Valves Training Level 2

Valves Training Level 2

This module outlines the 6 main components of a Gar-Seal valve, the available disc and liner materials, the 4 styles of valve offered, material testing and valve accessories. Then it reviews the advantages of our valve and pneumatic actuator. During the separate, onsite classroom hands on training we will be taking the valves apart and installing the repair kit, looking at common applications where these valves are used, reviewing competitor valves and performing failure analysis.

Main Components of a Garlock Plastic-Lined Butterfly Valve

There are 6 main components of a Garlock plastic-lined butterfly valve: the body, the stem, the stem seal, the backup elastomers, the disc, and the liner.

The Stem

Stainless Steel

  • Sizes 2-12” = CA6NM (1.4313)
  • Sizes 14-24” = 420SS (1.4021)
  • Other materials available upon request

The Stem Seal

  • PTFE carrier with Viton o-rings
  • Other rubber o-ring materials available upon request

The Disc

Encapsulated Metal Core Discs

  • Sizes 2-2.5” is CF8M (1.4408) Stainless Steel
  • Sizes 3-24” is A526 (0.7040) Ductile Iron

Encapsulation Materials Available:

  • PTFE
  • UMPE
  • Abrasive-Resistant PTFE
  • Anti-Static PTFE

The Backup Elastomers

  • Silicone (standard)
  • Viton, EPDM, Neoprene and Kalraz available upon request

The Body


  • Offered in sizes 150# 2-24” (PN 10/16 DN 50-600)
  • Comes in 2 options: Lug or Wafer


  • Graphite Cast Ductile Iron A395 (0.7043) (standard)
  • Cast Steel A216 WCB (1.0619)
  • Stainless Steel 316 (1.4581)
  • Other materials available upon request

The Liner

  • PTFE (standard)
  • UMPE (Ultra High Molecular Weight Polyethylene)
  • Abrasion Resistant PTFE (carbon-reinforced PTFE)
  • Anti-Static PTFE (graphite-reinforced PTFE)

The Stem Seal

  • PTFE carrier with Viton o-rings
  • Other rubber o-ring materials available upon request

Disc and Liner Materials


  • The standard material choice unless other characteristics are needed
  • Void-free material isostatically molded from virgin PTFE. 
  • High density PTFE >2.16g/cm3
  • Guaranteed lining thickness of at least 3mm (0.125”), plus high crystallinity
  • FDA-compliant
  • Operating temperature: -40⁰F to 400⁰F (-40⁰C to 200⁰C)

Material Characteristics


  • Best option for abrasion resistance
  • Lower temperature and chemical resistance compared to PTFE
  • Optional FDA compliance
  • Operating temperature: -40⁰F to 185⁰F (-40⁰C to 85⁰C)

Material Characteristics

Abrasion-Resistant PTFE

  • Carbon-reinforced PTFE
  • Used when temperature or chemical resistance is needed with abrasives
  • Not FDA-compliant
  • Operating temperature: -40⁰F to 400⁰F (-40⁰C to 200⁰C)

Material Characteristics

Anti-Static PTFE

  • Graphite-reinforced PTFE
  • For explosive medias, liner is conductive
  • ATEX-compliant
  • Surface resistance < 106Ω
  • Volume resistance < 106Ω cm
  • FDA-compliant
  • Operating temperature: -40⁰F to 400⁰F (-40⁰C to 200⁰C)

Material Characteristics

Styles of Garlock Plastic-Lined Valves

There are 4 styles of Garlock’s plastic-lined valves: GAR-SEAL®, SAFETY-SEAL®, STERILE-SEAL®, and MOBILE-SEAL®. All valves are offered in lug or wafer bodies, with various material options.

