Liquid level measurement in hazardous environments presents unique engineering challenges. Where flammable gases, vapours, hydrocarbons or combustible dusts may be present, level sensors must do more than detect the presence of liquid.
They must operate safely and reliably while meeting the applicable hazardous-area requirements. They must also support effective process control and preventative maintenance. This makes ATEX- and IECEx-certified liquid level switches essential in many industrial systems.
Hazardous areas are found in oil and gas facilities, chemical plants, pharmaceutical manufacturing, wastewater treatment and heavy industry. In these environments, an electrical spark or high surface temperature could ignite an explosive atmosphere.
Electrical equipment installed within a classified hazardous zone must therefore be appropriately designed and certified for its intended use.
A hazardous-area liquid level switch detects whether liquid is present in a tank, vessel, reservoir or pipeline. Certified intrinsically safe switches help prevent overfilling, leaks and pump damage. They operate without releasing enough electrical or thermal energy to cause ignition.
Why Liquid Level Monitoring Matters in Hazardous AreasÂ
Liquid level switches are critical components in many hazardous-area systems. They monitor liquid within tanks, reservoirs, vessels and pipelines, helping operators maintain safe operating conditions.
Applications involving fuels, solvents, hydrocarbons or volatile chemicals require reliable level monitoring. It helps prevent overfilling, leakage, contamination and the dry-running of pumps. It can also improve process consistency and reduce downtime caused by unexpected equipment failures.
Hazardous-area liquid level switches can help with:
- Preventing tank overfill and leakage incidents
- Supporting automated process control
- Providing early warning of abnormal operating conditions
- Protecting pumps and equipment from dry-run damage
- Assisting facilities with ATEX and IECEx compliance requirements
Understanding Hazardous Area ClassificationsÂ
Engineers must consider several factors when specifying hazardous-area instrumentation. These include the equipment category, protection method, gas or dust group and temperature class. ATEX and IECEx classify gas environments according to how often an explosive atmosphere may occur:
- Zone 0: An explosive gas atmosphere is present continuously or for long periods.
- Zone 1: An explosive gas atmosphere is likely to occur during normal operation.
- Zone 2: An explosive gas atmosphere is unlikely to occur during normal operation or will exist only briefly.
Equipment installed within these zones must carry certification appropriate to the intended location, equipment category, protection method and temperature classification.
Intrinsically Safe vs Flameproof ProtectionÂ
Intrinsic safety is a widely used protection method for hazardous-area instrumentation. Intrinsically safe liquid level switches restrict electrical and thermal energy to levels below those capable of igniting the specified hazardous atmosphere.
Flameproof equipment uses a different approach. Its enclosure is designed to contain an internal explosion and prevent it from propagating into the surrounding atmosphere.
Liquid level switches typically require little power and are therefore well suited to intrinsically safe designs. Their compact construction and straightforward connectivity can simplify installation and maintenance within the hazardous zone.
Intrinsic safety can also reduce the need for the heavy enclosures and conduits associated with flameproof installations. This may help lower installation costs, depending on the system design and certification requirements.
SST Intrinsically Safe Optical Liquid Level SwitchesÂ
SST’s intrinsically safe optical liquid level switches are designed for hazardous areas containing flammable liquids, fuels, hydrocarbons or explosive gases. Their ATEX, UKCA and IECEx certifications support compliant level detection in demanding industrial environments.
The switches use infrared technology and total internal reflection to detect the presence or absence of liquid. Unlike mechanical float switches, they contain no moving parts. This reduces mechanical wear and supports reliable long-term operation.
Key features of SST hazardous-area liquid level switches include:Â
- ATEX, UKCA, and IECEx certification
- Intrinsically safe design for hazardous environments
- Fast response times with repeatability of ±1 mm
- Stainless steel housing for durability and chemical resistance
- Operating temperatures from -30°C to +80°C
- No calibration requirements
These sensors support petrochemical systems, leak-detection equipment, hydraulic reservoirs, hydrogen generators and analyser protection systems. Reliable level monitoring helps maintain both safety and operational continuity within these applications.
Frequently Asked QuestionsÂ
What is an ATEX-certified sensor?Â
An ATEX-certified sensor is certified for use within specified potentially explosive atmospheres under the European ATEX Directive. Its certification defines the applicable equipment category, hazardous zone, protection method, gas or dust group and temperature classification.
Are ATEX sensors suitable for hazardous environments?Â
Yes. ATEX-certified sensors are specifically designed for hazardous environments where flammable gases, vapours or combustible dusts may be present.
What is the difference between intrinsically safe and flameproof equipment?Â
Intrinsically safe equipment limits electrical and thermal energy to prevent ignition. Flameproof equipment uses a protective enclosure designed to contain an internal explosion and prevent it from propagating into the surrounding hazardous atmosphere.
Where are hazardous-area liquid-level switches commonly used?Â
They are widely used in oil and gas facilities, chemical plants, pharmaceutical manufacturing, wastewater treatment systems, fuel storage applications, and heavy industrial equipment.
How can engineers determine whether a sensor is ATEX-certified?Â
Engineers should check for recognised certifications and product marking such as ATEX or IECEx, along with the indication of relevant hazard zone, equipment category, protection method, gas or dust group, and temperature classification for the intended application.
ConclusionÂ
Engineers increasingly require sensor technologies that combine hazardous-area compliance with reliability and straightforward integration. Selecting the right ATEX-certified liquid level switch can improve process safety, reduce downtime and support reliable long-term operation.
SST’s certified liquid level switches support safe, accurate monitoring in oil and gas, chemical, pharmaceutical, water-treatment and other industrial applications.
For help selecting a liquid level switch, contact our technical team to discuss your hazardous-area classification, liquid compatibility and installation requirements.
