Abstract
The core principles of collecting good quality data from site for creating CCTV inspection reports including some explanations of how to avoid common mistakes.
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The PLR Naming Convention
Most global drainage inspection standards include a system for naming pipes based on either the upstream manhole ID or a combination of both the upstream and downstream manhole IDs. The Manual of Sewer Condition Classification (MSCC) defines the naming convention for WRc pipe and sewer inspection using the Pipe Length Reference (PLR) system at all times:
Takes the upstream node ID and adds the PLR Suffix to the end.
This is consistent at all times throughout all WRc style reporting and is automatically applied by software applications such as WinCan VX. The PLR Suffix is simply an incrementing letter starting at X, so is X, Y or Z, where X is the most common, and often overlooked by CCTV report writers and inspectors.
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Basic single pipe setup.
In a simple straight forwards drainage system and in most cases with foul drainage systems, there is only one pipe leaving chamber MH1, so the PLR of that pipe becomes MH1X. This is the ID of the pipe, so when we talk about pipe MH1X, it is clear from the drawing which pipe this is, because it is the outgoing pipe from chamber MH1 and it doesn’t matter where it goes or what the downstream chamber’s ID is.
This logic happens all the time inside inside WinCan VX with WRc projects and a lot of people ignore the PLR field and the PLR Suffix field inside the section header because the PLR Suffix defaults to X for all new pipes, and the PLR itself is created automatically when the header is saved.
The big problems with CCTV inspection data begin when people use inappropriate naming conventions for the nodes in their project, and fail to follow the guidance warnings on screen that they are creating duplicate assets. Here is an example of common bad data:
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The start of data problems.
So, the user creates a drawing or starts to create headers inside the software application to inspection this network of pipes. They are going to inspect:
MH1 upstream to gully GY.
MH1 downstream to MH2.
MH2 upstream to gully GY.
Now let’s see what happens when we add the PLRs to this drainage network:
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Look carefully at the PLRs.
Look first at the PLR for the pipe from MH1 to MH2. It looks good. As explained, we take the upstream manhole ID and add the X to the end giving is MH1X.
But now look at the PLRs for the two gully legs. Notice that they are both GYX. Why? Because the upstream node ID of both pipe is GY, so the PLR of both pipes is GYX:
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Duplicate PLRs.
What does this mean in plain and simple terms? This means that there are 2 pipes with the same ID, so these are both the same pipe. But, I hear you say that, “They are not the same pipe because one goes to MH1 and the other goes to MH2.” Back to basics - the PLR is defined by the Upstream node ID and the PLR Suffix, and the downstream node ID has no affect on the PLR whatsoever.
WinCan VX will warn the user that they are creating a duplicate asset (remember, the PLR is the ID of the asset), but it will also allow them to ignore the warnings and carry on. The reason for this is there are a small number of drainage inspection standards around the world that do not define a naming convention for pipes, but not many.
How do we avoid problems like this? The simple solution is to use unique IDs for every node point on your site sketch regardless of whether it is a manhole, catchpit, gully, rainwater pipe or anything else. There is no specified way to do this, but a simple and robust technique is to use a few letters and a number which additionally describe the use of the asset (i.e. foul water, surface water or combined) and its type, like this:
Node Type | Foul Water ID | Surface Water ID | Combined Use ID |
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Manhole | FWMH1, FWMH2 etc | SWMH1, SWMH2 etc | CWMH1, CWMH2 etc |
Inspection Chamber | FWIC1, FWIC2 etc | SWIC1, SWIC2 etc | CWIC1, CWIC2 etc |
Gully | FWG1, FWG2 etc | SWG1, SWG2 etc | CWG1, CWG2 etc |
Yard Gully | - | YG1, YG2 etc | - |
Road Gully | - | RG1, RG2 etc | - |
Soil & Vent Pipe | SVP1, SVP2 etc | - | - |
Rain Water Pipe | - | RWP1, RWP2 etc | - |
Catchpit | - | CP1, CP2 etc | - |
Soakaway | FWSK1, FWSK etc | SWSK1, SWSK2 etc | CWSK1, CWSK2 etc |
Rodding Eye | FWRE1, FWRE2 etc | SWRE1, SWRE2 etc | CWRE1, CWRE2 etc |
Fresh Air Inlet | FAI1, FAI2 etc | FAI1, FAI2 etc | FAI1, FAI2 etc |
Ground Floor Toilet | WC1, WC2 etc | - | - |
Lamphole | FWLH1, FWLH2 etc | SWLH1, SWLH2 etc | CWLH1, CWLH3 etc |
Septic Tank | ST1, ST2 etc | - | - |
Cess Pit | CE1, CE2 etc | - | - |
Grease Trap | GT1, GT2 etc | - | - |
Petrol/Oil Interceptor | PI1, PI2 etc | PI1, PI2 etc | PI1, PI2 etc |
Connector Node | CN1, CN2 etc | CN1, CN2 etc | CN1, CN2 etc |
Outfall | - | OF1, OF2 etc | OF1, OF2 etc |
Inlet | - | IN1, IN2 etc | - |
Unknown | UKN1, UKN2 etc | UKN1, UKN2 etc | UKN1, UKN2 etc |
This list can be extended or modified as required by the user because it is only a suggestion for a simple and robust naming convention that is easy to follow and is informative. It should be remembered that the upstream and downstream node ID fields in the WRc reporting in WinCan VX only allow for 10 characters maximum. The reasons for this are because the manhole naming convention described in Appendix A of the MSCC only require 10 characters to name any manhole in the country, and the xml data format exchange file also limits this field to 10 characters. This naming convention is described in detail in Understanding STC25 Manhole References.
Because the name of the pipe (the PLR) is defined by the upstream node ID and the PLR Suffix, this allows a manhole or other node to have up to 3 outgoing pipes. This may seem a strange concept to many CCTV inspectors, particularly at a domestic level because they have very likely never seen a manhole with 2 or more outgoing pipes. However, this is extremely common in highways drainage and is constructed this way by design because on highways (more than any other place) it is essential to get the water off the road at all costs and as quickly as possible during heavy rainfall events so as to avoid traffic accidents.
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Good Site Drawings
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Understanding STC25 Manhole References
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