Intrinsically Safe

If you were to look up “versatile” in the dictionary, you might find a picture of APG’s new MNU IS Intrinsically Safe Modbus Ultrasonic Sensor. Ok, you might not yet, but you should, and soon. With features like APG’s new QuickMode, global Class I, Division 1 hazardous location certification, and RS-485/Modbus RTU standard on every unit, the new MNU IS is capable of handling just about any level measurement situation. Let’s take a look.

In a recent cooperation between NIOSH, the government agency for researching work-related injury and illness, and private partners in drilling and well servicing found that workers involved in flowback operations where exposed to elevated levels of benzene, a known carcinogen.

The preliminary results of their study were published on the CDC blog last month. The study was conducted by taking urine samples of workers at the end of their shift. The study also included, “short-term and full-shift personal breathing zone and area air sampling for exposures to benzene and other hydrocarbons.”

Level and pressure sensors for hazardous areas are designed in a number of ways to prevent ignition of an explosive mixture. Two of the more popular methods for low-power instrumentation are intrinsically safe and non-incendive.

Both limit power significantly, ensuring there is never enough energy to produce a spark and ignite a dangerous gas or dust mixture. In fact, there is more that is the same between the two protection methods than there is different. So, to help you know when & where they’re appropriate, we will focus on the differences.

Two of the most well known protection methods for instrumentation in hazardous areas are Intrinsic Safety and Explosion Proof. The difference between the two is quite large, and amounts to the idea of prevention vs containment. Then there are the practical differences, which are largely based on how the two are wired.

We’ll discuss these basic differences and the merits of each.

Prevention vs Containment

There are really three basic methods to stop the ignition of fires and explosions in hazardous areas. They are:...

Putting electrical equipment in a hazardous location is a big deal. Choosing the wrong sensor turns from expensive to life threatening. So how do you select the right level sensor or pressure transmitter?

You have to understand hazardous locations.

Sensor Design

This is even difficult for many who deal with hazardous locations on a day-to-day basis. If you’re ever confused...

Last week we defined hazardous locations, and discussed the basics of both protection methods and hazardous area classifications. This week, I want to discuss intrinsic safety, what it is, and how it prevents igniting a disaster.

James Wilkinson, Automation Specialist at R. Stahl, defines intrinsic safety as the following:

Intrinsic safety can be defined as an explosion protection technique that is applied to electrical equipment and wiring to limit both electrical and thermal energy under both normal and abnormal conditions to levels that are insufficient to ignite the hazardous mixture that is present in the hazardous area.