Cheap source of trouble

Operators assumed the light on this dryer meant that the power was on, but it actually indicated an alarm.

A power generation plant on a small island was havingtrouble. Its instrument air was supposed to be dry, but therewere many times where water was pouring out of drainsand collecting in low spots in piping. This left their engineersscratching their heads in puzzlement — the water issue was getting so bad that system outages were actually occurring.

The plant hired an expert to come in to have a look and recommend a solution to their problems. On first impression, the expert was struck by the high temperatures in which the compressed air system was operating. Outdoor temperatures were 80° F, but with a building full of diesel generators, the temperature rise in the building was nearly 20°. This was not a good place to operate refrigerated dryers.

On inspection it was found that the high temperatures had knocked out the air dryer (Figure 1). Operators were dismayed to learn the red light on the front panel was actually an alarm — they had assumed this was a power indicator. Due to high temperatures, the compressor discharge was quite hot, and the undried compressed air cooled in plant instrument air piping, some of which passed under floor, forming low spots where water and compressor lubricant would collect. The water would build up until, finally reaching a critical point, the whole mess would percolate up through the system, contaminating important control and measurement devices. Add to this a failed drain on the compressor’s wet receiver tank, and the situation lead to a failure that actually caused electrical system outages.

When performing maintenance checks, it is important to ensure air dryers are working in conditions that are within the maximum operating range for temperature. If not, corrections need to be made to the ventilation. Operators should also become familiar with the dryer manual so they can recognize proper or improper operation. And remember: all condensate drains need to be manually checked to ensure proper operation. These are usually $50 drains — quite inexpensive — but they can cause problems worth many thousands of dollars.

Ron Marshall | Contributing Editor