Abstract:
A gas flow test apparatus and method include a flow monitor that is selectively connectable to a gas pipeline. An air motor driven regenerative blower is used to increase the flow of gas through the around a blockage in the pipeline to simulate an increased gas loading condition on the intake side of the apparatus. The gas drawn from the intake side is not vented to the atmosphere, but rather, is discharged to the exhaust side of the apparatus back into the pipeline. Pipeline pressure is measured on the intake side of the apparatus to ensure that gas supply is adequate for blocking off the pipeline for maintenance.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. provisional application No. 61/708,290 filed 1 Oct. 2012, which is hereby incorporated herein by reference. 
     
    
     TECHNICAL FIELD 
       [0002]    The present invention relates to a method and apparatus for testing gas flow in a pipeline. 
       BACKGROUND 
       [0003]    Gas utilities that operate older cast iron systems often find it necessary to perform repair or replacement maintenance on these systems. In the case of low pressure gas mains, which typically operate at approximately 7 inches (in.) of water column—i.e., at about ¼ psig—the work may be performed “live”. In such a case, gas flow may be blocked off on both sides of a repair site, while leaving gas supply to other portions of the system in the surrounding area unimpeded. 
         [0004]    In order for customers to be unaffected while the work is performed, it is necessary to have adequate gas supply on both sides of the blocked-off work area. To ensure that adequate gas supply is available, a test, sometimes referred to as a flow test, may be performed on both sides of the blocked-off work area before the work begins. A flow test may include installing a bypass around the affected area of the pipeline and then stopping gas flow through the pipeline, thereby forcing the gas to flow through the bypass. A “bypass” is a temporary section of pipe that allows the gas to circumvent the main section of piping during maintenance activities. Gas flow through the pipeline may be stopped, for example, by using a bag stopper. Pressure gauges—e.g., manometers—are installed in the pipeline on either side of the stopper, for example, in the bypass piping, so that the pressure on each side of the affected area can be measured before work begins. 
         [0005]    When all of this is installed, a valve in the bypass is shut so that gas flow is effectively stopped on each side of the affected area of the pipeline. At this point, the manometers are measuring the pressure of the gas on each side of the affected area; however, this may not be adequate to determine if customers may be adversely affected by the shutdown. This is because gas usage could increase while the work is being performed, and the gas pressure that was previously considered adequate could drop to an unacceptably low level on one side of the affected area. Therefore, in order to simulate a spike in gas usage, some of the gas from the pipeline on one side of the stopper is vented to the atmosphere generally using a valve connected to the bypass that is open on one side to atmosphere. This venting may continue for 2-3 minutes or more to simulate a realistic gas loading condition. If, during the venting, the measured pressure on the vented side remains above a predetermined level, the gas flow for that side of the affected pipeline area is considered adequate. 
         [0006]    Following the venting process, or during an interval during the venting, the venting may be stopped by closing the valve, and manometers may be monitored. To ensure that the side of the main under test has adequate flow to support increased demand, the manometer should, upon closing the valve, quickly return to the nominal operating pressure of the main for example, 7 in. of water column. If the pressure does not return to the nominal level, it may be assumed that there is not sufficient flow from one side of the main to support the increase in demand. This would indicate to the utility that the bypass must stay in place during the repair/maintenance activity. This venting and measurement procedure is repeated on the other side of the stopper to ensure the pressure on that side is also adequate. 
         [0007]    Although this method has been shown to be effective, it would be desirable to have an alternative that does not require venting large amounts of natural gas into the atmosphere. Such a system could provide, for example, reduced repair costs, environmental benefits, and a better public perception for the utility. Therefore, a need exists for an apparatus and method that facilitate pressure testing under simulated load conditions similar to those described above, but without requiring large amounts of gas to be released into the atmosphere. 
       SUMMARY 
       [0008]    At least some embodiments of the present invention include an apparatus that impels gas flow from one side of a stopped pipeline to the other side so that the step of venting gas into the atmosphere to simulate a load is eliminated. 
         [0009]    At least some embodiments of the present invention include an apparatus that is connectable into a pipeline bypass, and which can simulate a gas loading condition on one side of the pipeline so that pressure measurements can be taken to ensure adequate gas supply on that side of the pipeline. 
