Abstract:
Disclosed is an apparatus and method of pressure testing an installed pipe by inserting a fitting into the internal threads found in saddle tee fittings. The internal threads of the fitting used by the cutting mechanism may allow a common apparatus to be used across different manufacturer&#39;s fittings without modification. Further, the device has a certain length of thread engagement to allow for proper engagement while maintaining the load carrying capacity required to properly perform the pressure test.

Description:
BACKGROUND OF THE INVENTION 
     a. Field of the Invention 
     The present invention pertains generally to pressure testing of pipe and specifically to the pressure testing of polyethylene gas lines. 
     b. Description of the Background 
     Polyethylene (‘Poly’) pipe has become popular for the construction of pipelines for various purposes. Poly pipe enjoys a low cost of installation and very efficient and quick joining technology in addition to being flexible and easy to install. Poly pipe is used for pressurized applications such as gas and water, and for unpressurized applications such as sewer. 
     In a natural gas distribution system for distributing gas to houses, a main line may be installed along a roadway initially and tees would be installed at a later date to complete the service from the main line to each house. The tee may be a saddle tap tee, such as shown in FIG.  1 . The tee fitting  100  is sealed to the pipe  102  using multiple methods. After the tee  100  is sealed to the pipe  102 , a cutting device located inside the tee  100  is engaged to penetrate the exterior surface of pipe  102  and allow communication of the fluid or gas inside the pipe  102  to flow through the tee  100 . Such fittings are commonly used in the industry. 
     As stated above, a main line may be installed in the ground and feeder lines installed using tees to individual houses. A feeder line may be fully installed except for the penetration of the exterior of the main pipe when a pressurization test may be necessary to ensure proper installation. 
     In pressurized applications, especially with natural gas or propane, pressure testing of an installation or segment of an installation is mandatory before the segment can be put into service. Such a test requires that the segment of pipe be sealed off and pressurized with a gage applied. When the pressure source is removed, the segment of pipe must maintain pressure for a certain period of time to ensure that the pipeline has no leaks. After the test is successful, the exterior of the main line pipe may be penetrated through the tee fitting and the feeder line is thusly placed in service. 
     There are many different designs of tee fittings in commercial use. For example, the saddle tees may be fusion welded to the main line pipe or resistive heating may be employed between the fitting and the pipe to affect a weld. The sizes of main line pipe may range from two inch outer diameter to twelve, fourteen, or even larger sizes. The tee fittings are available in many different sizes, however, two sizes are most commonly used in feeder line applications. These sizes are one inch and two inch diameter. 
     Several different manufacturers supply these tee fittings. Each manufacturer may use a different sealing system and slightly different design. Some pressure test devices exist that attach to the tee fitting using the same threads and sealing system as the cap of the fitting. With the great number of different sealing systems, such as having an o-ring on the body of the fitting or located in the cap itself, and the use of specialized buttress threads in some fittings, a specialized pressure test adapter must be created for each manufacturer&#39;s fitting design. 
     Alternative methods for performing a pressurization test is to install a special tee fitting along the course of the feeder line. The special fitting is installed solely for the purpose of performing the pressurization test and is not subsequently used once the feeder line is put into service. The disadvantage is that the additional test fitting is another potential leak path as well as being another expense. 
     It would therefore be advantageous to provide a device and method of testing a feeder line that would be applicable to many manufacturer&#39;s tee fitting designs without having any changeover. It would be further advantageous if the apparatus and method did not require any additional fittings to be installed in the feeder line. 
     SUMMARY OF THE INVENTION 
     The present invention overcomes the disadvantages and limitations of the prior art by providing a device and method for sealing pressure test apparatus using the inside threaded portion of a tee fitting. Further, the device may be simply adapted from one size of tee fitting to a second size. 
     The present invention may therefore comprise a method for pressure testing a branch circuit of polyethylene pipe that is connected to a main line with a tapping tee fitting comprising: removing the cap of said tapping tee; adjusting the position of the hole cutter inside said tapping tee to a depth at least approximately equal to the diameter of said hole cutter; installing a pressure test adapter to said tapping tee, said adapter being adapted to engage the internal threads of said tapping tee, said internal threads being the threads in which said hole cutter is engaged, said adapter having an o-ring seal, said o-ring seal being adapted to seal against the surface of said tapping tee that is perpendicular to said internal threads, said adapter having a valve and a pressure gage; applying a pressure source to said valve to pressurize said tapping tee; indicating a pressure on said pressure gage; removing said pressure from said valve, said valve being engaged to hold said pressure inside of said tapping tee; and ensuring that said pressure is maintained within a predetermined limit for a predetermined time. 
