Troubleshooting Guide: Deaerators

Technical Bulletin 1-011Boiler SystemsUpdated 10/17/11

IntroductionMonitoring deaerator performance can uncover problems resulting in inefficient dissolved oxygen removal, higher treatment cost, and/or oxygen pitting corrosion. Poor deaeration is usually the result of mechanical malfunction or flow control problems.

Problem Possible Causes and Corrective Action

Excessive dissolved oxygen or carbon dioxide levels in deaerator effluent

Inadequate venting. Check steam plume from deaerator. General rule: plume should be 18-24 inches of height without wind flow. Improper operation of manual and/or automatic vents. Manually increase the vent valve(s) to get adequate plume.Insufficient inlet steam pressure. Check inlet steam pressure reducing valve for proper operation. Ensure that control line is connected to the deaerator and not to the piping downstream of the valve. Increase steam pressure.Mechanical failure of or damage to internals, such as spray nozzles or trays. Collapsed trays could result from interrupted steam supply or sudden use of cold water causing a vacuum. Clogged spray trays/nozzles. Repair ASAP.Check chemical feed system for proper operation and feedpoint. Oxygen scavenger injection point should be to the storage section below the water level. Continuous feed of scavenger is preferred.Check water and steam flow rates versus deaerator design. Trays and inlet steam valves are designed for specific flow ranges. Install correctly sized equipment.Excessive free air inleakage due to leaking stuffing boxes on pumps upstream of the deaerator, especially if suction head.

High oxygen scavenger consumption

Inadequate venting (see above).Inadequate supply pressure for the distribution and atomization of incoming waters.Condensate temperature may be too high. Water entering deaerator usually must be cooled if temperature is within 18-20F of steam saturation temperature.Check operating pressure and temperature against design. Adjust as needed (see above).Check spray nozzles and trays (see above).Excessive free air inleakage.

High deaerator temperature and/or pressure

Steam regulating valve not functioning properly.Steam traps blowing live steam.

Low deaerator temperature compared to pressure or low deaerator pressure

Improper spray from spray nozzles. Check nozzles for clogging and deposits on seats. Check for broken or malfunctioning tension springs.Excessive free air inleakage.Malfunctioning steam regulating valve.Excessive load demand from boiler(s). Compare against deaerator design.No or greatly reduced condensate flow to deaerator.Overflowing deaerator.

2011 Chem-Aqua, Inc.

2011 Chem-Aqua, Inc.

Problem Possible Causes and Corrective Action

Fluctuating operating pressure

Insufficient steam supply.Poor control of steam supply.Batch addition of condensate and/or makeup water.Maintain storage section water level within tighter range. Check adjustment on boiler feedwater and makeup level controls.Pressure reducing station chattering due to being oversized.

High or low water level or overflowing deaerator

Malfunctioning water level control valve.Solenoid valve leaking if present.Leaking heat exchanger.

Vent plume inconsistent

Pressure reducing station chattering due to being oversized.Pressure reducing station sensor either improperly installed or faulty, causing large lag in response times.Cold water makeup addition control too broad.

Vent plume contains entrained water

Inleakage of water from the vent condenser.Cracked internal vent condenser or cracked condenser shroud.Blown spray nozzles or spray distribution system.

Pressure relief valve blowing Over pressurized due to excessive supply of exhaust or flash steam.

Vibration

Inadequate water supply pressure to spray nozzles for the operating pressure.Chattering of makeup and condensate control valves.High pressure drops across makeup and condensate control.

Storage tank water bouncing or hammer from flashing

Loss of steam supply.Poor control or improper sizing of pressure reducing station.Over-pressurization of deaerator for the design.

Hammer and/or vibration from water/condensate lines

Condensate return line undersized for carrying both condensate and flash steam. Resize the line.Insufficient back pressure.Failed check valve at point of discharge to the vessel.