Abstract:
A portable diagnostic system for testing gas pressure reduction equipment includes a computer arrangement  16  interfaced to an electro-pneumatic test unit  12  which provides test pressures for and receives information on displacement from the pressure reduction equipment. Unit  12  includes a number of valves including three solenoid on/off valves, a needle valve and an on/off ball valve. The position of the valve member of the needle valve is sensed by a position transducer. Displacement transducers  40  and  42  connected to the reduction equipment sense slamshut valve and regulator displacements pressure transducer  44  and a differential pressure transducer  102  are each connected to the equipment. Signals from the transducers are fed to a data acquisition system  210  which also drives the solenoid valves and the needle and ball valves, all under the control of the PC 16  to give an indication for example of how far the valves are open in the regulating equipment (ie from the valve seat).

Description:
BACKGROUND OF THE INVENTION 
     The invention relates to apparatus and methods for use in testing gas pressure reduction equipment. 
     Such equipment is usually mounted on so-called skid units or is more compact and in the form of control modules, which commonly are installed in a pit below the surface of the ground. Such equipment is hereinafter called “pr equipment”. 
     SUMMARY OF THE INVENTION 
     The apparatus is intended to form part-of computer-aided diagnostic test equipment by which diagnostic testing of skid units and gas control modules can be performed. In particular it is intended to form a portable diagnostic system for testing pr equipment in situ. Such testing is required to perform static and dynamic tests on the various regulator valves, and safety devices such as relief valves, slamshut and stream selection valves and so on incorporated in skid units or control modules without the need for any disassembly and to obtain accurate pressure set points. The testing also allows identification of changes in performance owing to gradual wear and tear by comparison of results with those obtained on a previous occasion. 
     According to the invention there is provided a portable diagnostic system for testing pressure reduction equipment in situ, said system including; 
     means for connecting at least one displacement transducer to the reduction equipment; 
     means for detecting a fluid pressure; 
     control means for selecting an output fluid pressure for 
     testing the reduction equipment; 
     means for receiving valve displacement information from at least one transducer in dependence on selected and/or detected pressure to determine the degree of movement of the valve relative thereto. 
     After the initial data gathering process has been completed it is possible for the operator to interrogate the computer preferably forming part of the system to identify which component may be at fault when the results criteria are not met. 
     A high standard of maintenance records will be achieved by the simple process of downloading and storing test results on the office computing system. 
     The computer includes a display and enables a knowledge-based expert system to be employed. The apparatus enables a very complex set of tests to be carried out relatively easily. A program disc used in the computer enables all instructions and prompts to be displayed on the computer display screen. 
     The apparatus supplies gas to various points on the equipment to be tested and gas flowrate and gas pressure are measured and this information is made available to the computer. Displacement transducers and gas pressure transducers are mounted on the pr equipment and the information derived by the transducers is made available to the computer. The duties of the computer include the calculation of the rates of rise and fall of pressure of the gas fed to the pr equipment as well as the calculation of the rates of rise and fall of pressure of the gas at the various components of the equipment. The computer&#39;s duties also include the calculation of the rates of opening and closing movement of the various components of the pr equipment. 
     The apparatus controls the supply of gas to the pr equipment by means of an array of valves, including a valve which passes gas at all positions of the valve member beyond the closed position and the computer&#39;s duties include the generation of signals controlling the actuator of that valve, as well as the actuators of the on/off valves. 
     The apparatus is used as computer-aided diagnostic test equipment to perform any combination of a number of tests which the software used in the computer has been written to perform. The apparatus enables such combinations of tests to be readily performed. 
     Further, according to the invention apparatus having a gas inlet and a gas port for use in testing gas pressure reduction equipment comprises: 
     first, second and third valves, 
     the first and second valve having a respective inlet and outlet, 
     the third valve having first and second valve ports, 
     the inlet of the first valve communicating with said gas inlet, 
     the outlet of the first valve communicating with both the inlet of the second valve and the first valve port of the third valve, 
     the outlet of the second valve communicating with the atmosphere, 
     the second valve port of the third valve communicating with said gas port, 
     the third valve having a valve member and means for moving the valve member to a fully closed position and to a fully open position and to intermediate positions therebetween. 
     Said third valve is preferably associated with a position transducer which can produce an electrical output indicative of the position of said third valve member. 
