Multi-Component Liquid (MCL)
As a result of the need to produce repeatable, high quality and reliable field joint coating systems, multi-component liquids (MCLs) have gradually become more widely used in the international pipeline construction industry as the coating system of choice for multi-layer and fusion bonded epoxy coated pipelines.
The liquid coated field joints offer
- Total compatibility with the factory applied coating
- Excellent adhesive bond to the factory coating overlap areas
- Repeatable and consistent on-site application
- Short application cycle time
- Fast cure allowing for reduced period before ditching of pipeline
- Simple non-destructive on-site testing
One other advantage of the liquid system is that the backup anti-corrosion system (the cathodic protection system) will not be compromised, hence ensuring a continuous flow of current to any defect location along the pipeline length. Many other field joint coating systems do shield the CP system and hence defect may go undetected leading to serious failure in the anti-corrosion coating system.
There are many different urethane and epoxy based liquids which offer particular properties appropriate for particular pipeline requirements. In general terms the urethanes produce a fast reacting and flexible coating which can be applied in most climatic conditions with the use of preheating and/or post heating. These liquids will be able to withstand operating temperatures of up to around 90°C. Tar extended urethanes provide a very economical field joint coating system for use on both 3LPE and 3LPP pipelines. Epoxy based liquids will offer higher operating temperature compatibility and are hence more widely used in 3LPP applications.
In order to make the most of the technical benefits of the multi-component liquids available in the market, PIH has designed and developed a family of automatic coating machines. Not only do these systems meter the individual components of the liquids in the correct ratio to the spray head, but the on-pipe rotating spray ring applies the material in a consistently even and repeatable manner to the specified thickness and band width. In this design the consumption of the liquid is reduced to the absolute minimum since over spray and wastage is virtually eliminated with obvious HSE benefits.
Since the application thickness is directly related to the number of rotations of the machine, once the procedure is proven by pre-production testing, the machine will be pre-programmed for the project and can then be operated by trained personnel under the supervision of our technicians. Relatively small coating crews will be required consisting mainly of locally supplied labour, making the use of liquid field joint coating systems very commercially attractive. The equipment can be trace heated to assist with application in low ambient temperature conditions.
Our automatic system has been refined over many years and now offers very high production rates of up to 350 joints per day by a single crew applying liquids to an overall 1,000 micron thickness and overlap onto the factory coating of 50 mm - 75 m.