What is the 45APE Series pressure gauge used for?

The 45APE Series is a mechanical pressure gauge that combines local pressure indication with two independently adjustable SPDT snap-acting switches. It is used to monitor system pressure and automatically trigger alarm, shutdown, or start-stop control actions when pressure rises above or falls below user-set trip points. Common applications include gas compressors, hydraulic systems, pumping stations, oil and gas production equipment, and any industrial process requiring both pressure readout and protective switching within a single instrument.

What is the difference between the 45APE and 45APEF models?

The 45APE is the surface-mount (square case) version, designed for direct panel-surface or wall installation with conduit entry via a 1/2 NPTF fitting and terminal block wiring. The 45APEF is the panel-mount (round case) version, configured for flush installation in control panels with wire lead terminations. Both models share the same dual-sector bourdon tube mechanism, SPDT switching capability, pressure range options, and accuracy specifications.

What bourdon tube materials are available?

Two bourdon tube and socket material combinations are available. The standard configuration uses bronze tube with a brass socket, suitable for general service with non-corrosive media up to 1,000 psi. For higher pressures or corrosive process fluids, a 316 stainless steel tube and 316 stainless steel socket combination is available across the full pressure range, providing superior resistance to chemical attack, moisture, and sour gas environments.

Can the 45APE Series be used in hazardous locations?

Yes. An explosion-proof (EX) enclosure option is available for the 45APE Series, rated for Class I, Groups C and D hazardous locations, covering pressure ranges through 5,000 psig. CSA-certified EX models are approved for hazardous area installation where flammable gases or vapors may be present. Standard models are CSA certified for non-hazardous locations. An explosion-proof less case (EL) option is also available for specific installation configurations.

How accurate are the 45APE Series switches and pressure indication?

The indicating pointer achieves ±2% accuracy in the first and last quarters of the scale, and ±1% in the middle half, with switch-point hysteresis below 1%. Switch point accuracy is ±1.5%. Accuracy above or below the trip point varies by range: ±10% for ranges below 100 psi, ±4% for 100–300 psi, ±2% for 400–1,500 psi, ±12% for 2,000 psi, and ±8% for 3,000–5,000 psi ranges. Switch reset deadband is approximately 10% of full scale.

45APE Series mechanical pressure gauge with dual adjustable SPDT snap-acting switches for alarm and equipment shutdown on compressors and industrial systems

45APE Series Pressure Gauge

4-1/2 in. Dial | Dual SPDT Switches | Bourdon Tube

Pressure Monitoring · Alarm & Shutdown · Industrial Control

45APE Series Pressure Gauge – 4-1/2 in. Dial with Dual Adjustable SPDT Snap-Acting Switches

The 45APE Series is a 4-1/2 in. (114 mm) dial mechanical pressure gauge that integrates real-time pressure indication with two independently adjustable SPDT snap-acting switches. Designed for direct wiring into alarm, start/stop, and equipment shutdown circuits, it delivers continuous pressure readout alongside reliable automatic switching action in a single rugged instrument — available in surface mount (45APE) and panel mount (45APEF) configurations for gas compressors, pumping systems, hydraulic circuits, and general industrial pressure control applications.

4-1/2" Dial Size

5,000 psi Max Range

2× SPDT Switches

2A/250V Contact Rating

Key Features

The 45APE Series pressure gauge delivers dependable local pressure indication and active process protection within a single, field-proven instrument. Its clearly readable 4-1/2 in. dual-scale psi/kPa dial gives operators an immediate pressure reference, while two independently adjustable SPDT switches enable precise low and high trip points for alarm annunciation, equipment shutdown, or start-stop control — all without requiring a separate pressure transmitter or external controller. Built around a stainless steel dual-sector bourdon tube mechanism in a die-cast aluminum enclosure, the 45APE Series handles pressures from 30 psi to 5,000 psi and is well-suited to the demanding environments typical of compressor stations, pumping skids, hydraulic power units, and oil and gas production facilities. Surface mount (45APE) and panel mount (45APEF) variants, multiple bourdon tube material options, and an explosion-proof enclosure for hazardous area installations make it straightforward to select exactly the right instrument for virtually any pressure monitoring and switching requirement.

