Manholes are among the best ways to facilitate underground flow measurement. They provide convenient and safe access to a measuring device, typically a flume, while keeping the system largely out of sight and operating underground. To keep the system contained, however, the manhole will need to have a cover in place. Learn how to choose a manhole cover, and discover which option is most suitable for your system.
If your manhole is going to be near frequent foot traffic, it’s generally best to use a flat cover. Typically made from aluminum, these covers blend in easily with the ground and don’t get in anyone’s way when they’re trying to traverse the area. If you opt for another kind of cover in an area with lots of traffic, people are likely to stumble on or run into the manhole cover.
If water leaking into the manhole is a concern, make sure you opt for a watertight option. These tend to be a bit more expensive, but they’ll be less costly than a compromised flow measurement system. Flat covers are also compatible with multiple lock configurations, which should generally be used when installing in high-traffic areas to ensure the safety of the system.
While typical flat covers are suitable for areas with high foot traffic, they’re not rated to withstand vehicles. If your manhole is being installed in an area where cars and trucks will frequently pass over, you’ll need a traffic-rated cover that can handle the additional pressure. Typically, these are installed on roads and highways and in parking lots.
In order for a cover to qualify as traffic-rated, it must meet the standard set by the American Association of State Highway and Transportation Officials. This is known as the H-20 loading standard. In order to meet the necessary criteria, the manhole cover must be able to withstand a wheel-load weight of 16,000 pounds, which is something a typical flat cover won’t be capable of.
Domed covers are the easiest to work with, but they’re really only suitable for manholes that are away from high-traffic areas. They are dome-shaped, as the name suggests, and tend to be set about a foot off the ground at their highest point. Given the nature of an easily missable 1-foot-tall protrusion from the ground, if you do have to install one in a high-traffic area, make sure you post the appropriate barriers and signage around it.
The design of a domed cover works to help both the flow measurement system and any workers. Surface water is effectively kept out, as the cover’s 1-foot protrusion from the ground makes it harder to access unless there are serious floods. Even then, the cover can be water-sealed. Additionally, dome covers offer the most room and best accessibility inside the manhole, so workers can more easily venture down to the flume.
Choosing a Manhole Cover
Whether you’re ready to purchase a manhole cover or need additional help finding the right fit, Tracom is at your service. Our experts are happy to craft customized manhole covers as well as entire manhole systems for use within your unique flow measurement system. Contact us today to request a quote.