A systematic innovation.

The GLD equipment system in detail.

The pig detector

The GLD 202 Leak Detector is in a pressureand explosion-proof housing. It is very compactly built. It works in a wide variety of pipe diameters, adapted by the GLD 303 Chassis. The liquid in the pipeline serves to transport it.

Leak detection is based on an acoustic measurement method. Leaks with a flow of more than 5 litres per hour cause a characteristic leaking noise in pressurized pipelines. The detector searches in the ultrasonic range for this noise. Interference caused by pumps, rivers, road traffic, etc, is recognized by spectrographic analysis and classified as harmless.

GLD 500 Marker

Each acoustic event is identified with a specific location in the pipe. Any unusual noise can be precisely located within a few meters, depending on system equipment. This is done by time and distance measurement.

The system uses detected sources of interference to measure distance. These are used as acoustic waypoints. If the number of existing sources is not sufficient, additional waypoints, the GLD 500 Marker unit and/or the GLD 600 Pig Detector can be used. The markers continually produce a prominent ultrasonic signal, which is recognized by the detector’s electronics.

The pig detector, however, serves two functions. It marks certain points while traversing the pipeline, and monitors the run. With ultrasonics, the pipe is scanned for leak detectors moving past. When a leak detector is recognized, a signal is conveyed to the control room and a marker signal is sent for a short time.

The number of the necessary marker units and/or pig detectors depends on the length and profile of the pipeline. Upward and downward gradients, which affect the running speeds of the GLD 202, can be marked acoustically. It may be necessary to be able to recognize such sections during later evaluation of the recorded data.

The highest location accuracy is achieved by equipping the chassis with the optional odometer wheels. The distance data from the odometer is later matched with the acoustic markers. The marker units can be fastened to threaded pipeline outlets (Thredolets™) with the GLD 510 Marker Attachment. However, the most flexible arrangement is assembly with the GLD 520 Marker Guide Tensioning Band, which allows them to be fastened to nearly any location on the pipeline. The pig detector assembly is held in place on the pipeline with the Tensioning Band.

Step by step to the result.

The operating procedure in practice.

Test detektor GLD 202 Nr. 000

Preparation for a pipeline run begins with putting the GLD 202 Detector into the receptacle of the GLD 406 Battery Charger. Then an electrical connection is made by cable between the detector and charger. Operating voltages of the GLD 202 are examined and if necessary, its batteries are charged. Removing the chassis, or opening the detector, is no longer necessary for charging.

Now the detector is set up with the help of a PC. The parameters for the start and end of data recording, as well as other settings necessary for documentation of the pipeline run, are adjusted. Subsequently, if needed, the protective cap over the plug connection is closed.

Pig Trap

Then the assembly is placed in the chassis. The optional odometer wheels are electrically connected to the detector. These signals are outside the danger zone in a potentially explosive atmosphere. The detector installed in its chassis meets all standards for explosion prevention. After insertion into the pig trap, it is flooded and the journey down the pipeline begins.

Are you on the same wave-length as your leaks?

The functionality of the GLD 202 Leak Detector.

The GLD 202 was developed to use multichannel spectrographic analysis. Leaks in pipelines produce sounds. Depending on the size and form of leaks, whether rips or holes, different pressures, the type of liquid and the temperature , certain sound signatures show up. Past investigations have shown that leaks generally show an increase in volume in the frequency range between 20 and 40 kHz. More exact analyses by the Gottsberg company in real-world operations, as well as extensive tests on our internal test stand, have confirmed these results and led to the following conclusions:

• Other acoustic sources, like pumps, impact or sharp noises, as well as flow disturbances, also produce harmonics in the relevant range.
• Brief events, like transients, may not be recognized when using a measurement window duration of one second.

The GLD 202 allows setting a longer duration than other detectors, and uses various algorithms for multi-channel frequency analysis as well as transient recognition. This makes it possible for it to distinguish mechanical interference from high-frequency leak noises. By using higher resolution in both frequency and time, the GLD 202 is able to make more exact and reliable distinctions between different sound signatures, and so ensure verified identification of leaks.

Numbers, data, facts.

Measurement recording and processing with the GLD 202 Leak Detector.

Signal and frequency analysis

• analog range limits 10-50,000 Hz
• digital sampling rate 128,000 samples per second
• data compression of the relevant measurement data to 1 kilobyte/second
• multi-channel spectral analyses
• Fast Fourier Transform (FFT) from 50Hz-50kHz
• transient recognition with classification, window width 2 ms
• recognition of marker signals in noise
• integral of the energy from 20-40kHz (results like the MLD 201)
  • average value over 1000ms (100 measurements)
  • peak values in 35kHz and 72Hz channels to identify markers
  • virtual marker recognition

Analog measurement processing

Pressure

• recording with piezoresistive sensor
• recording of the pipeline pressure 0 to 80 bar (atmospheres, 0 to 1176 psi)
• resolution 10 bits, < 0.1 bar (atmospheres, <1.8 psi)
• measurement accuracy 1%

Temperature

• temperature of the medium: 0 to 40/50°C (32 to 130-148°F)
• resolution 10 bits, < 0.1°C (0.2°F)
• measurement accuracy 1%

Time

• date and time
• resolution 1 sec

Digital measurement processing

Distance

• counting the signal impulses from the optional odometer
• two separate channels
• recognition of the direction of travel
• resolution <1m (3.3ft)

Battery life

• Monitoring of the charge and discharge, auto-matic switching to sleep mode when batteries are discharged.

