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Application of Ultrasonic Gas Leak Detection Technology in Natural Gas Pipeline Station
Release time:
2024-03-12 00:00
Source:
Abstract:
This paper introduces the current domestic natural gas long-distance pipeline gas transmission station combustible gas leak detection equipment set up. According to the principle of ultrasonic detection technology and its comparison with the traditional detection method, a combustible gas leak detection equipment based on ultrasonic technology is applied in the specific project.
1. Introduction
The open-air process equipment area of gas transmission station is the core area of long-distance pipeline, and the safety of process equipment area is very important. The leakage and diffusion of natural gas in the process equipment area are easy to cause explosion risk. For many years, catalytic or infrared point detector has been used to cooperate with the controller for combustible gas leakage detection in gas transmission station of long-distance pipeline. During the operation, there are serious faults and false alarms, and the detection effect is not ideal. At present, in the process of design and implementation, the guiding opinions are given in accordance with Section 6.1.6 of the GB50183 Code for Fire Protection Design of Petroleum and Natural Gas Engineering: "Other Class A production facilities arranged in open air or shed may not be equipped with combustible gas detection and alarm device". Under the guidance of this method, no combustible gas detection equipment is arranged in the open air process equipment area of the station at present.
With the promotion of "centralized monitoring" operation mode of PetroChina West-East Gas Pipeline Company, according to the concept of "people-oriented, energy saving and environmental protection, safety and high efficiency", regional management is adopted for pipelines. In order to reduce the internal risks of process equipment area to an acceptable range, the real-time detection requirements for gas leakage in open-air process area are greatly improved, and measures and methods to mitigate risks are needed. Now a "new" ultrasonic gas leak detector technology has gradually become a field-verified pipeline leak detection scheme, which improves the accuracy of pipeline leak detection and ensures the safety of gas transmission stations.
2. combustible gas alarm system
Overview of Combustible Gas Alarm System in 2.1 Domestic Long-distance Natural Gas Pipeline Station
Combustible gas alarm system is an important part of the station control system of gas pipeline station. It takes combustible gas leakage as the monitoring object and is designed according to the requirements and characteristics of different combustible gas types. The station combustible gas controller is connected to the combustible gas detector equipment in the jurisdiction area through the station control level hard line to form the station control level combustible gas alarm system, which is responsible for monitoring the operation status of the combustible gas detector equipment in the station and receiving the combustible gas detector alarm information. The combustible gas controller transmits the alarm and fault information of the combustible gas alarm system to the station control system at the same time, and then transmits it to the relevant control center through the station control system, and can carry out a series of fire control linkage, accept the command of the control center or independently organize and direct the disaster prevention and relief work within the jurisdiction.
Current Situation of Setting of Combustible Gas Detectors in Domestic Long-distance Natural Gas Pipeline Station in 2.2
During the construction of gas transmission pipeline stations, fixed point type and infrared radiation type combustible gas detectors shall be set in the generator room, kitchen, hot water room and other indoor places of each station to carry out automatic detection of combustible gas leakage at the above positions.
In the early stage, the open-air process equipment area of the station yard of the west-to-east gas transmission line and other branch lines was equipped with infrared-type combustible gas detection devices. During the operation, the faults and false alarms were serious. Since 2008, after expert discussion, the combustible gas detection device in the open-air process equipment area of all stations on the west line has been removed, and no gas leakage detection device has been set up after the removal of the open-air process area.
In the design of the Second West-East Gas Pipeline Project and the later long-distance pipeline project, according to the "Code for Fire Protection Design of Petroleum and Natural Gas Engineering" (GB50183-2004), "Other open-air or shed-type production facilities may not be equipped with combustible gas detection and alarm devices", and no combustible gas detection equipment is arranged in the open-air process equipment area of the station.
