Rapid processing of feed and grain can create high concentrations of particulate dust that, when exposed to a heat source, can result in a massive, deadly explosion.
Fortunately, accidents can be prevented, according to Scott Chant, president of Safe-Grain/Maxi-Tronic in Loveland, OH. “Most people have a ‘run to failure’ mentality where they’ll push equipment to the brink before doing anything to correct a problem,” he explained. “It’s like driving a car at 100 mph until it runs out of gas and everything comes to a halt.”
Chant’s company works with feed and grain operators to promote what he calls a preventive and predictive maintenance program that includes elaborate sensing equipment and frequent inspections. The equipment tracks minute-by-minute history of temperature, run times, speed and other important factors.
This type of predictive software collects massive amounts of data. The challenge lies in getting the data into a format that can be quickly and easily interpreted, he explained.
Technology now wirelessly delivers data to a central location. Systems send warning and alert text/email messages and online data pages directly from the controller mounted on a wall, without the need to go through a central computer. In fact, people can often review plant status from any computer anywhere in the world.
All sensors can be set to send alerts before a catastrophic event occurs. For example, if a bearing failure typically occurs at 160 F to 170 F, the system can send a text message alert when the temperature hits 135 F, followed by multiple visual and audible alarms at 150 F.
A sensor’s minute-by-minute data log history can be set up to inform an operator the equipment is trending toward failure before an actual failure event.
“The faster you know of a problem, the faster you can avoid failure,” said Chant. “The key is to investigate as soon as you get that first alert and especially when the alarm goes off before a failure.”
It’s not enough to install monitoring equipment; the staff must be trained on the nuances within the facility.
“Just like children, two identical pieces of equipment installed in the same environment and same culture don’t often behave in exactly the same way,” Chant explained. “When it comes to monitoring equipment, new hires may need babysitters. They don’t know the nuances of the system. They don’t know that this particular pit can’t be dumped at full speed when the system is processing a specific type of material. Because software gives an early warning, it allows even new people to investigate problems and learn the nuances. They learn they can’t always expect the same results from seemingly similar equipment. It’s interesting how two inanimate objects, identical in appearance, behave so differently.”
Three major hot spots
There are three major hot spots for fires and explosions in any feed and grain operation, said engineer Adam Dittbenner, an instrumentation service manager with Interstates Construction Services in Sioux Center, IA. They are:
- Rotating equipment where bearings overheat
- Grain legs when belt conveyors are constantly moving
- Failures within electrical gear
Motor control equipment that sends power to legs, conveyors, fans and mills can be a main culprit, as well, as loose wire terminations that can cause heat. For that reason, infrared scanning of motor control equipment should be employed to look for hotspots.
Motor control center (MCC) bucket cleaning may be necessary from time to time. “Over time, dust can settle on contacts within the electrical equipment, so annual cleaning and exercising breakers is a good means to prevent hazards from occurring within the buckets,” he explained.
The best warning devices are those that activate a control panel light as well as sound an audible alarm to draw attention. But, the systems should also be set up to trigger an automatic shutdown sequence if the warning isn’t addressed.
Equipment must be tested at least annually by a trained technician to physically evaluate each sensor. Inspections help reduce nuisance alarms by looking for faulty equipment, broken wires, electrical shorts, disconnected horns or reduced volumes.
“If alarms keep going off and no reason can be found, bring in a technician rather than just assume it’s a false alarm,” said Dittbenner. “The technician can help develop a game plan as to when the alarm should sound, and how to interlock equipment for the desired action.”
For advice on when to implement hazard monitoring equipment, he recommends consulting National Fire Protection Association Standard 61 concerning the prevention of fires and dust explosions in agricultural and food processing facilities.
A decade of useful life
Plants now have the opportunity to install new hazard monitoring systems that use new technology to provide better information, save time, money and resources. These technologies include wireless transmission, historical reporting and remote access to plant data, said Mike Kroening, Midwest regional sales manager for Electro-Sensors in Minnetonka, MN.
Some plants, especially smaller co-ops, are often hesitant to update equipment before it fails, he explained. Obsolete equipment has a higher propensity to fail, which can lead to unfortunate accidents because plants aren’t making safety upgrades.
“Everyone needs to comply with OSHA’s minimum standards. It’s still a little unnerving to walk into a facility that doesn’t have upgraded protection knowing that an explosion could happen at any moment,” said Kroening.
According to information collected by the U.S. Department of Labor, there were 503 explosions at grain elevators between 1976 and 2011 where 184 people were killed and 677 were injured.
