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Two automatic pump traps from Spirax Sarco have helped solve a serious control issue for Sembcorp, a UK industrial utilities and services company.

The pump traps prevent the company’s gas heater from stalling, which was previously making it difficult to control the gas temperature.

Sembcorp uses gas to produce electricity in its own power generation plant on Teesside, as well as distributing gas to some of its industrial customers.

The company must heat its gas supply to 40C to prevent it freezing as it enters lower- pressure lines downstream.

Development manager, Dr Michael Capstick, says: ‘Prior to the new systems being installed, the gas temperature varied widely, but the temperature control is now within 2C of the set point.’ Sembcorp’s shell and tube gas heater uses low-pressure steam on the shell side to heat gas in the tubes.

It handles around 20 tonnes of gas per hour on average, but demand can vary from just a few tonnes up to 40 tonnes per hour.

This type of variable load can result in a pressure drop or even a vacuum forming inside the exchanger, preventing condensate from escaping.

‘Sometimes the condensate backed up until it filled the whole heat exchanger,’ said Dr Capstick.

‘This build-up sub-cooled the system until the only way to reach the required temperature was to open up the steam valve to let the steam surge in and push the condensate out.’ This cycle led to temperature fluctuations in the gas, added Capstick.

The gas sometimes reached almost the same temperature as the steam, while at other times it froze in the lower-pressure pipes.

In addition, the thermal shock caused by pushing sub-cooled condensate out of the heater with a surge of steam put extra strain on the equipment, potentially causing maintenance issues in the future.

The two Spirax Sarco APT14 automatic pump traps eliminate all these problems by removing condensate in a controlled way, regardless of any back pressure.

The pump traps use plant steam to provide the motive power to pump out condensate.

Condensate enters the trapping chamber and, if there is no back pressure, it flows freely through the chamber and into the condensate return system.

However, if back pressure prevents the condensate from leaving normally, the pump trap’s condensate outlet closes.

Condensate continues to flow into and fill the chamber.

A mechanical float rises with the condensate level until a snap-action mechanism opens a steam inlet.

The resulting steam pressure in the chamber forces out the condensate, and the float falls until it re-engages the pump mechanism.

This closes the steam inlet and the cycle is repeated.

Spirax Sarco benefits built on knowledge. Spirax Sarco has all the products, services and expertise needed to make the best investments in building and maintaining a steam or industrial fluid plant.

A complete and flexible range of services is available to cover any need from supplying an individual steam trap, to a complete new plant and everything in between. Spirax Sarco Services can help identify, improve and sustain steam system efficiency at every point in the steam and condensate loop.

In addition, custom-built solutions can be created to take a project from design and build to commissioning, support and scheduled maintenance on time and on budget. Pioneers in steam, Spirax Sarco has developed longstanding relationships with customers across a wide range of industries, including hospitals; food & beverage; pharmaceutical; oil and petrochemical; and waste and waste water. Forward thinking to keep you one step ahead As the market leader in steam systems, Spirax Sarco has the market presence and resources to keep abreast of the latest legislative and technological developments.

At the forefront of training Well-trained personnel are essential to achieving the best plant performance.

Spirax Sarco can provide all the training that your staff requires, either on-site or at the Cheltenham-based training centre, for nationally recognised qualifications including BTEC, City & Guilds and the Boiler Operative Accreditation Scheme (BOAS).

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