- Locating Missing Manhole Covers
- Locating Missing Manhole Covers - Part 2
- Urban Gas Pipeline Defects and Gas Leaks
- Finding Pipe Joints in Cast Iron Gas Pipes
- Pinpointing Small Pipeline Faults
- Locating Deep Sewers
- Water Leaks From Plastic Pipes
- Internal Water Leaks and Pipe Bursts
- Using A Pipe and Cable Locator
- Cable Sheath Fault Location
- Avoiding Site Stupidity
- Cable Fault Location
Barney’s Blog No 11 - Become An Expert At Avoiding Site Stupidity
For more than 35 years, as part of a safe system of work on construction sites, in the street, or anywhere excavations are planned, it has been obligatory to use a cable locator to avoid damage to buried cables and other utility lines.
Before that there was only the simple "hum detector" type of cable locator, and this was unable to detect cables that were not carrying current, perfectly balanced, or pot-ended. Unfortunately, street works excavations often encountered these, and serious accidents resulted in several fatalities; also the simple "hum detector" had a nice pair of headphones to provide audio response to signal, and if broken or missing, the equipment was of no use.
In 1978 Electrolocation Ltd introduced the Cable Avoiding Tool. This commercialised the use of a pair of horizontal antennas, improved resolution for power frequency signals from current carrying cables and introduced the radio frequency method for detecting cables and pipes that might not have a detectable power signal. The CAT's strong polythene casing enclosed the aerials and electronics, and no headphones were necessary as the audio response was through a detachable loudspeaker.
The Health and Safety Executive produced a useful public information film "Alive or Dead?" to promote site safety and cable damage avoidance. The film showed the dangers of a cable strike by using a dummy dressed for a construction site and operating a jackhammer. The dummy was set on fire by the cable strike explosion. As a CAT was in use on site and the commentary ran to the effect that "most cable locators, unlike this one, do not detect cables that are not carrying current."
This statement was not totally true, but any contribution to improving safety should be welcomed, and the CAT and later the CAT and Genny transmitter were welcomed in quantities into the back of any contractors van.
The contractor became familiar with "waving the CAT about" and if they were well trained and also used a Genny correctly with the CAT, they would succeed in finding streetlight cables and other cables without current flowing. As the early Genny transmitter models also had a metal location mode for finding buried covers, the whole equipment was handy and useful to solve every day locating tasks.
However, when the CAT2 and Genny2 model was introduced, the CAT became shorter and lighter, lost the spare set of batteries, and the Genny also became smaller, and used a smaller wound ferrite coil for transmitting induced signals instead of the large open copper coil of Genny with metal detection. And the metal detection mode was no longer available, so users had to purchase a separate metal detector.
When Radiodetection introduced the C.A.T 3 and Genny 3 models in 2004 they added an extra detection method, the Avoidance mode. This combined the Genny detecting mode with power and radio, so the contractor could now trace the Genny signal on a chosen pipe or cable and also detect other nearby metallic lines simultaneously, helping to make excavating safer. If the contractor is interested to locate and pinpoint the other lines, there are methods using the Genny to eliminate the original line and determine the other ones. Once again the operator needed to have training and competence.
The other useful innovation was "Strike Alert". This system produced a warning warble if a cable or other metallic line was less than 30cm deep, and worked in Power and Genny detection modes, it was available whether or not a V version with a visual LCD display was specified, or the top version CAT3 Plus that also provided depth when Genny mode was used.
The Genny 3 had a switch to choose between a continuous or traditional pulsed signal, the main advantage of this was that the batteries lasted longer with pulsed signal, and the continuous signal was better for depth with the CAT Plus models.
Both CAT3 and Genny3 were now powered by easily available D cell batteries, and the CAT no longer had capacity for a spare set of batteries unlike earlier CAT 1 models
One of the concerns, apart from operator competence, is that the locator is actually working properly, because if the locator is switched on and does not detect anything, it could suggest that there is nothing to detect (apart from non-metallic services of course) or the locator has broken down; for this reason the locator manufacturers encourage annual calibration and performance verification, and provided a calibration certificate valid for a year. It is a nice money-earner for the manufacturer and gives the client peace-of mind. But we all know that the certificate is OK, but what happens to the equipment on site is never predictable.
SebaKMT produced the Easyloc locator system from 2006, and this incorporated a calibration check system. This checked the electronics and antennae both individually and together and gave the results on the LCD display as "OK" or an "ERR" error number to indicate the fault. As the operator could check the receiver at any time, and also check the receiver with the transmitter, the function, depthing and performance could be verified without the need to send the equipment to manufacturer. If the receiver was attached to PC, the total running time could be displayed (proving that the receiver had been used, but not exactly when) and any specific user settings could be changed.
