Metso Insights Blog Mining and metals blog Replacing filter components – what could go wrong?
Mar 2, 2023

Replacing filter components – what could go wrong?

Junbo Qin
Junbo Qin
Field Service Engineer, Filters, Metso Outotec
When it comes to maintaining filtration equipment, sites must carefully consider whether to do major component replacements in-house or take advantage of OEM service teams to complement their site personnel’s efforts. Junbo Qin, Field Service Engineer - Filters, with Metso Outotec, shares his point of view on what needs to be considered and what issues are often missed when dealing with these major service events.

When it comes to replacing major components for Filtration and other dewatering equipment, the challenge often revolves around finding personnel with the required expertise, correct tools, instructions and background to execute the service work both quickly and safely. Plates, filter cloths and other components need regular monitoring and timely replacement for equipment to run smoothly. Plates and plate packs can also be challenging to change-out due to the component’s size and weight and in addition, require careful handling as well as specialized tools to ensure safety.

Asking the right questions before starting the work

When servicing filtration equipment, it is important to objectively evaluate the site capabilities and the team who will be performing the work. Key questions to ask are:

  • Has the site planned this type of work before, and are all the right tools available?
  • Are all the service steps well understood to do the work safely and efficiently?
  • Are there experienced personnel available to execute the part change-out?
  • Does the site service team know what to look for to make sure the parts come together properly?
  • Will new parts be used or are the components part of a service exchange or plate refurbishment program?

Having a good feel for these questions can help determine the right mix of in-house work and what level of OEM support is required.

Knowing what to look for

In my time as a Field Service Engineer for filters in Australia and the USA, as well as during the period of serving as a site account manager for our eastern USA customers, many sites had a fine team of service personnel maintaining their equipment. However, even well-trained and knowledgeable teams would often run into issues with their filters. What was the reason and how did the problems go unchecked and escalate into larger mechanical issues? One common reason was simply personnel turnover. Maintaining filtration equipment demands both knowledge and experience and learning to look for warning signs is often gained over time. New team members require time and guidance before they spot the signs that filtration equipment could be about to run into an issue.  It often came down to service personnel simply not knowing where to look, what to look for and how often to perform their filter checks.

A second reason came down to not always using the right parts for the job. While performing my work on filters, one common issue I ran into was hydraulic and mechanical failures. In several cases, local 3rd parties supplied hydraulic components which were used during maintenance and breakdown events due to perceived faster lead times, rather than using standard OEM parts. However, some filter hydraulic systems components need to be pre-set and bench tested before installation. Several sites I visited had limited knowledge and capability to perform these checks before using the 3rd party parts. It generally caused more issues in the hydraulic system than expected and often led to extended downtime for the equipment. I would like to share a few additional examples of common filter issues I ran into over my time in the field.

Issue 1 – Oil contamination

Larox® PF – hydraulic system components failure is something I have seen at several sites. Generally, hydraulic components failure came from oil contamination and wear and tear when the equipment was not serviced regularly. Various alarms and oil leaks occurred when some components failed. Troubleshooting on hydraulic components failure can be difficult as you need to utilize multiple specific tools (Hydac measurement tools & PLC) and experience to locate the failed components.

How oil contamination can occur

Lack of maintenance on the hydraulic system is the most common reason. Typically, customers will repair oil leaks after they have been observed. Some customers have limited spare parts stock and maintenance time, which causes oil-leaking situations to continue for much longer than expected. These leaks often lead to the introduction of dust and particles into the hydraulic system.


Once hydraulic oil is contaminated and if the leaking continues, the system can pass beyond its self-cleaning capability. Oil contamination stays at a high level or starts to worsen. If oil sample analysis is not continuously conducted as scheduled or final analysis results are not reviewed by experienced personnel, hydraulic systems can be operated over their designed parameters, leading to hydraulic component failure. Once hydraulic components begin to fail, various alarms will start to occur and interrupt production. Some customers install non-preset components or fail to locate the components at the root cause of the failure, leading to the frequency of alarms eventually reaching unacceptable levels and finally filter shutdown.

Best practice

To reduce the chances of these types of events happening, Metso Outotec stocks preset hydraulic components ready to deliver to customers in a short period of time. Using preset components helps to eliminate incorrect initial settings of hydraulic components in the filter hydraulic system and minimizes confusion for local maintenance teams by reducing the number of components having issues. Metso Outotec also builds up knowledgeable local field service teams equipped with proper hydraulic and electrical tools to help customers to analyze the root cause of failures and replace critical components in a timely manner.

Here is an example of misaligned collectors (/plate pack) likely caused by improper plate alignment procedures.
Here is an example of misaligned collectors (/plate pack) likely caused by improper plate alignment procedures.

Issue 2 - Misaligned plates due to using improper plate alignment procedures

One site I made a service call to had a Larox® PF filter with 22 plates that had not been maintained properly. The plate pack was badly misaligned – dry air was leaking, and the filtrate was leaking from the collector. This was causing noise issues and could have led to the contamination of the entire filter building. No one was able to work close to the filter due to the leaks and noise caused by a misalignment when changing out the plates of the filter on a previous service stop. A shutdown of the filter was required to correct the alignment of the plate pack. The entire realignment took several days to fix and field tests to ensure all was working properly. The work required 3-4 people working over several days with specialized equipment and ended up costing the customer significant service work and lost production.   

How plate misalignment occurs

Many sites may not have the personnel trained to conduct a proper filter plate alignment. Plates may not be aligned at all or secondly even if they are aligned – a slide piece could wear out prematurely if too much torque is applied.


If the plates are not aligned, the site team would have to repeat the entire process again to ensure the alignment is correct.  If not properly aligned, cloth tracking issues could occur, or slurry can leak. In most cases, stopping the filter to conduct repairs results in unplanned downtime. A second option would be to leave the filter working as it is but, in most cases, the issues tend to escalate if not addressed.

Best practices

It is critical to adhere to OEM workbook procedures to ensure plates are aligned which reduces future service work. In some cases, certain components need on-the-spot repair such as the VAT, pin or other components linked to the plates. Inspections are also important to detect issues early with set inspection points checked regularly.  Safety issues can also cause issues – lifting methods need to be monitored and performed properly by the workers. Cranes need to be used, but specific tools are also needed – such as a lifting beam to stabilize the lifting procedure – some customers may perform the lift without the beam which causes issues.

Leveraging OEM Filter knowledge

Having a well-trained in-house service team can offer many benefits. However, for the change-out of large components that need accurate alignment, leveraging OEM support can make all the difference. By utilizing Metso Outotec filtration component replacement services, sites can benefit from the OEM team’s experience in scheduling and staging pre-outage activities, as well as executing the work quickly to significantly minimize downtime. There are other advantages in terms of having one point of responsibility for the entire maintenance event. In some cases, OEM warranties can often be extended when Metso Outotec crews perform the installation of major filtration parts. With access to global knowledge centers, troubleshooting, alignment and adjustments can often be done on the spot by our on-site crews, bringing additional uptime benefits.