ArmorThane Reverses Sewer System Deterioration In Hong Kong

Sewers deteriorate with age and typically require a high level of maintenance. In Hong Kong’s aging infrastructure, brick and mortar manholes are especially vulnerable to cracking and crumbling. These manholes vary from about 5 to 50 feet. Instead of patching existing problems or completely rebuilding, ArmorThane labored with their local distributor to propose a polyurea spray coating to stop corrosion and strengthen walls as a long-term solution.

International Opportunity

Like other densely populated areas, Hong Kong finds handling sewage a challenge. The network affects about 900 miles (1,448 km) of pipelines to 280 treatment facilities, treating 713 million gallons (2.6 million L) of sewage per day.

The first step in achieving project approval was to get the necessary product and equipment to Hong Kong. Because the contractor already did pipeline liner repairs, they had air compressors and generators needed for the local electrical systems. However, special high-pressure spraying equipment had to be retrofitted with 380 volts, three-phase wiring, and shipped from the U.S. facility. A transformer box was added to bridge the remaining discrepancies, which is common when working worldwide.

The second step was to demonstrate product applications and results to government officials. Rob Anderson from ArmorThane USA cleaned and sprayed a large concrete box culvert to divert stormwater runoff under roads. This was a straightforward location for the audience to watch and inspect. Because these are not brick and mortar like manholes, there is less deterioration, but the coating method is the same. An agreement was given to proceed to the final step in the approval process: a test trial.

Underground Infrastructure

Anderson scheduled a second trip for a multi-day demonstration and training session on an actual manhole. Because sewers are a grid of underground tunnels that carry waste throughout the city to the treatment facilities, there were several challenges facing the task. The first challenge was circumventing sewage flow to work on manholes and tunnels without creating significant problems upstream. Anderson selected a less-frequently-used line because of the extra time involved with demonstrating and training. He inserted an airbag upstream and inflated it to stop the flow. Next, the flow had to be diverted around the area to a downstream line using a trash pumping system.

Once the sewage was cleared, the surfaces had to be high-pressure power-washed and thoroughly dried before repairing. For the repairs, Anderson used ArmorCrete primer, specially formulated with lower viscosity than water. This allows the primer to seep into the brick and mortar to fill holes and cracks, and it completely seals weak areas. Because it prevents further cracking and crumbling, Anderson applied the primer in two coats to achieve an approximate total thickness of 3–5 mils (76–127 microns) to the entire surface rather than simply patching visibly damaged areas.

Anderson spray-applied HighLine 510 polyurea using his portable generator and air compressor mounted on a flatbed truck in the final step. He used a two-component pure polyurea coating that was heated and applied in two coats to yield an approximate total thickness of 60–80 mils (1,524–2,032 microns).

This polyurea was specially formulated not to react to residual moistures inherent in Hong Kong and sewer systems. The chemical sets quickly to form a seamless protective barrier, and it has moisture resistance and a fast cure time. This means it will not crack even as environmental conditions cause the surface to expand and contract. It is also extremely resistant to corrosive chemicals and temperature change.

Training Day

Anderson sprayed the manhole for about four hours using a PMC GH40 and a PMC AP1 spray gun. The total time to work on one manhole from start to finish is 1–2 days depending on the size and deterioration of the manhole. This accommodates the steps involved in cleaning, drying, repairing, spraying, and curing.

After completing the demonstration manhole, Anderson further trained six applicators using felt pieces and bricks. This involved equipment start-stop processes, spraying action, troubleshooting, and cleanup. A training manual was designed specifically for manhole rehabilitation and quality assurance.

The city decided to move forward because of the positive results on this first manhole; the first 40 manholes have been scheduled for maintenance. In addition, concrete box culverts were also approved for repair and preventive maintenance. Overall, Anderson’s willingness to show his potential client the benefits of using this polyurea demonstrates that a little work upfront can mean a lot of business!

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