Your Heat Rate Is Rising. Is Maintenance Looking at the Right Equipment?

The unit is on load.

Generation looks normal.

There has been no major trip.

But the daily performance report shows something uncomfortable:

Heat rate is getting worse.

Not dramatically.

Just enough to notice.

Yesterday it was slightly higher.

This week it is again above the recent average.

Fuel consumption is increasing for the same electrical output.

Operations starts checking the numbers.

Fuel quality is discussed.

Load variation is discussed.

Ambient conditions are discussed.

But there is another question worth asking:

Is an equipment problem slowly showing up through the heat rate?

In a thermal power plant, heat rate is not only a performance number.

Sometimes it is one of the earliest indications that the plant is no longer operating as efficiently as it should.

And maintenance may already have part of the answer.

First, What Does Heat Rate Tell Us?

Heat rate tells us how much heat input is required to generate one unit of electricity.

In simple terms:

Lower heat rate = better efficiency.

Higher heat rate = more heat, and therefore usually more fuel, required for the same electrical output.

Depending on the plant, heat rate may be expressed in:

• kcal/kWh
• kJ/kWh
• Btu/kWh

If a unit requires progressively more heat input to produce the same kWh, something has changed.

But heat rate itself does not tell you what changed.

That is where the investigation begins.

A Rising Heat Rate Is Not Automatically a Maintenance Problem

This distinction is important.

Heat rate is affected by many factors.

For example:

• Unit load
• Fuel quality
• Ambient conditions
• Steam conditions
• Operating practices
• Equipment condition
• Auxiliary power consumption
• Cooling water conditions
• Boiler performance
• Turbine performance

So if heat rate worsens on one shift or one day, maintenance should not immediately start changing bearings, cleaning tubes or opening equipment.

The first question should be:

Is the deterioration explainable by the way the unit is operating?

If it is not, then the plant should start looking for equipment-related losses.

This is where operations data and maintenance history need to come together.

Consider a Simple Example

Assume the unit has been operating around the same load for several days.

Fuel quality has not changed significantly.

Main steam conditions are reasonably stable.

But heat rate continues to deteriorate.

At approximately the same time, the following observations appear:

• Condenser vacuum is slightly worse
• Cooling water outlet temperature is increasing
• One cooling water pump has a pending maintenance issue
• The condenser cleaning history shows repeated fouling
• Operators have reported that vacuum recovery after load changes is slower than usual

None of these items individually looks like a major breakdown.

The unit is still running.

But together, they tell a different story.

The condenser system may now deserve serious attention.

This is exactly why equipment performance should not be viewed separately from maintenance history.

Condenser Vacuum Is One of the First Places to Look

Poor condenser performance can directly affect turbine efficiency.

If condenser vacuum deteriorates, turbine exhaust pressure increases.

The turbine then has less effective expansion available through the final stages.

The unit may continue generating.

But it may require more thermal input for the same electrical output.

Possible causes include:

• Higher cooling water temperature
• Reduced cooling water flow
• Condenser tube fouling
• Air ingress
• Vacuum pump or ejector problems
• Cooling tower deterioration
• Blocked or partially restricted condenser tubes

Now consider what this looks like from two different systems.

The performance report says:

Heat rate deteriorated.

The maintenance system says:

Cooling Water Pump B has a pending defect.

Condenser cleaning was postponed.

Vacuum pump vibration has increased.

Individually, those are maintenance records.

Together, they may explain a plant performance problem.

The Boiler Can Be Running and Still Be Losing Efficiency

The boiler does not need to trip before it starts affecting heat rate.

Small losses can accumulate.

For example:

• Excess air too high
• Air leakage
• Poor combustion
• Soot deposition
• Fouled heat-transfer surfaces
• Steam temperature below target
• Feedwater temperature deviation
• Burner condition problems
• Mill performance deterioration

The unit may continue producing the required MW.

But the boiler may need more fuel to do it.

That is why a plant should not evaluate boiler condition only through breakdowns.

Changes in process parameters can provide early warning that condition-based maintenance or corrective investigation is required.

Coal Mills Can Affect More Than Availability

Coal mills are often discussed in terms of availability.

A mill trips.

Maintenance attends.

The mill is restored.

But mill condition can also influence combustion performance.

If pulverization quality deteriorates, coal distribution becomes uneven or mill performance moves away from expected conditions, the boiler may not burn fuel as effectively.

The maintenance team may see:

• Increasing vibration
• Grinding element wear
• Motor current changes
• Reject problems
• Repeated mill trips
• Reduced mill output

Operations may see:

• Combustion instability
• Higher excess air requirement
• Steam temperature variation
• Difficulty maintaining load
• Higher fuel consumption

Again, these are two views of the same plant.

If they remain in separate systems, the relationship may be missed.

Boiler Feedwater Conditions Matter Too

Feedwater temperature and feedwater system performance also influence thermal efficiency.

