26/07/2013

Modernise To Make The Most of Steam

Think you know how to get the most out of your steam systems? The latest developments in steam trapping could make you think again.

A long established component of any efficient steam distribution systems, steam traps remove condensed liquid from steam lines to maintain optimum performance. Yet even these workhorses can sometimes offer room for improvement in terms of reduced maintenance, improved control and energy efficiency. 

The tried and trusted mechanisms at the heart of today’s steam traps have proved to be the best option for a wide range of applications, so these days it is often innovations in the surrounding installations that can help boost overall performance. New working practices and new control technologies can also provide opportunities to increase efficiency.

All-in-One Solutions

The popularity of steam trapping stations is a great example because steam traps are not installed in isolation, but alongside peripheral equipment such as isolation valves, strainers and connectors. In a conventional set up, all these components must be specified and installed separately, a time-consuming process that creates opportunities for human error to creep in, and where every connection poses a leak risk.  In contrast, a steam trapping station includes all the necessary equipment within a single entity - only the steam trap itself needs to be specified. The use of a ‘quick-fit’ connection system to fit the station into the steam line brings additional benefits.

In adopting this approach, it is important to ensure the internal components, such as the ball valves, check valve and strainer screen, can all be accessed for replacement. Lockable handles on the isolation valves are a good idea to minimise the possibility of accidental operation during maintenance, thereby improving safety. 

Glorious Isolation

Safety and speedy maintenance are also the key drivers behind the use of double block and bleed valves. These isolate steam traps or other components so maintenance can be carried out safely without having to shut down the entire system.

The most compact double block and bleed valve offers the same face-to-face dimensions as a single isolation valve. This makes it easy to retrofit double block and bleed valves without pipe cutting or welding.  Better still, each valve takes up only a third of the pipeline length compared with conventional safety isolation installations.

Listen and Learn

For steam users responsible for major installations, one of the most challenging aspects of maintaining peak performance comes from looking after large numbers of traps spread across entire sites, but the emergence of wireless technology could point the way forward.  Engineers could be alerted to any trap failures, whether they have failed open or closed, and the amount of steam being lost. They can also see if a trap is not working at peak efficiency and investigate why: blockages and leaks will also be easier to spot.

Crucially, all this could be observed from a single point of access.  Low-power, standards-based wireless communication devices such as ZigBee are already installed in millions of pieces of kit worldwide. In the case of steam traps, the techniques for recognising when a trap is underperforming will involve ‘listening’ to the sound frequencies generated through the equipment and comparing the acoustic performance with the expected sound profile to give a reliable assessment of condition.

 

 

Cool Possibilities

Energy efficiency is also a critical consideration. Steam traps must be specified and maintained to perform properly, but there are other ways in which they can be used to optimise energy usage, such as enabling users to extract more energy before returning condensate to the boiler.  The process works by reducing the temperature and pressure at which steam traps remove the condensate, often by changing the type or rating of the traps.

With energy, however, you can’t get something for nothing: the cooled condensate will be at a lower temperature when it eventually returns to the boiler feed, so any benefit might be undone by the need to augment feed water heating in the boiler room. In addition, it may not be practical because production quality or throughput might depend on delivering the maximum steam temperatures, or water logging may present a danger of corrosion and water hammer. On the other hand, this advanced condensate control can often improve the plant’s overall steam balance by, for example, eliminating excess flash steam and dealing with choking problems. 

With multiple factors to consider, it can be a tricky balance to get right and many users would be well advised to seek expert support if they are trying to decide if this extraction is right for their application, or even which steam trap to specify in the first place. 

There is no ‘one-size-fits-all’ solution. Some suppliers promote orifice traps as a universal, maintenance-free solution, but these only function well under pretty constant loads and pressures, while a tiny orifice can become blocked. Mechanical and thermodynamic provide a more adaptable and reliable alternative in the long run.

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