         [0010]    In at least some embodiments of the present invention, a flow test apparatus includes an air motor driven regenerative blower configured to increase gas flow through a pipeline bypass, thereby simulating a gas loading condition on an intake side of the air motor. 
         [0011]    At least some embodiments of the present invention include a method for testing gas flow in a pipeline, including the steps of installing a flow test apparatus in a bypass of a pipeline, or alternatively to fittings on the gas main itself, engaging a regenerative blower in the apparatus to increase gas flow through the bypass, and measuring gas pressure in the pipeline on an intake side of the air motor where the gas loading condition is simulated. 
         [0012]    Although the flow test apparatus is effective to simulate a loading condition on a portion of a pipeline prior to maintenance, it may also be used for other purposes. For example, in the case where a bypass is installed in a pipeline as a means to provide a relatively long-term solution to avoiding an obstruction in the main pipeline, embodiments of the present invention may be used to reduce the required diameter of the installed bypass. If, for example, a 4 inch diameter bypass is required in a particular application to ensure adequate gas flow around an obstruction, it may be possible to use a much smaller diameter bypass line if an apparatus in accordance with embodiments of the present invention is used to increase the flow through the bypass. 
         [0013]    At least some embodiments of the present invention include a method for characterizing gas flow in a pipeline that includes connecting an inlet of a blower arrangement to the pipeline on one side of a blockage in the pipeline. An outlet of the blower arrangement is connected to the pipeline on an other side of the blockage, and the blower arrangement is operated to impel flow of the gas from the one side of the blockage to the other side of the blockage. A pressure of the gas in the pipeline on the one side of the blockage is measured. 
         [0014]    At least some embodiments of the present invention include a method for characterizing gas flow in a pipeline that includes installing a bypass around a blockage in the pipeline. A blower arrangement having an inlet side and an outlet side is connected in-line with the bypass. The blower arrangement is operated to increase a flow of the gas through the bypass and around the blockage, and a pressure of the gas in the pipeline on the inlet side of the blower is measured. 
         [0015]    At least some embodiments of the present invention include an apparatus for characterizing gas flow in a pipeline. The apparatus includes a blower arrangement and a meter assembly. The blower arrangement has an inlet and an outlet, and includes a blower and a motor. The motor is connected to the blower and is operable to drive the blower to impel gas flow from one portion of the pipeline connected to the inlet to another portion of the pipeline connected to the outlet. The meter assembly is connectable to and disconnectable from an outlet side of the blower arrangement, and includes a flow meter disposed in relation to the outlet such that it is operable to measure a flow of the gas passing through the outlet. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]      FIG. 1  shows a schematic representation of an apparatus in accordance with embodiments of the present invention installed in a bypass line of a gas pipeline; 
           [0017]      FIG. 2  shows a perspective view of an apparatus in accordance with an embodiment of the present invention; and 
           [0018]      FIG. 3  shows a flow chart illustrating a method in accordance with the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0019]    As required, detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the invention that may be embodied in various and alternative forms. The figures are not necessarily to scale; some features may be exaggerated or minimized to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the present invention. 
         [0020]      FIG. 1  shows a flow test apparatus  10  in accordance with an embodiment of the present invention. As explained in detail below, the flow test apparatus  10  is used in conjunction with repair or preventative maintenance on a low pressure gas pipeline  12 . The dashed line  14  shown in  FIG. 1  indicates a point of repair, and in particular, a line along which the pipeline  12  may be accessed so that repairs can be effected. The flow test apparatus  10  is connected to the pipeline  12  first through flexible conduits  16 ,  18 , and then through rigid conduits, commonly known as “street tees”  19 ,  20 . The street tees  19 ,  20  and the flexible conduits  16 ,  18  make up a bypass  21  that allows gas to flow from one side of the repair site  14  to the other side when the pipeline  12  is stopped-off as explained below. As noted above, the flow test apparatus  10  can be connected to a pipeline, such as the pipeline  12 , by any effective means, including connecting it to existing pipeline fittings, or other fittings other than street tees. Therefore, the flow test apparatus  10  bypasses a portion of a pipeline, whether or not there is a bypass line, such as the bypass  21  installed on the pipeline. 
