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Electronic leak detection equipment
Development of flat roofing technology, products and construction techniques has improved massively in recent years and although a flat roof is now unlikely to leak due to poor design, construction or sub-standard materials, the nature of a flat roof makes it more susceptible to damage from external factors, and locating exactly where a leaky roof has failed has always been difficult to pinpoint - often resulting in the premature replacement of the entire flat roof covering; rather than pinpointing and repairing localised damage.
Flat roof leak detection guidance
Flat roofs can develop leaks for a variety of reasons and at any point in their lifespan. Workers can accidentally (and unknowingly) pierce a roof’s waterproof membrane even before construction is completed. Extreme weather, debris, and a variety of other factors can all conspire to create leaks. These leaks are often too small to spot with the naked eye yet, if left, can cause substantial damage to a building’s structure in no time at all.
Detecting and repairing leaks in flat roofs at the earliest opportunity simply makes sense; especially as Buckleys’ range of flat roof leak detectors offer a simple and easy-to-use way of quickly locating leaks.
Nowadays the vast majority of flat roofs are constructed from electrically conductive materials such as steel or concrete and many have a foil-faced insulation layer directly below the surface membrane. Buckleys’ leak detectors use the conductive properties of these materials to locate faults by passing current through defects to earth.
We offer two types of leak detectors; one which detects leaks in dry conditions and one which detects leaks in wet conditions. Both detectors are supplied as complete, comprehensive kits; providing the user with everything required to test for leaks.
Testing Wet Roof Surfaces
The Wet Roof Pro’ has been designed to locate leaks on flat roofing systems which incorporate dielectric membrane overlays such as single-ply, asphalt, bitumen and liquid applied roofs.
The Wet Roof Pro’ uses the conductive properties of water (from either rainfall or a hose) to pinpoint leaks.
The kit comprises two main elements; a generator unit and a detector unit. The generator unit creates an electrical field across the roof surface via a ‘boundary wire’ which is positioned around the perimeter of the test area and connected to the positive terminal on the generator unit. The negative terminal is connected to a suitable earth on the building’s structure.
Leaks in the roof membrane allow water to penetrate to the building’s structure; creating a short circuit. The detector unit is connected to two hand-held test probes which are held in contact with the roof surface.
By measuring the voltage differential between the test probes, the detector unit is able to direct the operator to the location of the leak.
Principle of operation
The generator of the Wet Roof Leak Detector delivers a stabilised low frequency pulse. The negative output of the generator is applied to the trace wire which borders the test area, whilst the positive output is connected to a suitable building substrate. If moisture has penetrated the membrane or coating of the roof within the test area, a current will flow from this source point, via the moisture on the roof towards the trace wire. The detector is used to identify the direction of electrical current and detect the point of origin (ie where moisture is penetrating the roof covering).
The generator is powered by rechargeable batteries which are included in the kit, along with a charger.
Both units feature automatic shut-down when left unused for a prolonged period of time.
Method of testing
The test procedure is performed within a test area, created with stainless steel wire, which must be in good contact with the wet surface. If necessary, weights or adhesive tape should be used to hold the wire in position and the ends of the wire must be clipped together to form a closed circuit (ring). Any areas which protrude from the roof must be screened off by using an additional loop of wire, which in turn must be connected to the main border.
Test electrodes are supplied in three parts which can be put together easily on site to form two probes (poles). These are connected to the small detector unit with the red and black leads supplied.
A suitable mechanically-fixed earthing point should be located on the building. Using the crocodile clip, the 10-metre lead (with red plug) should be securely attached to the earth point whilst the other end is connected into the positive (red) socket on the right hand side of the generator unit. The black plug on the other connecting lead should be fitted into the negative (black) socket on the generator unit with the crocodile clip attached to the trace wire. The clip must be positioned to clamp together the free end of the trace wire to the section of wire emerging from the reel to complete the loop around the test area. The generator unit should now be switched on.
When the detector unit is switched on the unit will self-calibrate ― it is important that the probes are not in contact with the test area at this point. The red probe should be held in the right hand and the black in the left, making sure that the leads do not cross over. Inside the test area, the probes should be positioned a distance apart either side of the body in contact with the wet roof. When the generator pulses the bar graph on the detector unit will show the direction of the fault. Starting at the edge of the screened area, re-positioning the probes and watching the detector will locate the direction of the fault (right or left). The search is continued in the direction of the pulse until the reading swings the opposite way. At this point, if the operator turns 90 degrees and repeats the procedure a crossover point can be reached to locate the source of the leak.
Wet Roof Pro’ (Ref: WRP01) comprises:
- Generator unit
- Detector unit
- 10m earth lead
- 10m boundary connection lead
- 2 x multi-section test probes
- 200m stainless steel boundary wire on a reel
- Red and black test probe connecting leads
- Batteries and battery charger included
- Black carrying bag for generator unit
- Adjustable neck strap for detector unit
- Comprehensive instruction manual
- Complete in robust carry case
Testing Dry Roof Surfaces
Buckleys roofing test kits have been used for many years to locate leaks in roof membranes.