Another concern from the employer's safety adviser's side was to verify that the locator was used, and when it was used. Radiodetection produced a small number of special RD432 PDL4 locator receivers for USA telecoms that incorporated early GPS and clock. The equipment was very expensive and suitable for surveying engineers, and crucial for winning expensive US legal cases and insurance claims for disputes against costly 3rd party fibre optic cable damage.
The first commercial manufacturer with datalogging and a date/time clock was Metrotech with the i5000 locator system. This was built for the underground utility survey companies, and if the GPS option was included, verified the operation time, general locate position and depth also possible signal distortions and accuracy – but again designed for surveyors and less suitable for the rough and tumble of construction site usage.
Metrotech also provided a logging software "My locator" and the main application of this was to provide a record that the survey company had performed a defined locate job, as the operator opened a "ticket" for the job as he started, and closed the "ticket" at the end of the location job. When the locator was connected to PC/server the tickets were updated, and the survey controller had complete job information.
The EziCAT locator system produced by Cable Detection, introduced a datalogging locator for everyday site use, with Bluetooth to download the saved logs. The system saved usage duration, time and date in each detecting mode. So for the first time it was possible with i600, i650, i750 and above versions to verify that the locator operator used their equipment. Additionally all the versions included Self- test/calibration check for both receiver and the transmitter, and the receiver display showed a spanner when calibration/service was due. The benefit to the operator was to see that the equipment would function correctly, and to the employer that the equipment had been used to carry out location work in each of the operating modes.
After 8 years producing the CAT 3 series, Radiodetection improved it with the CAT4 series.
For the CAT receiver they changed the Avoidance mode so that each mode is audible, and now included the option of datalogging, (eCAT4) so that usage information could be transferred to PC via a USB cable. To ensure that the user holds the CAT upright and does not "wave it about", its tilt sensor and the datalogging records misuse, and sounds a warning.
As management benefit the datalogging download was quick and easy, but the CAT Manager software has to be purchased and registered.
Extra and useful location problems that it could solve was the difficulty of locating small, short wires, such as telephone drop wires and streetlight cables from concrete streetlight columns. The Genny detecting mode now had the ability to detect high frequency 131kHz and well as the usual 33kHz – Using higher frequencies makes it easier to locate small diameter wires – and the Genny 4 transmits both 33kHz and 131kHz frequencies when connected to a line (but unfortunately not on induction). The benefit now is that if the connection cable (red lead) is wrapped around a telephone pole or the cable guard of a power pole and even the exposed end of a cable, there will be sufficient signal for the "wrapped" signal to transmit and enable the CAT operator to locate the cable. Previously it was necessary to use a very large and quite expensive signal clamp for this application.
The Genny 4 also has a "boost mode" when it outputs higher power, but with sacrifices in battery life – so the signal on a small cable can go further than before.
But, as before, the equipment needs to be "calibrated" once a year, but this can be done online by an operator using the CAT manager software and purchasing a calibration certificate – obviously a continuing benefit for the manufacturers!
The continuing expense of sending away the equipment for annual calibration was addressed by C-Scope when they introduced their CXL and DXL Cable avoidance tool models. Providing the aerials were well installed, and did not get damaged and the receiver used digital circuitry, they reasoned that future calibration was not necessary. But if there was a problem, it just would not switch on, and would have to be sent for repair.
The early models have 4 detection modes, Power, radio, transmitter and avoidance with or without depthing, and also had datalogging option with the locating information transferred by Bluetooth to free management software.
Recent improvements are introduced with the CXL2 and DXL2 models; they provide the dual frequency transmitter mode 33kHz and 131kHz, and the same cable wrapping ability as the Genny4. When datalogging is specified, the management software is a free download, and data transferred by USB cable – more quickly than Bluetooth version. One useful feature carried over from previous model, was the use of AA batteries and space for a second set of batteries in the receivers.
These new models also perform a self-test/calibration check every morning on start- up (and with models with datalogging record that it was done)
So the locator manufacturers have addressed many of the everyday locating problems and so after proper training can an operative be competent at avoiding site stupidity?
One of the problems on a new site is the new cables. These cables have been laid, backfilled or just covered over and are waiting testing and connection to put them into service. As we all know, cables that don't carry current can't be detected in power mode, and furthermore, if they are not connected to ground at both ends they will not carry the radio signal. So the site operative provided with a C.A.T alone will have no chance to detect them!
As there is a general trend to use the smallest and cheapest cables possible, usually a 3 phase system uses 3 individual cables for each phase, instead of the older
method using one single 3 or 4 core cable. So to have successful location the operator needs at least a transmitter with adequate power and higher frequency and connection to the cables at one end. This will enable successful tracing and locating and the 131kHz cable wrapping method is useful.
However, if the ends are not available and isolated from ground the only way to locate them will be to use an induction method - transmitter and receiver search, and to have successful results high frequency is required. Presently the locator manufacturers do not have this on their lower cost locator transmitters, and operatives will need to use the transmitters from higher specification locator that have high frequencies of 65kHz, 83kHz and 131kHz with lower spec receivers.
