by Tamara Scully
Every day, feeders at thousands of dairy farms deface the bunker silos in order to feed the herd. The job involves heavy equipment, operated in close proximity to a wall of grain. Too often, basic safety practices are overlooked during the filling, packing, feeding and maintaining of the bunker silo. Knowing the dos and don’t of bunker silo safety can prevent fatal accidents, still an all-too-common occurrence on farms across the United States.
Filling safety
While removing feed from the bunker can be dangerous, the danger starts as the crop is harvested, and the silo filled. Heavy equipment safety is a priority. During filling, dump trucks, front-end loaders and pack tractor operators are exposed to numerous risks, as are bystanders.
Piles that are too tall, looming over the side walls of the bunker, are not safe, but are a common sight. These overfilled bunkers offer the perfect setup for equipment to fall over the wall during filling.
“Equipment needs to reach the top of the pile safely,” Dr. Megan Smith, of Lallemand Animal Nutrition said during the recent Feeder School, held by the South Central New York Dairy & Field Crops at Walnut Ridge Dairy in Lancaster, NY. The two-day Feeder Schools were also held at other locations.
Height isn’t the only concern. The slope matters, too. No more than one foot of rise per three feet of run is considered safe for the front and sides of a drive over pile. Bunkers should be filled from back to front, also maintaining this low slope, resulting in a wedge-shaped design throughout packing.
Equipment can more readily overturn on silage that isn’t packed well or uniformly. Silage quality goes hand in hand with packing density, too. Delivery rate of crops into the bunk or pile, the packing tractor weight, the number of tractors used, the time spent packing and the packing layer depth are some factors which affect safety and quality.
Filling the bunk too quickly, or without any organized procedure for the silo traffic pattern when multiple operators are working the pile simultaneously, can lead to accidents. Tractors with roll over protection and a low center of gravity, dump trucks with evenly pressurized tires, and front-end loaders whose buckets are kept low throughout the packing process are the best bets for safe loading.
With equipment moving in many directions, the risk of running over a person is high. Back-up alarms, properly adjusted rear and side view mirrors and safety vests for any personnel within the vicinity of the silo are mandatory.
Whenever working with the bunker, a buddy system should be utilized. Safety vests should be worn. Warning signs, stating the potential for collapse, should be posted to warn visitors and remind staff of the dangers.
Feeding routine
Feeding can become routine. As such, appropriate safety procedures are often overlooked. If piles are filled, packed and covered properly, the risk of danger decreases. But silos aren’t ever safe, and avalanches and the threat of suffocation are always real.
Standing too close to a feedout face, even one that has been well packed and maintained, is dangerous. For many feeders and nutritionists who routinely work with silage, being around the bunker is a regular occurrence. While a pile collapse isn’t a regular event, it is often a fatal one.
The only safe distance from a silage face is that which is at least three times the height of the pile. If a pile is 10 feet in height, the safe distance is 30 feet away. Equipment, unless actively involved in feeding, should follow the same guidelines.
When taking samples, piles over eight feet in height should be analyzed via samples taken from the loader bucket, not by taking core samples, Dr. Smith said. Do not take core samples where the pile is taller than your height.
When feeding from the silage face, the loader bucket should never dig into the bottom of a pile. This creates an overhang, and drastically increases the chance of collapse. Piles should only be as tall as the walls of the bunker, and sized so that the equipment being used can safely reach the top of the pile.
Driving equipment parallel to the silage face, particularly when the bunker is overfilled, is also dangerous. Instead, equipment should be perpendicular to the face when working with the pile. Removing silage properly requires shaving silage down the feedout face.
Other concerns
Those tires and the plastic covering the silo need to be safely removed as the pile is fed. Maintaining the proper feedout face — without any overhang — is a first step. For those working near the top edge of the pile, particularly one which is overfilled or which has not been properly packed or maintained, require a safety line and harness, and safety vests should be used for visibility. Standing on or close to the edge of the face is unsafe in any circumstances.
Pushing spoiled silage over the face is not safe. Instead, any spoiled silage should be removed via equipment operated from the ground, not from the top of the pile.
While silo gasses are often associated with tower silos, be aware that deadly silo gases can and do form in any type of situation where forages are fermenting, including bunkers and bags. The danger is most severe from fill to 21 days post-fill in covered silo piles. Gases can form and be trapped in a covered pile, and removal of the plastic or the bursting of any bubbles in the plastic will release these gasses. Gases can also settle out around silage bunkers and piles that are not immediately covered after filling. The gas is heavier than air, and collects near the bottom of the pile.
Exposure to silo gases is quickly fatal. Within minutes, nitrogen dioxide (NO2) can combine with water in the lungs to form a corrosive acid. Even if exposure is not enough for immediate death, lung symptoms often will progress hours after the exposure, and can be fatal.
For those who don’t succumb to this initial ailment, the risk of relapsing two to six weeks following the initial exposure is real, and can be more intensive than the initial episode. Exposure to silo gases and the resulting lung damage causes coughing, burning, shortness of breath, fever, chills, headaches, nausea and vomiting and is known as silo fillers disease.
NO2 has a reddish color to it, and does have the odor of bleach. However, smell is not a reliable indicator as it is readily masked by other odors around silo storage areas. Carbon dioxide (CO2) is an odorless, colorless gas — although more of a risk with silo towers — is also present in bunker silos or bagged silo storage. CO2 can appear as a haze. Any exposure to silo gases requires immediate removal to fresh air and prompt medical attention.
Written policies and procedures for bunker silo safety should be readily available to all employees, Dr. Smith said. In addition, the silage team should meet at least twice per year to review safety procedures and proper bunker silo management.
“Silage accidents are avoidable,” Dr. Smith said.
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