Leaking steam traps lose significant quantities of steam, which result in large energy losses. Proper maintenance can reduce these losses in an efficient manner. In steam systems where the steam traps have not been inspected in the last three to five years, up to about 30 % of them may have failed allowing steam to escape. In systems with a regularly scheduled maintenance programme, less than 5 % of the total number of traps should be leaking.
There are many different types of steam traps and each type has its own characteristics and preconditions. Checks for escaping steam are based on acoustic, visual, electrical conductivity or thermal checks.
When replacing steam traps, changing to orifice venturi steam traps can be considered. Some studies suggest that under specific conditions, these traps result in lower steam losses and longer lifespans. However, the opinion between experts on the utilisation of orifice venturi steam traps is divided. In any case, this type of steam trap is a continuous leak, so it should only be used for very specific services (e.g. on reboilers, which always operate at a minimum 50 – 70 % of their design duty).
A programme to track down leaking steam traps and to determine whether steam traps need to be replaced is required for every steam system. Steam traps often have a relatively short lifespan.
The frequency by which steam traps are checked depends on the size of the site, the rate of the steam flow, the operating pressure(s), the number and size of traps, and the age and condition of the system and the traps, as well as any existing planned maintenance. The cost benefit of undertaking major inspections and changing programmes needs to be balanced according to these factors. (Some sites may have 50 traps or fewer, all easily accessible, where others may have 10000 traps.)
Some sources indicate that equipment with large steam traps (e.g. with steam flows of about 1 tonne of steam an hour or more), epecially operating at high pressure, may be checked annually, and less critical ones on a rolling programme of 25 % of traps every year (i.e. every trap is checked at least once every 4 years). This is comparable to LDAR ( leak detection and repair) programmes which are now being required in such installations by many governments. In one example, where trap maintenance was haphazard, up to 20 % of traps were defective. With annual follow-up, leaks can be reduced to 4 – 5 % o f traps. If all traps were checked annually, there will be a slow decrease to about 3 % after 5 years (as older traps are replaced by newer models).
In all cases, when checking steam traps, it is good practice to also check by-pass valves. These are sometimes opened to avoid over-pressure in lines and damage ( especially in tracer lines), where the steam trap is not able to evacuate all the condensate, and for operational reasons. It is generally more effective to rectify the original problem, make proper repairs, etc. (which may entail capital expenditure) than operate with poor energy efficiency in the system.
An automated control mechanism can be installed on each type of steam trap. Automatic steam trap controls are particularly applicable for:
●traps with high operating pressures, so any leakage rapidly accrues high energy losses
●traps whose operation is critical to operations and whose blockage will result in damage or production loss.
The costs for replacement are generally considerably less than the losses as a result of defective operation. Rapid payback, depending on the scale of the leakage. See example above.
Energy Efficiency (2009) 3.2.12