PRESSURE SWITCH · HAZARDOUS AREA
Explosion-Proof Pressure Switch — Digital, Multi-Setpoint, Custom OEM
A heavy-aluminium digital pressure switch with a built-in 4-digit LED display, 2 / 4 / 5 field-adjustable setpoints, and an optional 4–20 mA output. Built for hazardous-area service in oil & gas, chemical, and high-vibration hydraulic lines — every unit is custom-built to your range and process connection.
Digital LED display · Up to 5 setpoints · IP65 · Custom OEM
What This Switch Does
This is an integrated digital pressure switch — pressure sensor, microprocessor, LED display, and 2 / 4 / 5 relay outputs in a single hazardous-area enclosure. The setpoints are field-adjustable through the front-panel keypad, hysteresis is independently configured for each channel, and an optional 4–20 mA output lets the same device act as a transmitter to your control system.
Unlike a blind mechanical Bourdon or diaphragm switch, this unit shows live pressure on a 4-digit LED, settles in under 30 ms, and gives operators a record of exactly where each contact is set. For a deeper comparison of when to pick a switch over a transmitter, see our guide on pressure switch vs pressure transmitter.
Setpoint Variants — A / B / C
Variant A
2 setpoints
Single-row 4-digit LED
2 × SPDT 5 A / 250 VAC relay
Optional: 4–20 mA analog
Use case: high-alarm + low-alarm pair on a single line.
Variant B
4 setpoints
Single-row 4-digit LED
4 × SPDT 5 A / 250 VAC relay
Optional: 4–20 mA analog
Use case: cascaded alarm → trip → interlock with one spare contact.
Variant C
5 setpoints
Dual-row LED (0.56″ + 0.36″)
5 × SPDT 5 A / 250 VAC relay
Optional: 4–20 mA · RS485 Modbus RTU
Use case: full alarm tree + Modbus log into a SCADA / DCS host.
Technical Specifications
| Technical Specifications — all specs are customer-configurable at order entry | |
|---|---|
| Range | −0.1 ~ 100 MPa (vacuum + gauge full span; customer-specified at order) |
| Accuracy | ±0.5 % F.S |
| Overload | 150 % F.S |
| Long-term stability | ≤ 0.1 % F.S / year |
| Pressure type | Gauge / Absolute / Differential |
| Power supply | 24 VDC or 220 VAC |
| Display | Dual-row 4-digit LED (0.56″ + 0.36″ on variant C) |
| Display range | −1999 ~ 9999 |
| Response time | < 30 ms |
| Ambient temperature | −30 °C ~ +80 °C |
| Medium temperature | −40 °C ~ +150 °C (high-temp accessory required > 80 °C) |
| Humidity | 0 ~ 90 % RH (non-condensing) |
| Process connection | M20×1.5 standard (NPT ¼/½, G ¼/½ available per order) |
| Sensor element | Isolated diaphragm, oil-filled piezoresistive |
| Ingress protection | IP65 |
| Housing material | Die-cast aluminium alloy + epoxy coating |
| Wetted material | 304 SS standard, 316 L optional |
| Setpoint variants | A (2) / B (4) / C (5) field-adjustable contacts |
| Relay output | SPDT 5 A / 250 VAC per channel |
| Analog output (optional) | 4–20 mA on all variants; RS485 Modbus RTU on variant C |
Built for Hazardous Areas
The heavy die-cast aluminium enclosure, isolated-diaphragm sensor, and sealed electronics are built to operate in classified hazardous areas — oil & gas plant lines, chemical batch reactors, LPG storage and fuel handling. The construction is the explosion-proof type: a pressure-rated housing that contains an internal ignition rather than blocking it.
If your installation country requires specific hazardous-area certification paperwork, share the site spec with our engineering team and we’ll confirm what’s feasible within your timeline.
IP65 ingress protection 304 SS wetted parts (316 L optional) Field-adjustable push-button setpoints Factory inspection certificate with every unit
Field Setup — Push-Button Setpoint Adjustment
All setpoints are programmed from the front-panel keypad — no laptop, no HART communicator. The procedure is the same on every variant.
- Press SET — the display shows “LOCK”.
- Use ▲▼ to enter password = 1, press SET to confirm.
- Use ▲▼ to navigate the setpoint menu — AL1H (pull-in), AL1F (release), AL2H, AL2F, … AL5H, AL5F.
