Silo Filling Safety

Preseason Preparations

Since operators may be less familiar with seasonal equipment and the risks incurred, review the operator's manuals, and follow maintenance guidelines for corn and hay harvesting equipment. If you no longer have the manual, contact your equipment dealer, or do an online search for the make and model.

Seasonal maintenance activities include:

• Cleaning, lubricating, and replacing worn parts to ensure that the equipment is in good operating condition and to reduce the potential for a breakdown.
• Making sure that all guards are securely in place and replace guards if they are worn or damaged.

The initial preparation for filling the silo includes:

• Raising the distributor/unloader to the top of the structure. Choose a calm, dry day to complete this activity to decrease the potential risk of slips and falls.
• Carefully inspecting all cables, wires, pulleys, and connections to make sure they are properly working and securely anchored.
• A person at ground level raising the distributor/unloader while another person standing on the blower pipe platform watching the process and signaling if lines become tangled or other problems arise.

Caution

Under no circumstances should anyone enter the silo while the distributor/unloader is being raised or attempt to crawl onto it when it is suspended because a raised distributor/unloader can easily crush a worker should it fall.

Machinery Guarding

Harvesting

Tractors are used during the harvest season in varying capacities such as operating an unloader or transporting wagons. To prevent incidents during harvest:

• Choose a tractor that is equipped with a rollover protective structure (ROPS) and a seatbelt.
• Ensure the tractor has the correct horsepower and braking power for the job that you need to complete.
• Use a non-front-end loader equipped tractor because the loader can change the center of gravity on the tractor.
• Before entering a field on the tractor, examine the area for changes since last harvest such as debris, fallen limbs, or ditches. This will help you anticipate ruts, uneven terrain, and muddy conditions.
• Maintain a slower speed in the fields when turning.
• Plan the harvest so that you are traveling downhill on steep slopes with equipment to reduce the risk of an overturn incident.

Filling the Silo

One of the main risks involved in filling the silo stems from the operator being exposed to numerous moving machine parts in a relatively crowded work area. Mechanical hazards include pinch, wrap, shear, and crush points as well as freewheeling parts hazards.

To prevent incidents when filling the silo:

• Use guards on self-unloading forage wagon and silo blower when they are available; Unfortunately, not all self-unloading forage wagon and silo blower can be guarded.
• Make sure that the power take-off (PTO) shafts operating the forage wagon and silo blower are properly guarded.
• Avoid unsafe practices such as stepping over shafts or reaching into operating unloading wagons.

Working with the Self-Unloading Wagon

Hazards on self-unloading wagons include a combination of moving aprons, beaters, conveyors or augers, and an assortment of chains and sprockets.

To prevent incidents involving self-unloading wagons:

• All protective machinery shields must be in place.
• Operators should wear comfortable and close-fitting clothing.
• No one should even enter a wagon while the power is on.
• Do not reach into the unloading chute to help speed the unloading rate.
• If clogging occurs, first disengage the PTO, shut down the tractor and remove the keys from the ignition before removing the clogged area. PTO's can unexpectedly slip into gear, particularly if poorly adjusted, or on older tractors, so shutting off the engine and locking out the equipment is important.
• Keep the unloading wagon's emergency shut-off device in good working condition because it could be instrumental in saving your life.

Working Around the Silo Blower 

As forage is unloaded from the wagon into the silo blower hopper, it is moved by auger or conveyor to the blower fan which forces it into the silo. The main hazards of the silo blower are the PTO shaft, the exposed conveyor or auger, and the blower fan blades. Like the forage wagon, silo blower injury incidents are more likely to occur when the machine becomes plugged up.

 To prevent incidents when the silo blower becomes plugged:

• Do not climb onto the hopper or use hands or feet to force forage into the blower blades.
• Disengage the power, shut down the tractor and remove the keys from the ignition before removing the clogged area.
• Make sure the freewheeling blower fan blades have completely stopped turning.

Working around the Power Take-off

Another danger point in the silo filling process is the PTO shaft which powers the unloading wagon and the silo blower. A PTO shaft rotates at either 9 (540 rpm) or 16 (1,000 rpm) times per second at full operating speed. At these speeds, a person's arm can be pulled into and wrapped around the PTO stub or driveline shaft in less than a second. The main PTO hazards include the stub, driveline, and driveline separation.

To prevent PTO entanglement incidents:

• Ensure the PTO master stub and the driveline are properly shielded;
• Wear close-fitting clothing and secure long hair under a hat;
• Always walk around tractors and wagons instead of stepping over shafts;
• During silo filling, make sure that the unloading wagon and silo blower are securely fastened to the tractors' drawbars; otherwise, the PTO could separate. If the PTO separates on the tractor powering the blower pipe, it could also vibrate the blower pipe down.

Other Important Considerations During Silo Filling

Children and Bystanders

The silo filling area should be restricted to only those people directly involved with completing this task. This is especially true for children and unneeded helpers or bystanders. Non-essential persons could get hurt while also distracting the machine operator. Children are often curious during silo filling time, and they want to climb on wagons and tractors. Youngsters may also want to help with silo filling without fully understanding the hazards associated with the machinery.

Noise Exposure

The Occupational Safety and Health Administration (OSHA) recommends hearing protection when workers and bystanders are exposed to 85 decibels or more for an 8-hour workday. Sound levels of 100 dB or more, for even short periods of time, can result in permanent hearing loss. Farm tractors are known to generate sound levels in a range of 74-112 decibels. During silo filling, it is typical to use two tractors with one operating an unloader wagon, and the other a silage blower simultaneously. As a result, high noise levels exposure is common.

Silo Gas

Silo gas formation can begin immediately after filling and can peak within two to four days after filling if not properly vented or exhausted. Dangerous levels of silo gas may be present for an additional three weeks.

 To prevent exposure to silo gas:

• If you must enter the silo, wear a self-contained breathing apparatus (SCBA).
• Stay out of the silo as much as possible but if you need to enter and do not have a SCBA, do the following:
  • Run the silo blower for 30 to 45 minutes prior to and during entry.
  • Use a multi-gas meter to check for silo gas. 
  • Maintain visual contact with a second person outside the silo.
  • Wear a body harness attached to a lifeline and secure anchor point.

Summary

Remember, filling the silo is a complex operation which involves equipment hazards and potential exposure to deadly silo gases. A safe harvest can be completed if workers understand the dangers and following recommendations.

Remember the key recommendations:

1. tractor and equipment safety practices.
2. keep children and non-working adults away from the worksite.
3. wear appropriate clothing and hearing protection.
4. be aware of silo gas and ventilate, ventilate, ventilate.

Additional Resources:

Fetzer, L., Becot, F. & Murphy, D.  (2024) Penn State Extension. Practical ways to prevent hearing loss on the farm.

Murphy, D. (2022) Penn State Extension. Silo gases – the hidden danger.

Originally authored by Dr. Dennis J. Murphy, Nationwide Insurance Professor Emeritus and updated July 2024 by Dr. Florence Becot, Nationwide Insurance Early Career Professor, and Linda Fetzer, Extension Program Specialist.