- Ranges:
- 10 - 700 mbar
- 0,4 - 2,5 bar
- 2 - 6 bar
- 5 - 25 bar
- 20 - 60 bar
- 50 - 250 bar
- 240 - 400 bar
- PN in bar: 30, 400
- Material: Brass, CrNi-Steel
- Connection: G1/2
 Datasheet
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An overpressure protection device is a vital component to avoid overpressure situations. The pressure limiters in the device are constructed to protect the pressure system or delicate sensors against overpressure situations and faults.
Overpressure Protection Device for Gauges – Safeguard Against Pressure Spikes & Misoperation
Overpressure protection devices shield mechanical and digital pressure gauges from overload, pressure spikes and misuse. When a configurable set pressure is exceeded, the device automatically isolates the instrument from the process (shut-off/bypass function), preventing permanent deformation of the Bourdon tube, sensor or diaphragm-seal system.
Available as mechanical limiters (spring/cone), safety valves for instruments, snubbers/orifices for pulsation damping, or combinations with gauge cocks, siphons or cooling elements. Materials: brass, stainless steel 316L, with media-appropriate seals (PTFE, FKM, EPDM, FFKM). Thread sizes include G 1/4, G 1/2, 1/4″ / 1/2″ NPT, and M20×1.5.
FAQ on Overpressure Protection Devices for Gauges
Selection, sizing, installation, testing and best practices—so your indicators remain reliably protected.
How does an overpressure protection device work?
A spring/cone or diaphragm mechanism monitors inlet pressure. If pressure rises above the set point, the valve closes (isolation/shut-off) and decouples the gauge from the process. As pressure drops, it reopens—either automatically or manual reset, depending on the model.
Which types exist—and where are they used?
| Type | Function | Typical application |
|---|---|---|
| Automatic limiter | Closes at P > Pset, reopens automatically | General plant protection, varying loads |
| Manual-reset limiter | Closes at P > Pset, requires manual reset | Safety-critical loops, root-cause checks |
| Instrument safety valve | Limits/relieves at a defined pressure | Sustained overpressure, defined blow-off |
| Snubber/orifice | Damps pulsation/shocks | Hydraulics, compressors, presses |
How do I choose the right set pressure?
Rule of thumb: Pset = 1.1…1.3 × the gauge’s allowable continuous pressure. Consider the gauge range and overload rating (e.g., 1.3×/2× short term). Account for the device’s hysteresis.
What threads and sealing concepts are available?
| Thread | Standard | Sealing | Note |
|---|---|---|---|
| G 1/4, G 1/2 (BSPP) | ISO 228 (parallel) | Flat gasket/O-ring at seat | Keep faces flat and burr-free |
| 1/4″, 1/2″ NPT | ASME B1.20.1 (taper) | PTFE tape/paste | Wrap in screw direction |
| M20×1.5 | ISO metric | Usually flat gasket | Verify seat geometry |
Does it also protect against pressure spikes?
Yes—an overpressure limiter protects against sustained overpressure. For very short spikes/pulsation, add a snubber/orifice (sinter/capillary/needle type) close to the process.
Automatic or manual reset—which is better?
Automatic minimizes downtime and covers brief events. Manual reset enforces a visual check after incidents (audit/quality) and prevents unnoticed restart.
Does the device affect measurement in normal operation?
With a correctly sized flow cross-section, the impact is negligible. Minor damping may even improve readability.
What media and temperature limits apply?
Depends on materials/seals. Typical: −20…+80 °C with standard seals; higher with PTFE/FFKM. For steam/hot media, use a cooling element/siphon.
How is the device installed?
- Follow the datasheet (often any orientation); observe flow direction.
- Combine with a gauge cock/shut-off valve (service/zero check).
- Clean sealing faces; apply the correct sealing concept.
- After assembly, perform a leak and function test (P-test > Pset).
How do I set the trip pressure?
Via an adjustment screw under a cap (if provided). Increase pressure slowly with a reference gauge, verify closing point, and document (date, Pset, medium, temperature). Secure/lock the cap afterwards.
Compatible with digital gauges and diaphragm seals?
Yes. It protects electronics/sensors in digital gauges and the fill system of diaphragm seals from overload.
Common mistakes—and how to avoid them
- Pset too high → protection triggers too late.
- Wrong sealing concept (BSPP/NPT) → leaks/damage.
- No snubber with strong shocks → residual damage possible.
- No functional test after installation → unknown effectiveness.
How often should it be tested?
Recommendation: annually and after process events/service. Check closing/opening pressure, tightness, hysteresis and seal condition.
What about ATEX/Ex areas?
The device is mechanical—what matters is the overall installation. With contact gauges, use electrical components with appropriate Ex approval and ensure proper bonding.
Can it be retrofitted?
Yes, typically as an inline adapter between the process valve and the gauge. Check space and threads; plan elbows/tees where required.
Which documents can ICS Schneider provide?
On request: test/setting protocol, material certificates EN 10204 3.1, leak test, serial/setting labels and an installation guide.
Example of a recommended assembly
Process → Shut-off valve/gauge cock → Overpressure protection → Snubber/siphon/cooling element → Gauge/Digital gauge.