Lining a metal butterfly valve with a thermoplastic material, typically a fluorocarbon, means that media does not come into contact with any metal parts. This is particularly useful where corrosive liquids are being handled – for example, effluent, sludge or corrosive chemicals.

Thermoplastic liners are also chemically inert. This is useful where high purity media is required, for example in pharmaceutical and semiconductor high purity water applications.

So what are the best liners for the job?

 

Common valve lining materials

The main lining materials used for metal valves are:

  • PTFE (PolyTetraFluoroEthylene)
  • PFA (PerFluoroAlkoxy)
  • TFM

PTFE liners are isostatically compression moulded from sintered chips.

PFA linings are melt-processible which provides a far less permeable liner that can also be precisely moulded.

TFM™ PTFE incorporates a PerflouroPropyl Vinyl Ether (PPVE) modifier to the PTFE. This is a more advanced material which has the following improvements to PTFE:

  • Reduced cold flow by factor of 3
  • Firmer polymer structure
  • Less permeable (factor 2) for chemicals and gases
  • Weldable
  • Smoother surface for machining
  • More transparent
  • Injection-mouldable in special cases

The advantages of PFA and TFM™ lined butterfly valves are that they:

  • work well with most corrosive media to protect metal butterfly valve parts
  • can outperform more expensive alloy valves
  • are suitable for multiple-product processing lines being unaffected by media changes
  • are seldom affected by process temperature variations
  • are virtually impermeable

 

PFA and TFM Lined butterfly valves

GEMÜ 490 series lined metal butterfly valves are available with a moulded PFA or TFM™ body liner. These linings are achieved using the latest plastic injection-moulding machines to form a precise lining locked to the valve body. This is integral to the valve’s corrosion resistance.

Special silicon backing

As can be seen in figure 1, the valve body liner is backed by a specially design silicon rubber backing which provides the forces needed for effective media sealing downstream.

Figure 1 – Special design liner support

 

Special shaft seal system

Chemical handling requires specialist sealing to prevent leaks to atmosphere. A special 4 fold shaft seal system (figure 2) is also incorporated to prevent dangerous media leaks.

 

Figure 2 – Special design shaft seal

 

GEMÜ 490 series key features and benefits

GEMU 490 bare shaft butterfly valve

  • High-performance PFA or TFM™ lined metal butterfly valve
  • Wide range of sizes from DN40 to DN900 (1½” – 36”)
  • PN3/10/16 bar media rated (depends on size)
  • Suitable for use with temperatures up to +200°C
  • Pneumatic, motorised, manual and bare shaft options
  • Ideal for the distribution of corrosive chemicals, effluents and slurries
  • The valve of choice for high purity water applications in API pharmaceuticals and semiconductor plant

For more information on the GEMÜ 490 series

Visit the 490 Series product page

Download the 490 Series data sheet

 


Lining a metal butterfly valve with a thermoplastic material, typically a fluorocarbon, means that media does not come into contact with any metal parts. This is particularly useful where corrosive liquids are being handled – for example, effluent, sludge or corrosive chemicals.

Thermoplastic liners are also chemically inert. This is useful where high purity media is required, for example in pharmaceutical and semiconductor high purity water applications.

So what are the best liners for the job?

 

Common valve lining materials

The main lining materials used for metal valves are:

  • PTFE (PolyTetraFluoroEthylene)
  • PFA (PerFluoroAlkoxy)
  • TFM

PTFE liners are isostatically compression moulded from sintered chips.

PFA linings are melt-processible which provides a far less permeable liner that can also be precisely moulded.

TFM™ PTFE incorporates a PerflouroPropyl Vinyl Ether (PPVE) modifier to the PTFE. This is a more advanced material which has the following improvements to PTFE:

  • Reduced cold flow by factor of 3
  • Firmer polymer structure
  • Less permeable (factor 2) for chemicals and gases
  • Weldable
  • Smoother surface for machining
  • More transparent
  • Injection-mouldable in special cases

The advantages of PFA and TFM™ lined butterfly valves are that they:

  • work well with most corrosive media to protect metal butterfly valve parts
  • can outperform more expensive alloy valves
  • are suitable for multiple-product processing lines being unaffected by media changes
  • are seldom affected by process temperature variations
  • are virtually impermeable

 

PFA and TFM Lined butterfly valves

GEMÜ 490 series lined metal butterfly valves are available with a moulded PFA or TFM™ body liner. These linings are achieved using the latest plastic injection-moulding machines to form a precise lining locked to the valve body. This is integral to the valve’s corrosion resistance.

Special silicon backing

As can be seen in figure 1, the valve body liner is backed by a specially design silicon rubber backing which provides the forces needed for effective media sealing downstream.

Figure 1 – Special design liner support

 

Special shaft seal system

Chemical handling requires specialist sealing to prevent leaks to atmosphere. A special 4 fold shaft seal system (figure 2) is also incorporated to prevent dangerous media leaks.

 

Figure 2 – Special design shaft seal

 

GEMÜ 490 series key features and benefits

GEMU 490 bare shaft butterfly valve

  • High-performance PFA or TFM™ lined metal butterfly valve
  • Wide range of sizes from DN40 to DN900 (1½” – 36”)
  • PN3/10/16 bar media rated (depends on size)
  • Suitable for use with temperatures up to +200°C
  • Pneumatic, motorised, manual and bare shaft options
  • Ideal for the distribution of corrosive chemicals, effluents and slurries
  • The valve of choice for high purity water applications in API pharmaceuticals and semiconductor plant

For more information on the GEMÜ 490 series

Visit the 490 Series product page

Download the 490 Series data sheet

 


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Gemü Valves Ltd
10 Olympic Way
Birchwood
Warrington
WA2 0YL
Tel: 01925 824044
Fax: 01925 828002
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Best metal butterfly valve liners for demanding media