     Said apparatus preferably has a fourth valve having an inlet and an outlet, the inlet of the fourth valve communicating with the gas inlet and the outlet of the fourth valve communicating with said gas port. 
     Said apparatus preferably has a fifth valve having an inlet and an outlet, the inlet of the fifth valve communicating with said gas port and the outlet of the fifth valve communicating with the atmosphere. 
     Further, according to the invention a method of testing gas pressure reduction equipment using apparatus according to the invention comprises comparing the results obtained with results obtained on a previous occasion of carrying out the method in order to identify changes in performance of the equipment. 
     The method may comprise interrogation of said computer to identify which component of the equipment may be at fault when the results show that a predetermined standard is not met. 
     The method may comprise downloading and storing test results on a computing system in order to generate maintenance records. 
     The method may comprise controlling by means of software used in said computer the rate of pressure rise and the rate of pressure fall in the gas applied to a component of the equipment. 
     An embodiment of apparatus for use in testing gas pressure reduction equipment will now be described by way of example with reference to the accompanying drawings, in which: 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic view of the diagnostics system including the computer configuration and the electro-pneumatic test unit which is connected to pr equipment in the form of a skid unit in the example; 
     FIGS. 2 &amp; 3 are plan views of the electro-pneumatic test apparatus, each with parts removed, showing, respectively, pipe circuit-connections and electric cable connections; 
     FIG. 4 is a diagram showing the pr equipment and connections (shown by broken lines) to the test and diagnostics apparatus; 
     FIG. 5 is a diagram showing the apparatus in simplified form with a relay driver board used to control operation of the apparatus; 
     FIGS. 6A &amp; 6B show a diagram of part of the electrical circuit contained in the interface  14  showing details of the relay driver board used to control the actuators of the valves shown in FIG. 5; and 
     FIG. 7 is a block diagram showing the electrical connections between the valves and transducers on the one hand and the interface and computer on the other hand; 
     FIG. 8 is a flowchart for slamshut testing; 
     FIG. 9 is a displayed test result; 
     FIG. 10 is a flowchart for another slamshut test; 
     FIG. 11 is a displayed result. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1 shows: pr equipment  10  in the form of a skid unit and to be subjected to testing. An electro-pneumatic test unit  12  is connected to it and an interface unit  14  contained in a case is connected to a portable personal computer  16  having a keyboard  15  and associated display screen  17 . A 12-volt battery power supply  18  is shown available to power the system. The computer is of the type that includes a microprocessor, RAM, ROM, hard disc storage and serial and parallel ports. A floppy disc drive is also provided. 
     The inlet valve  20  and the outlet valve  22  are both closed. The unit  12  is connected by a hose  24  to the high pressure gas main  26  via an on-off valve  28 . The unit  12  is connected by a second hose  30  to an on-off valve  32  which is connected to a point in the pr equipment immediately upstream of the outlet valve  22 . 
     It should be noted that gas can both be supplied to the pr equipment and conveyed away from the pr equipment via the hose  30 . 
     Displacement transducers  40 , 42  are mounted on the pr equipment. For example, the transducer  40  gives an electrical analogue signal representing the movement of a slamshut valve member and the transducer  42  gives an electrical analogue signal representing the movement of a regulator valve member. 
     A pressure transducer  44  is connected to a pressure manifold (see FIG. 4) which is connected to an on-off valve (see FIG. 4) connected to a point in the pr equipment immediately downstream of a relief valve  46  (see FIG.  4 ). 
     The transducers  40 , 42  and  44  are connected by cables  48 , 50 , 52 , respectively, to a junction box  54  on the unit  12 . The box  54  is connected to the interface  14  by a cable  56 . 
     The apparatus included in the unit  12  comprises valves (see FIG. 5) operated by actuators (not shown) controlled by the computer  16 . The interface  14  is connected to junction box  58  by a cable  60 . 
     The interface  14  is connected to the battery power supply  18  by cables  62  and the computer  16  is connected by cables (not shown) to the interface  14 . 
     FIGS. 2 and 3 show more detail of the unit  12 . Gas reaches the unit  12  via the hose  24  (FIG. 1) and enters the unit through an on-off valve  66  (FIG.  3 ). With further reference to FIG. 3, the gas then enters a pressure regulator  68  and flows to a tee-junction  70 . One branch leads to a second tee-junction  72  and thence to an on-off valve  74  (communicating with the atmosphere) and the other branch leads to the inlet of a first solenoid valve  76 . The outlet of the valve  76  is connected to a tee-junction  78 . One outlet of the junction  78  is connected to the inlet of a second solenoid valve  80 , the outlet of which communicates with atmosphere. 
