Lighter, stronger, durable: Composite manhole covers utilizing Bayer polyurethane offer numerous benefits over traditional cast-iron covers

GMI Composites' manhole covers can slash weight by up to 83 percent

Orlando, Fla., January 29, 2013 — As traditional, heavy, cast-iron manhole covers corrode away, municipalities, utilities and industrial plant sites are replacing them with new, durable composite covers.

These composite covers, produced by GMI Composites, Inc. and utilizing polyurethane materials from Bayer MaterialScience LLC, weigh significantly less than cast iron. In fact, the composite covers, used by municipalities and plant sites, are significantly lighter with a 24-inch cover weighing only 25 pounds compared with a cast-iron equivalent weighing more than 150 pounds. Yet, they meet rigorous standards for cyclical fatigue, proof-load and durability that the market requires. Additionally, they are corrosion and slip resistant and non-conductive, providing added safety to pedestrians and utility workers who may come in contact with them.

A customized formulation of Baydur® RTM 902 polyurethane, developed collaboratively by Bayer and GMI, is used to mold the composite manhole covers through GMI's proprietary liquid resin injection process.

"We were on-site, providing hands-on support to the GMI team running tests to decide the best production process for the composite covers," said Harry George, manager, New Applications, Polyurethanes, Bayer MaterialScience LLC. "It is always rewarding to work from start-to-finish on a product like the GMI manhole covers and see a concept turn into reality."

GMI selected the Baydur polyurethane system for its strength, durability and ability to facilitate the creation of unique designs, according to Bob Brady, president, GMI Composites, Inc.

"After testing many different materials, we chose Bayer's polyurethane system to produce the manhole covers because of its high strength and durability," Brady said. "The material suited our cover well, but we also elected to work with Bayer MaterialScience because of its overall reputation. Bayer offered tremendous technical assistance to achieve the material requirements necessary to meet the highest standards for manhole covers."

GMI composite manhole covers and frames have an average proof load in excess of 100,000 pounds — more than five times the H-20 loading standard per AASHTO (American Association of State Highway and Transportation Officials) Standard Specifications for Highway Bridges.

GMI maintains world-class testing equipment on premises, allowing for production to be randomly sampled and tested during the manufacturing process. Independent certification and test witnessing is available for the following internationally accepted test standards:

  • United States Standard: AASHTO M 306 Standard Specification for Drainage, Sewer, Utility, and Related Castings, with a 40,000-pound proof load concentrated on a 9-inch-by-9-inch square area and held for one minute.
  • H-25 & HS-25: A 50,000-pound proof load concentrated on a 9-inch-by-2- inch square area and held for one minute. The 50,000-pound proof load represents a safety factor of 2.5 for H-25 & HS-25 loading.
  • European Standard: EN-124 for Gully Tops and Manhole Tops for Vehicular and Pedestrian Areas.
  • The composite covers are customizable and are available in a variety of shapes — round, square and rectangular — in sizes from 12 inches to 50 inches in diameter. GMI works with its customers to determine what attributes are needed for each application, and offers the ability to include a logo or lettering on each cover.

Additionally, the composite covers complement the bourgeoning smart grid market, allowing automation signals and wireless communications to pass freely through them. This also makes them ideal for electrical switching, water metering, and sanitary waste water and storm sewer monitoring applications.

Unlike cast-iron covers, GMI's manhole covers have zero scrap value and are therefore unattractive to thieves, helping municipalities avoid the cost and labor associated with cover replacement. GMI covers are compatible with a variety of retention and locking solutions for increased infrastructure security.

To learn more about the benefits of polyurethane materials, visit Bayer's booth, #1033, at Composites 2013 in Orlando, Fla., Jan. 29-31, 2013.

About GMI Composites, Inc.:

GMI Composites, Inc. was established in 1923 as George Morrell Industries. GMI made its first fiberglass reinforced composite manhole cover more than 19 years ago — these initial covers are still performing exceptionally in the field today. Through continued innovation GMI has made a variety of unique underground access covers. GMI is located in Muskegon, Mich., and all products are made in the USA.

About Bayer MaterialScience LLC:

Bayer MaterialScience LLC is one of the leading producers of polymers and high-performance plastics in North America and is part of the global Bayer MaterialScience business with approximately 14,800 employees at 30 production sites around the world and 2011 sales of 10.8 billion euros. Bayer MaterialScience's 2011 sales in North America were $2.9 billion. The company manufactures high-tech polymer materials and develops innovative solutions for products used in many areas of daily life. The main segments served are the automotive, electrical and electronics, construction, medical, and sports and leisure industries. Sustainability is central to Bayer MaterialScience LLC's business and is based around the key areas of innovation, product stewardship, excellence in corporate management, social responsibility and respect for the environment.

For more information about Bayer MaterialScience LLC's polyurethane technology, call 412-777-7454 or visit

For more information about GMI Composites, Inc. and the composite covers, call 877-755 -1611 or visit

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Media Contact(s)

Name: Thomas Erdner
Phone: 412-777-5200
Company: Bayer MaterialScience