Reduce Energy Losses by Monitoring Steam Trap Failure

Steam traps are used throughout process plant’s steam systems to remove condensate while losing the minimum amount of steam to the atmosphere. In large plants there can be over 1000 steam traps.

A significant amount of energy can be lost if a steam trap fails open - releasing steam to the atmosphere on a continual basis. For plants which do not have steam trap monitoring systems or preventative maintenance, these steam traps can leak for months or even years.

Steam is extremely expensive to produce, so any losses can result in huge costs very quickly. When considering the capital cost for boilers, the cost of makeup water, fuel, maintenance, and operation it can come to as much as $20 per tonne.

A single steam trap can lose as much as 15 kg/hour after failure, which depending on the temperature and pressure is a significant energy loss over time. This can be calculated by looking at the enthalpy of the stream and the number of traps that have failed.

Based on a trap lifespan of 4 years, it can be assumed that 25% of traps will fail every year, and knowing the cost of producing steam the cost of not repairing the failed traps can be calculated. This is an exponential cost over time as more and more traps fail.

Using the following assumptions, the difference in costs between not having a steam trap monitoring system and repairing all steam traps on a 6 month basis can be seen below:

  • $10 per tonne of steam
  • 15kg/hour steam loss for a failed steam trap
  • 25% yearly failure
  • All steam traps repaired after 6 months
  • $500 to replace a steam trap

In this example the $60,000 repair bill every 6 months can seem a lot just to save a little steam, and as can be seen it takes over 12 months for the savings to start to be seen. Savings of over $800,000 can be seen over a 3 year period, and saving nearly 150,000 tonnes of steam.

Introducing an extensive steam trap survey can be expensive and time-consuming, but it can pay for itself by reducing total plant losses. As steam traps fail their continual loss of steam becomes common place - often to the point where operators do not realize they should not be expelling so much steam. This can lead to a lack of urgency in repairing traps and stopping the energy loss.

Emerson were able to reduce energy losses on a major food manufacturing facility by installing wireless flow meters on steam traps. They found in a survey that 22% of the steam traps had failed for an unknown amount of time. With the installation of flow meters these steam traps could then be monitored continually, and if a leak was discovered it could be repaired or replaced - saving months of energy losses and tonnes of steam.

The use of instrumentation also introduces the additional capital cost as well as the cost of maintaining and calibrating more equipment, which may not be the preferred option of sites with limited resources. The cheaper option may be to simply set up a regular survey of all failed steam traps so that maintenance can be planned.

With ever increasing energy costs reducing steam losses is an easy way to improve process plant’s profitability by improving total fuel efficiency.

More Reading:

Understanding Steam Traps - Chemical Engineering Process

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