weathertight Housing Attach the device to a suitable surface or pipe stanchion bracket
with two 1/4-inch diameter bolts. Line mounting by either process or electrical connection
is not recommended.
Explosion Proof Housing The TA housing must be attached with 2-inch U-bolts over the
housing hubs or two 1/4-inch diameter bolts. Line mounting by either process or electrical
connection is not recommended.
Failure to mount the housing on a at mounting surface may result in
torsional forces on the housing that could cause false trips or render the
pressure switch inoperative.
When mounting to an irregular or uneven surface, install rubber washers
on the bolts between the housing and the mounting surface (except in
high-vibration applications) to prevent housing deformation, which could
change the relative positions of internal parts and affect calibration or
render the device inoperative.
The SOR pressure switches have been evaluated as Type-A safety related hardware.
To meet the necessary installation requirements for the SIL system, the following
information must be utilized:
Proof Test Interval shall be one year.
Units may only be installed for use in Low Demand Mode.
Products have a HFT (Hardware Fault Tolerance) of 0, and were evaluated in a
Ensure that wiring conforms to all applicable local and national electrical codes and install
unit(s) according to relevant national and local safety codes.
SOR Series 20 Differential Pressure Switches have 18”, 18-AWG, color-coded wire leads
which extend switching element contact circuits through a glass-to-metal seal. The
glass-to-metal seal assembly maintains Lo side pressure containment. Use two wrenches,
one on the seal assembly and one on the conduit fitting to avoid movement of the seal
assembly during installation.
Wiring Schematic
SPDT
No.1
LO
Differential Pressure
HI
2-SPDT
LO
No.2
Differential Pressure
HI
Blue (C)
Black (NO)
Red (NC)
Green (GND)
Blue (C)
Black (NO)
Red (NC)
Yellow (C2)
Brown (NO2)
Orange (NC2)
Before removing the cover during test or while the unit is in service,
relieve pressure inside the housing by venting Lo side pressure to
atmosphere. When replacing the cover, tighten it securely. Pressurize
the Lo side and apply a liquid leak test solution around the cover seal to
make sure that pressure is not leaking
If a set point was specified for factory calibration, there may be no need to remove the
pressurized electrical housing cover. Factory calibration can be verified on a test bench by
connecting a continuity tester across the common (C) and normally open (NO) wire leads.
Pressurize the Hi side pressure port and check actuation (deactuation) points on a
calibrated reference gauge.
Units in Hazardous Locations: Prior to calibration, make sure that the work
area is declassi ed before removing the explosion proof cover to calibrate
the unit. Failure to do so could result in severe personal injury or substantial property damage.
Disconnect electrical power before removing cover in hazardous area!
Avoid movement of the electrical switching element or its bracket. It has
been precisely positioned for optimum performance at the factory. Even
slight movement will affect performance; excessive movement can render
device inoperative.
If no set point was specified for factory calibration, or if the set point specification has
changed:
Remove housing cover. Calibrate the device as a gauge pressure switch. Turn the set
point adjusting nut clockwise to increase the set point, or counterclockwise to decrease
the set point.
To verify Series 20 operation under system operating conditions, install the cover and
tighten it securely. Connect the HI and LO sides to suitable pressure sources and raise
the pressures simultaneously to the expected system operating pressure. Apply a
liquid leak test solution around the cover seal to make sure that Lo side pressure is not
leaking. Vary Lo side pressure to verify actuation (deactuation) of the electrical
switching element at the desired Differential Pressure Set Point.
Dimensions in these instructions are for reference only. They may be changed without
notice. Contact the factory for Certified Drawings for a particular model number.
Weathertight — NEMA 4, 4X, IP65 Piston Number 22
Designator: RB, RH