Hot water circulation pumps for offshore economiser
EDITOR’ S CHOICE OFFSHORE PUMP UPGRADE
NORTH RIDGE PUMPS
Hot water circulation pumps for offshore economiser
We recently completed a project for a marine-sector client operating a floating offshore platform with a boiler system that includes an economiser served by two hotwater circulating pumps. These pumps were over 40 years old and nearing the end of their working life, so the client asked us to identify a modern replacement solution to improve reliability and performance.
What is an economiser and how does it improve boiler efficiency?
An economiser is a heat exchanger that recovers waste heat from flue or exhaust gases to preheat boiler feedwater or fresh air, improving system efficiency while reducing fuel use, costs, and emissions. Hot gases pass through a tube bank to transfer heat to incoming water, reusing energy that would otherwise be lost and enhancing overall thermal performance.
Because high-temperature boiler pumps are prone to mechanical seal failure, gland packing is commonly used; this consists of heat-resistant soft rings made from materials such as graphite, aramid, or PTFE, selected according to operating temperature, pressure, and chemical resistance.
Which pumps did we select?
We chose two hot water circulating economiser pumps from our XCP range. These are specially built for arduous duty in demanding industrial and marine environments.
In this design, the centrifugal process pump and motor have
The long-coupled design prevents fluid ingress and allows easy pump-head access for maintenance.
separate shafts. This means that only the pump shaft needs replacing if it breaks. Other less robust pumps available only incorporate a motor shaft. So, if the shaft breaks, the whole motor needs to be switched. The longcoupled design prevents fluid ingress and allows easy pump-head access for maintenance.
Above all, this unit is purposely designed for continuous use and long operational life. That’ s because it’ s fitted with extra bearings in the pump head which take a great deal of strain away from the motor during operation.
We supplied each economiser feed water pump with a flushing connection to make sure that the packing stays cool even in high temperatures. To put this in perspective, many centrifugal pumps have elastomers which can fail at temperatures as low as 65 ° C and in this application the pump would see temperatures as high as 170 ° C.
The pumps operate as hot-water circulation units delivering approximately 200 L / min at 3 bar and handling water at up to 170 ° C continuously. To achieve this, the motors were specially rewound for 460 V, 50 Hz operation, which is unusual as 460 V is typically used at 60 Hz.
The pumps were built with a ductile iron casing and a stainless steel 316 impeller, guaranteed to provide many years of uninterrupted service.
If you have a project where you are unsure of the solution, visit www. northridgepumps. com or call us on 01773 302 660
For further information, please visit www. northridgepumps. com
14 PECM Issue 79