DD274870A1 - PROCESS FOR LEAKAGE IN UNDERGROUND INSTALLED GAS PIPES - Google Patents

Abstract

The invention relates to a method for leak detection in underground laid gas pipes. The method is used to inspect filled gas pipelines, such as gas piping systems of regional and supraregional energy supply. According to the invention, a method is described which, by utilizing the "Joule-Thomson effect" and with the aid of an infrared camera system, detects leaks of suspected thermal anomalies on the earth's surface above the filled gas line.

Description

Characteristic of the known state of the art Underground gas piping systems are subject in the course of their lifetime signs of wear or interference, the

can lead to leaks (leaks). The early detection of these leaks is important to gas losses and

Dangers in the leak area to avoid. The leak detection is known by means of gas detectors. OS DE No. 2304330 describes a gas probe for use over the Rohrtrosso. In the patent DE 2414453 a method for determining a fracture? diner piping by measuring the Describe pressure change that results from the breakpoint. Methods are known for leak detection, which are based on auxiliary devices provided in addition to the gas line. For example, AS DE No. 2431907 describes a hollow conduit along the route which is charged with a test medium. The OS DE No. 1023102 provides a dissolvable from the dissolving gas hose with a spit. To arrange along the pipeline current-carrying insulated wires, provides the OS DE No. 721463. In this method, the outflow Rohrinhad destroying the insulation of the wires and based on the measured Insulation resistance, the leak detection done. Also known are newts for internal inspection of gas pipes. The use of pigs but sets piggable pipes

ahead.

Object of the invention

Has the object of the invention is a method for leak detection without additional cost of materials on the pipeline, which is feasible above the Erdberuiches.

Explanation of the essence of the invention The object of the invention is that a method is found which is not based on the many measuring points

but without mechanical ground contact, without excavation and complicated

Innqninspektionen a leak detection from the earth's surface permits. According to the invention, this is achieved by taking advantage of the "Joule-Thomson effect" and using a Infrared thermography device sine Undichti'oit is located at the filled gas line. Gas pipelines represent thermodynamic systems, which are starting points in the area of the generator b'w. compressor stations

continuously to a heat content Q according to

be lifted.

Due to the existing thermal conductivity λ of the gases and the soil, this heat potential builds over the Cable length increasingly from, that is, the gas temperature increases the temperature of the soil. Due to the "Joule-Thomson effect" of the gases, temperature drops occur in the event of pressure drops, depending on

the gas composition, up to 0.55 degrees per 0.1 MPa pressure drop. Under the simplified assumption of the heat conduction through a flat wall with the surface F of 1 m ² and thickness S of 1 m {laying depth) as well as neglect of the

Abkühlun.gsbeschleunigung by the migration of the gas is in the leak range, the temperature difference between Surface and 1 m soil temperature with chosen average soil S according to In it means:

- Cooling capacity of the "Joule-Thomson effect"

- t | Soil temperature 1 m depth after "Joule-Thomson effect"

- t ₂ earth tempature surface.

The anomsüe de J thermal image between the leak area and the surrounding area resulting from the earth's surface can be detected by means of the 'jas thermogram of an infrared camera system with maximum / η temperature resolutions of 0.2K and thus directly evaluable as a leak in the gray value image of the monitor.

Au & fuhrungsbeispiel

The inspection of a buried filled gas line according to the invention can be carried out with an all-terrain vehicle or a slow-moving aircraft, such as a helicopter.

The annual months from April to October are particularly suitable for the detection of temperature anomalies to the surrounding Bodenobt'fläche. If a gas pipe is now run over by a vehicle equipped with an infrared camera system, then the observer detects a concentrated darkening of the gray image at a leak of the gas pipe on the oem monitor. Immediate detection of a temperature anomaly suspected by leaks is facilitated by the display of an electronic isotherm of a temperature range dependent on the ambient temperature.

Claims (1)

Method for leak detection in underground laid gas lines taking advantage of the thermodynamic behavior of the gases at pressure changes, characterized in that the temperature drop, which arises at a pressure drop by the "Joule-Thomson effect" of the gases, using an infrared thermography device as Temperaturdiffert> nz is visibly detected to the ground temperature and thereby a leakage of a filled gas line can be located from the surface of the earth. Field of application of the invention The invention may be applied wherever buried pressurized gas pipelines are to be inspected and their technical safety ensured by gas tightness, such as gas piping systems of regional and supraregional power supply systems.