In the mid-1990s HERMES Technologie was already making a name in Japan for its own processes for rehabilitating buried pipes, sewer shafts and shaft cover frames. Further demonstrations, appearances at shows and participation in conferences in Korea, China and Australia then led to a request (via its English branch) to the medium-sized firm from Schwerte on the Ruhr to demonstrate the M-Coating rehabilitation process in manhole shafts in Singapore.

After some interesting negotiations and detailed discussion with Trenchless Technology (FE) Pte Ltd from Singapore, the mortars and machinery were sent off to Singapore in March. As in many regions of economic development in Asia, the protection of the environment is assuming increasing importance in Singapore, too, and in this case because it is important to avoid sources of fresh water being tainted by seawater or wastewater.

Surveys by the authorities responsible (PUB) in Singapore confirm that the wastewater network dating in part from colonial times is in serious need of rehabilitation. Because of the extremely high volume of road traffic till late at night, the Singapore authorities had to opt for repairing the sewer system rather than laying a new one. Moreover, it is clear from the plan of the state’s sewers that quite a few streets lay at sea-level, so that the sewers partly fill up at high tide, because they leak so badly. Any engineering operations in the sewers must therefore take place while the water-level is falling.  The M-Coating process developed by HERMES Technologie is ideal for just such cases, as it can use even short windows of opportunity for repairing shafts thanks to its fully automated routines in conjunction with early strength dry mortars.

As in previous cases in Asia and elsewhere, HERMES Technologie set great store on training a ‘local team’ right from the first renovation operations. Once the materials and equipment had arrived, theoretical training on the M-Coating process was given in the light of the survey of the damage found in the sewer shafts that were to be rehabilitated together with Trenchless Technology (FE) Pte Ltd.

The team that was assembled on the spot  (one foreman and 3 specialist operators) showed the kind of commitment and willingness to learn that is no longer that common in Europe. Although it seemed advisable to start the actual rehabilitation procedures at night or early in the morning because of the high volume of traffic and also on account of the temperatures that pertain near the equator, the first rehabilitation started around 10 a.m. Once the initial preparations were complete and just as the work was about to begin, the tide came in. We had to seal off the incoming water with balloon-plugs and pump it out.

Once the shaft was cleared of water, the walls were thoroughly cleaned robotically, using the TSSR. The TSSR works at 380 bar and 24 litres per minute, at a distance of 5-15 cm from the shaft wall. After cleaning, an inspection of the shaft revealed a 5 mm hard shell-like coating. Areas of leakage were obvious, and old packer holes pointed to previous injection with artificial resin. Behind the ‘shell’ lurked cement plaster and an unknown soil mixture.

In order to obtain a pefect repair, it was decide to remove the visible coating back to the original shaft wall. The TSSR was used once more for a final cleaning. In the remains of the shaft’s reinforced concrete cladding, some 20mm thick, about 40 holes were found, and these were plugged with ERGELIT-10SD. The stabilising injection which was planned  to follow that, had to be put of to the next day because of the rising tide.

The next day began with using the remote-controlled TSSR to remove the dirt which had built up overnight. The restaurants and fast food stalls connected to the sewer discharge a great deal of grease into it.

Next, the shaft was stabilised with an injection of ERGELIT-Kbi. In order then to seal the very small cracks that were present, and to speed up the subsequent coating operation, ERGELIT-10F was rubbed into the shaft wall.

In spite of the fact that the temperature had meanwhile reached over 49ºC in the sun – a tough test for mortar mixers, hosepipes and pumps – the shaft coating was begun. The dry mortar used: ERGELIT-KS 1. A 10mm thick coating was applied in a single operation, with the robotic centrifuge motor being lowered and raised in the shaft. A second coat of mortar was sprayed to a thickness of 40mm, which together with the original 20 mm cladding gave a rehabilitated sewer shaft wall of 70mm. According to the client’s spokesman, this was structurally satisfactory for this section of concrete road, exclusively used only by light and sporadic traffic. Immediately after the material had bonded and the equipment had been removed from the shaft, water flooded into the pipe, which made it unnecessary to keep the surface damp, as would otherwise have been essential in these temperatures.

The rehabilitation equipment now had to be moved on to the next shaft. As the dense afternoon traffic made further work impossible, the work on a 5m deep shaft began around midnight. The vertical shaft wall varied in diameter from 1.20m to 1.40m. The thorough cleaning and subsequent robotic coating of the lower part of the shaft wall was completed in the early hours of the morning, thanks to the Singapore team, who had now learned their job very well.

This shaft was the subject of operations during the following session. It served as a test piece for the new M-Coating team to demonstrate to the client. After a perfectly executed TSSR cleaning cycle, the team succeeded in applying a superb coating to the upper part of the shaft, using ERGELIT-KS1 supplemented with ERGELIT-KS2b. However, in the middle of operations the mortar supply hose suffered a blockage, due to the heat. The event showed that one must acquire a very fine feeling for the preparation and supply of the grout in these equatorial temperatures. However, the team’s calm reaction showed that one week’s training from HERMES Technologie – in this case led by the proprietor, engineer Rainer Hermes – can mean a good level of competence. Rainer Hermes was actually rather pleased to have the chance to train the new team to deal with such a problem, as he explained to the water & wastewater operating authority representatives.

In conclusion, with the co-operation with Trenchless Technology (FE) Pte Ltd we have set a bench mark for a new rehabilitation technique for the remaining 1001 shafts in Singapore. 

Source: HERMES Technologie GmbH & Co KG