As grain storage structures change, so do their safety and maintenance requirements.
Today’s grain bins are larger, taller and more complex, Jack Kenney, regional manager with D.C. Taylor Co., Cedar Rapids, Iowa, U.S., said during the 2008 Grain Elevator and Processing Society’s annual Exchange in Omaha, Nebraska, U.S. Maintaining bin roofs to prevent water infiltration and grain damage is vital.
Kenney said facility owners must adapt to changing technologies and stay current with the latest roofing maintenance techniques, waterproofing materials and safety information. His discussion covered materials and processes that can be used to maintain and/or replace an aging roof; safety requirements for accessing roofs and working on top of bins; and inspection and maintenance to manage the upkeep of bin roofs and extend their lifecycles.
MATERIALS AND PROCESSES
Many types of roof coverings and waterproofing materials are used on grain storage bins including metal or tin; conventional built-up roofs; single ply membranes; coatings (acrylics, silicones, epoxy, etc.); polyurethane foam with coating; and coal tar pitch built-up systems.
Not all bin tops have the same structural decking, Kenney said. Decking materials include metal, concrete plank, poured concrete and lightweight cellular concrete. The type of decking often determines the type of roofing material that should be used for repair or replacement.
Decking is much more costly to repair or replace than roofing, which is why it’s important to keep the elements away from the deck and stored product, he said.
Here are some typical conditions found on bin roofs and what is needed to repair or improve the performance:
1. Concrete damage. Areas of coating can wear away and expose the concrete decking to the elements. A lack of maintenance can lead to spalling of the concrete and loss of the overhanging edge. The area should have the perimeter edge rebuilt and sealed. The deteriorated coating should be peeled back and new product installed to level and waterproof the roof area.
2. Loss of coating. Left unattended or unrepaired, a roof that has lost its coating will lead to deterioration of the material below. Areas such as this should be cleaned and patched before moisture is allowed to travel between the membrane and the deck.
3. Single-ply replacement. When roofs are beyond repair, one option is to adhere a lightweight thermoplastic membrane. The heat-welded seams from this type of membrane outperform taped seams or built-up roof seams, Kenney said. The smoothness of the membrane does not allow vegetation to grow or other debris to build up on the surface. However, the surface can be slippery in wet or icy conditions, if employees have to work on it.
4. Liquid applied replacement. Not all bin tops can use a single-ply replacement, typically because of bolt mounted equipment. In this situation, a liquid applied polyester resin combined with a polyester fleece can be used to form a reinforced monolithic waterproofing and roofing membrane. The system also provides granular texture on the surface that reduces slip issues.
5. Difficult roof access. Facilities with difficult roof access still need regular maintenance to avoid costly internal problems. Dirt and sediment sitting on a roof at a high elevation indicates deflection or settling of the roof. If an area like this lets water into the bins, it should be immediately sealed before allowing free moisture under the felts. Moisture allowed to enter the system leads to adhesive loss, Kenney said, which can lead to premature roof failure.
6. Structural damage. Long-term moisture infiltration into a concrete topped bin can lead to structural damage. When moisture becomes trapped under a roof waterproofing system, freeze-thaw cycles can be destructive, Kenney said. This type of damage can undermine the safety of the entire building.
Before hiring a roof contractor, make sure he is serious about safety. Ask questions such as: Do they have a safety committee and dedicated safety director? Are roofing crews tested for illegal substances before being hired? Do they have a competent person in fall protection at each project site? Do they have a fall protection plan that defines safety setup prior to beginning a project? Do crews receive ongoing training?
Each employee that works on a facility’s roof should have training in the necessary topics which are directly related to safe roofing practices, Kenney said. Take a proactive approach to safety; if a roofing contractor is not talking about safety prior to starting the job, ask why not, he said.
Before a roofing job begins, the roofing contractor should complete a job hazard analysis and present a safety plan to the facility operator. The plan should include the work to be performed, hazards associated with the task, and countermeasures to avoid hazards.
Kenney said areas of particular interest for the safety plan include:
• roof access;
• loading materials;
• edge work/deck replacement;
• material handling;
• debris removal;
• working with electricity and chemicals; and
• working with flammables.
EXTENDING ROOF LIFE
A common problem with roofs is simple neglect, Kenney said. Many people don’t think about roof upkeep and maintenance until they are faced with a problem or water leak. He suggested seven steps to implement an effective maintenance program:
1. Inspect bin roofs at least two times per year and after any major weather events. Problems found early can cost less to repair than those left unattended.Prevent decking deterioration, water infiltration, loss of flashings and coating failures.2. Identify competent people to perform the work.
3. Gather and prepare information. This includes historical data (original roof date, repairs and additions, substrate materials, surface type, drainage and warranty information) and roof activity (previous problems, traffic patterns, maintenance needs and emissions or discharges onto the roof).
4. Conduct a rooftop inspection. Inspect roof edges, exterior walls, interior walls, projection flashings, surface conditions and rooftop equipment. Clear and clean drains, scuppers and drain lines. Remove storm damage and organic matter that may restrict drainage. Repair minor problems.
5. Develop a comprehensive budget. This includes yearly preventive maintenance, yearly repairs and end-of-roof life replacement costs.
6. Implement an ongoing preventive maintenance program. Decide who will do the maintenance and determine the frequency of the work, actions required and documentation needed.
7. Ensure a solid record-keeping and tracking system. Capture information so it is not lost when employees leave. Plan for current and future needs, and track roof performance and preventive maintenance.