We recently completed a project with a client who operates in the marine sector. They had a floating offshore platform with a boiler which incorporates an economiser with two hot water circulating pumps. These pumps were over 40 years old and reaching the end of their working life, so our client was looking for alternative solutions.
What is an economiser and how does it improve boiler efficiency?
An economiser is a specialized heat exchanger designed to capture waste heat from hot exhaust gases, such as flue gases from boilers or ventilation exhaust in buildings, and transfer it to preheat fluids like boiler feedwater or incoming air. By recovering energy that would otherwise be lost, the economiser reduces the fuel required to raise water to boiling point, improving overall system efficiency and lowering operational costs. Hot gases flow through a series of tubes within the economiser, while cooler feedwater passes around or through these tubes, absorbing the heat. This preheating process not only decreases fuel consumption and emissions but also enhances thermal performance, stabilizes boiler operation, and prolongs the life of heating equipment.
Economisers are widely used in industrial, commercial, and HVAC systems to maximize energy recovery, making processes more economical and environmentally sustainable.
Dealing with high temperatures
High-temperature boiler pumps often face mechanical seal failure, so gland packing is commonly used as the primary sealing method. Also called compression packing, it consists of flexible rings inserted into the stuffing box to seal rotating or reciprocating components. Packing can be made from graphite, aramid, or PTFE (Teflon), chosen based on temperature, pressure, and chemical resistance.
For our system, we selected two XCP hot water circulating economiser pumps. ISO 2858-designed, heavy-duty, close-coupled centrifugal pumps, the XCPs are built for demanding industrial and marine environments, offering high flow and pressure capabilities for reliable operation in boiler economiser circuits.
These pumps are designed to pump low viscosity clean or slightly contaminated fluids which don’t contain solid or fibrous solids, such as fuels like diesel, petrol and kerosene, as well as fresh water and sea water.
Typical applications range from irrigation, water supply and treatment, pressurisation, grey water and dewatering, to fuel transfer, firefighting, marine and mining applications.
A proven pump design with many benefits
In this design, the centrifugal process pump and motor have 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 long-coupled design has a large space between the pump and motor. This helps to stop fluid getting in if there’s ever a seal failure. The long-coupled configuration also means that the pump head can be reached without taking out the motor, making it all very easy to maintain.
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.
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.
Certified for use in explosive environments
These two XCP horizontal long-coupled pumps are also available in ATEX versions for handling flammable fluids or being installed in a non-safe area.
These pumps will primarily be working as hot water circulating pumps delivering around 200L/min at 3 bar, and handling water at up to 170°C* continuously for extended periods of time.
To produce this level of performance, we supplied the pumps with motors specifically rewound for 460V 50Hz operation. This is quite unusual as 460V is normally a 60Hz voltage.
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 which needs our help then please speak to North Ridge Pumps today.
