THE THAMES RIVER BARRIER PROJECT

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The Problem The Solution The Procedure The Movie

The Procedure: UHP Projects, Inc. supplied the following equipment which was loaded onto a barge and placed at the base of the gate; UHP pump, JetTracTM vacuum skid, JetTracTM crawler, filtration system, 185 CFM air compressor, 440V generator, two 5000 gallon tanks for fresh and effluent water storage, necessary painting equipment and materials. A tugboat was on 24 hour standby to move the barge in case of an emergency, and a rescue boat was always available during cleaning operations due to the swift tides. UHP Projects, Inc. staffed the project with a 4 man crew. The project was started with the gate in the vertical (defense position) and the JetTracTM cleaning the top 25% of the gate surface down to the high tide waterline. A cable support system was designed and installed to allow a self tensioning winch cable from the vacuum skid to run to the top of the gate and back to the JetTracTM crawler. This allowed the crawler to be lifted and placed onto the gate's surface from the barge deck, vacuum could then be applied to hold the crawler to the surface. This winch system also provided a safety backup to catch the crawler if vacuum was lost. After the top section of the gate was cleaned and painted, the gate was placed in the overhead (maintenance) positions. UHP Project, Inc. designed a lift system that allowed the crawler to be lifted into place from the barge deck to the underside of the gate during any tide level. Vacuum and UHP water pressure was then applied and the crawler would be remotely controlled from the barge deck. The remainder of the gate was cleaned in this position. Surface preparation in both gate positions was coordinated to be done on the outgoing tides down to the high tide waterline. Recoating was accomplished on the next incoming tide. In the vertical position this allowed the painter access to the area from the barge. Painting done in the overhead position was accomplished using a small manlift placed on the barge. A 2-part high solids epoxy from Kemira was used as specified by the Environment Agency. All coatings were applied using 45:1 airless spray equipment. The existing coating to be removed were a 20-50 mil hot applied 2-pack epoxy that had been applied at construction. The JetTracTM using ultra high pressure waterjetting removed the coating to a SSPC SP 5-WJ-2 condition with production rates of approximately 200 FT2 (18 M2) per hour. An independent paint inspector performed daily tests for chlorides, profile, holiday detection, and adhesion. Every effort was made to recoat as soon after waterjetting as possible to minimize flashrusting.

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