The purpose of a steam trap survey is to discover problems such as steam leaks, low energy efficiency, flooding, improper design or size, defective assembly, low discharge temperatures, excessive back pressure, obstructions, blockages, water pounding, and so on.
Typically, more than 20% of steam traps leak live steam, which is incompatible with energy efficiency, sustainable growth, and combating climate change.
Implementing a practical inspection and predictive, preventive, and corrective maintenance steam trap survey programme significantly reduces all of the abovementioned incidents. It is instrumental in lowering steam leaks, optimising energy efficiency, and lowering greenhouse gas emissions in steam networks. The table displays indicative incidence levels at purging stations about the frequency of inspection and maintenance.
Given below are some methods for steam trap surveys
Purge station verification must examine not only the condition of all of their components (steam trap, blocking valves, bypass…) but also their appropriateness and size for each application, as well as their energy efficiency. Consequently, this verification often necessitates considerable experience as well as the use of a mix of many inspection procedures of steam trap survey, which are outlined below
Visual steam trap survey Inspection by direct method
To discern between living steam and expansion steam when observing the atmospheric discharge steam trap survey of a purge element, considerable expertise is required. The presence of flash steam in steam trap discharge is regular and does not signify the presence of live steam leakage. However, the creation of flash steam is substantially decreased in tracing applications because of the partial utilisation of the sensible heat of the condensate, a suggested technique to boost energy efficiency, which is an unalienable goal at the moment.
Ocular inspection of a steam trap’s atmospheric discharge enables diagnosis, albeit it is difficult to distinguish between live and flash steam, leading to mistakes.
Visual steam trap survey inspection by peephole
Peephole inspection of steam trap survey substitutes test valves with a glass peephole inserted in the pipe in front of or behind steam traps. Peepholes are classified into three types:
- Simple
- Siphoned
- Electronics
A simple sight glass is often mounted behind the purging element and allows simply for the presence of flow through it, with no ability to distinguish between live and expansion steam. A syphoned peephole has an inbuilt syphon. It must be positioned in front of steam traps and, as a result, enables differentiating the condition of the fluid (condensate or live steam) since, when installed in this location, if a steam passage is seen, it can never be flash steam. Three distinct circumstances can be noticed on syphoned glasses, as listed below:
1. A thoroughly waterlogged aspect indicates that the steam trap has been inundated owing to a lack of discharge capacity, an impediment, or a blockage.
2. Liquid level up to the edge of the central section of the syphon: This indicates that the steam trap is operating well, and there is no loss of steam.
3. Lower liquid level than the middle area of the siphon edge: It signifies that the steam trap is leaking live steam.
This approach is only applicable to cyclic steam traps and measures the time elapses between two successive steam trap discharges. A timer is not required; mentally count 101, 102, 103, etc… to establish the steam trap cycle duration in seconds. If the trap runs continuously without a cycle, one of three things can happen:
1. Steam trap is cold: It means the trap is out of service or blocked.
2. Steam trap is warm: The trap is flooded (stack, undersized, high back pressure, …).
3. Steam trap is very hot: It means the trap is blowing steam.
If the trap opens cyclically, it must be ensured that the cycle’s duration is not unreasonably short. For example, the cycle duration in thermodynamic disc steam traps should not be less than 30 seconds; otherwise, the faster the cycle, the more degraded its internal valve will be and the more significant the energy loss.
Steam trap survey by measurement of temperature
This strategy, if not combined with another, frequently results in mistakes since it necessitates knowledge of more information than is typically accessible in the field, namely
Type of steam trap (continuous or intermittent discharge); discharge temperature (subcooled or at boiling point).
Implementation (drip well, process, normal tracing, critical tracing, turbine, tank heating, …).
Inlet pressure (may vary due to regulating valves, charge variations, …).
Outlet pressure. This is always an unknown quantity. (It is not sufficient to know the pressure in the overall return collector, but rather the pressure just at the outflow of the steam trap, where there may be significant fluctuations owing to the creation of local flash steam at this point. This figure has a substantial impact on the trap’s proper operation, producing considerable difficulties).
Temperature measurement in small-flow traps should be avoided in general since ultrasonic detection is reliable enough.
Steam trap survey with the help of ultrasound
It is a quick and dependable approach for steam trap survey. It entails collecting the ultrasonic produced by the passage of steam or gas via an aperture. In effect, the high-speed selection of gas or steam through a constriction causes noise across a wide range of frequencies, emphasising the harmonic that corresponds to a restricted band of frequencies approximately 39 kHz (+/- 2 kHz).
To use the ultrasound method, first understand how steam traps work, their type of discharge (continuous or cyclic), and then match the sensitivity of the ultrasound instrument to the steam pressure; finally, press the contact probe firmly against the steam trap to read the diagnosis on its LCD screen.