The higher frequencies are also helpful to locate small cables with metallic content such as telephone drop wires and CCTV and fibre optic cables with metallic content.
So it follows that using a newer type of locator successfully will avoid most site stupidity, but the usual locator will only find conductors – metallic lines –and non- metallic lines such as fibre cables, polyethylene water and gas pipes, drains and ducts will need a different approach.
Ducts and drains are easy enough – add a drain sonde to the standard kit, push it through the drain with standard drain rods or continuous fibreglass Flexrod, and locate it on the surface. Even smaller diameter pipes are also possible, provided that access is possible and they are not charged with gas or water – use a flextrace – very small sonde on the tip of fibreglass rod, powered by locator transmitter...but if the end of the pipe is not accessible, then the solution may be Ground Penetrating Radar.
GPR used to be very expensive to either purchase or hire with operator, and the operator probably had a Ph.D. after their name and was a member of the time team or worked with the police to discover missing persons. Results were difficult to interpret, and if the ground was wet the high frequency radar impulse was absorbed and no useful result was provided.
Now there is a new simplified GPR system from Pipehawk, the E-Safe. This has been designed for use by non-GPR specialists and uses a simple "traffic light" coloured display to provide a warning of the likely presence of services as it is wheeled across the area for exploration. If there is a high likelihood of a buried object close by is indicated by a red line, a moderate or cautionary likelihood is indicated by yellow line, and areas of low likelihood are indicated by green band. The width of the line displayed varies and provides a helpful indication of the target size. The rotation of the E- Safe unit's wheels moves the display's cursor up or down the screen, so it's easy enough to centre up the red line and mark to position a buried line.
As E-Safe does not indicate the direction like a normal cable locator, operator needs to make several traverses across the area and join up the markings to provide line direction. E-Safe does not give a traditional depth indication, but instead provides a 4 tier depth masking function which gives the operator a means to determine a relative depth for a detected object of interest (near surface, shallow, middle or deep).
For those needing more accurate means of determining line and depth of service, a different viewing screen is also available as an upgrade option that uses the traditional GPR display, showing the reflections from buried objects and indicates their depth. In any case, the standard e-safe is simple to understand and requires little training, unlike more sophisticated GPR units.
GPR can detect all types of utility lines and will not distinguish between them whether they are plastic or metallic. Cables that the standard pipe and cable locator cant detect, such as cables that are not connected or energised, such as pot ended power cables and non- metallic fibre optic cables, and polyethylene water and gas pipes, can be detected using GPR, so all the operator needs to do is to survey the site carefully and mark everything found, and join up the dots to build up accurate plans of the lines and avoid damage.
The E-Safe costs around £4500 approx. to buy and would quickly pay for itself when used successfully as a multipurpose avoidance tool, and it does not take much training to become expert at avoiding site stupidity!
Here are some photos of avoidable site stupidity.
This LV cable had been carefully installed in a duct and was due to be connected to the LV system to energise the whole new housing estate. Testing showed a fault.
Road-Pin through a duct into a LV cable
Some lucky idiot had hit a road-pin through the duct and into the cable!
Lucky because it was not energised. The hole in the cable is the exact shape of the road-pin tip we found nearby.(see photo)
These 11 kV cables were on a new construction site. They were partly ducted and when direct buried, they were carefully installed and buried in sand with warning tapes over the top. The position was known and marked so protective steel plates were laid over the cables to avoid damage from moving heavy equipment across them.
Damaged cable from plates dragged across
When the job finished the protective steel plates were lifted to be taken away, but the corners of the plates dragged across the cables...!**
Damaged cable from metal dragged across
A new solar farm site built at incredible speed, but because the cables were not clearly marked due to very muddy conditions, diggers pulled cables when installing other cables. This resulted in both external damage, and also stretched the cable causing poor internal insulation, failed test and required the cable to be replaced. Site was busy and cables routes not clear.
Damage caused by PV pillars thrust through the LV cable.
How to be incredibly good at avoiding site stupidity?
- Have good plans available and orientate the plans so operative understands the site
- If plans are out of date, have new prepared and/or get site professionally surveyed for underground lines.
- Have site operators using locators properly trained to use a variety of location techniques to pinpoint the locations of buried services.
- Tag and mark route position of new cables and existing utility lines.
- Ensure that site crews are aware of known utility routes and positions.
- Prevent digging/excavations until cables and pipes are located.
- Supervise digging and excavations with locators closeby in attendance.
Recently I was training a group on effective ways to use the CAT4 and Genny 4 to avoid buried services. The jobsite at a major container port, involved installation of truck security gates and was nearly completed. Good radar based service plans were available, and showed a telecoms duct and 11kV HV cable ran in the vicinity of installation points of a line of heavy traffic bollards. The planned positioning of bollards avoided the lines, and it was necessary to relocate both lines for confirmation.
