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Industrial Pressure Switches
Industrial Pressure Switches

Class 9012/9016/9025

CATALOG CONTENTS
Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Page

Class 9012 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-16
Class 9016 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-18
Class 9025 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19-20
Type XML, Type XMLE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21-60
Courtesy of Steven Engineering, Inc.-230 Ryan Way, South San Francisco, CA 94080-6370-Main Office: (650) 588-9200-Outside Local Area: (800) 258-9200-www.stevenengineering.com
� 1998 Square D All Rights Reserved

2

5/98
Courtesy of Steven Engineering, Inc.-230 Ryan Way, South San Francisco, CA 94080-6370-Main Office: (650) 588-9200-Outside Local Area: (800) 258-9200-www.stevenengineering.com
Industrial Pressure Switches

Class 9012, Type GDescription

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� 1998 Square D All Rights Reserved

DESCRIPTION

The Class 9012 Type G pressure switches are UL Listed and CSA Certied as industrial control
equipment. They are used to interface pneumatic or hydraulic systems with electrical control systems
by opening or closing electrical contacts in response to pressure changes in the system. They have
outstanding repeatability and drift performance. Their efcient design uses durable, low mass
components for excellent performance under heavy duty vibration and shock conditions.
The Type G pressure switches includes diaphragm and piston actuated devices with a variety of
modications (see page 14).
Type G diaphragm switches range from 0.2-675 psi falling pressure. Buna-N diaphragms and zinc plated
steel anges are standard. Diaphragms of Viton

and ethylene propylene are available as well as
stainless steel anges.
Type G piston actuated switches range from 20-9,000 psi falling pressure. They have sealed pistons and
can be used on air, water, oil, or any media compatible with the actuator material. Piston actuated
switches come standard with stainless steel pistons and housings, VITON

�

diaphragms and o-ring
seals, and Teon

�

retaining rings. Ethylene propylene diaphragms and o-ring seals are also available.
Features for both diaphragm and piston actuated pressure switches include:
High shock resistance
Dual numerical range scale (psi and kPa)
High set point stability
SPDT or DPDT double break contacts
Adjustable or nonadjustable differential
Internal or external range adjustment
No drain line required
Single stage operation
Dual stage operation
Differential pressure operation
Type G

industrial

switches are available as open type or in NEMA Type 1 enclosures. The backplate is
steel with a plastic cover. Open type devices in pressure ranges up to 250 psi are available with internal
or external threaded pressure connectors making them ideally suited for panel mounting.
Type G

machine

tool switches have NEMA Type 4, 4X, or 13 (IEC IP66) cast aluminum enclosures.
These devices are UL Listed and CSA Certied as industrial control equipment. They are UL Listed for
use in Class II, Division 2, Group G and Class III hazardous locations. They are also UL Marine Listed
for use on vessels greater than 65 feet long where ignition protection is not required.
Type G

machine

tool switches are also available in NEMA Type 7 & 9 cast iron enclosures. These are
UL Listed for use in Class I, Divisions 1 and 2, Groups C and D, and Class II, Divisions 1 and 2, Groups
E, F, G hazardous locations.
Courtesy of Steven Engineering, Inc.-230 Ryan Way, South San Francisco, CA 94080-6370-Main Office: (650) 588-9200-Outside Local Area: (800) 258-9200-www.stevenengineering.com
Industrial Pressure Switches

Class 9012, Type GApplication and General Information

� 1998 Square D All Rights Reserved

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5/98

APPLICATION AND GENERAL INFORMATION

Pressure switches are used in a wide variety of applications such as:
compressors
HVAC equipment
chillers
pumping systems
machine tools
stamping presses
automatic grinders
welders
process equipment
molding machines
Generally, Class 9012 pressure switches can be used in any application where electrical contacts must
open or close in response to a system pressure change, within the electrical and pressure ratings of the
switch.
Two typical functions of a pressure switch are to:
Monitor the pressure in the system. The switch can be used as either an interlock that will sequence
operations in an automatic system, or to give an audio or visual signal, typically an alarm of an
undesired condition, at predetermined pressures.
Control the pressure in the system by starting and stopping a pump or a compressor at
predetermined pressures.
Normally a switch with a nonadjustable differential is used in applications that monitor the pressure. An
adjustable differential switch is usually necessary in applications that require the switch to control the
pressure.

