Composition and process flow of gas regulator station

The main role of the regulator station in the gas transmission and distribution system is to regulate and stabilize the system pressure and control the gas flow, to prevent the equipment after the regulator from being worn out and clogged, and to protect the system from low or over-pressure outlet pressure.

The regulator station consists of regulators, valves, filters, safety devices, bypass pipes and measuring instruments. Some regulator stations are equipped with metering equipment, in addition to regulating pressure, but also play a role in measurement, so it is called as a regulator metering station.

First, the composition of the regulator

(A) valve

In order to overhaul the regulator, filter and cut off the gas source when the regulator is out of service, the import and export of the regulator station must be equipped with valves. In addition, 10 meters away from the regulator outside the total import and export pipeline should also be set on the valve. During normal operation, this valve is normally open. When an accident occurs at the regulating station, it is not necessary to approach the regulating station to shut off the valve to cut off the gas source to prevent the accident from spreading. When the regulator is overhauled, the valve should also be closed to cut off the gas source.

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 (ii) Filter

Various impurities contained in the gas are accumulated in the regulator and safety valve, which will impede the cooperation between the spool and the valve seat, and affect the normal operation of the regulator and the safety valve, therefore, it is necessary to install a filter at the entrance of the regulator. Regulator station commonly used bristle or glass wire as packing filter. As shown in Figure 7-1-1. Solid particles brought into the filter by the gas hit the baffles and accumulate in the lower part of the filter, where they are periodically discharged by the sweep holes 5. Small particles of solids and dust particles remaining in the gas are impeded on the filter element. Filter material is mounted between the two metal grids, cleaning should first remove the upper cover, and the filter element out of the pick. Filtering community before and after the differential pressure gauge should be installed, according to the measured pressure drop can determine the clogging of the filter. Under normal working conditions. The pressure loss of the gas through the filter shall not exceed 10kPa, and should be removed and cleaned when the pressure loss is too large.

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(iii) safety valve

Due to the regulator film rupture, close poorly or regulation failure, it will make the regulator lose the automatic regulation and pressure reduction effect, causing a sudden rise in the outlet pressure, resulting in system overpressure, endangering safety, therefore, the regulator station must be set up with a safety valve.

The outlet pressure of the regulator room is controlled by the safety cut-off valve and safety relief valve. The safety cut-off valve controls the upper and lower limits of pressure, and the safety discharge valve controls only the upper limit of pressure. The discharge pressure of the discharge valve should be lower than the closing pressure of the shut-off valve. When the regulator is working normally, only when it should be shut off when the closure is not tight (due to impurities accumulated on the valve, wear and tear, etc.), the gas is discharged into the atmosphere. At this point, the amount of gas flowing through the poorly closed valve is greater than the amount of gas used, and the outlet pressure increases. In order to avoid high outlet pressure, the excess gas must be discharged into the atmosphere.

1- baffle; 2- cartridge with filter material inside; 3- upper cover; 4- housing; 5- cleaning hole

If the regulator fails, the gas has been discharged through the discharge valve, but the outlet pressure continues to rise, such a situation is an accident. At this time, should cut off the valve action, close the gas pipeline in front of the regulator. Of course, when an accident occurs in the gas pipeline and the outlet pressure is too low, the shut-off valve can also automatically shut off. After eliminating the cause of shutdown. The cut-off valve can not automatically resume its work, but can only be opened by the maintenance personnel to re-supply gas.

1-guide lever; 2-positioner; 3-stopper; 4-safety lock; 5-seat; 6-spool; 7-stem; 8 -promotable lever; 9 -membrane; 10 -connecting rod; 11 -striker; 12 -support pad; 13 -weight block; 14 -adjustment nut; 15 - spring; 16 - pin buckle; 17 - packing gland; 18 - lever's shaft

The upper pressure of the cut-off valve action is regulated by adjusting the nut 14 so that the spring 15 is compressed differently. When the valve is open the spring is held against the flange of the upper cover of the membrane by means of a support pad 12. When the gas pressure on the lower side of the membrane is less than the spring force, the membrane remains stationary. When the detected pressure exceeds the upper pressure limit, the film is subjected to increased force and moves upward, so that the spring is pressurized, the bolt buckle of the crossbar is deflected downward, and the striker falls down to close the valve.

