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Frequently Asked Questions

Frequently Asked Questions

Below we have answered some Frequently Asked Questions (FAQ) for the SewerSerpent® technology. Please check back as we add more information or contact us for specific questions.

1       System Components

1.1    What are the key components of the system?

Serpent Cable Reel (SCR) with cable and Scan Head, Serpent Control Unit (SCU), Serpent Scan Centre (software than runs on user supplied laptop) and Ancillary Items: cables, connectors & earth stakes

1.2    Is a Pipe Stopper Required?

It is recommended. The pipeline must be filled with water to complete a scan. An inflatable pipe stopper or similar is recommended to for rapid and simple blocking to enable filling the pipeline.

1.3    How heavy is the SewerSerpent225™?

Reel with cable and Scan Head is approximately 25kg

1.4    What are the standard cable lengths?

A. Standard cable length is 75m for SewerSerpent 22®. The system and software is capable of a 75m scan.

In practice, some additional cable is required to reach the start position in the pipe, so depending on where the Serpent Cable Reel is positioned scan length is less than cable length.

1.5    Are different cable lengths available?

It is possible. Custom-engineered units can be provided.

1.6    What is the battery life?

7 hours of continuous discharge when full.

1.7    How long does it take to recharge the battery?

An overnight charge will give a potential 4h 30mins of continuous usage.

1.8    Is it possible to exchange the scan head between each unit?

The current version does not have this capability.

1.9    Does the unit come with a sonde for tracing the cable?

The current version does not have an integrated sonde. A portable sonde can be used with the system. 

2       Technical

2.1    What voltage does the SewerSerpent225® operate at?

The Scan Head output voltage meets AS3000 Wiring Rules Section 1.4.98 for Extra Low Voltage (ELV). The voltage does not exceed 50VAC or 120V ripple-free DC. No special precautions need exist as this voltage is “safe to touch”.

2.2    Is Extra-low voltage safe for the user?

The voltage does not exceed 50VAC or 120V ripple-free DC. No special precautions need exist as this voltage is “safe to touch

2.3    Does the unit come with a GPS?

There is a GPS installed in the Serpent Control Unit (SCU) and this data is recorded for each scan.

2.4    What is the accuracy of the GPS?

Approximately +/- 5 meters. All GPS accuracy depends on the satellites in view and other conditions such as obstruction by buildings or trees.

2.5    Why must the Scan Head be submerged in water?

The water around the Scan Head provides 'electrical contact' between the scan head and the pipe walls. This ensures there is a path for the ELV signal (electric current) to flow out through defects in the pipe walls.

When the Scan Head is near a defect a small amount of current flows from the head out through the defect (via the water) and through the ground back and is detected by the Serpent Control Unit.

2.6    Does the resistance of the soil have an impact?

Basic circuit theory tells us that if you add more resistance to a circuit then less current will flow. Similarly, if the soil around the pipe being scanned has a high resistivity, then less current will be able to flow back to the Serpent Control Unit.

Different soil types have very different electrical resistivity, and the range of variation is quite large (e.g. alluvial soil might be 10Ωm, while sandstone might be 10,000Ωm). SewerSerpent® has been designed to cope with this variation by automatically adjusting sensitivity for different soil conditions.

2.7    How close does the earth stake need to be to the pipeline?

The distance between the pipe and the earth stake itself is not critical, and the limiting factor may be the length of leads available.

The earth stake should be placed within approximately 50m of the pipeline. Where it is difficult to place the earth stake, (particularly in built-up environments), there may be other ‘opportunistic earthing’ alternatives, for example, roadside barriers & signage, that can be used. The SewerSerpent® earth can safely be connected to water pipes and any other ground connected infrastructure.

The most important aspect of the earth stake is that it provides a “good” earth, that is, a low resistance path for the test current to return from the soil to the Serpent Control Unit.

The target earth stake resistance should be less than approximately 5kΩ, which is generally achievable with a shallow electrode (20cm) depending on the soil resistivity. Simply wetting the area around the earth stake with water can lower the earth stake resistance, but the SewerSerpent® will operate at reduced resolution with higher stake resistances.

2.8    Does SewerSerpent® Indicate the Size of the Leak?

There is a relationship between the size of defects, and the amount of current that is detected by the Serpent Control Unit. Skilled operators will be able to characterise defects from the raw traces during a scan to prioritise remediation works.

The relationship is complex and depends on factors such as soil resistivity, and nearby conductive infrastructure. In a similar way that mobile phone signal strength does not directly tell you how far away from the tower you are in areas of ‘patchy reception’ where other factors such as shadowing from mountains or buildings is important, the amount of current that is detected by the Serpent Control Unit may not have a strictly direct linear relationship with the size of a defect in a pipe.

The relationship will be further investigated in future developments, and automated features to determine defect sizes or flow rates may be included once reliable algorithms are developed for the characterisation of defects from the raw test signal traces.

2.9    Does SewerSerpent® Detect Every Leak?

If water leaks from the pipe, then electric current will also leak and be detected by the SewerSerpent®.

The minimum detectable fault has been rested to be better than 1% of the pipe diameter.

While no test is infallible, when the correct test method is used the SewerSerpent® provides a reliable, objective measurement of pipe condition which can locate defects that you may not even be able to see.

2.10  What is the Accuracy of the Sab Head Position?

 Scan head position accuracy has been tested to be better than 1% of distance travelled. i.e. for a 60m scan, the position shall be accurate to within 60cm.

3      Serpent Scan Centre

3.1    What operating system can be used for the Serpent Scan Centre?

Microsoft Windows 7 and later. Other operating systems are not supported at this time.

3.2    Is there a licence required for the Serpent Scan Centre?

No. It is available to all users of SewerSerpent22® for management and reporting of SewerSerpent® scan files.

4      Robustness & Reliability

4.1    How Robust is the system?

Extensive robustness testing has been successfully conducted including:

·         Water ingress protection (SCU, reel and sensor head)

·         Button/overlay longevity (SCU)

·         Connector & cable robustness (SCU and reel)

·         Electronics survivability from general use and transport (SCU, reel and sensor)

·         Thermal shock etc. (SCU)

·         Robustness of spring/hose assembly from tension/compression/torque, in use and transport

·         Robustness of cable termination assembly at the probe end.

Like any electronic equipment the SewerSerpent225™ should be treated with appropriate care.

4.2    What is the required maintenance / calibration?

Earth Check and Pipe Check are standard procedures before scanning a pipeline. There is no other calibration required.

Verification that the SewerSerpent® is operating correctly can be achieved by scanning a pipeline with known fault locations. UVS can provide this service if required.

Recommended maintenance includes cleaning, protecting the earth stakes/clamps from corrosion, packing the cable neatly on the reel, and battery recharging.

4.3    Are spares parts available through the service centres?

All spares parts are available including: Reel with cable and Scan Head, Serpent Control Unit (SCU) and Ancillary Items: cables, connectors & earth stakes.