     The other outlet of the junction  78  is connected to first valve port of a third valve in the form of a needle valve  82 . The second valve port of the needle valve  82  is connected to a tee-junction  84 . 
     It is not possible to refer to an “inlet” or an “outlet” of the needle valve  82  because gas can flow in either direction through the needle valve  82 . 
     One port of the tee-junction  84  is connected to a tee-junction  85 , one outlet of which is connected to the outlet of a fourth valve in the form of a ball valve  86 . The inlet of the ball-valve  86  is connected to the second outlet of the tee-junction  70 . 
     The second outlet of the tee-junction  84  is connected to the inlet of the fifth valve in the form of a solenoid valve  90 . The outlet of the valve  90  is connected to the inlet of an on-off valve  92 , the outlet of which is connected to atmosphere. 
     The second port of the tee-junction  85  is connected to an orifice plate  94 . The orifice plate  94  is connected to the gas port  100  which is connected to the gas hose  30  (FIG.  1 ). 
     A differential pressure transducer  102  is connected by tubes  104 , 106  to opposite sides of the orifice plate  94 . 
     FIG. 2 shows an actuator  110  for the needle vale  82  and an actuator  112  for the ball valve  86 . It also shows cables  114 , 116 , 118 , 120 , 122  which convey the control signals from the junction box  58  to the solenoid valve  76 , the solenoid valve  80 , the ball valve  86 , the needle valve  82  and the solenoid valve  84 , respectively. The junction box  58  is connected to the interface  14  by the cable  60 . 
     FIG. 3 also shows a cable  140  which interconnects the valve  82  and the junction box  54 . This conveys the electrical signal from a position transducer (not shown) which is incorporated in the actuator  110  representing the position of the valve member (the needle) of the valve  82 . 
     FIG. 3 also shows a cable  142  which interconnects the differential pressure transducer  102  and the junction box  54  and which conveys the electrical signal representing the differential pressure measured across the orifice plate  94 . The computer calculates the rate of gas flow through the orifice plate  94  from this signal. 
     FIG. 4 shows part of the pr equipment, in the form of a skid unit. The pr equipment comprises a main stream (shown) and a standby stream (not shown in FIG. 4 but shown generally in the background of FIG.  1 ). It will be understood that the diagnostic system can be connected to first one stream (as shown) and then to the other stream as required. 
     For example, the main stream comprises: an inlet valve  150 ; a filter  152 ; a slamshut valve  154 ; a regulator  156 ; a relief valve  157 ; a wafercheck valve  158 ; and an outlet valve  160 . In parallel with the main stream there is an auxiliary rail comprising: a “J” Governor  166 ; a “J” relief valve  168 ; an inspirator  170 ; a K 1  pilot valve  172 ; and a K 2  pilot valve  174 . 
     Manually operable on-off valves are provided as follows: the valve  28  upstream of the valve  150  and to which the hose  24  is connected (FIG.  1 ); the valve  180  intermediate the slamshut valve  154  and the regulator  156 ; the valve  182  through which impulse pressure can directly act on the underside of the diaphragm of the regulator  156  is communicated; the valve  184  between the relief valve  157  and the wafercheck valve  158  and to which the pressure manifold  189  is connected. The pressure manifold was mentioned in connection with the description of FIG.  1 . The pressure transducer  44  is connected to the pressure manifold  189 ; and the valve  32  already mentioned (see FIG.  1 ). 
     In addition, the following manual on-off valves are provided on the auxiliary rail as follows: the valve  186  intermediate the main stream and the “J” Governor; the valve  188  intermediate the “J” Governor and the “J” relief valve; and the valve  190  immediately upstream of the connection between the auxiliary rail and the main stream. 
     Finally, a manually operable valve  192  is provided which is connected to sense the pressure below the diaphragms of the pilot valves  172  and  174  and a manually operable valve  194  through which the pressure downstream of the stream outlet valve  160  can act below the diaphragms of the pilot valves  172  and  174 . 
     FIG. 4 also shows a restrictor  199  intermediate the pressure manifold  189  and the manually operable valve  180  to restrict the flow of gas while venting the pressure upstream of the regulator  156 . 