     The present invention may further comprise a method for pressure testing at least two branch circuits of polyethylene pipe that is connected to a main line with at least two sizes of tapping tees comprising: removing the cap of a first tapping tee; adjusting the position of the hole cutter inside said first tapping tee to a depth at least approximately equal to the diameter of said hole cutter; installing a pressure test adapter to said first tapping tee, said adapter being adapted to engage the internal threads of said tapping tee, said internal threads being the threads in which said hole cutter is engaged, said adapter having an o-ring seal, said o-ring seal being adapted to seal against the surface of said first tapping tee that is perpendicular to said internal threads, said adapter having a valve and a pressure gage; applying a pressure source to said valve; indicating a pressure on said pressure gage; removing said pressure from said valve, said valve being engaged to hold said pressure inside of said first tapping tee; ensuring that said pressure is maintained within a predetermined limit for a predetermined time; selecting a second tapping tee for testing, said second tapping tee being a larger size than said first tapping tee; removing the cap of said second tapping tee; adjusting the position of the hole cutter inside said second tapping tee to a depth at least approximately equal to the diameter of said hole cutter; installing a size adapter into said second tapping tee, said size adapter having external threads adapted to engage the internal threads of said second tapping tee and internal threads adapted to engage the external threads of said pressure test adapter, said size adapter further having an o-ring seal adapted to seal against the surface of said second tapping tee that is perpendicular to said internal threads of said second tapping tee; installing said pressure test adapter to said size adapter such that said o-ring seal of said pressure test adapter engages said size adapter; applying a pressure source to said valve; indicating a pressure on said pressure gage; removing said pressure from said valve, said valve being engaged to hold said pressure inside of said second tapping tee; and ensuring that said pressure is maintained within a predetermined limit for a predetermined time. 
     The present invention may further comprise a pressurization test apparatus for performing a pressurization test on at least two tapping tees with internal threads of different sizes comprising: a pressurization test fitting having a valve adapted to receive pressurized air, a pressure gage adapted to indicate the pressure inside the pressurized circuit, and external threads adapted to fit inside the internal threads of a first tapping tee, said test fitting further comprising an o-ring seal adapted to seal against the surface perpendicular to said internal threads of said first tapping tee; and an size adapter having internal threads adapted to receive said external threads of said pressurization test fitting, a sealing surface perpendicular to said internal threads adapted to seal against said o-ring seal of said pressurization test fitting, external threads adapted to fit inside the internal threads of a second tapping tee, said second tapping tee being larger in size than said first tapping tee, said size adapter further having an o-ring seal adapted to seal against the surface perpendicular to said internal threads of said second tapping tee. 
     The advantages of the present invention are that several sizes of tapping tees may be pressure tested. Further, since the present invention will work with the tapping tees from many different manufacturers, custom test adapters for each manufacturer&#39;s fittings are no longer required. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the drawings, 
     FIG. 1 is an illustration of tapping saddle tee. 
     FIG. 2 is an illustration of a cross section of a standard tapping tee fitting. 
     FIG. 3 is an illustration of an embodiment of the present invention with the inventive pressure testing apparatus prior to being installed into a tapping tee fitting. 
     FIG. 4 is an illustration of an embodiment of the present invention wherein the inventive pressure testing apparatus has an additional fitting that allows the system to be utilized with a larger sized tapping tee fitting. 
     FIG. 5 is an illustration of a partial cross section of an embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 2 illustrates a cross section of a standard tee fitting. The fitting  202  mates to the pipe  204  along the sealing surface  206 . The fitting has an outlet port  208 , a cutter  210 , and a cap  212 . 
     The normal process for operation is to attach the fitting  202  to the pipe  204  by sealing along the surface  206 . In some cases, a hot plate is placed along the sealing surface of the pipe  204  and the fitting  202  until the polyethylene material is to a melted state. At that point, the fitting  202  is forced against the pipe  204  and the melted material is allowed to cool. In other cases, a resistive material is embedded in the fitting  202 . The fitting  202  is pressed against the pipe  204  and an electrical current is applied to the resistive material, causing the polyethylene to melt and the fitting to fuse to the pipe. 
     Once the fitting is sealed to the pipe, another pipe may be attached to the outlet port  208  to complete the installation. When the installation is completed, a pressurization test may be performed. 
