When a plant trouble occurs, maintenance engineers are often told,
“Do you understand how much loss one hour of downtime causes?”
and are pressured to restart the operation as quickly as possible.
Such direct expressions are less common today, but the underlying mindset has not changed.
From a maintenance perspective, however, it is not always clear how these losses are calculated or whether they truly reflect reality.
In this article, we estimate the loss caused by a one-day shutdown of a batch plant and break it down into its main components.
Estimated Loss from a One-Day Shutdown
Let us assume a simple case: a pump failure causes the plant to stop production for one full day.
The unit prices and quantities are simplified assumptions for explanation purposes.
| Item | Minimum Case | Maximum Case |
|---|---|---|
| Production opportunity loss | ¥1,000,000 | ¥1,000,000 |
| Equipment repair cost | ¥500,000 | ¥500,000 |
| Cleaning cost | ¥20,000 | ¥20,000 |
| Disposal cost | ¥50,000 | ¥500,000 |
| Total | ¥1,570,000 | ¥2,020,000 |
As shown above, production opportunity loss dominates the total cost.
Let’s look at each item in more detail.
Production Opportunity Loss
When a plant stops, it loses the opportunity to produce products that could have been sold.
In batch plants, short delays can sometimes be absorbed by cycle-time adjustments, but here we assume a full-day shutdown.
Assumptions:
- Daily production capacity: 1 MT (1,000 kg)
- Product price: ¥1,000/kg
The production opportunity loss is therefore:
1,000 kg × ¥1,000/kg = ¥1,000,000
This simple calculation is often what management refers to when they ask, “How much does downtime cost?”
Equipment Repair Cost
Next is the direct equipment repair cost.
In this example, we assume a pump failure with a repair cost of ¥500,000.
This includes:
- Mechanical seal replacement
- Removal and reinstallation of piping
Depending on the equipment and scope, this cost can vary, but several hundred thousand yen is a realistic figure in many plants.
Cleaning Cost
Equipment trouble often generates additional costs beyond the repair itself.
One typical example is cleaning.
In this case, we consider:
- Line flushing before pump removal
- Line replacement and flushing after restart
Assumptions:
- Water cost: ¥50/kg
- Volume: 200 L × 2 operations
Calculation:
200 × 50 × 2 = ¥20,000
This cost is relatively small, but it accumulates every time trouble occurs.
Disposal Cost
Depending on the trouble, process fluids may need to be discarded.
Minimum Case
- Unrecoverable process fluid: 1,000 L
- Disposal cost: ¥50/kg
1,000 × 50 = ¥50,000
Maximum Case
In the worst case, the entire batch must be disposed of.
- Batch volume: 10 kL (10,000 L)
- Disposal cost: ¥50/kg
10,000 × 50 = ¥500,000
Drum costs and transportation are assumed to be included in the unit disposal price.
A Reality Often Hidden from Maintenance
Looking at these numbers, it becomes clear why fast recovery is emphasized when a plant stops for a day.
However, in reality:
- Some inventory usually exists
- Products are not always sold immediately
- In some cases, long-stored products are eventually discarded
When disposal occurs, responsibility is often unclear, and the cost is simply paid and forgotten.
From the maintenance side, this raises a question:
What is the meaning of racing against the clock on the shop floor if the products are later wasted?
Conclusion
- A one-day shutdown of a batch plant results in significant losses, with production opportunity loss being the largest factor
- Repair, cleaning, and disposal costs may be smaller, but they are unavoidable
- The pressure for quick recovery becomes understandable when viewed numerically
- At the same time, there can be a gap between shop-floor efforts and actual business decisions
Estimating downtime losses is not about blaming maintenance work.
It helps clarify the difference in perspective between the field and management—and that understanding starts with numbers.
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