Integrated Pressure Indication and Dual SPDT Switching: The 45APE Series combines a precision mechanical pressure gauge with two independently adjustable SPDT snap-acting switches in one compact instrument. The indicating pointer displays actual process pressure across the full dial scale, while a concealed switch operator pointer tracks the indicating pointer and is arrested by the adjustable low and high trip point indicators. When pressure crosses a set threshold, the lost-motion principle trips the corresponding snap switch — completing the electrical circuit for alarm, shutdown, or control without any external power supply at the sensing point.
Stainless Steel Dual-Sector Geared Movement: At the heart of the 45APE Series is a stainless steel dual-sector geared mechanism that drives two separate pointers from a single bourdon tube. The primary sector drives the visible indicating pointer across the full graduated dial for accurate pressure readout. The secondary sector drives the switch operator pointer behind the dial. This dual-pointer design allows the indicating pointer to continue reading pressure above or below either trip point, giving operators a live pressure reference even after a switch has been tripped — a significant advantage for diagnostics and process recovery.
Independently Adjustable Low and High Trip Points: Both the low and high pressure switch setpoints are adjustable directly on the gauge front lens, without disassembly or special tools. Operators can reposition each trip point indicator independently to any point on the dial scale during commissioning or after process changes, providing maximum flexibility. The front-accessible adjustment eliminates the need to remove the gauge from service to change setpoints, reducing maintenance downtime on critical equipment.
Wide Pressure Range from 30 psi to 5,000 psi: The 45APE Series accommodates an exceptionally broad range of industrial pressure requirements. Standard ranges start at a combined vacuum/pressure span of 30 inches Hg to 100 psi and extend through eleven gauge pressure ranges to 5,000 psi (34.48 MPa). This coverage makes the series suitable for low-pressure pneumatic control systems, medium-pressure hydraulic circuits, and high-pressure gas compression and wellhead applications — all within the same proven instrument platform.
Choice of Bourdon Tube Materials for Compatibility: Two sensing element material configurations are available to match the process fluid. A bronze bourdon tube with brass socket provides reliable performance for general service with non-corrosive media in ranges up to 1,000 psi. For aggressive fluids, high-pressure service, or sour gas environments, a 316 stainless steel bourdon tube paired with a 316 stainless steel socket is available across the full range, delivering superior corrosion resistance and long service life in chemically challenging conditions.
Explosion-Proof Option for Hazardous Area Installations: For installations in areas classified for flammable gases or vapors, the 45APE Series is available with a CSA-certified explosion-proof (EX) enclosure rated for Class I, Groups C and D hazardous locations, covering pressure ranges through 5,000 psig. Standard non-EX models are CSA listed for non-hazardous locations. An explosion-proof less case (EL) option is also available for specific installation and panel configurations requiring the gauge mechanism without its own outer enclosure.
Dual-Scale psi and kPa Dial for Global Readability: Every 45APE Series instrument is fitted with a 4-1/2 in. white-on-black dial displaying pressure simultaneously in both psi and kPa. This dual-scale format eliminates unit conversion requirements for engineering teams and field operators working across different measurement standards, and ensures the gauge is immediately usable in any international industrial or marine environment without replacement or relabelling.

