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Adjustable Manhole Frames Avoid Costly Problems
Misaligned manhole frames in streets often cause driving hazards, failure of pavement around the frames, cause poor access to manholes, may be responsible for inflow and infiltration and can also result in other problems. Because manhole frames are not manufactured to be adjustable, efforts to make repairs is time consuming and often ineffective.
A Canadian company, Terminal City Iron Works, believes it has the answer to these problems.
“Our adjustable manhole frame and support ring eliminates problems associated with current adjustment methods,” said Bill Zielinski, Terminal City Iron Works general manager. “They can be manufactured to work with any existing frame and cover. They are simple and easy to use -- achieving perfect adjustment takes only minutes. Installing an adjustable frame and support rings will result in long-term cost savings for maintenance.”
The products and process are covered by Canadian and United States patents. They have been presented at various public works venues in Canada and the U.S. and have been favorably received, said Zielinski.
The support rings and adjustable frames have been successfully used by several cities in British Columbia and Western Canada for the past five years, and they soon will be available in Eastern Canada and the United States.
The support ring is made of ductile iron and is light, but very strong. With a frame in an adjusted position, the ring meets the highest H load requirements without concrete or grout support. The ring is designed to keep the adjustable frame stable and centered over the manhole opening. For maximum strength and sustainability, concrete -- not grout -- can be placed between the frame and grade rings to eliminate voids creating structural weakness or where moisture could accumulate and freeze causing frost damage which could weaken the structure.
The adjustable frame is manufactured of cast iron and in some cases ductile iron; weight depends on diameter, averaging between 175 and 225 pounds. High-strength, low alloy set screws with additional corrosion coating applied are used to make adjustments. With the set screws, one worker can easily adjust the frame for perfect alignment and a smooth surface in the roadway.
The city of Kelowna, BC, participated in initial development and testing of the products and has been the most extensive user of the adjustable frames and support rings.
Wayne Nadasde, construction supervisor of the city’s Design and Construction Services Department describes the installation process.