Seal control system
A sealing control system is a measuring system for the area-wide control of buried large-area waterproofing as well as for the location of leaks in buried plastic waterproofing within waterproofing systems. Depending on the selected construction and the materials of the system as well as the production, installation and quality assurance processes used, seal control systems are especially suitable for the long-term monitoring of sealing systems for landfills .
technical structure
A seal control system consists of the following functional components, depending on the system configuration to be implemented:
- underground components including the field distributors
- Measuring and evaluation unit
- if necessary, additional evaluation computer with evaluation and visualization function
Function description
The determination and evaluation of the local resistance distribution of the plastic seal by measuring potential or corresponding current density distributions by means of a matrix-like arrangement of measuring points below the building seal is fundamental for a seal control system . The measuring points are routed via measuring lines to the edge of the building seal and placed there on connection points in field distributors. In addition, depending on the size of the seal to be monitored, one or more counter electrodes are placed in the layer system above the seal, e.g. B. in the drainage layer and also placed on connection points in the field distributor via connecting cables. This makes use of the fact that the plastic seal is a flat electrical non-conductor which is embedded in a layer system that is usually moist and therefore electrically conductive.
To carry out the control measurement, a computer-controlled measuring and evaluation unit is connected to the connection points of the underground components in the field distributor. With this measuring and evaluation unit, the seal control system is measured automatically or partially automatically, depending on the expansion stage of the leak location system, whereby first the function of the seal control system itself and then the condition of the seal is checked.
The measurement is evaluated manually using standard software, depending on the expansion stage of the system, partially automated or automated using database-supported evaluation software. Regardless of the type of software used, the evaluation is based on the following relationships:
If the seal is intact, the voltage measured at all measuring points is ideally almost zero, since no current can flow through the seal to earth. If there is a leak in the seal, the leakage fluid creates an electrically conductive connection between the layer systems above and below. If a measuring voltage is impressed on the counter electrode, a measuring current flows from the counter electrode above the seal via the leakage to earth. This creates a typical potential distribution below the seal in the area of the leak, which can be recorded with the measuring arrangement and assessed as a leak. In the soil below the seal, the volume-related current strength of the leakage current is greater, the smaller the distance from the leakage point. Since the voltage measured below the seal is proportional to the current strength of the leakage current, the lower the distance from the leakage point, the higher the voltage.
Since the installation position of the measurement points is known, the evaluation software can be used to determine the exact position of the leak based on the measured voltage distribution.
A prerequisite for the basic function of a seal control system or for the underlying physical principle is on the one hand sufficient intrinsic conductivity of the layers adjoining the seal and a sufficient current flow through the damaged area in the seal, e.g. B. as a result of seeping liquid. If these physical prerequisites for function are met, seal control systems have a high level of security with regard to the detection and location of leaks.