Ashcroft B Series Pressure Switch

Ashcroft B Series pressure switches are designed to satisfy most switch requirements. Materials of construction have been selected for long life. A wide variety of precision switch elements are available to meet every application requirement, including hermetically sealed contacts for added reliability and safety. Special designs are available for fire safety, NACE, limit control and other more stringent requirements. Simplicity and ease of use are stressed to improve reliability of the installation.

Pressure and differential pressure switches use two different actuators depending on setpoint requirements. For setpoints between 2 and 3000 psi, the simple, rugged diaphragm-sealed piston actuator is used. This design features high reliability and choice of actuator seal materials for virtually every application. An optional welded design is also available for setpoints up to 1000 psi. Differential pressure models use a unique, dual diaphragm-sealed piston design that features very high static operating pressures and small size.

All standard models feature ±1 percent of range setpoint repeatability and a minimum of 400 percent of range proof pressures. These standard designs perform well in applications where shock and vibration could be a problem and may be used in conjunction with Ashcroft diaphragm seals in extreme services such as slurries or abrasive process fluids.

Ashcroft B Series Pressure Switch Applications

• Pumps
• Compressors
• Washers
• Filters
• Degreasers
• Evaporators
• Recovery systems,
• Food processing
• Ground support equipment
• Reverse osmosis systems
• Heat exchangers
• Hydraulic systems
• Lubrication systems
• Chemical and petrochemical plants
• Offshore oil rigs
• Water and sewage treatment plants
• Corrosive environments

Frequently Asked Questions

What is the Ashcroft B Series pressure switch?

The Ashcroft B Series is a mechanical pressure switch that monitors process pressure and changes the state of an electrical contact when pressure reaches a selected setpoint. It can be used to start or stop equipment, activate an alarm, or initiate a safety shutdown without requiring a separate pressure transmitter or controller. The series is designed for industrial, process, OEM, and hydraulic applications that require reliable switching and long operating life.

How does the Ashcroft B Series pressure switch work?

Process pressure acts on an internal sensing element that mechanically operates a snap-action electrical switch. When pressure rises or falls through the adjusted setpoint, the electrical contacts change state and send an on/off signal to the connected control circuit. Standard configurations use a diaphragm-sealed piston actuator for setpoints between 2 and 3,000 psi, while other actuator designs are available for different pressure requirements.

What is the Ashcroft B Series used for?

The B Series can provide pressure control, equipment shutdown, alarm indication, and process interlocking. Typical applications include pumps, compressors, filters, hydraulic systems, lubrication systems, heat exchangers, reverse-osmosis systems, food-processing equipment, chemical plants, offshore installations, and water or wastewater treatment facilities.

What pressure ranges are available?

Ashcroft B Series pressure switches are available in vacuum, compound, and positive-pressure configurations. The Instrumart product offering includes models with setpoint ranges beginning around 2 psi and pressure capabilities extending to 6,000 psi, depending on the selected actuator and configuration. The operating range should be chosen so the desired setpoint falls comfortably within the switch’s adjustable range rather than at its extreme limits.

What is a pressure-switch setpoint?

The setpoint is the pressure at which the switch’s electrical contacts change state. For example, a switch may be adjusted to shut down a pump when discharge pressure rises above a predetermined limit or to activate an alarm when lubrication pressure falls too low. B Series setpoints may be factory adjusted or field adjusted according to the selected model and application requirements.

What is deadband on a pressure switch?

Deadband is the difference between the pressure at which the switch activates and the pressure at which it resets. A switch adjusted to activate at 100 psi might not reset until pressure falls several psi below that point. Selecting the correct deadband prevents rapid cycling or contact chatter when process pressure fluctuates near the setpoint.

How repeatable is the Ashcroft B Series pressure switch?

Standard B Series models provide setpoint repeatability of ±1% of the adjustable range. Repeatability indicates how consistently the switch activates at the same pressure during repeated pressure cycles under similar operating conditions. This makes the B Series suitable for applications where dependable alarm, control, or shutdown operation is more important than continuously displaying the exact process pressure.

