GDS - gas distribution station, fitted with equipment allowing to lower the pressure coming from the backbone network of gas to the required level.In addition, the task consists of filtering stations and odorization, distribution and metering of gas.
Appointment
gas distribution station is the last object in the chain of the gas transportation system and at the same time the head structure for urban supply systems.Since the cessation of gas supply to cities and large industrial enterprises is unacceptable, GDS provides automatic protection.And protective automation is made on the principle of redundancy.The backup line is activated when out of service the main line reduction.
GDS is designed to:
- receiving gas from the main gas pipelines;
- cleaning it from a variety of mechanical impurities;
- reduced pressure to values necessary in urban systems;
- maintain the pressure at a constant level;
- odorization and heating gas;
- determine its flow.
Types stations
AGDS GDS and share in its purpose:
- automatically branches of major pipelines - gas for small settlements.Further divided into gas control points (1000-30000 m3 / h) and the gas control unit (up to 1500 m3 / h).
- Control and distribution points - feed industry and rural infrastructure, pipelines ring around large settlements and towns 2000-12000 m3 / h).
- Fishing GDS - installed on the gas fields, by purification of the extracted raw materials from moisture and impurities.
- End stations - are built directly from consumers (enterprises, communities).
Automation
In recent years, widespread automated gas distribution station.AGDS capacity of up to 200,000 m3 / h operate unattended.In this case, the station has a range of equipment and instrumentation, allowing to carry out its operation in automatic mode.
maintenance of GDS is performed remotely.Operator distribution station, usually located in the premises of the service organization, monitoring can be performed even at home.In case of an emergency sound and light signals are transferred to premises and homes operators who are located at a distance of no more than 0.5 km from the controlled station.GDS service capacity of over 200,000 m3 / h is done in the ship's operation.
equipment
gas distribution station includes a consistent set of process equipment:
- disconnecting device at the entrance;
- filters;
- heater;
- line reduction and regulation of the gas pressure;
- device for measuring the flow of gas entered;
- disconnect device output.
as pressure regulators are used at the plant regulators of direct action type RD and indirect type RDU.
technological cycle
entered the gas distribution station receives.Driving his move through the processing chain is as follows:
- From gas pipeline gas is first passed disconnect device and enters the filter.
- Thereafter it is injected into the first reduction stage, having two or three lines, one of which is a backup.When there are two pressure reduction lines, reserve thread at one hundred percent capacity is calculated, and in case of three lines - 50%.Reserve line under this scheme can be used to bypass the first stage.
- If the pressure at the inlet to the GDS is 4 MPa, in the first stage of the gas pressure is reduced to 1-1.2 MPa, and in the second stage to 0.2-0.3 MPa.After the second stage gas pressure will have a value of 0.6-0.7 MPa.
installation of filters and pressure control
Siting filters depends on the inlet pressure and the gas composition.If the gas distribution station receives the wet gas, the filter must be installed before the 1st stage reduction.The filters in this case will be as a condensate trap, and mechanical impurities.Thereafter, the mixture of dust with the condensate flows into the settler.The pooled product is sent to a tank, from which it produces periodic pumping and export tankers.
When entering the GRS operating pressure less than 2 MPa, the filters are installed after 1st stage reduction.In this scheme, the installation of filters produce bypass (bypass installation) of the first stage.The filters in this case is set to a pressure of 2.5 MPa.With increasing gas inlet pressure above 2.5 MPa and cut-out device on the bypass line is closed and the gas is fed into the line 1st stage reduction.After her passing gas is directed to the second stage, and after the 2nd - in the discharge pipeline.
If the gas distribution station equipment needs to be replaced on the main line reduction, as well as the creation of emergency, make off of this line and the opening of the bypass line provided with a tripping device and a reducing valve.Adjusting the gas flow rate and pressure in this case is carried out manually.
device automated GDS
Automated gas distribution stations have several options for configuration of the equipment.However, they should take into account both the risk of hydrate formation and freezing outdoor outside knots reduction.In this regard, during the winter station attendants have to pay particular attention to the above factors.In order to prevent hydrate formation in the GDS used gas heating units.
heating unit includes a heater and boiler.The water comes into the boiler of a special container, proper heating water in the boiler combustion for gas supplied to the GDS and the last reduction system.Gas-burning devices boiler runs on low pressure gas.To prevent the gas coming to the burning of the furnace boiler with pressure over the set limit, there is a safety device.Thus, gas supply pressure entering the SRS is sent at first cleaned in the filters, and then to the preheater.The heated gas preheater occurs, whereby it is removed from the hydrate.After Heater, dry gas is supplied to the line reduction and then to discharge pipeline.
Safety
To prevent explosions and fires in the GDS establish special units to impart odor gas.These settings are established when headworks odor producing no gas or degree below the prescribed limits.Installations for gas odorization divided into bubble, drip and wick.The latter are called still evaporating.
Automation distribution station
The principle of operation of the automated gas distribution station with home-based service is as follows.In the event the output gas pressure in excess of the permissible value, the sensor is tuned to a certain value, it gives the command to switch the tap while alerting staff the station with the help of sound and light alarm, located on the shield.
In the case where there is an increase of the gas pressure at the outlet of the GDS to 5% in excess of the nominal pressure, then the corresponding sensor is tripped.As a result, the control valve in one of the working lines reduction begins to close, thereby reducing the outlet pressure of the gas.If the pressure is not reduced, it will trigger another sensor that will give the command to cover even greater control valve, up to completely disable all line reduction.In the case of reduction of the output pressure to 0,95R, is the opening of the emergency line.
Technical condition
Despite the simplicity of the device, gas distribution stations need to be upgraded.Construction of gas distribution stations in most cases carried out in the 70's, when gas pipelines were laid thousands of kilometers from the Siberian fields to the European consumers, and carried out mass gasification of localities and enterprises of the Soviet Union.Almost 34% of GDS marked its 30th anniversary, 37% - over 10 years, less than one third of the stations are equipped with modern facilities under 10 years.Currently considered a comprehensive program of modernization and reconstruction of gas distribution stations.