When the spool 6 is closed, it is pressed against the valve seat by its own weight and by the action of the heavy block concentrated at the end of the lifting lever. In addition, gas pressure causes the spool to press against the seat. However, when the inlet pressure is high, it is more difficult to lift the spool. In order to equalize the gas pressure from both sides of the spool during opening, the shut-off valve is equipped with a special equalizing valve. When the valve is closed, the orifice of the equalizing valve is closed by the lower end of the lever 7. The lever also opens the equalizing valve when the main valve is opened, with the result that the gas pressure in the upper and lower chambers of the diaphragm is quickly equalized, making it easier to lift the spool.

Membrane spring-loaded safety discharge valves are shown in Figure 7-1-3. These valves are available in 25mm and 50mm diameters. Discharge pressure can be adjusted to gauge pressure 0.001-0.125MPa. The value of the detected pressure is given by changing the degree of pressure on the spring 2. The force on the upper side of the film 3 is adjusted pressure, when it is greater than the safety discharge valve adjusted discharge pressure, then the film force is greater than the pressure of the spring, so that the spring is pressurized and the valve opens, the excess gas is discharged into the atmosphere.

The water-seal safety valve is simple in construction and is sometimes installed at the outlet of the regulating station. Its working pressure is lower than the pressure of the safety valve action, so when the pressure rises, the water seal safety first role, when the overpressure, the gas breaks through the water seal discharged into the atmosphere; if the water seal safety through the ability is not enough to reduce the pressure of the gas behind the regulator, then the safety valve began to act, well cut off the gas road. Changes in the level of the water-seal safety device should be noted at all times; in the cold season, the regulator station should have battering facilities or be filled with antifreeze in the water seal.

Safety valve discharge pipe should be 1.5m above the roof of the regulator, should pay attention to the height of the surrounding buildings, distance and wind direction, and take measures to prevent pollution of the environment when the gas is discharged.

1-adjustment screw; 2-spring; 3-membrane; 4-padding layer; 3-slide valve; 6-housing

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 (iv) Bypass pipe

Any regulator station that cannot supply gas intermittently should be equipped with a bypass pipe to ensure that gas continues to be supplied while the regulator station is being repaired. When gas is supplied to users through the bypass pipe, the pressure and flow rate of the gas network are controlled by manually adjusting the valve on the bypass pipe. For high-pressure regulators, two valves are usually set on the bypass pipe for easy adjustment.

The diameter of the bypass pipe should be determined according to the minimum inlet pressure of the gas regulator, the required outlet pressure and the maximum outlet flow rate of the regulator. The diameter of the bypass pipe is usually 2-3 sizes smaller than the diameter of the regulator outlet pipe. To prevent noise and vibration, the minimum pipe diameter of the bypass pipe should be not less than DN50. during normal operation, the valves on the bypass pipe should be fully closed.

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(v) Measuring instrument

Usually, the regulator inlet installs the indication type manometer, and the regulator outlet installs the automatic recording type manometer, which is used to record the instantaneous pressure of the regulator outlet automatically, so as to monitor the working condition of the regulator. Some regulators also install flow meters.

Second, the process flow of the regulator

(A) single-channel regulator

Single-channel regulator station process flow, as shown in Figure 7-1-4. When this system is in normal operation, the inlet gas enters the regulator through the inlet valve and filter, and the regulated gas is sent to the pipeline network through the flow meter and outlet valve. When maintenance, you can close the inlet and outlet valves, open the bypass valve, and the gas flows out of the bypass pipe.

When the regulator outlet pressure is too high, the safety valve starts, and the safety valve needs to be reset manually.