         [0021]    Each of the street tees  19 ,  20  includes a shutoff valve  22 ,  23 , which allows gas through the bypass  21  to be shut off while the test flow apparatus  10  is installed. Pressure gauges, which in this embodiment are manometers  24 ,  26 , are attached to the pipeline  12  and are used to independently measure the pressure on either side of the repair site  14 . In order to independently measure the pressure on two different sides of the repair site  14 , an inflatable stopper bag  28  is inserted into the pipeline  12  through an opening  30 , which may be pre-existing or drilled specifically to insert the stopper  28 . The stopper  28  creates a blockage in the pipeline  12  to effectively stop the flow of gas through that portion of the pipeline  12 . This means that the pipeline on one side  11  of the blockage  28  may be fed from gas sources different from the pipeline on the other side  13  of the blockage  28 . Even if they are fed from the same source or sources, however, the gas will need to travel different routes to reach each side  11 ,  13  of the stopper  28 . This is why, as described in more detail below, it may be desirable to perform a test to characterize the gas flow on both sides  11 ,  13  of the stopper  28 . 
         [0022]      FIG. 2  shows the flow test apparatus  10  in detail. A volumetric flow meter  32  is used to measure the flow of gas through the bypass  21  during the test procedure. The flow meter  32  as an inlet side  33  and an outlet side  35 . A gas intake port  34  is attached to one of the conduits  16 ,  18 , while a gas exhaust port  36  is attached to the other of the conduits  16 ,  18 . In the embodiment shown in  FIG. 2 , the flow meter  32  is connected to a pair of conduits  37 ,  38 , with the conduit  37  including the exhaust port  36 . In at least one embodiment, the conduits  37 ,  38  and the flow meter  32  form a meter assembly  39 , which remains assembled and is quickly attached to a gas exhaust line  40  by quick-disconnects  41 ,  42 . This allows the flow meter  32  to be stored in a protective container separate from other components of the apparatus  10 , thereby helping to protect its sensitive measuring instrumentation. 
         [0023]    The flow test apparatus  10  also includes a device for increasing the flow of gas through the flow test apparatus  10  and ultimately through the bypass  21 . In the embodiment shown in  FIG. 2 , this is a blower arrangement  43 , which includes a regenerative blower  44  driven by a centrifugal air motor  45 , and a coupling  47  connecting the output of the motor  45  to the input of the blower  44 . The blower arrangement  43  includes an inlet and an outlet, which, in this embodiment, are respectively the intake port  34  and the exhaust port  36 . Because the outlet  36  is part of the meter assembly  39 , when the meter assembly  39  is not connected to the blower arrangement  43 , the outlet is at the location of the quick-disconnects  41 ,  42 , and is generally indicated as outlet  62 . 
         [0024]    The air motor  45  receives air through an air supply intake  46 , which is regulated by an air pressure regulator  48  disposed upstream from the pneumatic motor  45 . A pressure gauge  50  indicates the air pressure, thereby allowing an operator to adjust the regulator  48  to achieve the proper airflow to the air motor  45 . Valves  52 ,  54  can also act as regulators or be used to completely prohibit airflow to the air motor  45 . The air motor  45  is mounted on a support structure  56 , which includes a platform  57 , a baseplate  58 , mounting feet  60  (only two of which are visible in  FIG. 2 ), and a framework  64 , which not only helps to protect the other components of the flow test apparatus  10 , but also facilitates easy transport in and around a worksite. 
         [0025]    As described above, a flow test apparatus, such as the flow test apparatus  10 , can be used to simulate a gas loading condition and check the pressure on both sides of a proposed repair site in a pipeline without venting large quantities of gas to the atmosphere. Using the pipeline  12  and bypass  21  shown in  FIG. 1 , and the flow test apparatus  10  shown in  FIGS. 1 and 2 , for an example, at least some embodiments of a method in accordance with the present invention may include the following steps, as indicated in the flow chart  66  shown in  FIG. 3 . The method starts at step  68  after the bypass  21  is installed without the flow test apparatus  10  connected to it. As described above, the flow test apparatus  10  may be connected directly to the pipeline through conduits or other fittings other than a bypass line such as the bypass  21 . Even when it is connected to the bypass  21 , however, the flow test apparatus  10  is effectively connected to the pipeline  12 . 