Comms line easily pinpointed and marked using "2 man sweep techniques" and "broad induction techniques" but the 11kV HV cables were not locatable in any passive or active (induction) modes. Everything that could be done (except digging) was done, but the cables could not be located.
After the training was completed, the trainees were left with no doubts about limitations of simple avoidance equipment, but reinforced their need for careful digging.
I got out the Pipehawk e-Safe GPR, and found the HV cable run in a few minutes, and also cleared the area where the bollards' positions were planned.
I did not use the higher frequency induction available from the VlocPro2 locator system I had with me, as it was not appropriate at a training course.
After some discussion with the site engineer, we found out that the cable route had been abandoned and diverted, so that effectively the cable in the ground had no connections, could pass no current, was dead, and also safe if it was dug up.
This explained why it had no signal and could not have the 33kHz Genny signal induced into it, and could not be found with the CAT4/Genny4.
But if the cable had been discovered whilst digging, much time and effort would be expended on finding out what it was and why it was there.
In the beginning our CAT and Genny had a built in metal detection mode, and this proved useful for many excavation teams to find lost stop taps, manholes etc, This feature was omitted in later locators.
Now there is a new "kid-on-the-block", the new V-Scan manufactured by Vivax.
I have written about the VlocPro and SD locators in previous blogs, and the V- Scan system follows the Vloc philosophy and is an easy handling system that sets itself a little above the standard cable avoidance tools.
It is also well designed for the rough and tumble of site use –but time will tell on that score.
The cable avoidance locators (except the EZiCAT) have rather small LCD screens, and generally it's difficult to see the peak response clearly. The CAT4 screen is the same size as it has always been, but now has a helpful peak indicator bar to assist pinpointing, but the earlier Easyloc and EziCAT had this feature for a long time.
The V-Scan has a larger screen, a bold expanding peak display and also adds a compass to indicate line direction and help tracing when used with the transmitter.
When used with the transmitter the display can show depth and current measurement
To improve the audio/sound output, the V-Scan has 2 loudspeakers, one fixed and one removable for use in noisy sites.
The small size transmitter has 2 output settings, on high setting it outputs 1 watt, and like the Genny4 uses 33 kHz and 131 kHz simultaneously on connection. Transmitter accessories use the same connection plug as the more expensive Vloc Pro kits (incidentally it's also the same as the Genny4).
For the induction mode there is a simple and useful stand to hold the transmitter vertical for the broad method of induction, and as the equipment is yellow, its easy to see when left in the street.
Like the Easyloc and C-Scope DXL2 there is a build in self-test and calibration verification, so that the user can confirm that the kit is working whatever the calibration sticker says.
Datalogging and data management software is also included in the receiver.
The option list includes the VScanM and that also includes a metal location mode in the receiver, to find lost stop tap covers, valve covers and manholes, so at last a 2 part system is really useful again – full circle!
To add to the usefulness the V-Scan receiver can include Bluetooth for data transfer and positioning if GPS option is chosen, and rechargeable Lithium Ion battery packs.
A carry bag is included free when both receiver and transmitter are purchased together.
Barney's Blog no 12 will review the V-Scan.
Sadly, Andy Garnett died in September.
Andy Garnett was the Managing Director who evolved Electrolocation into Radiodetection and oversaw the first CAT's and gennys, ensured that the company grew from a small 12 person survey company into a specialised world-wide brand of locating expertise from 1978 to 2001. Under his guidance the company expanded into Europe and USA with 450 people with sales distributors in more than 60 countries.
Andy wrote the language and terminology that is used for the location business and produced a "bible" for the location technology, his "ABC-XYZ of locating".
He always said that 'a company's best asset is its employees' and he followed that belief during his tenure as MD, he had the knack of motivating people to get the best out of them and because the employees were well motivated and rewarded the company succeeded and expanded.
He retired at 63 and there was a management buy-out and the company continued on its upward path, and Andy followed his writing and travelling and creative pursuits.
Radiodetection was incorporated in to United Dominion Industries who assisted in its expansion and acquisition of companies with similar products for fault location and inspection cameras.
When UDI was brought out by SPX, the current owners of Radiodetection, Andy was heard to describe them as "asset stripping philistines" and he certainly was not wrong in that respect as they clearly did not follow his ideals as they fired half the Engineering and Research departments and downsized the employees worldwide.
It's interesting to note that many of the former employees now work for competitor companies, Seba KMT, Vivax-Metrotech, C-Scope, Cable Detection, and Radiodetection partially lost its skillbase and expertise due to thick headed short-sightedness by the "asset stripping philistines".
Andy Garnett, Rest in Peace.
Barney Walker, 15 January 2015