Bellows vs. Diaphragm

The three factors that affect bellows life are the compatibility of the pressure medium with the bellows
and bellows housing material, the amount of pressure change during each operating cycle, and the
speed of operation.
On wide pressure change applications, the bellows is exed over a wide portion of the range on each
operating cycle causing the metal to fatigue faster than if it exes over a small portion such as between
the operating points only. This will reduce life. The Type G is offered with either diaphragm or piston
actuators only for maximum versatility, speed of operation, and life.
Diaphragm life, like bellows life, is affected by pressure medium compatibility. Standard diaphragms on
Class 9012 Type G devices are nitrile (Buna-N) in zinc plated steel anges. Fluorocarbon (VITON

�

) and
ethylene propylene diaphragms as well as Type 316 stainless steel anges are also available.
The elastomer diaphragms used on Class 9012 switches are capable of withstanding high speed cycling
and wide pressure changes. Operating speeds up to 200 cycles per minute are not detrimental to the
life of the diaphragm.
Surges which exceed the maximum range value may occasionally occur, especially on start-up of the
machine (see section on surges). The switch will withstand these occasional surges if they are within
the maximum allowable pressure rating of the switch. However, frequently applying this higher pressure
will greatly reduce the life of the switch.
Although the diaphragm will withstand wide pressure changes on each operating cycle, the pressure
applied to the diaphragm during the normal operating cycle should never exceed the maximum value
listed in the Range column in the catalog listing. Life will be considerably reduced if regularly cycled
above this pressure. If signicant surges are common or if pressures are higher than listed in the
Range column, consider the use of a piston device.
Courtesy of Steven Engineering, Inc.-230 Ryan Way, South San Francisco, CA 94080-6370-Main Office: (650) 588-9200-Outside Local Area: (800) 258-9200-www.stevenengineering.com
Industrial Pressure Switches

Class 9012, Type GApplication and General Information

5

5/98
� 1998 Square D All Rights Reserved

Surges

One of the most destructive elements to a pressure switch is the hydraulic surge. A surge is a high rate
of rise in pressure, normally of short duration, caused by starting a pump or opening and closing a valve.
Extremely high rates of rise in pressure can be damaging even though they are within the limits of the
maximum allowable pressure.
To limit the effect of surges, the switch should be mounted as close to an accumulator and as far from
the pump or quick acting valve as possible. Type G piston actuated switches are supplied with a 0.020"
pressure orice to help reduce the effects of minor surges. Type G diaphragm actuated switches are
supplied with a 0.060" pressure orice. A restrictor with a small orice placed in the line between the
switch and pump or valve will further help to protect the switch. Using a surge snubber such as the Class
9049 Types A26 or A26S will also protect the switch.

Vibration

Among other things, excessive vibration can cause contact bounce, chatter or premature contact
transfer especially when system pressure is near the operating point of the switch. Remote mounting of
the switch is the best way to avoid problems.

Use On Steam

Switches should not be applied directly on steam exceeding 15 psig. However, with the installation of a
Class 9049 Type A7A steam capillary tubing kit between the pressure connection and the switch, steam
pressure up to 250 psig may be applied provided this does not exceed the maximum allowable pressure
rating of the switch or the maximum temperature rating at the actuator.

Piston vs. Diaphragm

Selecting between piston and diaphragm devices depends on several criteria: 1) maximum allowable
pressure, 2) range and differential, 3) surges and 4) media, whether hydraulic or pneumatic.
Maximum allowable pressures for piston devices are much higher than