Design of Ultrasonic Gas Leakage Detector in Open-air Process Area of 3. Gas Transmission Station
3.1 the working principle and application of common combustible gas detectors
At present, the domestic commonly used gas leak detection equipment has the following 6 basic principles,
Through the detection principle and economic comparison, it is considered that the gas leak detector based on ultrasonic principle is the most suitable technical product for leak detection in the "natural gas open-air process area. The specific reasons are as follows:
The highest sensitivity, in the detection of gas leakage before reaching the dangerous concentration;
The reliability of the best, not affected by any bad weather conditions, as long as the high-pressure gas leakage in the pipeline to produce ultrasonic can be detected, rarely leakage alarm, by setting the appropriate delay time can also greatly reduce the probability of false alarm;
③ Not subject to the conditions of the gas type;
④ The maximum detection distance of a single device (maximum radius of 20m);
The use of ultrasonic to receive the alarm, because the sound in the air is very fast, so the alarm response time is very short;
⑥ Excellent stability, the principle of the product is not a chemical principle, which will not produce any pollution and the sensor will not have any loss. Products with digital display decibels can be calibrated regularly. As there is basically no drift, the interval period can be set longer. The service life of the product is relatively long, generally more than ten years or even longer.
3.2 ultrasonic gas leak detector
3.2.1 Detection principle
Ultrasonic gas leak detector is a device that captures ultrasonic leak signals for leak detection, air tightness detection and predictive maintenance in the industrial field.
The detection principle is: when the container or pipe is filled with gas, its internal pressure is greater than the external pressure, due to the large pressure difference between inside and outside, once the leak hole, the gas will be punched out from the leak hole. When the size of the leak hole is small and the Reynolds number is high, the gas will form turbulence. The turbulence will produce sound waves of a certain frequency near the leak hole. The frequency of sound wave vibration is related to the size of the leak hole. When the leak hole is large, the human ear can hear the leakage sound. When the leak hole is small and the sound wave frequency is greater than 20kHz, it is no-load ultrasonic. Ultrasonic wave is a high-frequency short-wave signal with directivity, and its intensity attenuates rapidly with the increase of propagation distance. Using this feature, the leak point can be determined.
When the leakage hole is small and the sound wave frequency is 10 20kHz, it is no-load ultrasonic. Ultrasonic wave is a high-frequency short-wave signal with directivity, and its intensity attenuates rapidly with the increase of propagation distance. Using this feature, the approximate location of the leak point can be determined.
The ultrasonic gas leak detector uses this principle to make an alarm indication for pipeline leakage by detecting, collecting and analyzing the ultrasonic part of the sound wave in the leak sound.
3.2.2 Product Features
Ultrasonic leak detectors currently on the market. With ultrasonic sensing technology, a moving metal diaphragm (microphone) is used to detect leaks.
The latest ultrasonic sensor technology uses MEMS sensors for acoustic acquisition and monitoring. Broadband acoustic signal acquisition, acoustic signal analysis frequency 50Hz ~ 70kHz; This ultrasonic sensor has very high chemical resistance and a wide frequency range response band. The equipment can be installed in any direction. This equipment is calibrated by the manufacturer before leaving the factory and does not need to be recalibrated for life. The product has BKSN21EX ultrasonic gas leak detector with periodic self-checking function, and the alarm signal will be sent out in time in case of sudden use failure. Strong sensitivity, effective detection distance is about 5m ~ 20m; Strong reliability. The ultrasonic detection range of the product is 50Hz ~ 70kHz, which is not affected by the audible background noise in the open air. After setting the appropriate delay time, it can be not affected by extreme weather such as wind, rain and lightning. The product has obtained the explosion-proof safety certificate for use in flammable and explosive environments.
The gas leakage acoustic monitoring system is based on acoustic monitoring network, based on acoustic information detection technology, big data technology, artificial intelligence technology, Internet of things technology, high-performance computing technology, suitable for rapid deployment of integrated gas leakage acoustic monitoring solutions.
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