1. Field Of The Invention
The present invention relates to a method of and device for hot tapping a pipe at an angle with respect to the pipe's longitudinal axis. More specifically, the present invention relates to a method and device for hot tapping a pipe from two spaced apart locations to provide access extending into the pipe at an intersecting angle and using this type of hot tapping system for installing a transducer carrier in an alignment fixture attached to the pipe.
2. Description Of The Related Art
One method for measuring the flow of liquid within heating, ventilating, and air conditioning (HVAC) pipes utilizes a pair of sonic flowmeter transducers. This measuring method spaces the transducers apart on a side of the pipeline so that each transducer receives sound waves which originated from the other transducer and which were received after bouncing off of an interior surface of the pipe located on a side of the pipe opposite the side where the transducers are located.
The transducers insert into threaded sensor carriers which have previously been attached to alignment fixtures which were welded onto the pipe and through which the pipe has been tapped. Each of the threaded sensor carriers is provided with a window between the transducer and the interior of the pipe to prevent liquid within the pipe from reaching the transducer through the tapped opening in the pipe. The threaded sensor carriers and the alignment fixtures, by which the threaded sensor carriers are attached to the pipe, hold the transducers in place the proper distance apart and at the proper angle with respect to the pipe's longitudinal axis.
Previous methods and devices for tapping a pipe are designed to drill a hole perpendicular to the pipe's longitudinal axis. Therefore, when employed to drill a hole in the pipe at an angle approximately 45 degrees from the pipe's longitudinal axis, these devices tend to "walk" down the pipe unless provisions are taken to provide a starting hole at the desired angle. This tendency to "walk" makes it difficult to achieve the proper spacing required between the two transducers using previous methods and devices.
Also, existing devices provide only a means for cutting a hole through the wall of a pressurized pipe. After the hole is cut, some other device is passed through the hole to measure some property of the liquid.
The present invention addresses the problem of the drill bit "walking" down the pipe by providing a method and a device for drilling a hole through a pipe at an alignment fixture so that the hole is positioned at a specific location and is oriented at a desired angle to the pipe's longitudinal axis. Also, the present invention provides a means for cleaning out the metal shavings resulting from drilling the pipe hole and a means for inserting a threaded sensor carrier into the alignment fixture adjacent the pipe hole, after which the hot tapping equipment is removed. Once a pair of carriers are in place, a sonic flowmeter transducer may be removably inserted into each carrier to allow the flow within the pipe to be measured.