Samenvatting

The remaining lifetime of a pipeline system is very important to pipeline managers to get more insight in the moment you have to plan the renewal of the system. Before you can start the preparation of the renewal of a system, you also need to know the financial possibilities. But primarily insight in the condition and integrity of the system is crucial for the decision.

Wastewater pressure line managers find to their own cost also other problems. Most of the existing pipeline systems are not piggable, because of the obstacles that have been fitted in their piping systems, for instance butterfly valves and ordinary gate valves without full bore. At the same time these systems are not able to launch and receive a pig (pipeline inspection gauche). And last but not least, most of the pumpingstation have a strongly restricted period that they can put out of service without risks for the environment (by pollution). On the other hand all the different materials where the pipeline systems are made off do not make it easier for them (see Appendix IV).

For steel and cast-iron pipeline systems several internal inspection techniques and methods are available. One of the main reasons for an internal inspection is the assessment of internal and/or external corrosion. For crack detection you need a special tool.
As also “hard polyethylene” (HPE) piping systems are frequently used in the wastewater sector, the condition and integrity of this kind of piping systems are very interesting for the managers of these systems. So they are interested in methods to determine these condition and integrity. There is only one big problem. Nobody knows something about piping systems of HPE material. There are no test results for this material.
For steel and cast-iron piping you can choose out of magnetically (MFL) or ultrasonic (UT) technique. For asbestos cement (AC) and synthetic piping only UT techniques are suitable. However until now there are no operators who have some experience for synthetic material.

In order to provide for this shortcoming the ‘Röntgen Technische Dienst BV’ (RTD) and ‘A. Hak Industrial Services BV’ (HAK) have been asked to fulfil some laboratorial tests on HPE material.
To have some references to other synthetic material like “polyvinylchloride” (PVC), for which some experiences are acquired, also PVC material has been tested.
Before testing the material, I have prepared the material by introducing saw cuts in axial direction (inside and outside) and in radial direction (only on the outside). The only reason for these saw cuts is the fact that we do not know what with standard existing Ultrasonic Testing UT tools can be perceived in synthetic piping. And we know out of our own experience that PVC piping can crack e.g. as a result of settlements or ingrown tree-roots and stones, which cause pressure spots on the outside circumference (axial and or radial).

From the lab tests, carried out by HAK and RTD, we know now that standard UT tools are also suitable for internal inspection purposes in synthetic piping. However we are not sure if all possible failure modes can be detected under normal service conditions and in one run. That is why we will have carried out a test run through a HPE 250 pipeline with a length of ca. 640 m’ at the end of this year.
The experience from this test run can be important for further investigation of inspection tools for synthetic piping.
On the other hand the experiences from this test run also have to give us an answer to our question if we will be able to fulfil the Measurement 6.a-5 (see paragraph 3.1) from our “Municipally Sewage Plan” (“GRP”), when we use these techniques and methods.

If you like to tender such a cleaning and inspection session you have to be alert about the costs for the technique and/or method you prefer or not prefer. The prices can vary between € 30,00 and € 120,00 per meter. So it is worth to survey the market for inspection technologies.

On the other hand replacements costs for wastewater pressure lines may vary between € 140,00 and
€ 1.400,00 per meter, depending on diameters, material, depth of laying, and other local circumstances.



The costs for an internal cleaning and inspection run depend on several variables. The operators themselves, working in the inspection branch, are one of them. The piping material and the approachability of the launching and or receiving devices are other variables. And what do you want to detect? Wall thickness? Out-of-roundness of the piping due to internal stress? Cracks inside /outside? Corrosion inside/outside? Also butt fusion and electro fusion joints can be checked from the inside by the UT tools.
Some of these phenomenon’s can be detected with one standard UT tool. Other items need special UT tools.

From recently carried out examinations by Becetel and TNO for HPE, respectively PVC piping, show that the expected nominal life of both thermoplastics materials will be more than 100 years.
But in my opinion more investigation is necessary during the next coming years, also with DT techniques, to come to a better and well-considered (remaining) lifetime prediction, especialy for HPE piping. For both piping materials PVC and HPE internal inspections are recommended to check the inner pipe profile (out-of-roundness), because transformation of the pipe profile will give an indication of (local) external load, with internal stresses as a dangerous result. Dramatic declining of the remaining lifetime of this kind of piping could be the result of these internal stresses.

Also the latest developments (April 2007) about the new “Wet Informatie-uitwisseling Ondergrondse Netten” (“Soil Stirring Regulation”), the “Guideline careful digging process”, as well as the “Dutch Technical Agreement” (NTA 8000:2007), and the “Pipeline Information Management System” (PIMS) have been discussed in this dissertation.