Main gas control unit (MGCU)

GGRP-3, Almaty city, Kazakhstan

Application

MGCU is designed for natural gas purification from mechanical impurities according to GOST 5542-87, for commercial gas flow metering, the 1st category high gas pressure reduction to a high pressure of the 2nd category, for automatic keeping of output gas pressure within the specified limits, for automatic gas supply shutoff during emergency gas pressure increase (decrease) beyond the specified values.

MGCU is reliable in operation; it has a necessary redundancy of the main technological processes, a modern system of automated control of ACS of technological process of MGCU.

A product range is constantly upgraded on the basis of regular analysis of comments and wishes from operating organizations. A modular-packaged configuration of the MGCU allows to take into account the customer's requirements for the equipment.

This unit is applied in gas distribution systems and is installed at the entrance to the city's high-pressure networks as a main gas control unit (MGCU) after a gas distribution system. The unit reduces and supplies a high pressure of the 2nd category (up to 0.6 MPa) and medium pressure (up to 0, 3 MPa) to the gas network to supply it to large microdistricts and large industrial enterprises.

Working conditions

MGCU is designed for operation in the regions with moderate climate (N) and boreal climate (NF) as well as in regions with cold (F). Climatic type of MGCU is selected on the bases of construction area according to the requirements of GOST 15150-69. MGCU can operate in regions with magnitude 9 on the Richter scale according to the construction standards (SNiP) II-7-81. Rated snow load (200 kgf/m2) meets the requirements of the 5th territorial area; wind load (85 kgf/m2) meets the requirements of the 7th territorial area according to the construction standard (SNiP) 2.01.07-85.

Functions:

• gas purification from mechanical impurities;
• gas flow measurement with a long-term data recording and transfer of information to the upper control level;
• gas pressure reduction from a high one of the 1st category to high pressure of the 2nd category and to medium pressure and maintaining it with the specified accuracy during a change in the inlet pressure or gas flow rate;
• gas pressure reduction to own needs;
• autonomous power supply;
• heating of all skids of the unit to improve the reliability of the processing equipment.

MGCU configuration

MGCU is a modular-packaged processing equipment, consisting of various ready-to-operate processing units. The units are made on a supporting metal frame, the roof and walls of which are sheathed from the outer and inner sides by metal sheets (corrugated galvanised iron or metal siding) with a heat-insulating material between them. MGCU has a natural supply and exhaust ventilation, a gas pollution sensor as well as an unauthorized entry alarm. The heating of the units is carried out by means of explosion-proof electric heaters. It is possible to use water heating with the heat supply from gas boilers placed in a separate compartment or from an external source.

MGCU consists of:

• 1. switching unit;
• 2. gas purification unit;
• 3. bypass for gas flow measuring skid;
• 4. main gas flow metering line;
• 5. small gas flow metering line;
• 6. Valve DN300;
• 7. Valves DN300;
• 8. gas reduction unit;
• 9. Valve DN350;
• 10. Valves DN350;
• 11. Operator’s room

1. Switching skid

Switching unit consists of:

1. inlet and outlet insulated valves controlled remotely (butterfly valves with actuators);
2. a bypass line;
3. a set of safety relief valves;
4. a set of metering devices that provide metering and remote transfer of gas parameters at the inlet and outlet (pressure and temperature).

2. Purification skid

Gas purification skid components

Gas purification skid has 3 screen filters DN400 (2 working and one standby) and check valves with manual drive using to shutoff the filters.

Configuration

The equipment of the skid is placed on a rigid frame.

Gas flow metering skid

Gas flow metering skid components:

1. Main metering line DN600;
2. Small metering line DN300;
3. Bypass line.

Configuration

The equipment of the skid is placed on a rigid frame. Depending on the skid configuration various types of meters can be applied: turbine or ultrasonic meters. Gas low measuring is to be metered before its reduction.

4. Gas reduction unit

This unit has several reduction lines with partial redundancy for maximum capacity. If it is necessary to limit the gas consumption to the consumer, a pressure regulator with a gas flow restriction function may be provided in the gas regulating unit. It allows remote control of the gas flow to the consumer by a command from the control center of the operating organization or a digital throttling valve can be installed in MGCU, that also allows remotely control the gas flow. The applied pressure regulators automatically maintain the pressure with the accuracy of ± 5% regardless of the inlet pressure fluctuation and gas consumption by the consumer. It is possible to produce a reduction skid with automatic switching from a reduction working line to the backup one. If necessary, a low-cost line is provided for operation in the initial period of gas reduction unit operation.

Gas reduction unit components

Gas reduction unit consists of the following:

1. gas pressure regulator;
2. metering and control devices;
3. shutoff valves (outside of the unit on the rigid frame).

Manual shutoff valves are installed at the inlet of the gas reduction skid and shutoff valves of remote control are installed at the outlet of this skid.

Configuration and components

together with gas pressure reduction RU3-16/200 (DN200, PN1.6 MPa) - 3 working lines and 1 backup line.

5. Instrumentation and automated control unit ("Operator’s room") with ACS of technological processes of MGCU

Basic functions

Operator’s unit performs the following functions:

• automatic control of the technological equipment operation modes of the MGCU;
• implementation of control, measurement and signaling functions;
• coordination of interaction between local automation systems;
• emergency protection in case of fire;
• emergency protection when there is increase of output pressure;
• emergency signal initialization to an operator and a dispatcher of the operating organization in case of violations of the MGCU work.

ACS of technological processes of MGCU exchanges data with the dispatch center of the operating organization via the telemechanics channel. The choice of the way of integration of ACS TPMGCU into the telemechanics system is carried out at the stage of design of the MGCU according to the customers’ specifications.