1-insulation flange; 2- inlet valve; 3-filter; 4-regulator with safety valve, 5-outlet valve; 6-flow meter; 7- Bypass valve

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(ii) Parallel channel regulator station

The process flow of the parallel channel regulator station is shown in Figure 7-1-5. The given outlet pressure of the main regulator 4 is slightly higher than the given outlet pressure of the standby regulator 8, so that during normal operation, the standby regulator 8 is closed. When the normally operating main regulator 4 fails, so that the outlet pressure increases beyond the permissible range, the gas supplied through the main subline is automatically cut off by the safety shut-off valve attached to the main regulator, resulting in a lower outlet pressure. When the pressure drops to the given pressure of the standby regulator; the standby regulator 8 starts normal operation by itself.

1-Insulated flange; 2-Inlet valve; 3-Filter; 4-Normal operating main regulator; 5-Outlet valve; 6-Flow meter; 7 Bypass valve; 8 - Standby regulator

The scope of a regulator station typically includes the inlet and outlet valves outside the regulator room, the inlet and outlet piping, and the regulator room.

The inlet and outlet station valves outside the regulator room are usually installed in underground gate wells, with discharge valves and discharge pipes installed on one or both sides of the valves, and compensators connected after the valves. The distance between the inlet and outlet valves and the outer wall of the regulator room is generally within the range of 6 to 100 meters. If the regulator outside the inlet and outlet gas piping with the trench laying, inlet and outlet valves can be installed in the same underground gate well, but inlet and outlet valves should be set up on the distinguishing signs.

Pressure regulator room inlet and outlet gas piping is usually buried, no fittings on the pipe, slope to the outdoor inlet and outlet valves. The pipeline enters the regulator room through the outer wall of the regulator room, and the casing should be added at the wall, and no joints are allowed in the casing.

Pressure regulator room is generally an independent building on the ground, such as conditions, can also be semi-underground or underground structures, however, it should be easy for staff to enter and exit, often ventilated, and should be prevented from rain and groundwater into the indoor measures. When the natural conditions and the surrounding environment permits, regulator equipment can be arranged in the open air, but should be fenced or walled.

According to the type of regulator installed and customary designation, the regulator room can usually be divided into piston regulator room, T-type regulator room, Reynolds-type regulator room and self-powered regulator room. Piston-type and T-type regulator room has basically the same process arrangement form, its installation methods and installation procedures are basically the same. Due to the piston and T-type regulator room is widely arranged in various types of gas in various pressure levels of urban gas pipeline network, so it is the most common regulator room; Reynolds regulator room is generally used only for artificial gas arm network of low and medium-pressure gas regulator station, indoor process arrangement is not quite the same as the former; and the self-regulator room is more used for natural gas stations or storage and distribution stations.

The installation order of the regulator station is generally the first outdoor, after the indoor; first underground, after the ground; first pipeline, after the equipment. First, after the installation should be the same installation baseline as a standard to ensure the quality of the installation, for example, first, after the installation of the pipeline are pipeline centerline orientation and elevation as a benchmark, regulators and other equipment are axis orientation as a benchmark.

Third, the installation of the regulator room

(A) piston regulator room installation

For general regional piston regulator room system installation diagram. First of all should be in accordance with the design of the installation plan to check the material and equipment. In the pipe, fittings, equipment and instrumentation are fully equipped and intact under the conditions, in order to carry out the line, mark the center line of the pipeline and equipment axis of the location and relative elevation, and finally in accordance with the "underground, after the ground," "first equipment, after the instrumentation," the principle of the order of the Installation.

