Intrinsically Safe Systems

Operation of sensors and electronics in Hazardous Environments requires the use of Intrinsically Safe Systems that are rated and approved for the specific environment.  Sensing Systems supports the use of its sensors in Hazardous Environments by using Intrinsically Safe sensors, barriers, devices and electronics. 

We interface our sensors to intrinsically safe barriers/electronics to allow operation in hazardous environments up to Class I, Division 1, Groups C, D, E, F and G.  The barriers we utilize also conform to ATEX requirements for operation in European Community countries.

Safe and approved operation in Hazardous Environments can be achieved by the following methods:

• Use of Intrinsically Safe Sensors
• Use of Intrinsically Safe Electronics
• Use of Positive Pressure Cabinets / Junction Boxes

Sensing Systems utilizes any or a combination of all of these methods when applications involve Hazardous Environments.

Hazardous Environments vs. Safe Environments

Most Hazardous Environment applications fall into two types:

• Hazardous/Safe Areas
• Hazardous Area Only

The first type, Hazardous/Safe Areas, involves applications where two distinct sections of a building are available, a Hazardous area and a Safe area.  In this application, each area is separated from the other by a physical barrier such as a wall.  Measurements for this type of application are achieved by placing the sensor(s) in the Hazardous area and the intrinsically safe barriers/electronics in the Safe area.  The two sets of components are connected by cables that must breach the physical barrier between areas.  Proper seals must be used wherever a breach of a physical barrier is made.

The second type, Hazardous Areas only, involves applications where the only space available for all the measurement components (i.e. sensors, electronics) is the Hazardous area.  Measurements for this type of application are achieved by placing the sensor(s) in the Hazardous area and any required electronics inside of a Positive Pressure Cabinet or Junction Box also in the Hazardous area.   The sensor(s) and the electronics are connected by cables that must breach the Positive Pressure Cabinet.  Proper seals must be used wherever a breach of a physical barrier is made.

Intrinsically Safe Sensors

Load Cells, Force Sensors and Torque Sensors are passive electrical devices when they do not have built-in electronics.  While this is a positive attribute in a Hazardous Environment, they cannot be used in such an environment unless they have been certified by an independent and approved agency.  Sensing Systems utilizes Intrinsically Safe sensors when the application allows it.

The use of a certified intrinsically safe sensor permits operation in an area equal to the rating of the sensor (e.g. Class II, Division 1, Groups D and E).  Using certified sensors is a good approach; however, it is limited by the type of available sensors.  In many cases the certified sensors available do not match the application requirements.

Intrinsically Safe Electronics

Numerous applications require the use of sensors that have not been certified for Hazardous Environment operation.  In these instances sensors appropriate to the application may be used by interfacing them to Intrinsically Safe barriers or modules.  With this approach, the sensors do not have to be certified to be intrinsically safe.

Positive Pressure Cabinets / Junction Boxes

Positive Pressure Cabinets and Junction Boxes are used in Hazardous Environments where a Safe area is not available.  The Cabinets and/or Junction Boxes are used to house the Intrinsically Safe Barriers and any other electronics necessary to obtain the desired measurements.

In order to maintain a higher pressure than the surrounding environment, the Cabinets and/or Junction Boxes must be supplied with air under pressure.  In addition, any openings or breaches of the cabinet enclosure must be fitted with an approved seal to maintain the required high pressure.

Most cabinets are fitted with a transparent window to allow operators to view any displays contained inside.  Additionally, the cabinet must be fitted with switches that operate alarms whenever the cabinet is opened and/or loss of pressure occurs.

Technical Assistance

There are very specific requirements regarding the location and housing of intrinsically safe modules.  Each application must be fully described and analyzed to insure compliance with all requirements.  Sensing Systems engineers will analyze your project requirements and recommend the sensors, barriers and electronics to accomplish your objectives. 

Contact Us now to discuss your application.