Storage of measured values

• Currently on digital camera-type SD (Secure Digital) card, with a capacity limited only by card size (recording duration more than 200 hours)

After the measurement comes the evaluation.

The GLD 700 analysis software.

With the GLD 700 PC analysis software, before a pipeline run the operating parameters are sent to the detector, and after the run the stored data are selected, converted, and prepared for graphical evaluation.

Parameterization of a pipeline run

Different parameters for the starting and stopping conditions, as well as documentation of other run parameters, such as “run number” and “pipeline number”, can be set. The exact wheel diameter of the odometer is entered.

Preparation of pipeline run

All parameters that are set can be printed as documentation, and stored as a standard parameter set.

Graphical evaluation of data records

The data record can be displayed as an overview of the entire run, or in detail. All measured values such as leak, pressure and distance are shown both graphically and numerically.

Search algorithms for distance, marker and leak intensity, as well as others, allow you to seek out interesting ranges in the data record. The data record can be corrected and optimized by special features. Also, ranges at the beginning and end of the data record known to be of no interest can be eliminated.

Marked ranges of the data record can be printed or optionally exported as a text file, where the data can be processed with other programs. The battery discharge curve shows the change in capacity over time. So the correct time to recharge the batteries can be determined, and pipeline runs with weak batteries can be avoided.

The graphs for pressure, speed and odometer, and the search thresholds for leaks and markers can be suppressed for greater clarity.

Graphical evaluation - Overview

Self-checking

Before each pipeline run, a self-test of the unit can be done to guarantee correct functioning. The results of the test can be printed as documentation.

Creation of reference lists

Reference lists can be added, containing the different types of waypoints and their distances to the starting pig trap. These are also used to automatically compute all distances in the data record.

Graphical evaluation - Detail

Comparison of two data records

To compare two data records with each other, they can be displayed horizontally, one above the other. Noises of interest observed from run to run can be further analyzed and their positions better determined. Search algorithms can be used on all of the data graphically displayed in both data records.

Diagnostic tool

Diagnostic Tools

Unusual noise events can be more closely examined and evaluated with special diagnostic tools. These tools simplify leak detection and lead to more certain results.

Features

• Detector setup
  • Input of run parameters for documentation, such as pipeline number, sequence number, date, and time
  • Input of starting parameters to define the beginning of recording, such as date, time, pressure, or position (reset distance)
  • Eingabe von Stoppparametern zum Beenden der Aufzeichnung wie
  • Input of ending parameters for terminating the recording, such as running time, pressure, noise intensity, or duration of noise intensity
• Transfer of the data via USB cable
• Graphical evaluation
• Variable display width
  • Summary presentation of the entire run
  • 10-minute blocks (resolution 1 second)
  • Change between the two displays by mouse click
• Bars showing location within the run, for orientation in the entire data record
• Fast location of relevant points by mouse click in the overview, or by search function (marker, time, distance, etc.)
• Marking and printing individual data
• Automatic distance correction on the basis of a reference list and noted markers
• Inserting the distance measurement when used without the odometer
• Distance correction / setting zero point distance
• Comparison of two data records with the distance measurement as the reference point
• Cursor control of the comparison — independent or combined
• Finest resolution in the normal display: 1 second
• Display of peak and average values in the ultrasonic leak range, as well as peak value of the marker frequency in a bar graph
• Display of pressure, temperature and speed in a line graph
• Further detailed diagnosis with tools for digital signal analysis and processing
• Menus and online help in English, German or Italian; other languages available on special order
• Detector self-test
• Online assistance

It runs and runs and runs...

The GLD 303 Chassis.

GLD 302-700

The GLD 202 Detector can be used in pipelines with an inside diameter of 200mm or more. The original MLD Chassis is made from a special electrically conductive plastic. In recent practice a new model made of durable stainless steel has worked better: The GLD 303 chassis.

Fahrgestelle

Features

• Easy installation and removal of the detector in the chassis
• Reduction of flow noise and impact sound transmission, therefore less background noise, so leak and marker sounds can be recognized more clearly
• Basic parts of stainless steel make easy repair and refitting possible by welding
• Computer-aided development and production methods make it possible to adapt each chassis to special pipeline conditions
• Optional 3rd and 4th level wheels
• Retrieval grips and impact protection make operations easier for your technical personnel
• Explosion protection according to ATEX, Directive 94/9/EG and the relevant EN standards
• Plastic version certified for Zone 0
• Stainless steel version certified for Zone 0

From good to better.

The GLD system on the test rig.

Previous experience is not enough for new innovations. Tests and measurements on our inhouse test rig are essential.

	Adjusting the test pressure
	Closing the test rig
	Hydraulic test unit