Excess flow valves

An excess flow valve (EFV) for installation in a service line of natural gas distribution system serving an existing structure. The EFV has a cylindrical housing having a first length and a second length and a through hole therethrough for passage of gas. The EFV 11 engaged in the through hole of the first length and the second length has an expandable wall which can be expanded and fixed in said service line.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a pipeline excess flow valve (EFV) and its retrofitting with compatible installation equipment into an existing gas service line.

2. Prior Art

Conventional combustible gas distribution systems bring gas from a street main below ground level, through a tapping tee, a service line, a riser above ground level, a meter cock, a regulator, a meter and then into the customer's structure. An example of such system is shown inFIG. 1.

Rupture of the line or failure of fittings between the consumer property line and the served customer structure can occur for any number of reasons. Among these are digging by the customer or other party, vehicular impact, ground settling, failure of a regulator, failure of a meter, failure of fittings and earthquakes. Rupture of the line or failure of fittings can also occur on the inside customer fuel gas piping or flexible connection. Dangerous explosive conditions can arise when any such rupture occurs.

Prior art patents show various structures for shutting off the gas flow when the flow exceeds a predetermined value, e.g. due to the downstream rupture. Excess flow valves are used in the natural gas industry to prevent explosive pipeline gases such as natural gas, propane, methane, coal gas, town gas, etc. from escaping when a pipe is ruptured. These safety valves will remain open during normal use, when there is backpressure downstream from the valve, but will trip (snap shut) when the downstream pressure disappears. This prevents fires and explosions when gas lines are ruptured.

In operation, the stem of a conventional EFV such as that shown in U.S. Pat. No. 5,551,476 is spring biased opposite to the direction of gas flow. Under normal conditions the poppet on the stem is held away from a valve seat by the bias spring. When the flow is excessive such as when the service line ruptures downstream of the EFV, the forces from the flowing fluid overcome the spring bias and the poppet closes against the seat, shutting off the flow. Thus, the dangerous flow of combustible gas is stopped.

Presently, in order to install an EFV in an existing service line a hole or trench must be dug, the service line pressure must be reduced to zero, and the service line must be cut. This is not only expensive, time consuming, and disruptive to customers and traffic flows, it is also impractical in terms of the human resources required.

The main technology barriers to retrofitting EFVs without digging have been the actual anchoring of the device in the service line. The anchoring of the device has been an issue since it is unacceptable to damage or otherwise alter the interior wall of the service piping. The method of insertion has been an issue because the valves and fittings attached to the meter set have unpredictable geometry and the bend in the service riser presents a constraint in terms of the length of the EFV and the rigidity of the installation tool.

OBJECT AND SUMMARY OF THE INVENTION

The object of the present invention is directed to a unique EFV and installation equipment engaged to the EFV during its installation which together overcome the deficiencies and problems in the prior art discussed above. The compatible EFV and installation equipment provides a new solution for retrofitting EFVs in service lines that involves no digging, thereby causing far less disruption to the community. The installation is effected from the customer meter set, using a hydraulically expandable element integral with the EFV that anchors the EFV inside the existing service line by the force of an interference fit.

A primary feature of the engaged EFV and compatible installation equipment provides an external geometry that is initially smaller in diameter than that of the inner diameter of the service line in which the EFV is to be installed. This permits passage of the EFV through the service line and its appurtenances to the point of installation without damage.

When the EFV has been inserted to a predetermined point in the service line, it can be expanded to the diameter needed for secure anchoring. The EFV is made of a material that allows for enough expansion to anchor the EFV without cracking, splitting, or otherwise deforming in an irregular manner. Put simply, this portion of the EFV is blown up like a balloon.

The method for the actual hydraulic expansion is and has been for some time in the public domain in the form of a method of power plant steam turbine condenser tube sleeving (repair), however the concept for using this for anchoring an EFV is entirely new and constitutes a secondary component of this original idea and application.

The installation equipment consists of a hydraulic pump, a flexible water line, and a mandrel that slides into the unique hydraulically expandable element of the EFV. The anchoring force, measured by a pressure gauge on the installation equipment, is high enough that the mandrel can simply be pulled out of the EFV when the expansion cycle is finished.

Thus, the features of the EFV according to the invention in cooperation with its installation equipment are intended to permit a user to:(1) Retrofit the EFV in the customer's meter piping while the service line remains pressurized.(2) Insert the EFV through the service line up to the tee that is attached to the gas main, and(3) Use hydraulic pressure to expand a specific portion of the EFV so as to contact the inside of the service line and lock the EFV in place.

Though the device is metal, its design would be such that the metal expands much like a balloon under the applied pressure. This would have the further benefit of insuring that no sharp edges are in contact with a plastic service line.