     After the pressurization test, the cap  212  may be removed and the cutter  210  may be engaged so that it penetrates the exterior surface of the pipe  204 . The cutter  210  typically has a receptacle for a wrench for a pipefitter to engage the cutter. The cutter  210  travels down the internally threaded portion of the fitting  202  until it engages the pipe  204 , penetrates the surface, and produces a hole. At that point, the cutter  210  may be retracted to the top of the fitting  202  so that the full volume of gas or fluid may transfer between the main line pipe  204  and the fitting outlet  208 . 
     The pressurization test may be performed by installing a special tee fitting into the feeder line. The special tee fitting may be used only for the pressurization test wherein the pipefitter may apply the pressure testing apparatus. 
     FIG. 3 illustrates an embodiment  300  of the present invention with the apparatus  300  prior to being installed into a tee fitting  302 . The apparatus  300  is installed into the inner threads  304  of the fitting  302 . The threads  304  are the threads that propel the internal cutter into the pipe during installation as discussed for FIG.  2 . 
     FIG. 4 illustrates an embodiment  300  of the present invention wherein the apparatus  300  has an additional fitting  400  that allows the system to be utilized with a larger sized fitting  402 . The fitting  400  is specially made to emulate the internal threads of the smaller sized fitting such that the embodiment  300  is adaptable to two commonly used fittings. 
     The apparatus  300  and the fitting  400  comprise a device and method for pressure testing a pipe prior to engagement of the cutter that penetrates the exterior of a main line, allowing a pipefitter to install and test a feeder line without the use of additional special fittings for pressure testing. Further, the internal threads tend to be common between various fitting manufacturers, allowing the apparatus  300  and fitting  400  to be used across multiple manufacturers without any changeover or different fittings to be used. 
     In prior art, the pressurization test adapters have been manufactured that fit over the exterior threads used by the cap on the tee fitting. Such adapters have the distinct disadvantage that the fittings are changed periodically by the manufacturers, causing the pressure test adapters to become obsolete. Further, there was no convenient way to create a pressure test adapter system that operated on more than one size of fitting. 
     FIG. 5 illustrates a partial cross section of an embodiment  500  of the present invention. A tee fitting  502  connects a valve  504 , a pressure gage  506 , and the first adapter  508 . The first adapter  508  fits into the second adapter  510  to test larger sized fittings. The first adapter  508  has an o-ring  512  that seals the first adapter  508  to the second adapter  510  or to a small sized fitting when the second adapter  510  is not present. The second adapter  510  has an o-ring  514  that seals against a fitting  516  when the embodiment  500  is in service. 
     The o-rings  512  and  514  are an effective method of sealing the embodiment  500  to the fitting during use. The o-ring  514  seals against the top surface of the fitting  516 . When the embodiment  500  is used on a smaller sized fitting, second adapter  510  would not be used and o-ring  512  would seal against the top surface of the smaller fitting. 
     The fittings  508  and  510  may be installed by hand or with a wrench. In some embodiments, the fittings  508  and  510  may be fabricated of metal, such as aluminum, steel, or brass. When the threads of the metal fittings  508  and  510  are inserted into the polyethylene tee fittings, only a limited amount of force is necessary to affect a seal on the o-ring. Excessive tightening may result in stripped threads on the tee fitting. In order to prevent stripped threads, a long length of threads is provided in the fittings  508  and  510 . In the present embodiment, the thread length  518  is approximately equal to at least 75% of the diameter  520 . In a similar fashion for the first adapter  508 , the thread length  522  is approximately equal to at least 75% of the diameter  524 . 
     The long thread length compensates in part for the relative weakness of the plastic threads of the fitting. When the embodiment  500  is in service, the pressure applied to the inside of the fitting may be in excess of 100 psi or higher, causing a large load on the threads. In addition, the long lead length assists the pipefitter during installation since a cross-threaded joint will be quickly determined and backed out before the fitting was completely installed. If a thread were cross-threaded, it could be repaired and the adapter may still be used, since good threads may still exist for the adapter to engage. 
     The foregoing description of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed, and other modifications and variations may be possible in light of the above teachings. The embodiment was chosen and described in order to best explain the principles of the invention and its practical application to thereby enable others skilled in the art to best utilize the invention in various embodiments and various modifications as are suited to the particular use contemplated. It is intended that the appended claims be construed to include other alternative embodiments of the invention except insofar as limited by the prior art.