CTM has successfully engineered, tested, and delivered the world’s largest PU system dispensing machine to Trelleborg Offshore UK in Skelmersdale, Lancashire, UK. Taking 16 weeks from concept to delivery, the team at CTM, custom built and fully tested equipment capable of dispensing 2000 kg of PU system per minute into a mould. Trelleborg Offshore UK designs and produces bend stiffeners for use as rigid riser end fittings. These conically shaped PU mouldings are used in offshore oil and gas installations to add stiffness to the riser, flowline cable or umbilical to limit bending stresses and keep curvature within acceptable limits.
In total 5360L system, weighing just over 6000 kg was used to manufacture the world’s largest bend stiffener. Typically bend stiffeners are around 1000 kg in weight and up to 16 m in length. However, the world’s largest, is 11.3 m long, with an overall diameter of 1.315 m weighs 8340 kg. The fully cured bend stiffener contains just over 2 tonnes of structural steelwork. The part was specifically developed for use by StatoilHydro, who are responsible for the Vega field in the North Sea and produced for Aker Solutions a service and technology provider to the oil and gas industry.
The complete equipment supplied by CTM, comprises a dispensing unit, pumping unit mixing head and control unit. In the case of the PU chemicals used for this application, the MDI based system is a solid at room temperature, so requires heated tanks. The mixing head is powered by a massive 75KW power unit, ten times the size of what would be considered a large unit. “When handling volumes of this magnitude, it isn’t just a question of scaling up a typical unit by twenty times”, declared Shane Wootton, Managing Director, CTM “Moving large volumes of chemicals at high velocity and under high pressure is like working with a time bomb”.
Every element of the equipment had to be fully tested with real time data captured and monitored during the pouring and curing process. Trelleborg needed to know exactly how the bend stiffener is made to provide quality assurance and avoid failure in the field. The challenge is to mix the chemicals and pour them into the mould without creating turbulence. Turbulence introduces air which results in a fault within the moulding. The pressure flows within the dispensing equipment must be controlled and are accelerated and decelerated up to twenty times during the mixing cycle to ensure an even pressure throughout the cycle. In the event of overpressure, CTM have incorporated stringent safety systems that are tested at the start of every cycle. Instead of a simple safety valve, the dispensing unit has an automatic pressure release valve that diverts surplus material into a zero-pressure zone.
Undergoing final inspection and testing at CTM before delivery
The equipment also ensures that when material is diverted to the recycle line at the end of a moulding, the system does not experience hydraulic shock and eliminates any maximum pressure spikes. “There is no room for error when ramping down at the end of a cycle, our control unit has to anticipate all eventualities and ensure the integrity of the machine and safety of operating staff at all times” added Shane.
The dispensing process takes only a matter of minutes, however, the heat generated by the reaction is enormous and cooling the moulded part takes several hours, after which the part is further cured in an oven to provide it high performance properties.
Although the manufacturer is used to custom designing smaller pieces of moulding equipment, dispensing 100kg/min, CTM is no stranger to this size of equipment, having supplied a 1,500kg /min dispensing unit to Qingdao Rubber Tire Co. This machine was designed to mould a PU elastomer “retread” to earthmoving tyres. A service exchange system allowed earthmoving equipment operators to exchange a worn tyre for a previously repaired tyre immediately. Meanwhile, the original worn tyre could be placed into a mould, a PU elastomeric system is dispensed around it which when cured bonds directly to the tyre. This reprocessing system provides a faster replacement service and a cost saving of up to 50%.
CTM has supplied several machines to Trelleborg in the past and has been involved in manufacturing equipment for glass syntactic pipeline coatings.
To discuss how CTM can assist with your project, you can reach our technical team at sales@ctmukltd.com or call us on 01226 245533.
