Helium tracer-gas leak detection - Implemented during the normal operation of the pipeline without interruption of the supply

District heating supply systems are regularly checked for Ieakages. A commonly applied procedure is based on the use of a tracer gas to check underground supply systems or individual pipe sections for Ieaks. For this purpose, a tracer gas is charged into the pipe and pressurized. If the gas can be detected anywhere at the surface it is a sure indication that a leakage does exist. However, this method has significant disadvantages such as the interruption of supply, as the relevant pipe section will have to be closed off and emptied to perform the leakage test procedure.

To enable simpler and less costly Ieakage detection, DELU and Fraunhofer Institute have developed a new leak detection technique using helium as a tracer gas. It can be implemented during normal operation of the pipeline without interruption to the supply. This procedure, which is especially but not exclusively advantageous for district heating, is based in principle on the tracer gas procedure with helium, however the gas is dissolved and added to the water supply in small quantities. In this way the district heating water is marked and can be distinguished from water of other origin, such as precipitation water or humidity from the soil. If needed, the marking of the water can be implemented at regular intervals or continuously. For this purpose a helium-charging unit is used to mix a low concentration of helium gas into the district heating water (Figure 1), thus avoiding the formation of bubbles. The latter has to be guaranteed to avoid malfunctions in the district heating system.

The helium-containing district heating water exits at a leak and enters the surrounding sand bed, the soil, the sheathing or the pipe duct. Subsequently, the dissolved helium gas will be desorbed from the water and released. The helium diffuses rapidly and penetrates the surrounding soil to the surface. Depending on the size of the leakage, the depth of the installation, the density of the soil and the consistency of helium in the water, helium can be detected at the surface a few hours after the leakage has occurred. After the addition of helium to the water and a certain walting period, a helium tracer unit is used to check the district heating line. The system functions up to a route length of 500 km.

The advantages of the system are obvious: Interruptions to or effects on the supply system and co-ordination with the end user or drainage of the system are excluded. The leakage can be detected within the entire systern and is not subject to any time restrictions. The combination of these advantages presents a unique cost/benefit ratio.

Pilot project

E.ON Fernwärme GmbH, a subsidiary of the worldwide E.ON group, has recognised these unique advantages. This supplier recently signed an agreement with DELU to detect a leak in a steel jacket pipe. The background to this assignment was the fact that E.ON Fernwärme GmbH had been trying in vain over a lengthy period of time to find the leak. Based on the technology applied by DELU, the leakage could be detected successfully (Figure 2) and at rational cost to E.ON Fernwärme GmbH.

Given the close contacts among the municipal utilities in Germany, strong multiplication effects can be expected from this successfully completed pilot project. To this end, the municipal utility in Annaberg-Buchholz has already expressed its intention to go ahead with DELU’s tracer gas leak detection technique.

The helium tracer gas leak detection has a significant growth potential. All municipal utilities on a national as well as international level are potential customers. As the product can be applied to all media, chemicals companies are also likely to become major users of this DELU product.

Procedure can be used for all media

• Aqueous media in closed circuits: district water heating systems, cooling water, cooling circuits
• Drinking water, waste-water, process water, slurry, brine, special material flows (food industry, medicine, pharmacy)
• Non-aqueous media: Oil, fuel and related material
• Gases: Air, natural gas, compressed air, process gas

The DELU AG

DELU AG was founded in 2000 with five shareholders. The basis of the company is the proposed patents and developments that have meanwhile attained market maturity. Through research, development and presentation, particularly with well-known institutions, further technologies and solutions have been developed in the areas of information technology and environmentally oriented service technology.

Procedures and devices have already been developed in conjunction with other institutions, to which the DELU AG Company has the exclusive rights to license marketing agreements. The following are examples:

• ABS-Fittings
• Tracer-Gas leakage locating system
• In-Sense sensor management system. 

The products developed, which are now ready to begin production, and the innovative solutions, can be implemented in multiple areas and are utilized by companies, private consumers and communities.

For 2006, a test vehicle has been commissioned. In addition to the leak detection system, the features in the vehicle include correlation measurement methods, ultrasonic flow measuring methods, wire detection devices for selectively locating cables and metal pipes, as well as for cable selection and thermographic camera measuring methods.