     FIG. 5 shows the apparatus incorporated in the unit  12  and described with reference to FIG.  3 . FIG. 5 is a simplified drawing but shows the valves  76 ,  80 ,  82 ,  86  and  90  which form one embodiment of the present invention. The regulator  68  and the tee-junction  72  and the on-off valve have been omitted from FIG. 5, as well as the orifice plate  94 . 
     At its broadest, one aspect of the invention comprises only the valves  76 ,  80  and  82  arranged as shown in FIG. 5 the valves  86  and  90  being omitted. However, FIG. 5 in its entirety shows-the preferred form of that aspect of the invention. In FIG. 5 the inlet port is marked  75  and the gas port is marked  77 . The solenoid valve  80  has an outlet communicating at  79  with the atmosphere and the solenoid valve  90  has an outlet communicating at  81  with the atmosphere. 
     The solenoid valves  76 , 80  and  90  and the ball valve  86  all handle flow of gas in one direction only. However, the needle valve  82  handles flow in either direction. The solenoid valve  76  may be termed a feed valve; the solenoid valve  80  may be termed a slow vent valve, although the rate of venting is dictated by the setting of the needle in the needle valve; and the solenoid valve  90  may be termed a fast vent valve. 
     FIG. 5 also shows a relay driver printed circuit board  200  in which the board is represented diagrammatically and FIG. 6 shows the board and associated circuitry in more detail. The relay driver printed circuit board is located in the interface unit  14 . The relay driver board energises enoid valves  76 , 80  and  90  and the actuators of the valves  82  and  86 . The relay board includes inrush current suppressors at  202  in each of the ten leads SK 1  to SK 8  and SK 10  and SK 12 . In the “off” condition shown in FIG. 5 the pins PL 1   37 , PL 1   39 , PL 1   41 , PL 1   43 , PL 1   45  and PL 1   47  are all de-energised and the voltages are shown at the leads SK 1 -SK 8  and SK 10  and SK 12 . 
     The plug PL 1  shown in FIG. 5 is connected to an interface between the PC  16  and the remainder of the system. Inputs from the transducers are also connected to the interface, which also has input/output connections to the PC 16 . 
     PL 1   37  controls the relay RL 6  and power to RL 5  (FIG.  6 ). PL 1   39  controls RL 5  and in turn switches power on/off SK 3   1 ,  2  and  3 . PL 1   41  controls RL 4  and in turn switches power on/off SK 3   4 ,  5  and  6 . PL 1   43  controls RL 3  and in turn switches power on/off SK 3   8 . PL 1   45  controls RL 2  and in turn switches power on/off SK 3   10 . PL 1   47  controls RL 1  and in turn switches power on/off SK 3   12 . 
     FIG. 6 shows the inrush current suppressors (numbered  202  in FIG. 5) CSR 1 -CSR 10 . The chip shown at 1C1 is a driver chip and provides the current to drive the relays and inverts the voltage from its input to its output. In other words, 5 volts at the input gives 0 volts at the output. 
     It should be remembered that actuation of the needle valve  82  can either close the valve, fully open the valve or set the needle to some intermediate position depending upon the requirement of the software and the particular test being carried out. Also, the position of the needle is monitored by the position transducer (not shown) incorporated in the actuator  110  and the resulting electrical signal is used by the computer, together with a signal from the pressure transducer  44  or from the transducer  102 , in order to calculate the correct setting of the needle. 
     In this embodiment, the diagnostic system is designed to perform sixteen tests on the skid unit  10 . The tests are: 
     1. Leakage Test: Equipment Test Lines 
     2. Wafercheck Valve: Reverse Flow Test 
     3. Relief Valve Performance 
     4. Slamshut Valve Repeatability 
     5. Leakage Test: Slamshut Let-by 
     6. Leakage Test: Slamshut Stem Seal 
     7. Active Regulator Static Performance 
     8. Slamshut Response 
     9. Relief Valve Repeatability 
     10. Leakage Test: Slamshut Diaphragm Chamber 
     11. “J” Governor/Relief Set-point Check 
     12. Leakage Test: Active Regulator Diaphragm Chamber 
     13. K-Pilot Set-point Check 
     14. Snowflake K-Pilot Set Point Check 
     15. Leakage Test: Stream Isolation Valves 
     16. Leakage Test: Pressure Soundness 
     By way of example, the operation of the valves shown in FIG. 5 will now be described in order to carry out Test No 2 and Test No 7. 
