Structures

Dockside maintenance and repair with drydock and Humidur® paint

Sjotaekni ltd. is currently sealing a contract with Acotec in Belgium for the use of a drydock or cofferdam for dock repair. The method of dewatering steel sheetpiles and quay walls for maintenance and repairs is not new overseas, but has not been used in Iceland. We believe that this method is the only one fitting, to do this hard but necessary work under the right conditions.

An inspection cofferdam is typically 2 meters wide and can be set up according to the requested inspection depth. This cofferdam fits on the back of a truck and can be transported as such. An inspection of a quay wall in detail will be executed with reference setups (decided in a joint decision between the client and Acotec) where the cofferdam will be placed. This will generally be on location, where damage, such as holing or even a subsidence of the quay, can be seen.

An inspection can be performed by Acotec, by the client itself or by a third party which is mostly an engineering company.

The view inside a deep cofferdam. Lighting and ventilation are included

When Acotec performs the inspection, a typical setup includes:

• dewatering,
• visual inspection,
• cleaning of the biofilm and vegetation,
• remaining steel thickness measurements on every inpan, flange and outpan for every meter below the waterline,
• potential measurements,
• coupon analysis to determine corrosion from the backside,
• test to determine bacterial corrosion,
• measuring remaining film thickness of possible old coatings,
• inspection of former corrosion protection tools present (such as cathodic protection),
• possible repairs when requested by the client.

Cleaning of steel sheets inside a drydock

An inspection under dry conditions gives a number of advantages:

• The infrastructure is clearly visible
• Ability to wash away the biofilm and vegetation and collect any loose material
• Independent of the diver’s interpretation, instead the client can inspect or verify himself
• By taking away the front pressure on the waterside, any leakage and holing will become visible - even the smallest
• Any holing found, can be repaired immediately during the inspection
• Labour is not as expensive as divers
• Labour is faster and more safe
• Labour can be monitored better by the client
• client is able to get a quote for each job, like high pressure water cleaning, steel repair, putting up anodes and painting.

A detailed cofferdam inspection is often required prior to a full renovation project or refurbishment of a jetty or bulkhead structure. The results of the inspection can be a direct input to determine the size and budget for the project for a possible repair or rehabilitation project.

An employee of Sjotaekni ltd at a dry dock in Belgium. “It´s surprising to see how fast and effective the system works and to have full access to the harbour, down to 15m.”

Heavy-duty performance and outstanding properties

The Humidur® coatings are on the market since 1984. Since that first application, the system is claim-free from any failures on the coating and on the application, even in highly corrosive environments. The system has proven to be maintenance-free when there has been minimal or no mechanical impact.

Humidur® is a system designed to use in all kinds of water and has a high chemical resistance at the same time. The system has proven to be effective in salt, brackish, fresh, drinking and even waste water. It also protects steel tanks and pipes containing more aggressive chemicals.

In the marine- and shipping industry, the products may also be used in submerged, splash zone, tidal areas and in atmospheric zones. In other words, Humidur® is able to function on the complete structure. This is proven in practice on multiple structures for several decades!

Application of Humidur® on a steel quay wall.

Other properties include:

• Proven lifetime of over 30 years in highly corrosive environments
• Stops biological corrosion
• Practical results show adhesion strengths of over 20 MPa
• Can perform in a wide range of temperatures from -35°C up to 150°C
• Resistant to most fluids between pH 0 and 14
• Excellent abrasion and impact resistance
• Surface tolerant: minimal surface preparation can be done
• Unlimited overcoating
• Excellent cathodic disbondment resistance
• Any RAL-color is available (except for anti-fouling)
• • Humidur® gives a very smooth surface to increase the flow velocity of pipe structures

Humidur® has approvals for drinking water, offshore, petrochemical, etc. The coating system has also been approved by several governmental agencies such as: ABS (American Bureau of Shipping), CCS (Chinese Classification Society), USACE(United States Army Corps of Engineers), BAW (Bundesanstalt für Wasserbau), Norwegian Defense, etc.

Technical back-up is available from TNO, SGS, Royal Haskoning, University of Ghent, University of Antwerp, Maritime Academy of Antwerp, EXOVA, TÜV Rheinland, etc.

The Humidur® coatings have proven to be the most cost-effective solution, according to a life cycle cost analysis conducted by Royal Haskoning. This can be explained by the fact that the coatings are maintenance-free and by the durability of the system (proven life time of over 30 years). Furthermore, Humidur® is a one-coat system, which is reducing the application- and labour costs as well as the amount of waste.

All Humidur® coatings are single layer systems. The application can be done straight onto the substrate after surface preparation, which means that no primers are required. This makes the Humidur® coating probably the fastest applicable liquid epoxy on the market. There will be no risk of contamination between layers or problems with interadhesion.

If requested, several layers can be applied wet-on-wet without waiting time, as no individual layer needs separate curing because of the absence of solvents (WFT = DFT). This is in contrast to alternative solvent-based coatings, which are limited in layer thickness as solvents need to evaporate after every layer.

Other advantages of Humidur® include:

• capability of curing under water and at freezing temperatures: the structure may be submerged immediately after coating applicatio
• applicable in a relative humidity up to 95%
• Humidur® is safe to work with: flashpoint >100°C and even >120°C
• can be applied easily by spray, brush, roller or caulking method

Eco-friendly

The Humidur® coatings were developed “avant-la-lettre” and were composed with a clear vision towards the future. The coatings contain no solvents, no heavy metals, no coaltar, no isocyanates, no VOC’s and no TBT. The product has 100% solids and is perfectly safe for the environment.

Humidur® is capable of curing under water without leaching taking place and has no detrimental effect on the sediment, fauna and flora in and out of the water. When using Humidur® on static marine structures, the biofilm can form itself on top of the Humidur® coating without affecting the substrate and without any loss of properties. For the anti-corrosion coatings, almost 30-year old coupons proved there is no migration of the corrosive elements towards the substrate. Humidur® stops biological corrosion and MIC without affecting or killing the bacteria.

Humidur® AF is the anti-fouling coating in the product range when the formation of a biofilm is unwanted.

As Humidur® is a single layer system, less waste will be created in the process.

Here is a barge with cofferdam doing maintenance and paint job on steel sheet harbour. The finale result is clearly seen on right.