CRC Evans

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When CRC-Evans Pipeline Induction Heat (PIH) decided to develop a pioneering new fused field joint for three layer PP coatings to be used as a field joint, it required ground breaking engineering solutions to make the process work effectively, smoothly, reliably and in very unusual conditions.


PIPELINE TO SUCCESS 

The last few years have seen a significant and increasing demand for insulated pipelines in the world of offshore pipeline construction.

When CRC-Evans Pipeline Induction Heat (PIH) decided to develop a pioneering new fused field joint for three layer PP coatings to be used as a field joint, it required ground breaking engineering solutions to make the process work effectively, smoothly, reliably and in very unusual conditions.

The new development is part of an ongoing process by CRC-Evans, a UK based company founded in 1980, specialising in the on and off site anti corrosion coating, heat treatment and other support services during construction of on shore and off shore oil, gas and product pipelines around the world.

Challenges of this product development :

From the beginning of the developmental stage, CRC-Evans assessed the possible challenges and issues to be resolved to ensure a successful product development, including:

  • This was to be the largest IMPP field joint
  • Moisture of material and conditions at sea
  • Manufacturing conditions at sea
  • Minimum available space/height as this had to fit into a sea container (transport globally)
  • Special voltages as this was supplied from the ship
  • High instantaneous demand of the polymer/system
  • Blending, drying and conveying of materials to automate the complete process
  • Final integrity of the field joint
  • Accurate and consistent dosing of materials/blend accuracy
  • Material handling system suitable for sea conditions
  • Corrosion of joint/equipment
  • Even surface temperature of the field joint

In October 2011 after an extensive R&D process initial prototyping and testing of the product proved successful, CRC-Evans approached Motan Colortronic Limited.  This was to discuss the automation of the material handling equipment required in the automated process.

Extensive discussions took place between the two technical teams as to the total requirements of the process, material throughputs, location, restrictions, lead times etc as this was a totally new process unlike standard injection, blow moulding or extrusion processes.

‘So How Does It Work’

The injection moulded PP equipment consists of a specialised extruder, accumulator assembly and a hydraulic powered mould.

The PP blend of 3 materials are blended, then conveyed to a pre-drying hopper, then to a second hopper to be dried to the final moisture requirements and then finally to the specialised extruder head.

The specified amount of material is delivered to the extruder accumulators where the material is held.

When injection is ready to commence, the accumulator assembly injects the molten material through the injection point into a heated steel mould secured around the field joint area.  The shot weights of the joints vary from 60-120 kg.

Once filled, the mould is then cooled and removed leaving a solid polypropylene field joint.  The total cycle time is 5-6 minutes.

This special injection/batch process together with discussions between the customer and supplier led to the following requirements and system design to ensure the best possible results to suit the customer specification.

  • Initially blend the required 3 materials to the desired rates.  As the units would be at sea with the motion of the sea, volumetric blending was chosen to eliminate any error possibly caused by a gravimetric weighing process.
  • It was felt best to blend materials first to ensure all materials were dry due to the high moisture/humidity at sea.
  • After blending, the materials were then vacuum conveyed to a first drying hopper, pre-dried and heated and then conveyed to a second hopper to be dried to the final moisture requirements for the process.
  • The material was then conveyed from the last drying hopper to the special extruder accumulator and held ready for injection in the mould.

The reason for this solution, in particular the 2 smaller drying hoppers, was due to the height limits of the storage container.

The maximum height for all equipment assembled was 2,228 m where typical blending, drying and conveying equipment in a standard design to suit the throughput would be 3,025 m.

In addition to this, special voltages were required of 440V/60Hz/+E (no neutral) as the mains were supplied from the transport ship.  These requirements resulted in a mechanical and electrical re-design of the complete equipment to suit the special requirements whilst the customer had only allowed 8 weeks lead time which was typical for standard equipment.

The systems were designed, delivered and installed within the customer’s required time frame and are now in use around the world enabling CRC-Evans, a UK engineering company to compete worldwide.

There are now several new projects in the pipeline for CRC-Evans which would mean new orders for Motan Colortronic Limited.

19 March 2014

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