• ZCorr DCL’s are locally intelligent. They feature auto-power management (have no on/off switch) and never require user intervention.
• The ZCorr system features both overnight and short-term deployment modes. The user can select recording times and intervals best suited for the pipeline environment.
• Downloading the data from the ZCorr logger to the computer is fast via the USB port.
• ZCorr is fully upgradeable through software, making the latest technical advances available to all users.

The ZCorr Concept

The ZCorr system is a flexible leak detection tool that allows a distribution system leak detection program to be efficiently managed and directed from the office or the field, integrating leak detection data, maps, and database tools to:

1. Plan the deployment and print deployment orders
2. Place the loggers on a map image

The ZCorr survey has 3 steps: DEPLOY, RETRIEVE and ANALYZE. Each step can be performed either in the office or in the field.

1. Deploy

Up to eight ZCorr loggers are held in a compact docking station, connected to a PC via a USB cable. The PC communicates with the ZCorr logger through the docking station electronically, without cables.
Using the ZCorr software the user:

• Sets the synchronized recording times
• Places the loggers on a map image
• Optionally prints a deployment work order

The ZCorr loggers are then deployed in the field, usually on valves or hydrants.

2. Retrieve

The synchronized ZCorr loggers record at the user-programmed times. Recorded vibration samples are saved in memory. The loggers then enter low-power mode until they are reconnected with the docking station.

3. Analyze

The recorded data is downloaded from the ZCorr loggers via the docking station to the PC. ZCorr analysis finds all significant leak noise correlations automatically. The results are ranked by Correlation Score (0 – 100) based on the determination of leakage versus usage, correlation signal quality, and the smallest estimated error in pinpointed location of any leak(s).

How ZCorr Loggers Work

The ZCorr system has several patented¹ innovations, described in the next sections, areas of synchronization (timing), data recording, processing, and PC software analysis.

Real-Time Clock

At the heart of the ZCorr logger is an ultra low-power, temperature-compensated Real-Time Clock (RTC). ZCorr's patented method of timing compensation restricts errors in leak location to typically less than 3 feet.

Recording

The ZCorr logger is fitted with a low-noise piezo-ceramic acceleration sensor, known as an accelerometer. Accelerometers sense vibration and convert it to a tiny electrical charge. Sensitive conditioning electronics amplify and filter this electrical response. As with audio and other amplifiers, the accuracy, precision, and intrinsic noise level of the amplifier is more important to the recording quality than the gain or volume level, per se. In an accelerometer, intrinsic noise is often defined by resolution and gain is referred to as sensitivity. In ZCorr, a sensitivity of 1V/g at a resolution of 0.025 µg /vHz is followed by additional electronic gain. The earth´s gravitational field is defined as having a constant acceleration of 1 g. In contrast, leak signals are sensed from pipes as a varying pattern of acceleration as small as µg´s, i.e. millionths of g´s. These are imperceptible levels of vibration to humans and require very low-noise, precise electronic amplification and filtering to preserve the leak signal. In addition, in a correlating logger the sensor is positioned very close to the logger´s electronics. Most realtime correlators can advantageously separate the sensor and recording electronics by a long cable. To overcome this potential interference problem, the ZCorr logger uses a custom-designed discrete amplifier and filter circuit, integrated very closely with the sensor.

Digitizing of the analog signal is performed with a 23-bit ADC. Most acoustic loggers use between 8 and 12 bits, allowing a digitizing resolution of between 1 part in 256 and 4096.

Vibration signals on pipes have a useful dynamic range of up to 80 dB, i.e. one part in 10,000. A 23-bit ADC, with a resolution of 1 part in over 500,000, is therefore adequate and necessary to preserve the fine detail of pipe vibrations and the leak signal.
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¹ U.S. Patent #6,567,006

Data Processing

After digitizing, the pipe vibration signal is encoded and saved in low-power memory. The ZCorr data processor is programmed to employ special encoding techniques in different situations. For example, different pipe materials (plastic, cement or metal), large-diameter pipes, and long distances between loggers (with the presumption of very small leak signals), are all situations where the encoding is set to enhance the leak acoustic signature.

Data Downloading

Data is downloaded to a PC via the ZCorr docking station using the USB port. A waterproof connector facilitates a high-speed data link between the logger, docking station and PC. This is the final link in the chain of high resolution recording, processing, and data transfer for correlation analysis.

ZCorr Data Analysis

ALFA Optimal Correlation

ALFA™ (Automatic Leak Frequency Analysis) is an advanced leak noise correlation method developed by Flow Metrix. ALFA works by identifying an acoustic leak signature between two loggers. The leak sound may be very different between the two loggers, both in sound level and frequency pattern, and is often not audible or otherwise discernible to the human ear. The ALFA process identifies the acoustic signature of the leak sound at each logger and designs an optimal correlation filter that is unique for that recording. The ALFA filter concentrates on the leak sounds and discards other vibrations, for example those due to normal flow, transient usage, and environmental sounds such as traffic.

Data Management

The ZCorr PC software includes an integrated Data Manager module that:

• Stores an unlimited number of ZCorr recordings in a database
• Provides typical database functions, such as searching and sorting
• Can export recording information to other software programs

Financial Benefits of a ZCorr Leak Survey Program

• 100 miles of mains pipe
• 10,000 service connections
• Daily production of 4 million gallons
• Unaccounted for water of 15%

Using the Flow Metrix Water Loss Calculator software program ², approximately half of unaccounted for water (UFW) is likely to be recoverable leakage (the remainder is due to meter error and un-metered or unauthorized usage). Recoverable leakage is expected to be 312,000 gallons per day, with 4 mains leaks at 30 gallons per minute (gpm) and 15 service line leaks at 6.5 gpm.

Eight ZCorr loggers deployed overnight at spacings of 1,000 feet will survey an estimated 2½ miles of pipe. This pipe mileage includes lateral mains and services that convey leak sounds to the loggers. The operational expense is calculated for one leak detection crew for 3 hours, at a total cost of $100 per hour. The end distribution system is surveyed in 44 nights. The value of lost water is taken to be $1.50 per thousand gallons.

The chart below shows a benefit of over $170,000 per year, with a total cost of $17,700 , i.e. an annual crew cost of $13,200 plus the ZCorr equipment cost amortized over 5 years ($4,500/year). The financial benefit of recovered leakage pays for the entire leak detection program and generates a considerable surplus to invest in other operations and maintenance activities.