A lot of legacy systems were prone to false alarms, said Kroening, which actually led to more safety problems because frustrated maintenance personnel would bypass a sensor, or simply disable buzzers and horns thinking it was another false alarm. Newer technology increases the reliability and accuracy of the system, thus greatly reducing false alarms.
“Wireless takes time and cost out of the equation. The systems are extremely reliable and easily expandable,” he explained. “Best of all, wireless systems permanently log every alarm event and can send email or text alerts to several people to ensure that someone knows of a problem before it becomes a major issue.
“OSHA loves logs and our system lets managers record what corrective action was done after an event,” he added. “The system offers a high level of accountability in that someone in authority must acknowledge a problem and what was done to fix it.”
Systems require the right sensors, too
“It’s not just a matter of updating equipment; it must be the right equipment,” said Johnny Wheat, president of 4B Components in Morton, IL.
“Facilities in the United States are required to install Class 2, Division 1, Group G sensors that are approved for use in hazardous locations,” he explained. “You don’t want a sensor to become a source of ignition itself.”
More sensors often make a system safer. Wheat said sensors should be installed on all critical bearings, especially drive- and tail-pulling shaft bearings on elevators and conveyors.
Speed sensors located at the tail-pull shafts are essential to determine if a belt slips on a drive pulley. Belt misalignment sensors detect a belt rub on the machine case. There are two types of belt misalignment sensors:
- Force-activated sensor, which sends an immediate signal on belt misalignment.
- Heat-activated sensor with brass rub block.
Brass rub blocks can wear very quickly and should be regularly inspected, especially after every rub alarm. To facilitate inspections, installers use a special inspection door to make it easier to check equipment status.
“When installing sensors, you need to select those that are designed with testing in mind. If testing is easy to do, it will be completed more often,” said Wheat. “You don’t want to rely on simulated test routines. The sensors need to be tested much like smoke, and heat alarms are tested with real heat and real smoke.”
For bearing sensor tests, he recommends using a handheld, battery-operated device designed to heat the sensor to the tipping point of activating an alarm.
Speed switch tests can be conducted using a battery-operated testing device, like a target-masking pulse generator. Belt misalignment testing should either manually force a belt to misalign, activate the force sensor to initiate an alarm, or use a hand-held device to safely heat a rub block sensor.
“When you test this way, you ensure the sensors, wiring, controls and associated equipment will function properly in a real-life situation,” said Wheat. “Simulated tests don’t do that. It’s important that information is logged, recorded and stored off-site for future access, like in a cloud-based portal. After any event, the logs will be important to help learn what happened and why in order to prevent it from happening again.”
Not your grandfather’s equipment
Jason Grahek, Northern regional sales manager for CMC Industrial, agrees aging equipment is a problem for the industry, noting that thermocouples, which are still commonly used, are “old technology.”
A thermocouple is basically two specific types of wires joined together. When these alloys are connected, it becomes a thermocouple. Thermocouple lead wires can short anywhere upstream of the sensor, which essentially becomes the new sensing point. In the event wires short, the temperature is recorded at that location rather than at the actual sensor location, said Grahek.
The key to developing a reliable safety system is to analyze OSHA rules, but also to take reasonable steps beyond basic requirements to ensure safety.
“People will put up with nuisance alarms because many of them think that is just the way the systems are functioning,” said Grahek. “Apathy is a great killer. People often don’t treat alarms seriously because of faulty systems and sensors. So they silence horns over and over again thinking it is a faulty sensor until one day, they experience an avoidable, dangerous incident.”
CMC’s digital sensors are set up so that if anyone tampers with a sensor or a sensor fails, an alert is immediately generated.
“We make the system as human-proof as we possibly can,” he explained. “A well-implemented hazard monitor system integrated with the facility control system, or with CMC’s stand-alone controller, will remove the temptation to bypass the sensors or warning alarms.”
Systems can be set up so that if a plant in Anywhere USA has too many alarms over a set period of time, then alerts are escalated to company officials, even if they are in other states.
“When it comes to safety, it’s really hard to put a number of the cost,” said Grahek.
Someday, he hopes insurance companies catch on to the importance of properly implemented safety equipment and offer discounts for disciplined implementation, documentation and annual verification.
Failure is not an option
When a system fails and causes a fire or an explosion, the downtime is costly. The business loses money when not processing material plus added costs for emergency repairs and liability lawsuits, should an injury or death occur.
“When is it a good time to have a failure?” Chant asks. “Never. If your plant goes down, you’re out of business. Failure means lost opportunity. The good news is that failure can almost always be prevented.” ❚