Systems For Sealing and Venting a Manhole

Abstract

A manhole cover system (10) for sealing manholes to minimize water infiltration includes a manhole cover (12) re-movably inserted into a manhole cover frame (14) having a compressible gasket (28) attached thereto. Manhole cover (12) includes a base (16) and a peripheral rim (18). Peripheral rim (18) includes a cover outer peripheral surface (20) and a horizontal cover seat (22). Manhole cover frame (14) includes a frame cover restraint wall (24) and a frame seat (26). During assembly, peripheral rim (18) is removably seated on frame seat (26) of manhole cover frame (14). Compressible gasket (28) forms a seal within a vertical clearance space (32) between cover outer peripheral surface (20) and frame cover restraint wall (24).

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]This application claims priority to U.S. provisional application 62 / 430,418, filed Dec. 6, 2016, U.S. provisional application 62 / 470,937, filed Mar. 14, 2017, and U.S. provisional application 62 / 512,439, filed May 30, 2017, and U.S. provisional application 62 / 522,385, filed Jun. 20, 2017, the entire contents of each application being incorporated by reference herein.FIELD[0002]The subject technology relates generally to manhole covers and specifically to systems and methods for sealing and ventilating manholes, to minimize unwanted water infiltration, and for inducing air flow, including gasket systems.BACKGROUND AND SUMMARY[0003]The subject technology is useful for underground vaults, manholes, conduits, boats, or any other structure where sealing to minimize water infiltration (e.g. rain water) and / or ventilation is important. In some aspects, the subject technology can be utilized in both new construction and in retrofit applications. ...

AI Technical Summary

Benefits of technology

The patent text describes a need for a simple and economical manhole cover sealing system. The system uses a compressible gasket and silicone coating to seal the space between the cover and frame. The gasket is attached to the frame and the cover is seated on top, forming a tight seal. This design prevents debris from entering and ensures a long life for the seal. The dome-shaped cover also allows for proper venting and minimizes water infiltration. This is useful for a variety of manhole cover applications.

Problems solved by technology

Unwanted water infiltration significantly burdens sanitary sewer collection system capacity, pump capacity, wastewater treatment plant capacity, and causes sanitary sewer overflows to the environment and public waterways.

However, venting or ventilation of sealed covers is oftentimes necessary, for instance, to mitigate sewer gas buildup in the manhole.

Manhole covers typically leak significant amounts of rain or surface water and oftentimes lie in flood-prone areas.

There is a problem created by the clearance space between the cover's outer peripheral and the frame as rain water and debris can enter the manhole through the clearance space.

However, if the frame seat area is not clean upon setting of the cover, water will still flow in between the cover and frame seat.

Horizontal gaskets are sometimes used but they are ineffective.

If debris is present between the horizontal seats the sealing action is compromised.

Even a small pebble wedged between the gasket and manhole cover can cause 20 gallons per minute of leakage when the manhole is submersed by only a ¼ inch of water.

Known sealing systems experience problems that occur due to road traffic.

Even if existing horizontal seats worked properly, the vertical annular space between the cover and frame invites standing water after rainfall.

Debris builds up in this annular space upon evaporation of the water, which causes corrosion between the two surfaces which makes the cover extremely difficult to remove.

Typically, this is not the case due to the fact the horizontal seat leaks rain water and carries debris into the horizontal seat area and into the sanitary sewer collection system.

Some known sealing systems utilize loosely secured gaskets recessed into the cover seat that can become easily lost when removing or installing the cover by dragging the cover across the frame.

The cast iron manhole cover is frequently dragged instead of lifted because of its heavy weight.

The system can shed debris because of its vertical position and is configured such that no dead weight load from the cover is directly applied to the seal itself, and the seal materials have a relatively longer life span.

Bonding the chimney and frame together to make a water-tight seal is difficult due to surface load (i.e., traffic loads) and freezing / thawing conditions on both the manhole frame and chimney area.

Furthermore, it can be difficult to achieve and maintain an acceptable seal between the frame and the chimney, since the frame and the chimney are typically made of differing materials and thus expand and contract at different rates.

Also, the chimney section constructed of brick or precast concrete rings can deteriorate over time due to load and freeze / thaw conditions.

However, once installed, the mortared seals and the chimney bricks or riser rings can be a significant source of unwanted inflow and infiltration of ground water into the sewer system.

However, installation and repair of such external seals usually requires removal and reinstallation of the frame.

In addition, such systems are problematic in that the seals provide limited flexibility to conform to the contour of the pipe.

Additionally, bonding to the pipe is both costly and labor-intensive to install.

Today, manhole covers are oftentimes sealed against water which incidentally prevents air from flowing into and out of the sewer system.

However, ventilation is oftentimes necessary, for instance, to mitigate gas buildup.

This in turn, when combined with moisture, forms sulfuric acid which degrades the concrete / masonry material in both the pipes and manholes causing significant long term damage.

There can be a problem during flooding as the elevated vent does not keep water out when the water depth exceeds the height of the raised vent, nor does it address snow plows hitting the raised vent.

Known systems are both costly and labor-intensive to install.

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