The cleaning of large profile sewers poses special challenges to skilled workers.

This module deals exclusively with the cleaning of large profile sewers. Among other things, the module focuses on the presentation of machines that have been specially designed for this purpose.

After completing this module, you will have knowledge regarding:

• procedures for cleaning large profiles;
• general conditions for large profile cleaning.

Mechanical cleaning can be carried out:

• manually with supplementary apparatus,

• with cleaning apparatus, or

• with special apparatus

Manual cleaning with supplementary apparatus in non-accessible drains and sewers is carried out using tools such as rods or coils. In the process, an appropriate cleaning attachment is fixed on to a flexible rod or coil which is spun and forced through the line to remove obstacles or deposits in its way.

The cleaning apparatus includes a channel bucket, channel plow, invert scoop, channel scraper, cleaning brushes or a pull-through squeegee. They are brought into the sewer through the manhole and then pulled through the section to be cleaned using a winch [NASSCO1989] [ATV1995a] [Tchob1989] [FI-Müller] [WPCF1985].

(Image: Sand Scraper for Sewer Pipe)

Depending on the degree of pollution and the nominal size of the pipe, hand winches or motor winches with pull forces of 5 kN to 20 kN and 25 kN to 50 kN respectively are used [Führb1980]. The use of these cleaning tools in non-accessible sewers has shown good cleaning results.

The section by section assembly of the winch system as well as the insertion of the winch cable and the cleaning devices is a very complex, time consuming and physically demanding …

Special apparatus has been developed in the past few years, especially in the non-man-accessible sections of sewers, for removal of hardened deposits, internally projecting laterals or artificial obstacles and roots, as well as for achieving a high degree of cleanliness.

Remotely controlled special mechanical methods:

• Rotary chain cutters

• Drilling and milling apparatus
  • Without impact DN80 to 600

  • With impact DN 100 to 1000

• Cutting apparatus

• Sandblasters

• Sewer robots.

In the following section, the most common mechanical methods are introduced along with their field of application and use limitations.

Rotary chain cutters are composed of a guide sled with three or more skids and a rotating head with steel chains. The rotating head can either be driven hydraulically using high pressure water or via an electric motor. The device installed on the guide sled is pulled through the section using a cable winch. The skids ensure the stability of the rotary chain cutter during its operation in the sewer. The steel chains installed on the rotating head …

The type of the chains used depends on the type of the deposits and agglomerations.

When using the rotary chain cutter, it is recommended to proceed as follows [FI-KEG]:

• Loose deposits are to be flushed out in advance.

• Working in one location involves the risk of scouring the pipe.

• Carefully select the appropriate chain lengths. The chains should brush past, but should not touch, and on no account hit the pipe wall.

• After each use, the rotary chain cutter is to be visually inspected to find possible damage. Defects are to be …

When using the rotary chain cutter, it is recommended to proceed as follows [FI-KEG] (cont.):

• A swivel joint should be arranged between the hose and the rotary chain cutter to prevent the HP hose from twisting.

• The use of clean water is a basic precondition for a trouble-free operation and a long service life of a hydraulically driven rotary chain cutter.

• Storage: It is recommended to store the device after its use with its top pointing upwards (…

Drilling and milling apparatus are remotely controlled, and commonly used in conjunction with camera supervision, in pipe sizes ranging from DN 200 to DN 600 to remove solidified/hard deposits, protruding connection sewers, roots, and other obstacles. They are driven hydraulically using oil or water pressure. To ensure that no pipe damage occurs, these devices are fixed in a central position. In individual cases they are also equipped with varying …

The automatic impact boring machine falls within the category of “drilling and milling apparatus with and without impact“. It was developed to remove solidified deposits, congestions and root intrusions for nominal sewer sizes ranging from about DN 100 to DN 1,000.

The drilling tool is composed of a steel drilling head equipped with exchangeable carbide metal cutting knives dimensioned to the sewer diameter. In the case of root intrusions or other soft material deposits, the drilling head is equipped with serrated knives made of steel.

The following recommendations apply to the impact/milling tools:

• The use of milling and impact milling tools requires a good structural condition of the pipe.

• Milling is not permitted in sewers made of vitrified clay.

• The use in PVC pipes is not recommended.

Cutting apparatus are used to eliminate protruding obstacles in sewer lines such as lateral connections, artificial obstacles as well as roots in pipe sizes ranging from DN 100 to DN 600, and often under video supervision [NASSCO1989] [WPCF1985].

The operating principles are different for devices that use mechanical cutters versus those that use pressurised water jets.

The root cutter is equipped with a cutting blade that is hydraulically operated for removing severe root intrusions. The cutter is also equipped with a HP flushing device and can be used in nominal pipe sizes ranging between DN 100 and DN 400.