RU2748862C2 - System for monitoring sealing capacity of waterproofing roof covering layer - Google Patents

Abstract

FIELD: sealing.

SUBSTANCE: invention relates to systems for monitoring sealing capacity of the waterproofing roof covering layer. Substance: the system includes a measuring sensor cable net with sensors located on the surface of the waterproofing layer. An electrically conductive sheet in form of a foil-clad roll material based on fiberglass is placed underneath the waterproofing layer. The measuring sensor cable net is connected with a computing module configured to collect and process the readings of the sensor cable. An excitation electrode connected to one of the poles of the voltage source, the other pole whereof is connected with an electrically conductive sheet, is located on the roof covering surface. An electrical contact of the electrically conductive sheet with the wet waterproofing roof covering layer is formed therein at the point of the leak. The position of the leak is determined using a superposition method based on the electric potential distribution measured by the sensor cable over the surface of the waterproofing roof covering layer, the value of the potential at the excitation electrode and the known position in space of the sensor cable sensors and the excitation electrode.

EFFECT: identified presence of a leak and accurately determined coordinates of the position in space thereof.

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Description

Technology area

The invention relates to the field of construction and can be used to diagnose the tightness of roof waterproofing.

State of the art

Known device disclosed in the description of the article Ceja C. Recommended test procedure for high-voltage membrane integrity testing // 28TH RCI International Convention and Trade Show, Chicago. - 2013. The known device allows for instrumental diagnostics of the tightness of the waterproofing of a flat roof by the high-voltage method. For this, on one side of the waterproofing, an electrode with a potential from a power source is supplied, and a ground wire is connected to the conductive base. Where there are defects in the coating, the current passes through the coating and enters the grounded substrate. As a result, a short circuit occurs, that is, an electrical connection of two points of an electrical circuit with different potential values. The result of a short circuit is a spark and thus damage to the insulation coating is detected.

The known method disclosed in the document Electronic Leak Detection High vs. Low Voltage // WATERPROOF !. - 2013. The known method involves the detection of leaks in the roof covering during its diagnosis. Uses opposite voltage potentials. In this case, an energy source is used, which contains two leads that provide opposite potentials: one lead provides a negative potential "-", which is fed to the brush electrode, and the other lead is a positive potential "+", which is fed to the base.

A known system for monitoring the tightness of the waterproofing layer of the roof, disclosed in US patent 7652481 (publ. 01/26/2010). The known system makes it possible to determine the fact of a leak and its position in space. The system includes a waterproofing layer, an electrically conductive layer placed under the waterproofing layer, a sensor cable mesh located on the surface of the waterproofing layer and connected to a computing module capable of collecting and processing the sensor cable readings and determining, taking into account the obtained data, the presence of a leak and its position in space.

A disadvantage of the known invention is the use of a supporting roof deck as an electrically conductive layer. This narrows the scope of the present invention, since not every supporting roof deck can be electrically conductive, and in the case of insufficient electrical conductivity of the roof deck, it can be difficult to determine whether a leak has occurred and its exact position in space.

Disclosure of the essence

The technical objective of the present invention is to expand the range of technical means for monitoring the tightness of the waterproofing layer of the roof.

The technical result achieved by the implementation of the present invention consists in determining the presence of a leak and accurately establishing its coordinates in space.

The technical result is achieved in that the monitoring system for the tightness of the waterproofing layer of the roof includes a grid of a measuring sensor cable connected to a computing module, which is configured to collect and process the readings of the sensor cable, a voltage source, to one of the poles of which an excitation electrode is connected, located on the surface roof, and the second pole of the voltage source is connected to an electrically conductive sheet, which is placed under the waterproofing layer. In contrast to the prototype, a foil-clad roll material based on fiberglass was used as an electrically conductive sheet, while the mentioned material forms an electrical contact with the wet waterproofing layer of the roof at the leak site, the position of which is determined using the superposition method based on the electric potential distribution over the waterproofing surface measured by a sensor cable the roof, the value of the potential at the excitation electrode and the known position in space of the sensors of the sensor cable and the excitation electrode.

Implementation of the invention

For a system for monitoring the tightness of a waterproofing layer in real time, which includes a mesh of a measuring sensor cable , as well as an electrically conductive fabric with a resistivity in the range from 100 to 500 kΩ⋅hm, a flat wire with 3 cores is used, each core must be exposed at a distance 0.3 meters from the end of the wire. At the end of each wire, a stainless steel sensor with a conductivity of at least 0.028 Ohm⋅m is soldered. At the beginning of the cable, a connector is mounted on all three wires to connect to the system indicators collection module. Diagnostics of the cable operability is checked by a multimeter as follows: The measuring part of the multimeter is set to measure the resistance at 20K, the negative terminal is installed at the beginning of the cable on the corresponding wire, the positive terminal is installed on the sensor. The value should be equal to "0", which corresponds to absolute conductivity. If the value is greater than "0", the cable must be replaced. The protective polyvinylchloride (PVC) cable sheath is also checked by the spark method. In case of defects in the protective insulating sheath, the cable must be replaced.

As an electrically conductive canvas , the material control GL, (foil roll material based on fiberglass), which is located under the waterproofing layer, as well as needle-punched geotextile, located on top of the waterproofing, can be used. When preparing this unit of the module, it is necessary to check the contact of the foil layer of all individual parts of the material, which is controlled by the GL, as well as the quality of the contact of the contact electrode with the conductive foil.

Waterproofing roll material must be checked for defects in tightness. If defects are found, they must be eliminated, or the waterproofing must be replaced.

