The subject matter disclosed herein relates to gas distribution system, and in particular to a natural gas distribution system having a drip riser.
Conduits or pipes are used in a variety of applications to either transfer a material, such as a gas or liquid for example, from a first area to a second area. Other applications make use of conduits as a type of shield to protect an object, such as an electrical, telecommunications or other cable for example, from damage. Often, these conduits are located underground, such as beneath roadways or sidewalks for example. Access points to the conduits may be provided, such as through manhole covers for example, to allow service personnel access to the conduits.
One application that makes extensive use of conduits is in the delivery of natural gas from a provider to a residence. Natural gas main conduits are typically installed under a street and have branch connections that couple the gas main to a residence, office building or other facility. Often, the conduits used in a natural gas system are made from nonmetallic-plastic material, such as polyvinyl chloride or polyethylene (PE) for example. The branch natural gas conduits are usually installed underground and have a first valve (sometimes referred to as a curb valve) adjacent the main conduit near the street and a second valve adjacent the gas meter located in or near the residence or building.
It should be appreciated that since the gas being transferred through the conduit contains moisture, water may build up within the conduit, such as through condensation with the walls of the conduit. In some cases, the water within the conduit may build up over time and collect, such as at low points in the conduit. When sufficient water collects, the flow of the natural gas may be interrupted or impeded.
In some natural gas delivery systems, a fitting sometimes referred to as a drip riser may be installed periodically. The drip riser includes a trap that captures water and an access fitting. To check for the presence of water, the service personnel open the access fitting to check for the presence of water. Typically, the access fitting is a threaded plug disposed on an end of a riser pipe. The riser pipe is typically about 1 inch long and extends from the top of the conduit. One issue that arises is that the gas pressure within the conduit may force water out of the riser pipe causing a gas release or a gas liquid spill. Since the liquid may be contaminated, costly cleanup procedures may be needed to remove the gas liquid spill.
Further, in areas prone to flooding or high ground water, sometimes the access fitting may be submerged, such as during a storm for example. Due to the potential for the release of a contaminated liquid or gas, the inspections of these drip risers may be delayed until the water recedes below the top of the riser pipe. As a result, water collects within the conduit in an area that is flooded, the delivery of gas downstream may be interrupted for an undesired period of time.
While existing drip risers for gas delivery systems are suitable for their intended purposes, a need for improvement remains in providing a drip riser system that reduces or eliminates the risk of a liquid spill and allows for inspection of the drip riser in flood or high ground water conditions.