Applications

Gas Compressor Pressure Monitoring and Shutdown: Suction and discharge pressure management is critical to compressor efficiency and mechanical integrity. The 45APE Series, installed at compressor inlet, interstage, or discharge points, provides continuous pressure readout while the high-pressure switch initiates automatic shutdown if discharge pressure exceeds safe operating limits — and the low-pressure switch detects suction loss or downstream line breaks before equipment damage occurs.
Hydraulic Power Unit and System Protection: Hydraulic circuits depend on precise pressure management to protect pumps, actuators, and valves from over-pressure conditions. The 45APE Series monitors hydraulic system pressure and can trigger bypass valve actuation or pump shutdown through its high-pressure switch contact, while the low-pressure switch provides early warning of line rupture, filter blockage, or pump failure — protecting costly hydraulic components from pressure-induced damage.
Pump Station Pressure Monitoring: Water, chemical, and hydrocarbon transfer pump stations require pressure monitoring at suction and discharge to confirm proper flow conditions and detect abnormal pressure events. The 45APE Series provides both local pressure readout for field operators and automatic switch outputs for remote alarm panels or PLC inputs, supporting safe and efficient pump station operation without requiring a separate pressure transmitter for switching functions.
Oil and Gas Production and Wellhead Equipment: Surface production equipment — including separators, treaters, wellhead Christmas trees, and test manifolds — routinely requires pressure indication with high and low switching for process safety and regulatory compliance. The 45APE Series, with its stainless steel bourdon tube option and explosion-proof EX enclosure, is suited to these environments, delivering both the pressure readout and the switching capability needed for safe production operations at a single installation point.
Industrial Process Equipment and Machinery: Across a broad range of manufacturing and process industries — including chemical production, food and beverage processing, and general plant utility systems — the 45APE Series provides reliable pressure monitoring and alarm switching for air receivers, boilers, heat exchangers, filtration systems, and piping networks. Its adjustable trip points can be configured to match any process operating window, and its snap-acting SPDT switch output integrates directly with existing alarm and control panels without additional signal conditioning.
Control Panel Integration with 45APEF Panel Mount Model: The 45APEF panel-mount round case variant is designed specifically for flush installation in compressor control panels, engine management cabinets, and pump skid electrical enclosures. Its round case fits standard circular panel cutouts, and wire lead terminations simplify panel wiring to the terminal arrangement. The front-accessible trip point adjusters remain fully operable after panel installation, enabling setpoint changes during commissioning without the need to open the panel enclosure.

Technical Specifications

45APE Series instruments are available in surface mount (45APE) and panel mount (45APEF) configurations across eleven pressure ranges. Key specifications are listed below for engineering reference and procurement purposes.

Parameter	Specification
Dial Size	4-1/2 in. (114 mm) diameter
Dial Display	White on black; dual scale, psi and kPa standard
Sensing Principle	Stainless steel dual-sector geared bourdon tube mechanism
Pressure Ranges Available	30" Hg vac–100 psi \| 0–60 \| 0–100 \| 0–200 \| 0–300 \| 0–400 \| 0–600 \| 0–1,000 \| 0–1,500 \| 0–2,000 \| 0–3,000 \| 0–5,000 psi
Case Material	Die-cast aluminum; surface mount (square case) or panel mount (round case)
Sensing Element Options	Bronze bourdon tube / brass socket (standard, ≤1,000 psi); 316 SS tube / 316 SS socket (full range)
Process Connection	1/4 NPTM (ranges through 1,000 psi); 1/2 NPTM (1,500–5,000 psi)
Overrange Limit	Do not exceed 10% above full scale range
Indication Accuracy (within switch points)	±2% (first and last quarters of scale); ±1% (middle half of scale); hysteresis <1%
Accuracy Above/Below Trip Point – <100 psi range	±10%
Accuracy Above/Below Trip Point – 100–300 psi	±4%
Accuracy Above/Below Trip Point – 400–1,500 psi	±2%
Accuracy Above/Below Trip Point – 2,000 psi	±12%
Accuracy Above/Below Trip Point – 3,000–5,000 psi	±8%
Switch Point Accuracy	±1.5%
Switch Reset Deadband	Approximately 10% of full scale
Switch Type	2 × SPDT snap-acting switches (low and high)
Switch Contact Rating	2 A @ 250 VAC
Pressure Relief Disc	Located at rear of case (not fitted on EX explosion-proof models)
Wire Connections – Surface Mount (45APE)	1/2 NPTF conduit entry with terminal block
Wire Connections – Panel Mount (45APEF)	Wire leads, 18 AWG (1.0 mm²) × 9 in. (229 mm) long
Available Models	45APE (surface mount, square case); 45APEF (panel mount, round case)
Enclosure Options	Standard; Explosion-Proof EX (Class I, Groups C & D, ≤5,000 psig); EL (Explosion-Proof Less Case)
Weight – Standard Models	5 lbs 6 oz (2.4 kg) approximately
Weight – Explosion-Proof Models	21 lb (9.5 kg) approximately
Shipping Dimensions – Standard	10 × 9 × 6 in. (254 × 229 × 152 mm)
Shipping Dimensions – Explosion-Proof	12 × 12 × 9 in. (305 × 305 × 229 mm)
Certifications	CSA certified for non-hazardous locations (all ranges); CSA explosion-proof EX models: Class I, Groups C & D (≤5,000 psig)

