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Operational Checklist

A checklist can be used to evaluate the operational integrity of a deaerator unit. Checklist items should include:

• Storage-section volume for 13 min of water (from NOWL to pump low-level trip).

• A normal pressure of 5 psig, ensuring a minimum temperature of 225°F.

• Readily accessible utility-grade pressure and temperature gauges and/or sensors.

• A ½-in. vent gas-purge pipe with a plume of 18 to 24 in.

• A stainless-steel sulfite chemical feed line inside the vessel storage section.

• A sulfite line (quill) located 6 to 12 in. below the NOWL.

• An evaluation of daily sulfite use. (A large change can indicate a spray-valve or tray-box malfunction.)

• Semi-annual testing of unit performance/dissolved O₂ without chemical feed.

• Quality liquid-level gauge glass easily visible by operators to monitor and confirm water level.

• A well-insulated tank, including valves and man-heads.

• An unrestricted discharge pipe to ensure adequate net positive suction head available for feed pumps.

• An annual internal inspection for debris, corrosion, or defective components.

• Annual planned maintenance and calibration of all instruments.

• Nondestructive tests of all vessel welds on a five-year basis.

Conclusion

A deaerator is not only an essential auxiliary component of a reliable feedwater system, but the heart of a boiler mass-flow and thermal-energy database that can be used to critique plant operations and identify energy-savings opportunities. For facilities that have boiler-efficiency discrepancies (generally fuel- and steam-meter inaccuracy and/or rudimentary combustion controls), the equations in Figure 5 can be used to identify these issues.

Whether a deaerator is for a large 80,000-pph watertube boiler system or a small 300-hp firetube unit, significant energy savings may be possible in plants that do not monitor feedwater-system performance closely. If boiler efficiency is not at its peak (and the cause of the inefficiency cannot be identified), a critique of the feedwater system may be revealing.

Many facilities use steam and fuel meters to determine boiler efficiency. Frequently, these meters are not accurate and utilities staff members may have a false sense of boiler efficiency. If a facility spends more than $50,000 per month on boiler fuel, a 5- or even 10-percent efficiency improvement may be possible.

An unscheduled deaerator outage can be a serious issue, affecting process operations, energy costs, maintenance budgets, and the long-term integrity of the entire boiler system. Get to know and respect this unit as a boiler plant's major auxiliary system.

Did you find this article useful? Send comments and suggestions to Associate Editor Megan White at megan.white@penton.com.

President of JoGar Energy Services and a member of HPAC Engineering's Editorial Advisory Board, Gary Wamsley, PE, CEM, is a mechanical engineer with 40 years of technical management and operational experience in plant and staff engineering. He has developed and presents training programs on the energy optimization of boiler operations, water and steam treatment, industrial energy management, and combustion, compressed-air, centrifugal-pump, and thermal-process systems. He can be contacted at gary.wamsley@comcast.net.