Gas distribution points are designed to automatically lower the gas pressure and further maintain it at a given level, regardless of flow fluctuations within the nominal range. Consider the features of hydraulic fracturing.
Classification
Hydraulic fracturing is divided into the following types depending on the method of equipment placement:
- Gas distribution points are cupboard . In this case, the equipment is placed in cabinets made of non-combustible materials.
- Gas control installations. The equipment is mounted on a frame. It is placed in a room in which the installation itself is used, or in a room that is connected to the units with an open opening.
- Gas distribution points block . In this case, the equipment is placed in a container type building (one or more).
- Stationary gas distribution points . The equipment is placed in specially designed rooms, structures or in open areas.
The fundamental difference between the hydraulic fracturing of the latter type is that they are not typical prefabricated products.
Requirements for Production Facilities
Gas distribution points with a pressure of up to 0.6 MPa at utility and industrial enterprises, in boilers standing separately, are located in buildings near the inlet of the gas pipeline, in rooms in which gas-using equipment is located. GRU is not allowed to be installed under staircases.
The arrangement of gas distribution points in the basement, semi-basement facilities, in extensions to the buildings of hospitals, schools, child care facilities, administrative and residential buildings is not allowed.
Separate hydraulic fracturing should have one floor and a combined roof. The roof must be easily removable (weight of 1 m of overlap - no more than 120 kg).
Installation of ventilation and smoke ducts in the dividing floors and walls of structures to which the gas distribution point is attached is not allowed. All rooms should be provided with artificial and natural lighting, a permanent ventilation system (natural) with triple air exchange.
Electric lighting and electrical equipment are made of explosion-proof materials. Inputs of power supply networks should be cable.
In the regulatory room can accommodate a telephone. Moreover, it must be protected from explosions.
Heating
When installing the local system, the heating installation is placed in an isolated room with a separate exit. It should be separated from other premises of the gas distribution point by blank walls made of fireproof and gas-tight materials. The temperature of the coolant should be no more than 130, and the heating equipment - 95 degrees.
For hydraulic fracturing, lightning protection must be provided. The floors are made of materials that prevent the formation of sparks.
Additional requirements
On the facade of the building in a prominent place put a warning sign "Flammable." Letters must be at least 300 mm high.
Doors from the gas distribution point open outward. The sheet is sheathed with galvanized steel (0.8 mm thick).
Equipment
It is placed taking into account the appointment of hydraulic fracturing. The gas distribution equipment includes:
- Pressure regulator, providing automatic pressure reduction and maintaining it at a given level.
- Safety valve With a decrease / increase in pressure, the gas supply is automatically shut off.
- Reset safety device. It provides the discharge of excess gas into the atmosphere, necessary to maintain the pressure level. The device is connected to the outlet gas pipeline or behind the flow meter (counter).
- Filter to eliminate mechanical impurities.
A bypass (gas bypass) is installed in front of the shut-off valve with 2 shut-off devices arranged in series. Bypass gas is supplied during revision and repair of equipment on the reduction line. For points with a pressure of more than 0.6 MPa and high (more than 5 thousand m / h) throughput, an additional control line is installed instead of a bypass gas pipeline.
Verification of indicators
Using special measuring tools, determine:
- Gas pressure in front and behind the regulator. For this, self-recording and indicating pressure gauges are used.
- Differential pressure on the gas filter. These indicators are checked by technical pressure gauges or differential pressure gauges.
- Gas temperature. To determine it, use self-recording and indicating thermometers.
Blowdown and waste pipelines
They are used to discharge gas into the atmosphere and purge equipment. Purge pipelines are installed on:
- Inlet gas line behind the first connecting device.
- Bypass between locking mechanisms.
- A plot with equipment shut down for repair and inspection.
Pipelines lead out to places where safe gas dispersion is provided (at least 1 m above the eaves of the structure).
Due to the locking devices, it must be possible to turn off the gas distribution point, measuring instruments and equipment without stopping the gas supply.
Regulators
Hydraulic fracturing can be one- or two-stage. In the first, the inlet pressure is regulated to the outlet one, and, secondly, respectively, by two regulators installed in series. The performance of the devices should be approximately the same.
Single-stage models are used, as a rule, with a difference in the inlet and outlet pressure indices within 0.6 MPa.
Pulse sampling sections for regulators and safety shut-off valves are defined in the equipment certificate, but they can be changed.
Start of gas distribution points in operation
It is carried out according to a written order recorded in a shift journal. Before starting, it is necessary to familiarize yourself with the contents of the work that has been done since the shutdown, as well as the reasons for the termination of hydraulic fracturing.
Start-up is carried out in 2 stages:
- Inspection of equipment, devices, fittings.
- Direct start.
Inspection
During it it is necessary to state:
- Serviceability of control and measuring devices.
- Stability of pressure indicators (are in the range of the norm). It is determined by opening the tap of the measuring device, showing the magnitude of the pressure at the inlet.
- Completeness of the gate valve at the entrance. It must be closed.
- Serviceability and completeness of the filter.
- Complete safety valve. The hammer and levers must be disengaged, the crane on the line to it must be closed.
- Serviceability of the pressure regulator. The pilot screw must be turned out, the crane on the line to it must be in the closed position.
Also, during inspection, you must make sure that:
- At the inlet of the process line, the valve is assembled and closed.
- The safety relief valve is in good condition, assembled, and the tap to it is in the open position.
- Both valves on the bypass are assembled, closed, the tap between them on the purge line is open.
Hydraulic fracturing
The opening is carried out sequentially:
- Gas purge valve.
- Crane on the manometer.
- Gate valves at the gas outlet from the point.
- Crane on impulse line to pressure regulating device.
Further specialist:
- Engages the levers of the safety shut-off valve.
- Slowly opens the gate valve at the entrance. Gas pressure should be at zero.
- Closes the purge line valve after the inlet valve.
- Slowly unscrews the pilot screw of the regulating device, brings the pressure to the working one.
- Checks the stability of the regulator, opens on the impulse line the crane to the slam-shut gun and engages the hammer and rocker.
- Slowly closes the purge valve.
- Opens taps to working devices, checks for malfunctions, leaks.
The journal records the work done.