What is the difference between the B4 and B7 pressure switches?

The B4 is a watertight pressure switch with a NEMA 4X and IP66 enclosure, making it appropriate for industrial environments exposed to moisture, dust, corrosion, or outdoor conditions. The B7 uses a NEMA 7/9 explosion-proof enclosure and is intended for approved hazardous locations where flammable gases, vapors, or combustible dust may be present. The required enclosure must be selected according to the installation’s environmental conditions and hazardous-area classification.

Can the Ashcroft B Series be used outdoors?

Yes. The B4 watertight model has a NEMA 4X and IP66 enclosure designed for outdoor and washdown-prone industrial environments. Properly installed conduit, electrical connections, process fittings, and enclosure seals are necessary to maintain the environmental rating of the completed installation.

Can the Ashcroft B Series be used in hazardous locations?

The B7 explosion-proof configuration is available for hazardous industrial and process locations. Depending on the selected model, certifications and approvals may include FM, UL, CSA, ATEX, and IECEx. The exact model number, electrical rating, approval markings, and hazardous-location classification must be verified before installation.

What electrical switch outputs are available?

The B Series is available with several snap-action switch elements, including SPDT and DPDT contact arrangements. Hermetically sealed switch contacts are also available for applications requiring added protection from corrosive atmospheres or improved electrical reliability. The correct switch element should be selected according to the circuit voltage, current load, switching function, and required number of independent contacts.

What is the difference between SPDT and DPDT contacts?

An SPDT, or single-pole double-throw, switch provides one common terminal that can switch between normally open and normally closed contacts. A DPDT, or double-pole double-throw, switch performs the same function for two electrically separate circuits at the same setpoint. DPDT contacts are useful when one pressure event must activate two independent control or alarm circuits.

What process media is the Ashcroft B Series compatible with?

Media compatibility depends on the selected actuator, diaphragm, seal, and process-connection materials. Multiple actuator seal materials are available to accommodate a broad range of industrial liquids and gases, while welded configurations are available for certain applications where elastomer seals are undesirable. Compatibility should be verified against the exact process fluid, temperature, pressure, and concentration before ordering.

Can the B Series be used with corrosive or abrasive fluids?

Yes, but the switch may require compatible wetted materials or an Ashcroft diaphragm seal. A diaphragm seal isolates the switch from corrosive, viscous, abrasive, crystallizing, or slurry-type process media while still transmitting process pressure to the sensing element. The seal and fill fluid must be selected for the specific process conditions.

Is the Ashcroft B Series suitable for hydraulic systems?

Yes. The B Series is designed for hydraulic equipment and other applications where pressure shock, vibration, and repeated cycling may occur. Its diaphragm-sealed piston actuator, high proof-pressure capability, and rugged enclosure options make it suitable for hydraulic power units, mobile equipment, lubrication systems, pumps, and related machinery when properly ranged and installed.

How much overpressure can the B Series withstand?

Standard models have proof-pressure ratings of at least 400% of the selected adjustable range, subject to the limits of the specific actuator and process connection. Proof pressure is the pressure the switch can withstand without permanent damage, but it is not the recommended continuous operating pressure. Expected pressure spikes and surge conditions should be considered when selecting the range.

Can the Ashcroft B Series be used in safety shutdown systems?

Certain B Series configurations are suitable for use in safety-instrumented applications and are listed as SIL-capable when the complete system is properly designed, installed, tested, and maintained. Suitability depends on the exact model, trip direction, system architecture, proof-testing program, and required safety integrity level. The product nameplate and applicable safety documentation should be verified before using the switch as part of a safety function.

Where should the pressure switch be installed?

The switch should be installed where it is accessible for wiring, adjustment, inspection, and proof testing. Excessive vibration should be avoided or reduced with appropriate mounting or damping methods, and pressure tubing should be arranged to prevent leaks, blockages, trapped condensate, or damaging temperature exposure. Installation must also remain within the switch’s pressure, process-temperature, ambient-temperature, enclosure, and electrical ratings.