If feedwater entering the boiler is colder than expected, the boiler has to supply additional energy.

The reason might not be the boiler itself.

The problem may be somewhere in the regenerative feed-heating system.

Potential areas include:

• Feedwater heaters
• Extraction steam systems
• Heater drains
• Control valves
• Bypass conditions
• Tube leakage
• Poor heater performance

The plant can still be running normally from an availability point of view.

But it is using more fuel than necessary.

This is why maintenance should sometimes investigate performance loss before failure occurs.

Auxiliary Power Consumption Can Quietly Reduce Net Plant Performance

Another important area is auxiliary power.

A thermal power plant uses a significant amount of electricity internally.

Large consumers may include:

• Boiler feed pumps
• ID fans
• FD fans
• PA fans
• Cooling water pumps
• Condensate pumps
• Coal mills
• Ash handling equipment

Suppose an ID fan becomes inefficient because of fouling, damper problems or another mechanical condition.

The fan may continue doing its job.

But the motor may draw more current.

Likewise, a pump operating away from its efficient point may continue delivering flow while consuming more power.

Gross generation may look acceptable.

But auxiliary consumption increases.

Net generation falls.

This is why energy and maintenance data should be reviewed together. Energy monitoring becomes more useful when abnormal consumption can be traced back to the equipment responsible.

The Turbine Should Not Be Ignored

When heat rate deteriorates, turbine condition is naturally another area of interest.

Potential losses may relate to:

• Steam path deterioration
• Deposits
• Seal leakage
• Valve condition
• Steam parameter deviation
• Increased exhaust pressure
• Internal efficiency deterioration

But maintenance teams should avoid jumping immediately to the turbine simply because it is the largest machine.

The deterioration may actually originate from:

• The condenser
• Feedwater heaters
• Boiler combustion
• Cooling water
• Auxiliary equipment

The useful approach is to narrow the problem using plant data before deciding where maintenance effort should go.

One Number Is Not Enough

Suppose the daily report shows:

Heat Rate: 2,560 kcal/kWh

Is that good or bad?

By itself, the number does not tell the complete story.

The plant needs context.

Compare it with:

• Previous shift
• Previous day
• Similar unit load
• Monthly average
• Design or expected performance
• Fuel condition
• Ambient condition
• Relevant equipment readings

The trend matters more than one isolated reading.

This same principle applies to meter readings.

A bearing temperature of 78°C may not be meaningful by itself.

But if it has moved:

65°C → 68°C → 72°C → 75°C → 78°C

while load remains similar, maintenance has something worth investigating.

Heat rate should be treated the same way.

Do Not Look at Heat Rate in Isolation

Imagine the unit heat rate has worsened over five days.

Now place several trends next to it:

Parameter	Day 1	Day 5	Direction
Heat Rate	2,445 kcal/kWh	2,535 kcal/kWh	Worse
Condenser Vacuum	-0.91 bar	-0.87 bar	Worse
CW Outlet Temperature	34°C	38°C	Higher
Auxiliary Power	7.1%	7.7%	Higher
Main Steam Temperature	535°C	533°C	Stable

Now the investigation becomes more focused.

The objective is not to prove that one parameter caused another from the dashboard alone.

The objective is to identify where the plant should investigate first.

That is a much better use of operating data.

Maintenance History Can Provide the Missing Context

Suppose condenser vacuum has deteriorated.

What should maintenance know immediately?

Ideally:

• When was the condenser last cleaned?
• Are there any open tube leakage observations?
• Is the vacuum pump healthy?
• Has air ingress been reported before?
• Are cooling water pumps performing normally?
• Has the same deterioration happened previously?
• What corrective action was taken last time?
• Did vacuum improve after the work?

Without this history, each performance deterioration becomes a new investigation.

With proper asset management and work history, the team can see whether the plant is repeating an old problem.

The Same Failure Should Not Be Investigated From Zero Every Time

Consider a vacuum pump.

Three months ago:

• Vibration increased
• Vacuum deteriorated
• Bearing was replaced
• Condition improved

Now:

• Vibration is increasing again
• Vacuum is starting to deteriorate
• Heat rate is moving upward

Maintenance should not treat this as an unrelated event.

The previous failure history immediately becomes relevant.

If the same pattern keeps returning, it may be time for proper root cause analysis rather than another bearing replacement.

Plants can also use Pareto analysis to identify which equipment or failure modes repeatedly contribute to reliability and performance losses.

This Is Where Operations and Maintenance Usually Disconnect

Operations sees:

Heat rate is high.

Maintenance sees:

Vacuum Pump-2 has an open work order.

The two pieces of information may never be connected.

The operator may record the daily plant parameters in one system.

Maintenance may record work in another.

Performance engineers may maintain another spreadsheet.

The management dashboard may show another set of KPIs.

Everyone has data.

But nobody has the full sequence:

Performance deviation → Equipment condition → Maintenance action → Performance recovery

That sequence is where real value exists.