         [0026]    The flow test apparatus  10  is placed on the ground near the excavation of the pipeline  12 , and at step  70  the meter assembly  39  is attached to the gas exhaust side of the flow test apparatus  10  using the quick-disconnects  41 ,  42 . At step  72 , the airline valves  52 ,  54  are maintained or placed in the closed position. At step  74 , the gas inlet  34  is connected to the one side  11  of the pipeline  12 ; in the illustrated embodiment, the inlet  34  is connected to the conduit  16  of the bypass  21 . The blower arrangement outlet is connected to the other side  13  of the pipeline  12 . Specifically, in the illustrated example, the gas exhaust  36 , is connected to the conduit  18  of the bypass  21  at step  76 , and the blower arrangement  43  is effectively connected in-line with the bypass  21 . At step  78 , a blockage is created in the pipeline  12 , and in particular, a bag stopper  28  is inflated to force the gas through the bypass  21 . It is worth noting that the illustrated and described body&#39;s herein generally referred to creating a blockage in the pipeline for purposes of infrastructure maintenance; however, embodiments of the present invention may be used with a pipeline having an existing blockage. In such a case, the goal may be to increase the gas flow from one portion of the pipeline to another around the blockage, and to maintain it on a long-term basis. 
         [0027]    At step  78 , the air supply intake  46  is connected to an air supply, for example, a motor-driven air compressor. Depending on the size of the air motor used in the flow test apparatus, a minimum air supply pressure of 90 pounds per square inch gauge (psig) may be required. The valve  54  is opened and the air pressure is regulated so that the air pressure gauge  50  reads approximately 70 psig. The valve  52  is slowly opened to engage the air motor  45 , which powers the blower  44 . The valves  52 ,  54  can be adjusted to increase or decrease the speed of the air motor  45 , and ultimately the output of the blower  44 , thereby increasing or decreasing the flow of gas through the bypass  21 . The volumetric flow of gas passing through the flow test apparatus  10  is monitored using the flow meter  32  to ensure that it is at a predetermined level. It may also be monitored to ensure that it remains at the predetermined level for a predetermined time. Each of these steps is summarized at step  80  in the flowchart  66 . 
         [0028]    At step  82 , the gas pressure in the pipeline  12  is then measured using the manometer  24 . The measurement is taken on this side  11  of the pipeline  12 , since, as described above, the intake side of the flow test apparatus  10  is connected to the conduit  16 , which is on the left side of the diagram shown in  FIG. 1 . By measuring the pressure on the inlet side of the blower arrangement  43  while the blower  44  is operating, the gas flow through the pipeline  12  can be characterized—e.g., it can be evaluated to determine whether or not it is sufficient to meet purposes of the end users. As described above, the parameters for this characterization can be determined by, for example, the utility company providing gas service through the pipeline, and may include one or more of the following: the pressure reaching a predetermined minimum, the pressure maintaining at or above the minimum level for a predetermined period of time, or the pressure returning to a level above the predetermined level within some period of time after the blower is shut off. 
         [0029]    In some embodiments of the present invention, the flow test apparatus can remain in place and the blower reversed so that the pressure on the other side of the pipeline can be monitored, and thus the gas flow characterized. In the embodiment shown in  FIGS. 1 and 2 , the flow test apparatus  10  is disconnected from the gas intake  34  and the gas exhaust  36 , and the entire apparatus  10  is turned around and reconnected with the opposite orientation. The flow test is then performed again with pressure measurements taken by the manometer  26  to characterize the gas flow on the other side  13  of a blockage  28 —see step  84 . In either case, the direction of operation of the blower arrangement is reversed. Although the steps illustrated in the flowchart  66  and described herein are presented in a particular order, embodiments of the invention may perform one or more of these steps in a different order, while in some embodiments at least some of the steps may be omitted or others added. 
         [0030]    While exemplary embodiments are described above, it is not intended that these embodiments describe all possible forms of the invention. Rather, the words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the invention. Additionally, the features of various implementing embodiments may be combined to form further embodiments of the invention.