Technical FAQ

Common Questions Answered

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The 45APE Series is a mechanical pressure gauge that combines local pressure indication with two independently adjustable SPDT snap-acting switches. It monitors system pressure and automatically triggers alarm, shutdown, or start-stop control actions when pressure rises above the high trip point or falls below the low trip point. Common applications include gas compressors, hydraulic power units, pumping stations, oil and gas production equipment, and any industrial process requiring both local pressure readout and automatic protective switching within a single instrument — without the need for a separate pressure transmitter or controller.

The 45APE is the surface-mount square case version, designed for direct surface or wall mounting with a 1/2 NPTF conduit entry and terminal block for wiring connections. The 45APEF is the panel-mount round case version, designed for flush installation in control panels with wire lead terminations. Both models use the same stainless steel dual-sector bourdon tube mechanism, identical SPDT switching capability, the same range of pressure options, and equivalent accuracy specifications — the choice depends solely on the preferred mounting configuration for the installation.

The 45APE Series covers an exceptionally wide pressure range, from a combined vacuum/positive pressure span of 30 inches Hg vacuum to 100 psi, through eleven standard gauge ranges up to 5,000 psi (34.48 MPa / 344.73 bar). Available gauge ranges include 0–60, 0–100, 0–200, 0–300, 0–400, 0–600, 0–1,000, 0–1,500, 0–2,000, 0–3,000, and 0–5,000 psi. When selecting a range, the normal operating pressure should fall within the middle half of the dial scale to take advantage of the ±1% indication accuracy in that zone.

Two sensing element material configurations are offered. The standard option pairs a bronze bourdon tube with a brass socket, well-suited to general industrial service with compatible, non-corrosive process media in ranges up to 1,000 psi. For higher-pressure service, corrosive fluids, wet gas environments, or applications where sour gas (H₂S) may be present, a 316 stainless steel bourdon tube with a 316 stainless steel socket is available across the full range up to 5,000 psi. The stainless steel option is strongly recommended for offshore, marine, and petrochemical installations.

Yes. An explosion-proof (EX) enclosure option is available for the 45APE Series, CSA certified for Class I, Groups C and D hazardous locations, covering pressure ranges through 5,000 psig. This option houses the complete gauge mechanism and switch assembly within a certified explosion-proof enclosure, making it suitable for natural gas compressor stations, oil and gas wellheads, refineries, and other classified areas where flammable gases or vapors may be present. An explosion-proof less case (EL) option is also available for specific panel integration requirements. Standard models are CSA certified for non-hazardous locations.

Within the normal switch point window, the indicating pointer achieves ±2% accuracy in the first and last quarters of the scale, and ±1% in the middle half, with switch-point hysteresis below 1%. Switch point repeatability is ±1.5% of full scale. Indication accuracy above or below an active trip point varies by pressure range: ±10% for ranges below 100 psi, ±4% for 100–300 psi, ±2% for 400–1,500 psi, ±12% for the 2,000 psi range, and ±8% for 3,000–5,000 psi ranges. The switch reset deadband is approximately 10% of full scale, preventing repeated cycling near the trip point.