The Better Workflow

Suppose heat rate begins to deteriorate.

A practical workflow might be:

1. Detect the deviation

Heat rate exceeds the expected range for comparable operating conditions.

2. Review contributing parameters

Check condenser vacuum, auxiliary consumption, steam temperatures, feedwater conditions, cooling water and other relevant operating values.

3. Identify likely equipment

For example, condenser system, CW pumps or vacuum system.

4. Review equipment history

Look at previous defects, breakdowns, readings and maintenance actions.

5. Raise corrective work

Assign inspection or maintenance to the relevant equipment.

6. Complete the work

Repair, clean, align, adjust or replace as required.

7. Verify the result

Did the equipment parameter improve?

And importantly:

Did plant performance improve?

That last question is often missing.

Closing a Work Order Is Not the Same as Solving the Performance Problem

Suppose maintenance cleans the condenser tubes.

The job is completed.

The work order is closed.

But the important questions are:

• Did vacuum improve?
• Did turbine backpressure reduce?
• Did the expected MW improve?
• Did heat rate recover?

If those numbers do not improve, the investigation is not finished.

The maintenance activity may have been completed correctly, but the assumed cause may have been wrong.

This is why verification matters.

A work order management system should help preserve the relationship between the original problem, the work performed and the condition afterward.

Maintenance KPIs Need Plant Context

Maintenance teams commonly monitor:

• Breakdown count
• PM compliance
• MTTR
• MTBF
• Open backlog
• Work order completion

These are useful.

But none of them directly answers:

Did our maintenance work improve plant performance?

Suppose MTTR improves substantially.

That is positive.

But if the same condenser problem occurs every month and continues affecting heat rate, fast repair alone is not enough.

Likewise, 100% PM compliance does not guarantee good plant performance if PM tasks are not addressing the real degradation mechanisms.

Maintenance KPIs should therefore be viewed alongside operating and performance measures.

That is where maintenance analytics can become much more useful.

Heat Rate Can Help Prioritize Maintenance Work

Imagine two open jobs.

Work Order A

Lighting problem in a non-critical area.

Work Order B

Cooling water pump showing declining flow and increasing motor current while condenser vacuum is deteriorating.

Both work orders may technically be open.

But their plant consequences are very different.

The second job may be contributing to a performance loss that is costing fuel every hour.

This is why maintenance priority should consider operating consequence rather than relying only on a manually selected priority.

The principles of risk-based maintenance apply here as well.

Risk is not only about catastrophic failure.

It can also include sustained production or efficiency loss.

Some Performance Losses Should Become Shutdown Work

Not every efficiency problem can be corrected online.

A turbine inspection may require an outage.

Major condenser work may need a planned opportunity.

Boiler pressure-part repairs may require shutdown.

Internal inspection of some equipment cannot happen while the unit is operating.

But the evidence should already be collected before shutdown begins.

If the plant has seen:

• Repeated vacuum deterioration
• Recurring mill problems
• Persistent steam temperature deviation
• Repeated auxiliary equipment inefficiency

those issues should feed into shutdown maintenance planning.

The shutdown should not simply contain routine jobs.

It should be used to remove known performance constraints that cannot be corrected online.

A Better Question for the Daily Performance Meeting

When heat rate moves in the wrong direction, asking:

Why is heat rate high?

is only the beginning.

A better sequence is:

What changed?

Which parameters moved with it?

Which equipment is associated with those parameters?

Do we already have maintenance history on that equipment?

Is there an open defect?

What action are we taking?

How will we verify improvement afterward?

That turns a KPI discussion into an executable maintenance process.

A CMMS Should Help Connect the Dots

For a thermal power plant, a CMMS should not try to replace the DCS or plant performance system.

Those systems have different responsibilities.

But a CMMS can play an important role once an equipment-related issue requires maintenance action.

It should help connect:

• Asset
• Operating reading
• Deviation
• Inspection
• Work order
• Failure history
• Corrective action
• Technician findings
• Condition after maintenance

That gives the plant a traceable maintenance story.

The DCS tells you what the process is doing.

The CMMS should tell you what maintenance is doing about the equipment behind it.

The Important Question Is Not Just Whether the Unit Is Running

A thermal unit can be running at target MW while slowly becoming less efficient.

There may be no breakdown.

No trip.

No urgent alarm.

But every additional unit of heat required to produce the same electricity represents a performance loss.

Sometimes the cause is operational.

Sometimes it is fuel-related.

Sometimes it is environmental.

And sometimes the equipment has been warning the plant for days.

That is why a rising heat rate should not remain only a number in the daily performance report.

When the operating conditions do not explain it, maintenance should ask:

Which equipment condition could be contributing to this loss?

Then look at the readings.

Look at the history.

Find the deviation.

Take the corrective action.

And finally, check whether the heat rate moved back in the right direction.

Because the real objective is not merely to complete maintenance.

It is to restore plant performance.