Whilst is may seem obvious, the simplest of Renovation technology is cleaning, although to many it is not always seen as a Renovation technique, just something that is done in the normal course of things. In many instances pipelines that are under-performing are structurally sound and do not need to have costly repair works done or linings installed and need little more than a thorough clean to bring them back to full servicability.
Also whilst this may be the case, cleaning is also a very important part of any repair or lining operation because without it, any work programme may simply be a waste of money.
There are a number of techniques for cleaning out pipelines and which technology is most applicable is mainly dependent on the level of cleaning necessary and the types of debris or build up that is likely to be encountered. Three main types of cleaning system are used inlcuding: Jetting/Flushing, Scraping and Pigging.
This is a commonly used technique that employs high-pressure water jets from a specially designed pressure head that is fed from a surface pumping unit. The jetter head is passed through a pipe line at any desired speed and the water jets from the head are designed to hit the inner pipe wall so dislodging and debris attached to it, The jets also pick up and remove any sediments in the pipe invert ‘stirring’ them into the outflow of water from the pipe. The pressure of the water ensures that all debris and silt are removed from the pipe in the direction of travel of the jetting head. Some water jets are also designed to be powerful enough to cut through root intrusions. Where water jets are insufficient to achieve root removal specially designed robots are available with low volume, very high pressure jets or rotating blades that will make removal possible. Further pressure jetting is then used to remove the debris created.
In terms of flushing, there are two possibilities for cleaning. Retaining a water/effluent flow volume using a temporary seal may allow for a flow to be generated occasionally that will clean the pipeline in question but this cam bring with it access and potential worker safety problems so is rarely if at all used in more modern societies. Some manufacturers have also developed flush gates, that can be temporarily or permanently installed in a pipeline, that hols flows upstream of the gates until a pre-set level is reached. At that time the gates open automatically to allow high volume flow to pass through the pipeline, flushing the system and cleaning the pipes. These flows can clean pipe both above and below the gate position.
Where harder build ups of material are encountered and Jetting/Flushing is insufficient, a more physically aggressive device may be required. This is normally in the form of a scraper. Various types of scraper are available, each designed to handle different forms of build up/encrustation. Most however do need to have an open pipe to some degree as most do require the installation and use of a winch wire to progress the scraper through the pipe.
Scrapers can take many forms but generally are either in the form of a wire brush, sprung metal teeth or circular rubber sections that are designed to fit snuggly inside the pipe diameter being cleaned.
Another form of scraper is the rotating flail which comprises a metal flail on the end of a rotating rod system operated from surface by a rod pulling machine. The rotating flail dislodges unwanted material from the pipe inner wall. Jetting is then used to remove this debris.
The disadvantage of scraping as a technique is that, unless managed very well, and undertaken with the minimum of force required to make cleaning happen, severe damage can be caused to pipe being cleaned. At times this damage has been known to change the status of the pipe from simply requiring cleaning to one requiring physical repair work, simply because of the damage caused during cleaning.
Pigging as a cleaning technique can have two functions. First where other cleaning methods have been utilised, a close fit pig may be passed through a pipe to make a final cleaning run to ensure that all possible debris has been removed. Secondly, where a limited amount of cleaning is required some pigs are designed with rough out surfaces that in themselves may offer sufficient cleaning for the pipe. Pigs are normally pushed through pipelines using either compressed air or water pressure, between two access points.