The PD Range of pinhole/holiday detectors can be used to find faults in non-conductive roof membranes with great success.
The PD 130 Holiday Detector (PD30R) is recommended for roof membranes as it can test thicknesses between 16 microns and 14.4mm. The PD 240 Holiday Detector (PD40R) will test roof membranes from 64 microns to 25.6mm.
Principle of operation
The earth lead from the PD unit is connected to a convenient earth point on the structure. A high voltage ― calculated against the membrane thickness ― is applied (using an electrode) to the dry surface of the membrane.
When there are no faults present the membrane acts as an insulator by stopping the flow of current out of the PD unit. When the electrode passes over a fault or hole, the high voltage jumps the gap between the electrode and the water (or conductive layer) under the membrane, causing a current to flow. The audible and visual alarm on the PD unit will alert the operator, who can then mark-up the points in need of repair.
Two types of electrodes are recommended for testing; a phosphor bronze brush for uneven surfaces, or a special roller for large smooth areas.
Buckleys PD30R and PD40R Roof Testing Kits comprise:
- Detector unit
- Battery charger and rechargeable batteries
- Shoulder bag
- Test probe handle
- Coiled interconnecting lead
- 5m earth lead
- 50m earth extension lead
- 2 x 460mm extension rods
- Electrode shoe
- 450mm phosphor bronze brush electrode
- Drum brush electrode
- Pointed probe
- Test voltage calculator
- Robust high-visibility carrying case
- Comprehensive instruction manual with calibration certificate
Method of testing
A suitable point on the structure should be identified as an earth connection for the earth lead of the pinhole/holiday detector.
Following the instructions in the operating manual of the PD unit, the output voltage should be set according to the calculation made using the formula shown above. The earth lead and test probe handle should be connected to the PD unit whilst the unit is turned off.
The other end of the earth lead should be attached to the earth connection point of the structure ensuring that a good electrical contact has been made.
With the PD unit still turned off, extension rods should be connected to the test probe handle. Using the shoe attachment, a suitable electrode should be attached to the opposite end of the extension rods. Any electrode used must be in good condition as a damaged one will not make full contact and faults could be missed.
The operation of the pinhole/holiday detector should be checked by touching the electrode onto the substrate. The audible alarm should then be activated, but if not, the lead connections should all be checked. Sometimes it may be necessary to adjust the sensitivity control on the unit. Reducing the setting will make the unit more sensitive, while increasing the setting will make the unit less sensitive.
The electrode should be passed slowly over the membrane surface at a maximum rate of 100mm per second, paying particular attention to edges, holes and irregularities in the coating. The test voltage may need to be reduced to test the edges as the coating may be thinner.
When a fault is identified by the detector, the electrode should be moved sideways in order to identify the precise location of the problem. All faults should be ringed with a suitable marker so that repairs can be carried out at a later date. The identification of the fault should be far enough away from the defect to allow the repairs to be made without covering the markings, as the substances contained in some markers can affect the adhesion of the repair material.
Testing should be continued across the complete surface and all faults marked. Damaged areas should be re-tested after repairs have been carried out.
Criteria for successful testing
There are a number of criteria that need to be met for successful detection of membrane faults:
- The test can only be carried out on roof membranes which have a conductive substrate (aluminium foil, concrete, brick, steel or water etc).
- The surface must be dry when the testing procedure is carried out. As water is a conductor of
- electricity, it would be impossible to find faults in a wet surface.
- The membrane material must be able to withstand the test voltage ― testing a sample laid on a sheet of metal would confirm this (see below).
- The thickness of the waterproof membrane must be known so that the test voltage can be calculated.
Testing a sample
A sample of material of uniform thickness (approximately 30cm square and less than 2mm thick) should be laid onto a metal sheet. Whilst the pinhole/holiday detector is turned off, the test probe handle (fitted with a pointed probe electrode) and earth lead should be connected to the unit. The other end of the earth lead should be attached to the metal sheet.
With the output of the PD unit set at minimum to start with, the probe should be placed onto the membrane surface. The high voltage output should be turned on and slowly increased until the material beaks down and activates the alarm on the holiday detector, or the output reaches maximum. The electrode should then be lifted off the surface and the output voltage shown on the PD unit which caused the material to break down should be noted. The process should be repeated a number of times on new areas of the sample, allowing at least 20mm from any previously used areas, noting the break- down voltage each time
A calculation should be made to find an average of the voltages. The dielectric strength of the material would be approximately 75% of the average of the voltages. If the material will not break down, the thickness of the membrane material should be reduced by half and the above processes repeated. The results obtained can vary from 8kV to 40kV per mm.
For a material to be tested using high voltage, its dielectric strength must be greater than 4kV per mm and preferably 8kV per mm. The greater the dielectric strength the less chance there is of making a fault during the testing process.
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