     Test No 2 Wafercheck Valve: Reverse Flow Test 
     The needle valve actuator  110  is controlled to open the needle valve  82  by 50%. The feed solenoid valve  76  is opened. When 35 millibar pressure is reached (as monitored by the pressure transducer  44 ) the ball valve actuator  112  is controlled to open the ball valve  86 . Flowrate is then monitored (by the transducer  102 ) passing (in reverse) through the stream wafercheck valve  158  from the right-hand side of the valve to the left-hand side. 
     After 10 seconds, the ball valve  86  is closed but solenoid valve  76  remains open to check the partial open pressure of the relief valve  157 . At 30 seconds the solenoid valve  76  is closed and the re-seat pressure of the relief valve  157  is recorded. 
     At 50 seconds the fast vent solenoid valve  90  is opened and the test terminates. 
     The monitored results are displayed on the screen of the computer  16 . 
     Test No 7 Active Regulator Static Performance 
     The slow vent solenoid valve  80  is opened to release the stream pressure to a pre-determined level (monitored by the transducer  44 ) until the regulator valve  156  starts to move. The needle valve actuator  110  is controlled to set the needle of the needle valve  82  to adjust the rate of venting and hence the rate of movement of the regulator valve  156 . 
     When the regulator valve  156  is fully open, the slow vent solenoid  80  is closed. The feed solenoid valve  76  is opened to close off the regulator valve, with the rate of closure movement determined by computer control of actuator  110  and the needle, valve  82 . The feed solenoid  76  is then closed to terminate the test. 
     The monitored results are displayed on the screen of the computer  16 . 
     FIG. 7 shows the electrical connections between the valves and transducers described above the one hand and the interface  14  on the PC  16  on the other hand. 
     The PC  16  runs the test and diagnostic software for either the skid unit (as shown) or for the control module. By switching outputs on its parallel port it can perform the diagnostic tests described above and by reading inputs on its parallel port it can gain information on how the skid unit has performed during the tests. 
     The data acquisition system  210  interfaces the computer  16  and the remainder of the system and includes analog to digital convertors. It uses the parallel port of the computer  16  and from this is able to drive outputs and also provide inputs that the computer can read. 
     The relay driver board  200  takes the digital outputs from the data acquisition system  210  driven by the computer and uses them to energise the solenoid valves  76 ,  80  and  90  or the needle valve  82  or the ball valve  86 . Basically, it takes low power digital signals and with appropriate buffering/drivers provides high power output signals for the solenoid valves and the actuators of the ball and needle valves, using relays. 
     The isolators  220  provide electrical isolation between the unit  12  and the inputs to the data acquisition system  210 . This is an intrinsically safe system and should a fault occur in the PC  16  or the interface  14  there will be no danger of an explosion or ignition of gas at the unit  12  which is in a hazardous area. 
     The display  17  of FIG. 1 provides a graphical display of test results for the various pr equipment tests to aid diagnosis. Tabular results on the display may also be provided. Taking for example tests on the slamshut valve it is possible for the system to check: 
     (a) Slamshut response with regard to trip level and any evidence of stiction. 
     (b) Slamshut trip point under a fast pressure rise and evidence of any leakage past the actuator diaphragm and seals. 
     In order to carry out check (a) the computer flowchart operates as shown in FIG.  8 . Here the test will automatically increment the pressure under computer control and detect and measure changes as pressure rises to detect operation. Results measured and stored can be compared with set parameters and a graph and table of results produced for display as shown in FIG.  9 . 
     The automatic sequence can follow ‘prompts’ shown on the display to assist the operation, such as shown below: 
     1 Check slamshut is set. 
     2 Connect test line to the pressure transducer. 
     3 Connect test line to the slam shut test point. 
     4 Check slam shut test valve is set to ‘Test’. 
     To carry out the check (b) the computer flowchart in software form will operate as in FIG.  10 . The displayed results are shown in FIG.  11 . 
     Similar sequence of combined test steps will allow testing of all valves. Repeat tests will allow information on repeatability results to be stored for diagnostic purposes. 
     The description given above with reference to the drawings concerns apparatus to test gas pressure reducing equipment in the form of a skid unit. However, it will be appreciated that apparatus according to the invention can be used to test other gas pressure reducing equipment in the form of a gas control module for example.