Process Equipment Update
to the complexities of detection. One of the common locations for leaks is in a steam trap, an essential component of any system. Because of their critical importance, it’s worth exploring this technology in more detail. In a typical system, steam flows
through a network of mains and branch pipes, all configured to deliver steam at specific points. The steam is propelled by differences in pressure and temperature caused by steam condensation. To control and eliminate this condensation from the system, steam traps are established at critical locations. These steam traps purge condensate and other incondensable gases, allowing the steam to reach its destination in as dry a state as possible in order to perform its task efficiently and economically. Because of its function, the steam trap is the most important link in the condensate loop. There are three basic types of steam
traps – all classified by International Standard ISO 6704:1982. Thermostatic traps react to changes in steam temperature, and will pass condensate when lower temperatures are reached. Mechanical traps – which include ball float and inverted bucket traps – sense and respond to changes in the difference in density between steam and condensate. Finally, thermodynamic (disc, impulse and labyrinth) steam traps are operated by changes in fluid dynamics and rely partly on the formation of flash steam from condensate. Combined with other variations – including continuous flow, intermittent or fixed – it is clear that there is a broad spread of technology available, each presenting unique challenges in terms of diagnosis and maintenance. Steam trap surveys test and document the operational status of traps, utilising both ultrasound and temperature differentials and create a comprehensive trap inventory including location, type and application engineering. Survey reports also include a full economic analysis to determine return on investment, as well as recommendations for specific trap improvements.
Typically, industry takes three broad approaches to aid accurate diagnosis of steam trap leaks, each of which can be highly effective in the right conditions. The first is visual inspection. The use
of a testing-tee arrangement, test cock, or an inline sight glass for reviewing the steam trap discharge to the atmosphere can accurately determine: blow-by steam or a failed open condition; severe steam leakage; improper installation; under-sizing; incorrect type; and incorrect installation practice.
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f leaks are ignored, they can cause a drop in system pressure leading to lower operating efficiency, while over time the corrosive power of steam can cause equipment failure.
This demands an in-depth understanding of the difference between flash steam and blow-by steam, while by their very nature, visual inspections expose the technician to the potential and damaging release of hot steam. Though a relatively low-cost option, even visual inspections involve a small additional cost associated with installing the components that permit online visual testing. The second method of inspection involves temperature or thermal
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Planned maintenance can go a long way towards eliminating the damage caused by leaks.
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