Scheme of instrument control system for full tank

Design principle of instrument control system for full tank

(1) Implement the national capital construction policies, strictly abide by the national laws and regulations, implement the national industry and local regulations and the current design standards and specifications;

(2) Implement the guiding ideology of "safety, universality, efficiency and environmental protection" to ensure high efficiency, energy saving and safe production;

(3) Learn from the construction experience of similar projects at home and abroad, and combine with the actual situation of project development, adopt advanced, appropriate and open control technology and means to implement centralized control and management mode; The automatic control system will ensure the normal operation of the plant and the safety of people, devices and equipment, and it is economical and reasonable. At the same time, the automatic control instrument and system are easy to operate and maintain; Select the detection instrument and control equipment suitable for local characteristics to ensure the reliability of instrument equipment and system; Electrical instruments and equipment in inflammable and explosive places shall be designed according to relevant standards and specifications.

(4) The accuracy of the servo level gauge is better than 0.5mm and the repeatability is 0.1mm in the range of 0-30m.

(5) Servo level gauge and radar level gauge are the same manufacturer. The radar level gauge of storage tank shall be suitable for LNG medium measurement, and the evaporation gas generated at the upper part of LNG level shall not affect the measurement of radar level gauge. The principle of radar measurement should be FMCW.

(6) Type approval certificate and type approval report of Chinese measuring instruments shall be provided for servo / radar level meters. Servo liquid level meter is used as the measurement data source of storage tank, and the type evaluation report of measuring instrument corresponding to the certificate shall be provided. In the report, the measurement accuracy index and the report proving the value transfer benchmark shall be provided, including temperature, humidity, free fall, vibration during transportation, continuous collision, electromagnetic compatibility, anti static discharge interference, anti pulse train interference, etc Surge interference test, and measurement performance test after performance test under abnormal environmental conditions.

(7) Low temperature detector requires signal converter and PT100 temperature sensor integrated installation, with LCD display on site, accuracy: ± 0.5 ℃, stability: ± 0.1% / year, explosion-proof grade: Exia Ⅱ cT4, protection grade: IP65 (iec529).

(8) The control valve is equipped with pneumatic shut-off valve and control valve in the process battery limit according to the process requirements, including the shut-off valve of the liquid inlet and outlet pipeline of the storage tank, the shut-off valve of the air supply pipeline, the shut-off valve of the vent pipe orifice, the outlet control valve of the submersible pump, the pressure regulation of the flare pipeline, etc., the intelligent electric valve positioner (with HART Protocol), the filter pressure reducer, the hand wheel, the explosion-proof solenoid valve, the control valve, etc Limit switch and other accessories. In case of power loss, gas loss, signal loss or DCS / SIS system failure, the pneumatic control valve can move to the safety direction or remain in place. The pneumatic control valve shall meet the fire safety type of API 607 or API 6fa standard.

(9) The instrument selection requires that the supporting instruments of storage tank should be advanced and reliable products, and the electrical interface of imported or joint venture instruments should be 1 / 2NPT; The remote transmission instrument is required to be intrinsically safe, and the explosion-proof grade is not lower than Exia Ⅱ cT4; The protection level of field instruments shall not be lower than IP65. Field instruments and actuators entering SIS system shall have SIL level corresponding to LOPA analysis

The design and selection of instruments for storage tanks must follow the relevant national standards.