Improving Reliability in Pharmaceutical Mixing Equipment with a Retrofit Rotary Shaft Seal
When a shaft seal repeatedly fails, replacing it with another standard component does not always solve the underlying problem. In demanding pharmaceutical processing equipment, the seal material, design, energisation system, chemical compatibility and physical constraints of the equipment all need to be considered.
This was the challenge faced by a UK-based equipment manufacturer supplying the pharmaceutical sector. Repeated failures of rotary shaft seals on mixing equipment were creating reliability and maintenance concerns, prompting the manufacturer to look for a more robust sealing solution that could also be retrofitted to existing equipment.
Fluorocarbon worked closely with the customer to develop a spring-energised PTFE rotary shaft seal designed around the application requirements, providing a solution suitable for both retrofit and future new-build equipment.
Table of Contents
What causes Rotary Shaft Seal Failure in Pharmaceutical Equipment?
Why Material Selection Matters in Pharmaceutical Sealing Applications
Developing a Retrofit Solution
Fluorinoid® FL117 Spring-energised Shaft Seals
From Prototype to Retrofit and New-build Applications
More than a Replacement Component
Why work with Fluorocarbon on Sealing Applications?
What causes Rotary Shaft Seal Failure in Pharmaceutical Equipment?
Rotary shaft seals operate at the interface between a rotating shaft and stationary equipment. This makes them particularly sensitive to the combination of mechanical, chemical and environmental conditions within the application.
Seal failure can be caused by a number of factors, including:
- Chemical attack or incompatibility with the process media
- Excessive wear or friction
- Temperature outside the material's operating range
- Inadequate or inconsistent sealing force
- Incorrect seal geometry
- Shaft surface condition
- Incorrect material selection
- Operating speeds or pressures beyond the seal's capabilities
- Installation or equipment alignment issues
In pharmaceutical mixing applications, chemical compatibility can be particularly important. Cleaning processes and process chemicals can expose sealing components to aggressive environments, while the seal must continue to perform reliably around a moving shaft.
When a standard seal repeatedly fails, the solution may therefore require a review of the complete sealing system, rather than simply selecting another seal of the same type.
The Engineering Challenge
The application involved rotary shaft seals used on pharmaceutical mixing equipment, where the sealing material needed to withstand exposure to a range of process chemicals.
The equipment manufacturer required sealing solutions for shaft diameters ranging from 6 mm to 25 mm.
The replacement solution needed to provide:
- High chemical resistance
- Reliable rotary sealing performance
- Compatibility with different shaft diameters
- A PTFE-based sealing element
- A corrosion-resistant Hastelloy spring
- Compatibility with existing equipment
- Minimal modification for retrofit applications
- A solution suitable for future new-build equipment
The challenge was therefore not simply to identify an alternative catalogue seal. The component needed to be engineered around the existing equipment while addressing the causes of premature seal failure.
Why Material Selection Matters in Pharmaceutical Sealing Applications
The material used for a rotary shaft seal can have a significant influence on its performance.
PTFE is widely used in demanding sealing applications because of its excellent chemical resistance and low coefficient of friction. These characteristics make it particularly suitable where the sealing element is exposed to aggressive process media while operating against a moving shaft.
However, selecting PTFE is only part of the engineering process.
Different PTFE formulations can provide different combinations of wear resistance, friction, mechanical properties and chemical performance. The grade therefore needs to be considered alongside the application's operating conditions.
The seal's energising mechanism is also important.
In this application, a Hastelloy spring was incorporated into the seal design. The spring provides the force required to maintain contact between the sealing element and the shaft, while Hastelloy provides the corrosion resistance required for the demanding chemical environment.
This combination of material and design allowed the sealing solution to be developed around the actual application rather than relying solely on a standard component.
Developing a Retrofit Solution
Fluorocarbon worked with the equipment manufacturer to understand the existing seal arrangement, dimensional constraints and operating requirements.
The engineering team developed a flanged rotary shaft seal configuration designed to fit within the customer's existing equipment envelope.
This was particularly important for the retrofit application.
Replacing a seal should ideally not require extensive modifications to the equipment. Significant redesign can increase engineering costs, installation time and equipment downtime.
The flanged design provided a practical way of integrating the replacement seal into the existing mixer assembly with minimal modification.
The same design approach could also be applied to future new-build equipment, providing the manufacturer with a consistent sealing solution across both existing and new machinery.
Fluorinoid® FL117 Spring-energised Shaft Seals
The resulting solution was the Fluorinoid® FL117 spring-energised shaft seal, supplied for 12mm and 25mm shaft diameters.
The design incorporated:
- A chemically resistant PTFE sealing element
- A Hastelloy energising spring
- A flanged configuration
- Precision-manufactured geometry suited to the customer's equipment
The spring-energised design maintains sealing force against the shaft, while the PTFE sealing element provides the chemical resistance required for the application.
Rather than simply replacing a failed component with another standard seal, the solution was developed specifically around the customer's equipment and operating environment.
From Prototype to Retrofit and New-build Applications
Prototype quantities were initially supplied to allow the equipment manufacturer to evaluate the new seal design within its mixing equipment.