1-RTJ-218 regulator; 2-bellows; 3-filter; 4-gate; 5-water seal; 6-connect the automatic recorder; 7 -Connect the U-shaped mercury manometer: 8 -Connect the U-shaped water column manometer; 9 -Spring pressure gauge

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(ii) Piping installation

Piping installation should preferably be carried out in close coordination with the progress of building construction. When excavating the foundation of the building, the indoor underground pipes are pre-buried, and the underground pipe through the wall is reserved for wall holes when the wall is being built. Indoor above ground piping can be done before interior decoration or before ground repair. In order to reduce the site installation workload, should maximize the prefabrication, that is, the required elbow, pipe sections with branch pipe and flange short pipe, etc. pre-production. Fabrication size and weight should be based on the principle of easy field assembly.

The installation of buried pipeline should strictly control the plane position and elevation of each section of pipeline to ensure that the slope of indoor pipeline to outdoor pipeline. Stretching out of the ground vertical pipe section, its height should be given to the installation of the ground on the arm of the road to leave enough cutting margin, and then welded steel plate plug, strength test, test after passing the anticorrosion backfill, backfill, to the vertical section of the pipe set to put through the ground casing. Backfill tamping process, shall not make the underground pipeline movement, and keep the vertical pipe section perpendicular to the ground. Prefabricated buried pipeline, can also be assembled once to the ground flange interface; tighten the flange cover plug for strength test, but need to produce grams to control the installation size, backfill fixed, check the flange center elevation is in line with the design requirements, the flange surface should be perpendicular to the center line of the pipeline to be connected.

Installation of pipeline on the ground is carried out after the indoor backfill is compacted. If it is installed before the construction of the ground, the road should first find out the indoor horizon, marked on the wall, as the elevation of the pipeline installation benchmark, and then according to the plane position and elevation marked out during the installation of the pipeline segments.

Regulator before and after the valve between the pipe section, it is best to valves, filters, bellows compensators and regulators, etc. according to the plane position and allegory stable, flange connection with bolts first tighten the shield, with short pipe wells for straightening and leveling, and then the flange point solid welding. To be completed after all point solid welding, loosen the bolts, short pipe and flange bad seam welding. Finally add flange gasket for equipment installation.

DN ≤ 50mm above ground pipe is generally threaded connection, DN> 50mm pipe is generally welded or flange connection.

Pipe support can be welded steel bracket or masonry brick pier.

Pressure regulator room safety discharge pipe should be connected to the outdoor, above the top of the layer 1.5 m. Regulator on both sides of the pipeline should be respectively sloped to the buried pipeline, instrumentation pipe should be sloped to the main pipe, the slope is 2 ‰.

Buried steel pipeline all for the strengthening of the insulation corrosion layer, the pipeline on the ground required to be painted with anti-rust paint one, two blending paint.

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(iii) Equipment installation

First of all, proofread the regulator model is in line with the design requirements. Gas regulator model consists of two groups of symbols and numbers, two groups separated by "a"; the first group has three symbols, the first two "RT" that the gas regulator, the third symbol for "Z "(direct-acting) or" J "(indirect-acting); the second group often has four symbols or numbers, the first digit indicates the regulator inlet pressure level (low-pressure, medium-pressure A, medium-pressure B and the second high-pressure), the second digit indicates the outlet pressure level, the third digit indicates the nominal diameter 1 /25, the fourth symbol for the L (threaded connection) or F (flange connection), if the fourth symbol does not write out the DNa≤50 for threaded connection, DN> 50 must be flange connection. For example, BTJ-218 indicates that the inlet pressure can be medium or low pressure, the outlet pressure is low pressure, DN200 indirect action gas regulator, flange connection.

All equipment in the regulator room should be checked and cleaned before installation, valves and regulators should also check the flange gaskets and gland under the cover packing, if any damage should be replaced.

Valves in the station using open stem valves or better sealing performance of the oil-sealed plug valves, can also be used butterfly valves. DN≤50 valves using gland plug valves. The valve should be installed before the air pressure test, there is no condition to do the pressure test should be done when the penetration kerosene test. After installation of the valve handwheel (handle) should be painted according to the different operating pressures of different colors, such as high-pressure brush red, medium-pressure brush yellow, low-pressure brush green and so on.