As indicated above, installation equipment consists of a hydraulic pump, a flexible water line and a mandrel that slides into engagement with the hydraulically expandable element of the EFV. The anchoring force, measured by a pressure gauge on the installation equipment, indicates when the expandable element has expanded to contact the service line. Thereafter, the mandrel can be withdrawn out of the EFV when the expansion cycle has ended.

EFV1shown inFIG. 2is intended for installation in an existing conventional natural gas service system such as that shown inFIG. 1to prevent escaping gas entering the home of a customer from a ruptured gas line downstream from the gas meter. The distribution system ofFIG. 1is shown connected between a tapping tee on a gas main and a gas meter located in the home of the customer. The service line shown in the system is normally buried after these connections have been made.

Installation of the EFV1is accomplished by inserting it through the bypass tee shown inFIG. 1on the inlet side of the gas meter and fixing it to the inner wall of the gas pipe which extends to the gas main. Insertion under pressure is accomplished by way of a “stuffing box”, a conventional device that consists of a sealed chamber which is attached to the bypass tee and allows control of a sliding rod or cable (not shown). One end of the rod or cable is outside of the stuffing box, allowing direct control by the operator while the opposite end is sealed inside the pressurized system. The seal is maintained via a gland nut and elastomer that compresses around the rod or cable when the nut is tightened. Such a device is well known within the industry and accordingly not an inventive feature of the claimed invention. The progression of drawings fromFIG. 2throughFIG. 8illustrates the structural components and steps involved in the installation of EFV1in such gas pipes and removal of the installation equipment after the installation.

As shown inFIG. 2, EFV1has a continuous cylindrical housing10made preferably of metal that has the same outer diameter throughout its length and a through hole11that has inner diameters over selected lengths of the housing10which are different from each other so as to support the different functions of housing portions2,4of housing10discussed below.

Portion2extends over a length6of cylindrical housing10and houses conventional hardware12similar to that shown in U.S. Pat. No. 5,551,476 to control the opening and closing of an EFV valve therein. As hardware12is not an inventive feature of the present invention, it will not be addressed further.

Portion4extends over a length8of cylindrical housing10and is integrally formed as a unit with portion2. Located within the length8of portion4is a laterally expandable wall14. The inner diameter16of through hole11over the length of wall14is larger than inner diameter18located at opposite ends15,17of portion4. Thus, expandable wall14is thinner and more flexible than the wall of housing10located at opposite ends of portion4.

FIG. 4shows the installation equipment20which serves to locate and fix EFV1at a predetermined position in the service line downstream from the customer's gas meter. This equipment consists of a hydraulic pump22, flexible fluid line24, and a mandrel26designed for sealed engagement with opposite ends15,17of portion4.

Mandrel26comprises a cylindrical housing28a closed first end30and a second end32having an inlet engaged to an end of fluid line24. The other end of fluid line24is engaged to hydraulic pump22.

Housing26is closed with the exception of fluid outlet hole34and the inlet in its second end32. Finally, elastic O-rings36are fixed to housing26near opposite ends30,32so as to be spaced apart substantially the same distance as opposite ends15,17of portion4of EFV1.

Retrofitting EFV1into an existing gas service line begins with inserting mandrel26into EFV1as shown inFIG. 5so that O-rings36are respectively engaged to opposite ends15,17of portion4to seal mandrel26in portion4. This engagement creates an annular sealed space37and confined between mandrel26expandable wall14. After mandrel26is engaged in EFV1, they can be easily inserted into service line38as shown inFIG. 5since the outer diameter of the engaged EFV1and mandrel26are smaller than that of the inner diameter of service line38. The engaged EFV1and mandrel26can then be moved to a predetermined position in service line38by manipulation of flexible fluid line24.

After the engaged EFV1and mandrel26have reached the selected position in service line38, an operator can initiate operation of hydraulic pump22to force fluid through fluid line24into mandrel26and out fluid outlet hole34into sealed space37. The pressure created by the influx of fluid into sealed and confined space37results in the lateral expansion of expandable wall14into fixed engagement with the inner wall of service line38as shown inFIG. 6.

FIGS. 3 and 8respectively show cross-sections of annular expandable wall14before and after its expansion by the fluid pressure created by hydraulic pump22in annular space37.

After the operator is satisfied that EFV1has been successfully fixed in service line38by engagement of expandable wall14against the inner wall of service line38as shown inFIG. 6, the hydraulic pump22is turned off. This permits removal of mandrel26from the EFV1engaged in the service line by withdrawing the fluid line from the service line.

Thus the expression “means to . . . ” and “means for . . . ”, or any method step language, as may be found in the specification and/or in the claims below, followed by a functional statement, are intended to define over whatever structural, physical, chemical or electrical element or structure, or whatever method step, which may now or in the future exist which carries out the recited function, whether or not precisely equivalent to the embodiment or embodiments disclosed in the specification above, i.e. other means or steps for carrying out the same function can be used; and it is intended that such expressions can be given their broadest interpretation.