The last couple of weeks, the topic of our blogs has included deaerators (DA) and how that piece of equipment plays a vital function in the efficient production of steam. You may find that as time goes on, your deaerator's performance may begin to decline. Many times the water treatment chemical supplier is asked if the oxygen scavenger they are providing is off spec because the customer is using more of that chemical than they used to a few months ago, yet all of the operating factors (boiler load, cycles of concentration) are the same. The truth is that in the vast majority of instances, the poor performance of a deaerator is due to a mechanical issue. Here is a troubleshooting list that may be used to help identify the source of the decreased performance:
- Check the DA temperature and pressure. The temperature of the deaerated water should be within 1-3 degrees of the saturated steam temperature being fed. Contact Watertech for a saturated steam temperature chart. Pressure which is too high can indicate a faulty steam pressure reducing valve. Low pressure or fluctuating pressure also indicates a problem with this reducing valve. Many times an adjustment to this valve is all that is required.
- Check the vent. You should see a continuous 18" to 24" visible steam plume.
- Check the water level gauge glass. These should be checked to ensure that an adequate storage level is being maintained by the makeup regulating valve.
- Check the overflow valve. It should be closed and not bleeding off steam. If the unit is equipped with a loop seal, make sure the seal is not blown and that steam is not being lost for lack of a seal.
- If you have a spray type DA, check the makeup water temperature. This type of DA generally works best if the makeup temperature is 30 degrees F less than the DA operating temperature.
- If you are operating a spray type DA, check your lead versus the design load. Spray type deaerators typically have a problem operating at peak efficiency when the load is less than 25% of design because of insufficient steam flow.
Still unable to identify the problem? You may consider shutting your deaerator down and doing an inspection. Tune in to tomorrow's blog for the 8 items to inspect.