Part 6: Cases where material replacement is not recommended

Not every application needs to be upgraded to a material with a longer service life.

In some cases, a technically superior material does not create a corresponding increase in operational value. Service life may increase without reducing the number of interventions, the actual cause may lie in the flow design, the material may be used for the wrong function, or the new service life may far exceed the remaining useful life of the equipment.

Before changing materials, it is therefore necessary to determine whether the additional service life will actually change how the plant operates.

1. The value of service life should be considered together with the shutdown cycle

Many equipment linings are replaced only during planned shutdowns.

In such cases, material service life should be considered in terms of how many planned shutdown cycles the material can pass through, rather than only as an absolute number of months.

For example, if the plant shuts down every six months:

Increasing service life from 10 to 12 months still leaves the material within the same shutdown interval. The plant has not reduced the number of replacement interventions.

Increasing service life from 12 to 13 months, however, allows the material to pass into the next shutdown cycle.

In this article, the term service-life tier refers to the number of planned shutdown cycles a material can pass through before replacement is required.

Therefore, increasing service life without moving into a new tier may mean that the plant still shuts down at the same time and still replaces the material at the same time, while material costs increase.

2. The service-life tier calculation does not apply directly to every location

Three situations should be assessed separately from the normal shutdown-cycle check:

The third situation is particularly important.

A single location that has previously forced an entire line to stop can create operating costs far greater than the cost of one scheduled lining replacement.

For this reason, the service-life tier is only an initial screening tool, not a complete economic assessment.

3. Material replacement may not be justified if the new service life remains within the same tier

Before replacing the current material with an option offering longer service life, three pieces of data are required:

• the plant shutdown cycle
• the current service life at the location
• the expected service life of the new solution

The next step is to determine whether the new solution allows the location to pass through at least one additional shutdown cycle.

If it does not, the actual number of replacement interventions remains unchanged.

In that case, the additional service life may not create enough benefit to justify the additional material cost.

This does not mean that the new solution should always be rejected. If the location is causing unplanned downtime or creating risks for other equipment, its operational impact should be assessed before a conclusion is made.

4. Material replacement should not continue if the root cause lies in flow design

A location may continue to fail even after several different materials have been tried if the primary cause lies in flow direction, drop height or equipment geometry.

One warning sign is a location where the material has already been changed two or more times but the same failure mode continues to occur.

Before moving to another material option, check:

• flow direction
• drop height
• impact angle
• load concentration zones
• equipment geometry

If the root cause lies in the design, a material with a longer service life may only delay the failure, while the mechanism causing the problem remains unchanged.

In this situation, further material replacement should not be the first priority.

5. Service life beyond the required equipment life does not create equivalent additional value

A component may only need replacement once every three years, while the equipment itself is scheduled to be replaced after five years.

If the material is upgraded to one with a ten-year service life, the portion of service life extending beyond the remaining equipment life does not create additional value for that equipment.

This is a case of buying more service life than the plant can actually use.

Service life should therefore be considered together with:

• remaining equipment life
• maintenance cycle
• investment plan
• actual number of interventions

The objective is not to achieve the longest possible service life. The objective is to achieve a service life that matches the plant’s operating and investment plan.

6. A technically good material can still be the wrong choice if used for the wrong function

Wear resistance does not automatically mean that a material is suitable for every mechanical function.

One example in the source material is the use of wear-resistant steel for a load-bearing beam.

Wear-resistant steel is developed for wear conditions. Its requirements for hardness, weldability, formability and toughness are not automatically the same as those of steel designed for load-bearing structures.

Similarly, with two-component wear-resistant steel, the backing plate should not automatically be assumed to be suitable as a load-bearing structural element unless the manufacturer guarantees it for that application.

Before using a material for a structural function, check:

• the material’s intended application range
• relevant mechanical properties
• the manufacturer’s guaranteed properties
• the actual function the component is required to perform

Do not infer structural load-carrying capacity from wear resistance.

7. Without location-specific data, there is not enough basis for predicting service life

When operating conditions have not been measured, it is difficult to make a well-supported service-life prediction.

If the result after implementation does not meet expectations, the plant will also lack the evidence needed to determine whether the cause lies in the material, operating conditions or the original assumptions.

In this situation, a more appropriate approach is to run a controlled trial at one location before extending the solution across the entire line.

The trial should generate location-specific data that can be used to:

• compare conditions before and after the change
• monitor the rate of deterioration
• identify the failure mode
• assess whether the solution can be scaled up

You can learn more about how to design a controlled trial and establish comparison data in Part 6: Designing a trial at a single location in the Field Survey, Measurement and Diagnostics knowledge series.

8. Four questions to screen a solution before changing materials

Before looking at specific material grades or quotations, start with four questions:

• What is the plant’s shutdown cycle?
• How long does the current material last before replacement is required?
• What service life is expected from the new solution?
• Will the new service life allow the location to pass through an additional shutdown cycle?

These questions do not require specialized measuring equipment.

However, they can quickly identify cases where the additional service life does not yet change the actual number of interventions.

9. Locations that have caused unplanned downtime should be assessed separately

There is one situation where a new solution may still be worth considering even if its service life does not move into the next tier: the location has previously caused unplanned downtime.

In this case, the objective is not only to reduce the number of scheduled replacements.

Longer service life may also help reduce the risk of failure between planned maintenance periods.

The service-life tier calculation should not be used as the sole reason to reject a solution if the location has previously caused:

• unplanned downtime
• loss of production capacity
• consequential damage to other equipment

In these situations, operating costs and operational risks also need to be evaluated.

You can learn more about how downtime, intervention frequency and production-line impact can be compared within the same assessment in Part 6: The technical and operational consequence chain from a single wear point in the Material Wear Mechanisms knowledge series.

10. Responsibilities of each team

The first two inputs are plant-specific data.

The material supplier should not fill in these values without confirmation because all subsequent comparisons depend on them.

11. Notes on applying this knowledge

First, the service-life tier calculation is suitable for locations where replacement can only be performed while the equipment is stopped. For locations that can be replaced while the system remains in operation, a different evaluation method is required.

Second, the assessment needs to be expanded if the location has previously caused unplanned downtime. In such cases, the value of longer service life lies not only in reducing the number of replacements but also in reducing risk between planned shutdowns.

Third, expected service life is only meaningful when the input data is sufficiently clear. If the operating conditions at the location have not been measured, data should first be generated through a controlled trial before the solution is expanded.

Fourth, changing the material does not replace the need to address root causes related to flow design or incorrect material function.

Fifth, the service-life tier calculation is an arithmetic screening tool to support decision-making, not a complete economic model. Downtime costs, labor, spare parts, lost production and operational risks may need to be assessed separately depending on the location.

A material with a longer service life only creates additional value when the plant can actually use that extra life. Before replacing the current material, service life should be considered together with the shutdown cycle, remaining equipment life, failure cause and operational risk. If these factors do not change, a more expensive material does not necessarily mean a better solution.