Synchronized Pumping Chambers for Pipeline Field Joint Coating
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Solution Overview
Problem
The existing field joint coating techniques for subsea pipelines, particularly using cast-moulded polyurethane, face challenges due to chemical dissimilarity with parent coatings, leading to bond strength issues and potential cracking, while injection-moulded polypropylene (IMPP) processes are cumbersome and inefficient for subsea operations due to high viscosity and equipment bulkiness.
Innovation Solution
A novel injection moulding apparatus with synchronized pumping chambers and valves allows for alternating injection of molten polymer into a mould cavity, optimizing filling and cooling processes to create a durable PP field joint coating compatible with parent coatings, reducing equipment bulk and improving efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If cast-moulded polyurethane (CMPU) is used for field joint coating, then the coating can be applied, but bond strength is compromised due to chemical dissimilarity with PP parent coating
Solution Approach 1:
The patent applies homogeneity by using polypropylene (PP) material for both the parent coating and the field joint coating. This ensures chemical and material consistency across the entire coating system, eliminating the bond strength issues that arose from using chemically dissimilar polyurethane material. The PP field joint coating is injection-moulded to match the thermoplastic nature of the existing PP parent coating, creating a homogeneous coating system throughout.
2Strength
If injection-moulded polypropylene (IMPP) process is used, then bond strength and compatibility are improved, but equipment bulk and complexity increase due to high viscosity requirements
Solution Approach 1:
The patent applies segmentation by dividing the injection moulding process into two separate pumping chambers that operate alternately. One chamber draws in molten PP while the other injects it into the mould cavity, then they switch roles. This segmentation allows the system to handle the high viscosity of molten PP more effectively by separating the suction and injection functions, reducing the bulk and complexity of the overall equipment while maintaining the benefits of IMPP bonding.
Solution Approach 2:
The patent implements periodic action through the alternating operation of the two pumping chambers. While one chamber is drawing in molten polymer, the other is expelling it into the mould cavity. This periodic alternation optimizes the injection process for high-viscosity materials by ensuring continuous operation without requiring excessively large equipment capacity, thus reducing overall equipment bulk while maintaining effective coating application.
3Duration of action of stationary object
If traditional IMPP process is used, then durable coating is achieved, but processing time increases due to sequential injection steps
Solution Approach 1:
The patent applies continuity of useful action by having two pumping chambers operate in alternating sequence, ensuring that while one chamber is drawing in material, the other is continuously injecting into the mould cavity. This eliminates idle time between injection cycles and maintains continuous productive action, reducing total processing time while still producing the durable PP coating that requires proper curing time for long service life.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution enhances the bond strength and service life of field joint coatings by ensuring compatibility with parent coatings, while reducing the complexity and cost of equipment, enabling faster and more efficient coating processes even in restricted subsea environments.
Implementation Method 1
each chamber being reciprocally expansible in an induction stroke for drawing molten polymer into that chamber from a melt supply and reciprocally contractible in a compression stroke for driving molten polymer out of that chamber into the mould cavity
Implementation Method 2
PP is a thermoplastic material and therefore sets by cooling during and after injection
Data Source
AI summary
An injection molding apparatus has a mold tool that is positioned around a field joint of a pipeline to define a mold cavity. Two or more pumping chambers communicate with the mold tool. Each chamber is expansible to draw in molten polymer and contractible to drive the polymer into the mold cavity. Expansion of one chamber is synchronized with contraction of another chamber. The operation of supply and injection valves associated with the chambers is also synchronized, both with each other and with expansion and contraction of the chambers. In the embodiment described, two pumping chambers are defined within a common pressurizing cylinder, in which the chambers are separated by a piston. The piston is movable within the cylinder to determine and to synchronize expansion and contraction of the chambers.