Pressure regulator should be installed according to the valve body on the arrow pointing to the gas import and export direction, the installation of the regulator should be in the closed state, the installation should be checked before the main regulator and commanders and exhaust valves and other components such as whether the action is sensitive, whether the joints are solid. The regulator should be installed flat, so that the main regulator valve stem is vertical, not tilted and inverted. Each main regulator should be set in front of the filter, the filter should be removed and cleaned before installation.

Regulator room of the low-pressure outlet piping must be installed on the safety valve or water seal type safety device. Safety valve should be checked before installation of the spring, membrane, valve stem and valve port for damage, whether the action is sensitive. Water seal construction as shown in Figure 7-1-7, can be welded in the field to produce, the installation of the strength of the test before the water seal inlet pipe and discharge pipe can be used flange connection (A type), can also be used threaded connection.

1- Water tank; 2- Water (or non-freezing liquid); 3- Gas pipe; 4- Exhaust port flange; 5- Inlet port flange; 6- Fill port: 7- Liquid level meter angle valve; 8-glass pipe; 9-discharge pipe; 10-discharge port

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(iv) Installation of Reynolds-type regulator chamber

Figure 7-1-8 shows the installation of the Reynolds-type regulator chamber without a filter. As can be seen from the figure, the Reynolds-type regulator consists of four parts: the main regulator, the medium-pressure auxiliary regulator, the low-pressure auxiliary regulator, and the pressure equalizer (also known as the intermediate pressure regulator). The main regulator and regulator room import and export valves directly with a flange connection, the inlet side and the outlet side of the connection of a flange interface tee, inlet and outlet tee between the connection of the bypass pipe, the bypass pipe centerline and the main centerline of the same elevation and parallel to each other, the bypass pipe installed on the flange connection of the bypass valve. Inlet and outlet tee each connected to a pressure conduit with medium and low-pressure auxiliary regulator connection, medium and low pressure auxiliary regulator connected to each other with the pressure conduit, the pressure conduit and the pressure equalizer film connected to the lower cavity. The inlet and outlet tees are connected to the 90° elbow pipe sticking out of the ground with a flange, and the main regulator and the membrane lower chamber of the pressure equalizer are connected to the low-pressure outlet pipe with a pressure-conducting pipe, respectively.

1-Main regulator; 2-Intermediate pressure regulator; 3-Low-pressure auxiliary regulator; 4-Medium-pressure shaft-assisted regulator; 5-Inlet valve;

6-Outlet valve; 7-Bypass valve; 8-Water seal; 9-Inlet pipe; 10-Outlet pipe; 11-Low pressure connecting pipe

1-Inlet valve; 2-Outlet valve; 3-Medium-assisted inlet valve; 4-Low-assisted outlet valve; 5-Medium-pressure auxiliary regulator; 6-Low-pressure auxiliary regulator; 7 -needle valve; 8- main regulator valve; 9- intermediate pressure regulator; 10- heavy block; 11- connecting rod; 12- lever; 13- Bleeder valve; 14 - Main membrane

The main and bypass pipes of the Reynolds-type regulator chamber can be made of either cast iron or steel pipes, since they have a fixed shape and size. The pressure-conducting pipes, on the other hand, are threaded and, for ease of installation, each section of the pressure-conducting pipe can be fitted with a loose fitting. When the main pipe is made of cast iron, the outlet pipe can be connected to the type B water seal in Figure 7-1-7.

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(v) Delusion of the self-regulator chamber

The process system inside the self-regulator room is basically the same as the piston regulator room, the main difference is that the conductor and needle valve belong to the accessories of the regulator, and should be installed on-site in accordance with the position and size shown in Figure 7-1-10. The ends of the conductor pressure pipe are with live joints and are threaded. The inlet and outlet of the regulator can be connected by smooth straight pipe according to its nominal diameter, or can be connected by tapering pipe, but the pressure guide pipe for inlet and outlet pressure should be installed on the smooth pipe, and the distance between its pressure point and the tapering pipe is not less than 500mm.