Sea Water Intake Riser System Pressure Stabilization
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Solution Overview
Problem
Existing submerged sea water intake riser (SWIR) systems experience large and frequent pressure variations due to vertical and axial accelerations, which can compromise cooling operations and damage equipment, especially with longer riser pipes.
Innovation Solution
A sea water intake riser system with multiple caissons and a sump tank that stabilizes water pressure by acting as a buffer volume, reducing pressure variations through a constant water body and minimizing water level fluctuations around lift pumps, using flexible and reinforced pipes to maintain stability and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If longer riser pipes are used to access colder water at greater depths, then cooling efficiency is improved, but pressure variations increase causing equipment damage and operational compromise
Solution Approach 1:
The system divides the single long riser pipe into multiple separate riser pipes (at least two), each connected to its own caisson. This segmentation reduces the pressure variations experienced by each individual pipe and prevents the propagation of pressure waves through a single long conduit, thereby maintaining reliable cooling operations while still accessing cold water at depth.
Solution Approach 2:
The system incorporates air pockets or air cushions within the caissons to absorb and dampen pressure variations before they reach the lift pumps and process equipment. This beforehand cushioning protects the system from the harmful effects of pressure hammering and vacuum conditions that would otherwise compromise cooling operation reliability.
2Temperature
If longer riser pipes are used to access colder water at greater depths, then cooling efficiency is improved, but pressure variations increase causing equipment damage
Solution Approach 1:
By dividing the water intake system into multiple separate riser pipes and caissons, the system reduces the magnitude of pressure variations transmitted to equipment. Each shorter pipe experiences less pressure hammering and vacuum effects, preventing equipment damage and extending durability while still achieving the required water temperature for efficient cooling.
Solution Approach 2:
Air cushions are strategically placed within the caissons to absorb pressure surges and vacuum conditions before they can damage equipment. This protective measure shields pumps, valves, and connections from the extreme pressure variations that occur in long vertical pipes, thereby preserving equipment strength and preventing failures.
3Reliability
If multiple caissons are used to reduce pressure variations, then operational stability is improved, but system complexity increases
Solution Approach 1:
The system uses multiple caissons and riser pipes arranged in a modular configuration, where each unit is relatively simple in design. This segmentation approach improves operational stability by reducing pressure variations, while the modular nature allows for scalable implementation that balances complexity with performance benefits.
Solution Approach 2:
Multiple caissons are positioned to share a common water source and can be integrated into the existing hull structure, reducing the overall complexity compared to using a single extremely long riser pipe. The combined system achieves improved reliability while utilizing shared infrastructure and space efficiently.
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 system achieves more consistent operating efficiency and reduces equipment damage by stabilizing pressure variations, allowing for efficient cooling even in unsteady sea conditions, with potential weight savings and reduced carbon emissions.
Implementation Method 1
a sump tank, attached to the bottom side of each of the caissons such that each through-opening thereof is in fluid communication with a volume inside the sump tank... the sump tank... defining a sump volume extending between the bottom side of the hull... and the bottom side of each of the caissons... which acts as a buffer volume between the water inflow at the bottom side and the water outflow at the lift pumps
Implementation Method 2
a lift pump arranged inside each of the caissons and having an inlet at a vertical distance with a predetermined minimum submergence (d) and adapted for pumping cold water from the caisson up to the floating production unit for use as cooling medium
Implementation Method 3
During normal pumping operation, the water level in the caisson is lower than the outside water surface, generating a pressure difference for the lower temperature water at the inlet at the bottom of the riser piper to flow into the caisson
Data Source
Figure 1
Figure 2~3
Figure 4A~4B
AI summary
A sea water intake riser system (100; 100') for a floating production unit (1), comprising at least two caissons (120), wherein the height of each caisson is substantially equal to a vertical height (L) of a hull (5) of the floating production unit (1) and extends, when mounted to the hull (5) of the floating production unit, from a predetermined minimum distance (126) from the bottom side of the hull up to at least the water-line (WL) during use, each caisson (124) comprising an open top side and a through-opening in a bottom side (123); a lift pump (140) arranged inside each of the caissons (120) and having an inlet at a vertical distance (141) with a predetermined minimum submergence (d) and adapted for pumping cold water from the caisson (120) up to the floating production unit (1) for use as cooling medium by production equipment (10) of the floating production unit, and a sump tank (125), attached to the bottom side (123) of each of the caissons such that each through-opening thereof is in fluid communication with a volume inside the sump tank (125), the sump tank being located between the bottom side of the hull and the at least two caissons (120) when mounted and having a through-opening (155) in a bottom side (128) and being connectable to an upper end of a riser pipe (150).