The ELMESS DSTR/DSTB/EBR series comprises explosion-proof control thermostats (DSTR), safety temperature limiters (DSTB), and electronic safety temperature cut-outs (EBR 6001) designed for monitoring and regulating room, medium, and surface temperatures in ATEX/IECEx Category 2 and 3 hazardous areas. Combining rugged electromechanical construction with self-powered switching, these devices serve as both everyday temperature controllers and last-resort safety devices within ELMESS' certified explosion-proof heating systems.

Which Type Do You Need? — Control Thermostat vs. Safety Limiter

• Control Thermostats (DSTR series): Designed for routine heating/cooling control. On reaching the setpoint temperature, the internal changeover contact switches the connected heater or fan on or off. The device automatically resets when the temperature moves back through the setpoint—ideal for freeze protection (e.g., DSTR60ALD with fixed 5/10/15 °C setpoints) or for controlling gas preheater temperature in pipelines (DSTR60ALE with immersion tube).
• Safety Temperature Limiters (DSTB & EBR series): Provide over-temperature protection. Unlike control thermostats, once the preset limit is exceeded, the limiter permanently cuts off the connected heater and locks out—even if the temperature subsequently drops. Manual intervention (pressing a reset button or closing an external dry contact) is mandatory to restart. The electronic types (EBR 6001) achieve SIL 2 functional safety (EN 61508) and Category 2 (EN 13849-1) for integration into safety instrumented systems (SIS).

Mechanical, Self-Powered Switching — No Power Supply Required

• Liquid-Expansion Principle: DSTR and DSTB models use a fluid-filled capillary sensor that expands in proportion to the measured temperature. This mechanical energy directly actuates a snap-action micro-switch without requiring an external 24 V or 230 V supply.
• Zero-Voltage Safe: Since the switching element is purely mechanical, the devices can operate in applications where loss of control power would be unacceptable—critical for freeze-protection circuits in unheated, unmanned substations and remote gas pressure regulating stations.

ATEX & IECEx Certification — Zones, Gas Groups, Dusts

• Intrinsic Safety (Ex ib): The DSTB60AL safety limiter is classified as Ex ib—the electrical circuit inside the device stores insufficient energy to ignite an explosive atmosphere even under fault conditions. This allows direct installation in Zone 1 and Zone 2 gas environments without additional explosion-proof enclosures.
• Dusts (Ex ib, Zones 21 & 22): The same Ex ib design also certifies the DSTB60AL for combustible dust atmospheres (grain handling, coal processing, pharmaceutical powder manufacturing).
• Ambient Capability: All thermostats operate reliably in ambient temperatures from -40 °C to +60 °C, permitting deployment in Arctic and desert climates alike.

Factory-Preset & Tamper-Proof Safety

• Pre-Calibrated at ELMESS: Each safety limiter (DSTB/EBR) has its cut-off temperature set during routine factory testing, engraved on the type plate, and mechanically/electronically protected against subsequent adjustment. This ensures that the safety setpoint cannot be changed in the field—a requirement for ATEX conformity and functional safety management.
• Fail-Safe Detection: Any breakage or short-circuit in the measuring line or probe is detected as a fault condition. The safety limiter immediately opens the output contacts (de-energising the heater) and locks out, preventing unprotected continued operation.
• Reset after 20 K Cooling: After the monitored point has cooled by at least 20 K below the cut-off threshold, the manual reset function becomes operable—either via the built-in button or via a customer-supplied potential-free remote reset contact.

ELMESS Integration — Plug-and-Work with ELMESS Heaters

• DSTRALD Mounting Kit: The DSTR60ALD thermostat is supplied with a dedicated mounting kit that directly attaches to ELMESS R4 finned tube heaters. This mechanical integration ensures the thermostat sensor is thermally coupled to the correct point on the heater surface, eliminating field wiring and placement guesswork.
• Immersion Tube (DSTR60ALE): For gas pipeline heating applications, the thermostat ships with a sealed immersion tube that protrudes into the gas stream, directly sensing the post-regulation gas temperature and controlling the electric preheater accordingly.
• Built-in TSH/TSHH Dual Protection: ELMESS immersion heaters include an internal temperature limiter (TSHH) and temperature monitor (TSH) as standard, providing both control and safety functions without additional external devices. The Ex e terminal box facilitates straightforward field wiring.

Typical Applications

• Freeze protection of instrumentation lines, valve actuators, and sample tubing in petrochemical plants
• Gas pressure regulating station preheater control (prevents hydrate formation downstream of the regulator)
• Surface temperature monitoring and limitation of finned tube and immersion heaters in Zone 1 & 2
• Compressor room anticondensation heater control on offshore oil & gas platforms
• Over-temperature safety shutdown of electrical trace heating circuits in hydrogen and acetylene environments (IIC gas group compatible)