This stage provided an opportunity to assess the solution before moving towards wider implementation.
Following successful evaluation, the sealing solution offered two potential routes:
Retrofit Applications
Existing mixing equipment could be upgraded using a seal designed around the established equipment envelope, helping to minimise modification requirements and reduce disruption.
New-build Equipment
The same sealing technology could also be incorporated into future equipment designs, providing greater consistency between replacement components and new machinery.
For equipment manufacturers, this type of flexibility can be valuable. A sealing solution needs to work not only as an individual component but also within the wider lifecycle of the equipment.
More than a Replacement Component
The project demonstrates why solving a sealing problem often requires more than simply changing the material or selecting another catalogue product.
When a seal repeatedly fails, the underlying application needs to be understood.
Factors such as:
- Process chemicals
- Operating temperature
- Shaft speed
- Pressure
- Shaft diameter
- Shaft surface finish
- Seal geometry
- Energising force
- Installation constraints
can all influence sealing performance.
In this application, Fluorocarbon combined polymer material expertise, seal design and precision manufacturing to develop a solution around the customer's specific requirements.
The result was a chemically resistant, spring-energised PTFE shaft seal designed to improve reliability while providing a practical retrofit solution for existing pharmaceutical mixing equipment.
Why work with Fluorocarbon on Sealing Applications?
Fluorocarbon combines materials science, engineering design and precision manufacturing to develop high-performance polymer components for demanding applications.
Our capabilities extend beyond supplying standard materials or catalogue components. We can work with engineering teams from the initial application assessment through material selection, component design, prototyping and production.
This approach can be particularly valuable when:
- An existing sealing component is experiencing premature failure
- A standard seal does not meet the application requirements
- Equipment cannot easily be redesigned
- A retrofit solution is required
- Chemical compatibility is critical
- A component needs to be manufactured to a specific geometry
- A new sealing solution needs to be developed for future equipment
By bringing material expertise and manufacturing capabilities together, Fluorocarbon can help customers address the underlying engineering challenge rather than simply replacing the failed component.
Frequently Asked Questions About Rotary Shaft Seals
What causes rotary shaft seal failure?
Rotary shaft seal failure can result from a combination of factors, including chemical attack, wear, friction, temperature, incorrect material selection, inadequate sealing force or unsuitable seal geometry. In demanding pharmaceutical mixing applications, the seal needs to be selected around the complete operating environment rather than simply the shaft dimensions.
Why use PTFE for pharmaceutical rotary shaft seals?
PTFE offers excellent chemical resistance and low friction, making it suitable for demanding rotary sealing applications. However, the specific PTFE grade and seal design should be selected according to the application's process media, temperature, speed, pressure and other operating conditions.
What is a Spring-Energised PTFE seal?
A spring-energised PTFE seal incorporates a spring within the sealing element to provide continuous energising force against the mating surface. This helps maintain sealing contact as operating conditions change and makes spring-energised seals suitable for a range of demanding static and dynamic applications.
Why is Hastelloy used in spring-energised seals?
Hastelloy is a corrosion-resistant alloy that can be used for the energising spring where the seal is exposed to aggressive chemicals. In this application, the Hastelloy spring was combined with a chemically resistant PTFE sealing element to create a sealing solution for demanding pharmaceutical processing conditions.
Can a rotary shaft seal be retrofitted into existing equipment?
Yes. A replacement rotary shaft seal can be designed around the existing equipment envelope, potentially reducing the need for extensive redesign. In this application, Fluorocarbon developed a flanged rotary shaft seal configuration that could integrate into the customer's existing mixer assemblies with minimal modification.
What shaft sizes can spring-energised PTFE seals accommodate?
The appropriate seal dimensions depend on the equipment and application. For this pharmaceutical mixing application, Fluorocarbon supplied Fluorinoid® FL117 spring-energised shaft seals for 12mm and 25mm shaft diameters, while the wider application required sealing solutions for shaft diameters from 6mm to 25mm.
Are spring-energised PTFE seals suitable for pharmaceutical applications?
They can be suitable when the seal materials, design and manufacturing requirements are appropriate for the application. Chemical compatibility, temperature, operating speed, pressure, shaft condition and applicable regulatory requirements should all be considered when selecting a seal for pharmaceutical processing equipment.
What are the benefits of a custom-engineered shaft seal?
A custom-engineered seal can be designed around the actual operating conditions and physical constraints of the equipment rather than requiring the equipment to accommodate a standard component. This can be particularly useful where an existing seal has repeatedly failed, where equipment cannot easily be redesigned or where a retrofit solution is required.
How can Fluorocarbon help with rotary shaft seal problems?
Fluorocarbon combines polymer material expertise, seal design and precision manufacturing to develop sealing solutions for demanding applications. Our engineering team can assess factors including material compatibility, seal geometry, energisation requirements and dimensional constraints before developing prototype or production components.
Need help solving a shaft sealing problem?
If a rotary shaft seal is repeatedly failing, or an existing seal needs to be replaced without extensive equipment redesign, Fluorocarbon can help assess the application and develop a suitable material and seal configuration.
Talk to our engineering team about your sealing application
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