UPSET CONDITIONS AND COUNTERMEASURES

The first action to be taken in case of exceeding specified chemical limits is to check the sampling system for the following:

  • • Adequate sample flow
  • • Correct sample temperature
  • • Exhausted cation exchanger cartridge
  • • Out-of-calibration analyzer (oxygen, silica, pH, conductivity, sodium)

Table 5 lists some of the more typical problems, their causes and the necessary countermeasures. Use of blowdown as a corrective action should be a temporary action until the chemistry parameter is brought back into conformance. NOTE: This list is an example only and may be incomplete. Each deviation from a specified value requires careful investigation.

Table 5. Upset Conditions and Countermeasures

Out of limit condition

Possible Cause

Possible Troubleshooting Actions

High

feedwater

oxygen

concentration

(separate

deaerator)

Condenser air inleakage

Verify condensate pump discharge oxygen concentration

Check air ejector flow rate compared to design

Poor deaerator performance

Verify oxygen concentration in deaerator outlet

Check deaerator vent

Check deaerator temperature and pressure

Check deaerator internals

High feedwater cation

conductivity

Condenser leak

Check for contamination. If condensate or demineralizer storage is free of contamination, increase the blowdown

If chemistry limits for drum pH

or steam chemistry cannot be maintained,

shut down unit

High

feedwater

cation

conductivity

Makeup

contamination

Check makeup treatment plant operation

Determine the source and amount of contamination and isolate makeup system

If chemistry limits for drum pH

or steam chemistry cannot be maintained,

shut down unit

Process return

condensate

contamination

Dump process return condensate

Contamination by organics

Decrease TOC of feedwater. Determine source and correct

High drum water specific conductivity

Contamination entering the system or lack of blowdown

Check for contamination.

If condensate storage and/or demineralized water storage is free of contamination, increase blowdown

High treatment concentration

Decrease treatment feed rate

Low drum water specific conductivity

Excessive

blowdown

Decrease blowdown flow

Low treatment concentration

Increase treatment feed rate

Drum water pH at 25oC low but > 8.0

If drum pH at 25oC is <8.0, shut down

Contamination

Minimize superheat and reheat attemperation

Condenser tube leak

Check for condensate storage contamination, if condensate purity is good, increase blowdown

If drum pH or steam chemistry limits cannot be maintained, shut down unit

Makeup

contamination

Determine the source and degree of contamination and isolate

If steam chemistry limits cannot be maintained, shut down unit

Process return

condensate

contamination

Increase blowdown

Determine the source and amount of contamination and dump the contaminated condensate

High drum water pH at 25oC (>11.5 for demineralized water systems)

High phosphate

Decrease caustic and phosphate dosing

Increase blowdown

Contamination

Check makeup treatment plant and condensate storage

Check steam chemistry. If limits cannot be maintained shut down unit

High saturated steam cation conductivity

Condenser leak

Check for condenser contamination

Check condensate storage. If purity meets limits, increase blowdown

Makeup

contamination

Determine the source and degree of contamination and isolate

If steam chemistry limits cannot be maintained, shut down unit or bypass the steam turbine

Process return

condensate

contamination

Isolate process return condensate

Contamination by organics

Apply technologies to maximize TOC removal in pretreatment equipment

Mechanical

carryover

Verify by checking saturated steam sample for sodium concentration

Reduce drum level and check for improvement

Reduce steam flow by throttling the turbine

Shut down and inspect drum internals

High silica in saturated steam

High boiler water silica concentration

Increase blowdown

Condenser leak

Check condensate storage. If purity meets limits, increase blowdown

Check other parameters such as cation conductivity and sodium for evidence of contamination

Makeup contamination

Check for colloidal silica in makeup

Check makeup treatment plant

Process return

condensate

contamination

Dump contaminated condensate

High sodium in steam

Attemperator

problems

Check attemperator operation

Check attemperation source (feedwater) for contamination

Mechanical

carryover

Check steam separation and steam drum level

Contamination

Check attemperation source (feedwater) for contamination

If steam chemistry limits cannot be maintained shut down the unit

Condenser leak

Check condensate storage. I If purity meets limits, increase blowdown

Makeup

contamination

Check for caustic in makeup

Check makeup treatment plant operation

Process return

condensate

contamination

Dump contaminated condensate

 
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