By: Jason Grahek
Most grain industry professionals will agree: hazard monitoring systems -- which identify operational “hotspots” like belt slippage, hot bearings and misaligned belts -- are paramount to the safe day-to-day operations of every facility. And yet, we see a number of facilities that put up with nuisance trips and unreliable sensors. This very dangerous apathy can lead to poor decision making and horrible outcomes like the Atchinson, Kan. dust explosion in 2011(Pictured on the right). Lakeland believes fully functional hazard monitoring systems not only place the proper emphasis on accurate design, but more importantly how the system is implemented. Without using the rigors described below, the sites are often left with a system that lulls them into a false sense of security, unsafe operations and one that could lead to an explosion or fire.
A quality commissioning is the biggest step towards a fully functioning and dependable system. Beyond having the sensors in place and mounted properly, the correct validation process is key to knowing 100 percent that you have a completely functioning system. The process requires that a sensor-by-sensor documented verification is signed off by the integrator, the contractor and owner, validating that the critical functions of the system have been tested in the following ways:
Freeze Spray Test: Verify that each sensor was properly wired and digitally mapped in the control system.
Standard Procedure: One person watches the Operator Interface Terminal to ensure that the right temperature reading changes when the sensor in the field is freeze-sprayed.
Why is this important? Many times, this important step is not followed and the graphical interface displays a temperature reading for a completely different sensor point. This is a safety hazard.
Caution: Typically, a site will send a person to check on what they think is the hot bearing and they report back that it is fine, and they continue to operate. Meanwhile, across the facility, they truly have a hot bearing that they are neglecting.
Real World Example: Recently, a customer went through this safety process at a facility that they had implemented. They found while emulating shutdown conditions at a few sensors that they were shutting down the wrong equipment! The mapping of the sensor was incorrect. Stop and think about how dangerous this situation is. This is a fire or explosion waiting to happen.
Test warning and shutdown alarms for each and every sensor.
Common Method: Sensors are tested against the warning alarm and then progressed into the shutdown alarm.
Why do you do this? This gives you confirmation that the system is properly configured. Also, it indicates the proper alarms and shuts the equipment off at the configured shutdown point.
Importance: Verify the functioning and accuracy of temperature set points.
Check for failed sensors by unplugging sensors from sensor bus network.
Process: Each sensor is tested for “health” by unplugging it. The system should alarm on this condition to indicate to the facility that a sensor has gone bad.
Why? By doing this, you identify any failed sensors within the system. With certain systems such as Extron’s BusMux “smart” thermocouples or CMC Industrial Electronics, there are health bits to indicate when a sensor goes bad.
Know: If your system has a failed sensor, you could end up in a world of trouble.
Real World Example: Just this past month, a facility had a belt misalignment that had not indicated an alarm due to a failed sensor. Fortunately, someone caught this before a great deal of damage occurred to the leg. With a formal system validation process and the right hardware, this situation is entirely preventable.
By following the proper discipline and rigors of a complete commissioning, the facility is left with a documented record indicating that every critical point was validated and the assurance that the hazard monitoring system truly acts in its intended fashion. It is also key to make sure you partner with a company that truly understands the critical finer points of implementing a hazard monitoring system. This will keep your facility protected and employees’ lives safe. I often hear plant personnel say, “Yes, we have a hazard monitoring system…we have sensors in place.” I challenge these statements and ask: “You have sensors, but do you have a fully functional hazard monitoring system?” When the sites that we work with understand why we go through these rigors and what they gain, this process becomes an absolute for them moving forward. So, consider a re-examination of your hazard monitoring system and make sure you can say with 100 percent certainty that you know your system will act appropriately when the moment of truth occurs.