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Hydrogen fuelling systems and intrinsically safe temperature switches

As demand for hydrogen fuel rises, so does the requirement for hydrogen fuelling systems. Acting as a design partner, we recently manufactured a custom temperature switch for a hydrogen fuel project.

A temperature switch was needed for the project but, due to the presence of highly flammable hydrogen, the switch needed to be intrinsically safe to ensure it could not be the source of an ignition.

Pyropress supplied an intrinsically safe Ex-ia temperature switch with thermowell suitable for 690 Bar working pressure, while retaining the ½” NPT threaded connection needed.

The thermowell was custom manufactured in Inconel 725 which was machined at Pyropress in Plympton, UK. Inconel 725 is a nickel-chromium alloy used for its high strength, excellent fabricability and out-standing corrosion resistance. It provides service temperatures ranging from cryogenic to 1800degF (982degC).

The intrinsically safe Ex-ia temperature switch from Pyropress’ Perseus range also featured internal spark eroding to obtain the optimum profile and ensure suitability for 690 Bar pressure. The design was assisted by use of FEA (Finite Element Analysis) calculations. This gave the ability to minimise the thermowell wall thickness yet maximise the strength and ensuring suitable sensor reaction time.

Intrinsically safe Perseus temperature switch

The Perseus range of switches features a robust high quality housing with 1 or 2 sealed SPDT microswitches and has been designed for use in environments where explosive gases can be present (e.g. gas fields, oil rigs & chemical plants etc). Microswitches can be set for single, dual simultaneous, or dual independently adjustable operation. Environmentally sealed or hermetically sealed microswitch options are available.

The Perseus range of temperature switches has separate electrical and adjustment chambers meaning that set point adjustment can be carried out with the power on and the switch in operation. The stainless steel housing is available with one or two electrical entries.

Intrinsically safe certified Ex ia switches

With SIL 2 - IEC61508 proven reliability, there are numerous flameproof and intrinsically safe options including:

  • ATEX/IECEx Intrinsically safe Gas & Dust version II 1G Ex ia IIC T6 ...T2 Ga Tamb -50 to +78degC...+93degC / II 1D Ex ia IIIC T135degC Da Tamb - 50 to +70°C (without resistors)
  • ATEX/IECEx Intrinsically safe Gas version II 1G Ex ia IIC T5...T2 Ga (Tamb -50degC to +72degC...+122degC) (with resistors).

Download the full technical data sheet for the Perseus flameproof and intrinsically safe temperature switch.

Pyropress design and manufacture a wide range of explosion proof (ex-d) and intrinsically safe (Ex-ia) switches, transmitters and valves which can be found in oil and gas production (onshore and offshore facilities), power stations (nuclear, coal, oil and gas) and many other industries.

For the hydrogen fuel industry Pyropress can act as a design partner to support product developments and provide a range of premium quality intrinsically safe, ATEX 2014/34/EU and IECEx products.

For more information contact +44 (0)1752 333 933 or This email address is being protected from spambots. You need JavaScript enabled to view it..

Intrinsically safe Ex ia temperature switches for hydrogen applications