Steam traps: Key to cutting costs

Steam can account for as much as 40% of a company's fuel bill. Here, Grant Bailey of Thermal Energy International, explains the importance of efficient steam traps

In addition to steam being used to heat raw material and semi-finished products, it is also used to evaporate, distil, boil, brew, react, agitate, clean and sterilise for a wide range of equipment in a diverse range of industries. However, it is not free and as fuel costs increase, so does the cost of producing steam. Therefore it is essential to: Determine how efficiently your steam generation is operating based on steam output versus fuel input Determine how much steam is being used and how much it is costing to generate Determine the effectiveness of steam traps and whether they are working efficiently A steam trap gets rid of condensate, air and non-condensables as quickly as they accumulate. In addition, for overall efficiency and economy, the trap must provide: Minimal steam loss Long and dependable service Corrosion resistance Air and Non-condensable gas venting Operation against back pressure Freedom from dirt problems Malfunctioning steam traps represent a significant source of wasted energy and condensate losses in addition to replacement and maintenance costs. Depending upon an individual maintenance routine, around 15% to 25% of steam traps can be leaking within any factory or site at any one time resulting in hundreds of thousands of pounds of energy being lost annually. This not only represents a major cost in expensive lost steam but means additional expenditure in maintaining, stocking, checking and replacing mechanical steam traps.

Why do steam traps fail? Pressure surges due to sudden steam valve openings and improper piping or trap misapplication, which in addition to malfunction can result in water hammer, are some of the reasons for failure resulting in either it leaking or the trap failing closed.

When steam traps fail open, and discharge into condensate return systems, they cause pressurisation of the condensate lines, which inhibits trap drainage and often reduces heat output and production.

Steam traps need to work at optimum efficiency to minimise the impact on the environment. For each litre of heavy fuel oil burned unnecessarily to compensate for a steam leak, about 3kg of CO2 is emitted to atmosphere. This equates, over a year, to the CO2 emissions from 25 cars

The venturi orifice design According to research carried out by Queen's University, Belfast, venturi orifice designed steam traps, such as those produced by Thermal Energy International, have been proven to be the most efficiently designed steam traps, providing an average reduction of 11.5% in the portion of the boiler fuel bill used to generate trapped steam.

While the venturi orifice design retains its initial efficiency indefinitely, the mechanical trap, with its moving parts, gradually deteriorates. With mechanical steam traps, when heat from steam is lost, vapour condenses to the bottom of the pipe and finally makes its way to the mechanical trap. With the venturi orifice trap, the difference in density between steam and condensate and the continuous flow preferentially discharges the higher density condensate resulting in less condensed water on the heat transfer side of the equipment.

This also maintains the steam on the heat transferring side of the equipment resulting in better thermal efficiency.

As the venturi orifice steam trap enables continuous condensate discharge, the trap is equipped with an orifice, sized to the application. Therefore the live steam loss is lower than the loss through a conventional mechanical trap, even when new. Through the correct application of venturi throat design and orifice size, the capacity of the venturi orifice design can be self-regulated, dependant on load, and operated from the maximum running conditions to zero. This provides increased capacity during start up.

The venturi orifice steam trap effectively drains condensate from the steam system. As it has no moving parts to wedge open or fail, it provides a high degree of reliability and needs only minimal maintenance. Since the trap can handle variable loads and accommodate wide load changes it is suitable for a wide range of applications. Those produced by Thermal Energy International, for example, are usually made from highgrade corrosion resistant stainless steel and are performance guaranteed for 10 years, obviating the need for repair or replacement.