- Press SET to enter a value, ▲▼ to change, SET to confirm.
- Choose END + SET to save and exit.
Setpoint logic — pull-in vs release
- High alarm (NO): pull-in > release → relay closes when pressure rises past pull-in, opens when it falls below release.
- Low alarm (NC): pull-in < release → relay opens when pressure rises past pull-in, closes when it falls below release.
- Hysteresis (dead band): the absolute difference between pull-in and release values — set wider to suppress chatter on pulsating media.
Heads up: if 30 seconds pass without a key press the unit auto-exits the menu without saving. Press SET → END before walking away.
On pulsating lines (pump discharge, hydraulic cylinders) the display can be damped through the FILt coefficient (3–10). Higher values steady the LED reading but slow the visible response — relay action is unchanged.
Where Our Customers Use It
Hydraulic & Pneumatic
Press, injection mould, machine-tool circuits — multi-setpoint alarm/trip with one device replacing two mechanical switches.
Petrochemical Process
Zone 1/2 plant lines — gauge or differential service on reactor jackets, recycle loops and feed headers.
Water & Wastewater
Municipal pump stations, lift stations, booster sets — high-low setpoints + analog out for SCADA telemetry.
Mechanical OEM
Compressor packages, hydraulic power units, fire-suppression skids — integrated switch + transmitter saves panel real estate.
Chemical Batch
Reactor and storage vessels — multi-setpoint alarm tree with field-changeable hysteresis.
LPG / Gas Storage
Filling skids and bulk-storage manifolds — explosion-proof construction for routine classified service.
Installation Notes
- Panel-mount geometry: 100 mm dial — drops into the same cut-out as a standard gauge with no panel retrofit.
- Vertical orientation required for ranges < 100 kPa — horizontal mounting on low-range units shifts the zero by the weight of the silicone fill.
- High vibration or pulsation: install via a micro-hose for mechanical decoupling, and ground the housing separately so vibration-induced cable strain doesn’t lift the chassis off ground.
- EMI hygiene: shielded signal cable, keep wiring runs away from VFDs / contactors / motor leads, and use one cable gland per signal type.
Digital vs Mechanical Pressure Switch
| Specification | HMK (this unit) | Ashcroft B7 | Barksdale D1X | WIKA MA |
|---|---|---|---|---|
| Switch type | Digital electronic | Mechanical | Mechanical diaphragm | Mechanical, hazardous-area-rated |
| Setpoints per device | 2 / 4 / 5 selectable | 1–2 | 1–2 | 1–2 |
| Accuracy (F.S) | 0.5 % | ~1–2 % | ~1–2 % | ~1 % |
| Live pressure display | Dual LED + optional 4–20 mA | None (blind) | None (blind) | None (blind) |
| Response time | < 30 ms | 100+ ms | 100+ ms | 100+ ms |
| Aux power required | 24 VDC / 220 VAC | None (mechanical) | None (mechanical) | None (mechanical) |
| Setpoint adjustment | Push-button + display readout | Adjustment screw + reference gauge | Adjustment screw + reference gauge | Adjustment screw + reference gauge |
Honest framing: mechanical switches win on power-free sites and pure budget plays. Digital wins when you need accuracy, multi-setpoint logic, remote read-back, or a transmitter and switch in one device.
Custom OEM — What You Can Specify
| Specify these at PO — every unit is built to your config | |
|---|---|
| Range | Any segment within −0.1 to 100 MPa (vacuum + gauge) |
| Process connection | M20×1.5 standard · NPT ¼ / ½ · G ¼ / ½ · custom thread per drawing |
| Wetted material | 304 SS standard · 316 L optional |
| Cert paperwork | Discussed per project — share your installation country and project requirements |
| Setpoint count | A = 2 · B = 4 · C = 5 |
| Output options | Optional 4–20 mA (all variants) · RS485 Modbus RTU (variant C) |
| Display | Dual-row LED (variant C); single-row LED (A / B) |
| Lead time | Standard ≈ 1 week from PO; longer if cert paperwork is required |
| MOQ | 1 piece |
Frequently Asked Questions
Need an Ex pressure switch sized for your line?
Tell us your range, process connection, and setpoint count — we’ll send a quote within 24 hours. MOQ is one piece and standard lead time is about a week.
Hanmonk (HMK) — Chinese-manufactured pressure & temperature instrumentation · factory inspection certificate with every unit · 20+ years delivering custom OEM builds.