Every steam systems contains impurities:
- metal particles detached from pipe walls as a result of corrosion
- by-products of construction or pipe repair
- particles of mud or other matter sent into pipelines as a result of boiler carry-over
Impurities can prevent proper operation of steam traps. Even with the best care, and in spite of filters, there are always unwanted particles in steam pipes. These particles can lodge themselves between the valve and the seat of steam traps and cause steam leaks. A leaking steam trap means avoidable costs. It is therefore necessary to insure regular maintenance of steam traps.
Steam traps that require no maintenance don’t exist: all types of steam trap require a certain amount of maintenance.
It is always profitable to quickly repair or clean a steam trap once a leak is detected. In steam systems where steam traps haven’t been serviced for 3 to 5 years, 15 to 30% of traps can be defective. The cost of a single leaking steam trap in a typical system can amount to thousands of dollars per year.
Evaluating steam trap operation
It is important not to confuse flash steam and and steam leaks. We know that condensate going from a high pressure (before the trap) to a lower pressure (after the trap) partly vaporizes. We might be tempted to think that it is possible to evaluate a steam trap discharging into open air by examining the plume of steam at the trap’s outlet. However, this method is not reliable because it is impossible to distinguish between flash steam and live steam.
That said, if we are very familiar with the normal appearance of the plume that comes out of the steam trap, an increase in the size of that plume can be a visual indication that the steam trap is not functioning properly. In a closed system, since steam traps don’t discharge into open air, it is impossible to draw this kind of conclusion. On the other hand, an increase in pressure at the dearator can be a sign that one or more steam traps are leaking.
A temperature decrease in a heat exchanger can result from a clogged steam trap: since condensate cannot be evacuated by the trap, it accumulates in the exchanger, which causes the decrease in temperature.
In any case, when a steam trap malfunction is suspected, it is necessary to test the trap objectively before drawing any definitive conclusion.
Steam leak detection is made with the assistance of a special device designed to detect ulrasounds generated by a leak in a trap. A steam leak in a trap generates a very specific whistling noise that the human ear cannot detect. The leak detector is designed to to measure these ultrasounds and indicate if there is a leak. It is important to use the detector properly in order to avoid erroneous diagnosis.
A leak detector can detect external noises if the noise level is very high in the area surrounding the trap. This can lead to a bad diagnosis. Whenever possible, it is preferable to test steam traps at a time when the noise level is lower.
A working steam trap that receives a lot of condensate produces ultrasounds that can be interpreted as a leak by the detector. Steam makes this noises as it flashes in the trap. It is thus important not to test traps during system start up, at a time when traps have a lot of condensate to eliminate. It is better to test traps once the system has stabilized.
A leak in a steam trap that receives a lot condensate is not necessarily problematic since a trap full of condensate doesn’t allow steam to escape. The impact of a leak in this kind of situation is minimal as long as the load is high. If the load in the exchanger varies and becomes almost nil, then the leak will become important and the detector will be able to measure it.
In order to verify a steam trap’s ability to open, it is necessary to test the trap under full load. Ideally, we must then test the trap under no load in order to determine if the trap closes correctly. End of lines are often used for that purpose.
Cleaning steam traps
Cleaning of steam traps requires a specific technique. Our team offers a complete cleaning service on all steam traps installed by Lalonde Systhermique. Parts are subjected to special acids that remove iron particles stuck to the stainless steel. In cases where capsule is clogged by oily matter, a solvent is used. Each capsule is then evaluated individually on a test bench under steam pressure. Bad capsules are identified and returned to the owner.
Identification of steam traps
Identification and tagging
Plants often use a great number of steam traps and it happens that the existence of some of them becomes forgotten about, especially if they are in poorly visibles locations. It can also happen that some of them are skipped during maintenance rounds.
In order to insure the perennity of the system, each steam trap must be identified with a tag that is robust and highly visible.
Once steam traps are tagged, they must be recorded on a location plan.
Following major works in a plant, we discovered steam traps hidden between two walls – there was no location plan to indicate their presence to the maintenance team and consequently they hadn’t been serviced in 10 years. The steam traps had been leaking for at least 5 years and steam was getting out of them at full flow rate. Imagine the costs associated with this kind of situation!
A well-conceived location plan makes it easy to quickly locate any of the plant’s steam traps, making this kind of incident unlikely. The location plan facilitates planning and execution of adequate maintenance operations.
The last element of a good maintenance strategy consists in keeping a technical record of steam traps. This record is in fact a list that specifies the brand, the type, the model, the size and the date of installation for each steam trap. The technical record also contains maintenance instructions (required tools, spare parts, etc.) as well as a technical sheet for each type of trap.