On top of the waterproofing, a needle-punched geotextile can be mounted, which acts as a second conductive layer, while the actual conductor is water, located and retained by the geotextile.

The performance check of the computing module is carried out with the assembled system elements, under the conditions of the operating system. In case of contact of the contact electrode with a specific sensor, the potential value at this point should be equal to the "maximum value within 1590", while all other sensors should show the value "0".

The developed system is based on the fact that water is a poor conductor of electric current, and the materials used for waterproofing, for the most part, are very good dielectrics. In this regard, it becomes possible, using the properties of the electromagnetic field and its interaction with matter, not only to determine the very fact of the presence of a leak, but also to quite accurately establish its position in space.

As noted above, water, and with it a wet roof, are conductors, but their electrical resistance is relatively high compared to materials traditionally used as conductors of electric current (steel, copper, aluminum, etc.). If a good conductor is placed under the waterproofing layer of the roof (a substrate - a metal sheet or foil), then at the place of the leak (if any), an electrical contact will be formed between the upper wet layer of the roof and the conductor. If now an “excitation” electrode is placed on the roof, to which one pole of the voltage source is connected, and the other pole of the voltage source is connected to the substrate, then an electric current will flow through the circuit “electrode - damp roof - leak - substrate”. Since the resistance of the roof is relatively high, the current flowing through it will create a noticeable voltage drop between points located in different places of the roof, moreover, this drop will depend only on the position of the measuring points relative to the electrode and leakage. Such a distribution of potentials created by a current flowing in a conducting medium is called a current field. The distribution of the current in such a conducting medium, as well as the potentials created by it, is described by equations similar to the equations of electrostatics, describing the fields of electric charges. Thus, if the dimensions of the electrode and the leak are neglected (they are considered pointwise), then we can assume that in the case under consideration, on the roof surface, under the influence of the current flowing from the excitation electrode to the place of the leak (and further into the conducting substrate), an electric potential distribution is formed similar to the distribution of the potential of the electrostatic field of two point charges. Moreover, the position of one "charge" (excitation point) is known.

The potential created at a point in the medium by the current flowing from the excitation electrode is determined as follows:

φ = φ_0 + I / 2πγ ∙ 1 / R (1)

where R is the distance from the point of measurement to the electrode, I is the current flowing through the electrode, and γ is the conductivity of the medium. Now it is necessary to take into account the presence of the second electrode (leak) using the superposition method:

φ = φ_0 + I / 2πγ ∙ (1 / R_1-1 / R_2) (2)

where R1 and R2 are the distances from the measurement point to the excitation and leak points.

Therefore, by measuring the distribution of the electric potential over the roof surface, it is possible to determine the position of the second "charge", i.e. leaks.

To measure the distribution of the electric potential, a system of point electrodes located at the nodes of a rectangular grid can be placed on the roof. Since the excitation electrode is neither electrically nor structurally different from the measuring ones, the excitation voltage can be applied to any electrode. Moreover, it becomes possible to select the point of excitation directly at the time of measurement, if required by the technique.

Thus, after making measurements, it is possible for each point of the surface at which the potential was measured, to compose the equation (2). Having processed the entire set of measurements, we obtain a system of equations from which the position of the leak point will be found. However, the number of equations in the system will exceed the number of unknowns. Moreover, the quantities included in the equations have certain errors, so the solution will have to be sought using the least squares method.

The least squares method can be used to "solve" overdetermined systems of equations (when the number of equations exceeds the number of unknowns), to find a solution in the case of ordinary (not overdetermined) nonlinear systems of equations, to approximate the point values of some function.

The engineering problem is based on the development of the order of data collection in the nodes of the measuring grid, which allows obtaining the most correct data.

It is necessary to determine the optimal parameter for measuring at the nodes of the measuring grid. The following parameters were investigated as options: resistance, current, voltage potential. As part of the selection of these parameters, resistance and current were discarded, for the following reasons:

The resistance of the medium can vary within a fairly wide range depending on the moisture content of the coating, the thickness of the water layer, and its chemical composition. Moreover, known techniques obtain resistance in an indirect way, for example, by measuring the current through the medium and the voltage drop it creates.

The value of the current flowing through the excitation electrode or the substrate itself carries little information, and can indirectly speak only of the very fact of the presence of a leak (or its absence). Direct measurement of the current distribution in the roof surface is not possible, since it is impossible to allow the flow of current through the measuring electrodes: in accordance with the first Kirchhoff's law, an additional "measuring" current will distort the picture of the current distribution on the roof surface. That is why laboratory techniques for studying the current field in conducting media are based on measuring the voltage drops created by the studied currents.

In this regard, the measurement parameter was chosen - voltage potential, since its direct measurements are possible using simple electronic means. Moreover, the obtained values of the potentials of the roof points make it possible to indirectly evaluate other electrical characteristics, including resistance and current.

Claims (1)

A system for monitoring the tightness of the waterproofing layer of the roof, including a grid of a measuring sensor cable connected to a computing module, which is configured to collect and process the readings of the sensor cable, a voltage source, to one of the poles of which an excitation electrode located on the roof surface is connected, and the second pole the voltage source is connected to an electrically conductive sheet, which is placed under the waterproofing layer, characterized in that a foil roll material based on fiberglass is used as an electrically conductive sheet, while said material makes electrical contact with the wet waterproofing layer of the roof at the leak, the position of which is determined using superposition method based on the electric potential distribution measured by the sensor cable over the surface of the waterproofing roof, the value of the potential at the excitation electrode and the known position in the space of the sensors waste cable and excitation electrode.