The GAR-SEAL® Valve

  • The standard, default, general-purpose valve
  • Used where corrosive, abrasive, and toxic media need to be reliably controlled
  • Used in the chemical, petrochemical, chlorine, paper, and electro-plating industries
  • Offered with all material options except the Anti-Static PTFE, which is only available in the SAFETY-SEAL® Valve


  • Used for applications needing static dissipation
  • Used where corrosive, abrasive, and toxic media need to be reliably controlled and electrostatic charges need to be avoided
  • Used in the chemical and food industries
  • Valve is ATEX- and FDA-compliant
  • Comes with a grounding strap which connects every part of the valve
  • Offered with all material options; however, the liner must be Anti-Static PTFE, and the disc must be Anti-Static PTFE


  • Unique valve used in applications requiring a heated disc and stem seal
  • Used where sterile processes need to be maintained in the food or pharmaceutical industries or in applications requiring the disc and stem seals to remain hot
  • This completely unique valve has a steam inlet in the neck, an outlet at the bottom, and a specially-crafted stem, which allows steam to travel the full length of the valve without entering the process
  • The steam heats up the surrounding areas and sterilizes the valve from the inside out
  • Offered with all material options except the Anti-Static PTFE, which is only available in the SAFETY-SEAL® Valve


  • Used on European road tanker vehicles, railway wagons, silos, and other transportation and storage containers where high chemical resistance, reliability, and safety are required
  • Valve is EN 14432 approved
  • Comes with a grounding strap which connects every part of the valve
  • Available in sizes DN 50-100 (2-4”)
  • Offered with all material options

Material Testing

  • All valves are designated according to the European Pressure Equipment Directive (PED 97/23/EC Module H1)
  • Material Test Reports are available for all valves, inspection according to EN 10204
  • All disc and liners are tested for thickness
  • All vacuum service valves are tested for strength
  • All valves are tested for body strength, body tightness, and seat tightness (bubble tight) according to EN 12266-1 or API 598
  • All SAFETY-SEAL valves are tested for conductivity
  • All PTFE and UMPE disc and liners are spark tested at 35,000 volts for density

Valve Accessories

Vacuum applications

  • We have thicker liners available for increased resistance to vacuum or for full vacuum applications.
  • Liner thickness varies from 3mm to 10mm depending on the size valve (3mm is default).
  • To calculate the required liner thickness, we need to know the valve size 2-24” (DN 50-600), the temperature, and the amount of vacuum.

Disc Liner Repair Kits*

  • We offer inexpensive repair kits* as an alternative to replacing the entire valve.
  • Kits* include all wear components: Disc, Liner, Backup Elastomers, Stem Seals, Gaskets, and Washers.
  • * Repair kits are only available in the Americas. In Europe and Asia, individual parts can be ordered as needed.

Handles and Gear Operators

Gear Operator

Standard product does not have a locking feature, though it is available. Gears are offered on all sizes.


Available on sizes 2-8” (DN50-20). Comes with a lockable hole.

Bare Stem

Valves can be sold without any accessories.

Air Actuators and Accessories

  • We Offer Scotch Yoke pneumatic actuators and electric actuators for all sizes
  • We offer both double- and single-acting
  • A mounting plate and coupling are used to attach the actuator to the valve
  • To recommend an actuator, we need to know:
  • The size of the valve and liner material
    • Actuator Type: Pneumatic or Electric
    • Actuator Function: Double-Acting, Single Spring Closed, or Single Spring Open
    • If Pneumatic: Air pressure available for actuator
    • If Electric: Voltage and Frequency
    • If any accessories are needed: limit switch, positioner, solenoid valve, etc.

Pneumatic Actuator Performance

Garlock’s primary actuator offering is the Scotch Yoke pneumatic actuator; however, we can offer electric actuators upon request. This section will focus on the advantages of Scotch Yoke over rack and pinion.

Rack and Pinion


Rack and pinion uses a rack and a pinion gear to open and close the stem. This creates a level, linear torque to open and close the valve. This actuator can be used for both on/off and throttling..

Scotch Yoke

Scotch Yoke uses the cam principle, which varies the torque to open and close the valve. This actuator is unable to hold a mid-point position, and therefore cannot be used for control purposes (i.e. throttling).

Rack and Pinion vs. Scotch Yoke Actuators

Butterfly valves require different torques depending on where the disc is in the open/close cycle. When the disc is just starting to open (0-10⁰) or nearly closed (10-0⁰), it requires the highest torque. During the remainder of the disc movement, it requires much less torque.

When the sides of the disc are pressing against the liner, it requires more force to move.

Scotch Yoke actuators closely align with the torque needs of a butterfly valve; from 0-20⁰ and 20⁰-0, it applies 50% more torque than during the remainder of the cycle. This creates a smooth opening and closing, and extends actuator and valve liner life.

Rack and Pinion actuators better align with the torque needs of ball valves. When using them on a butterfly valve, you can select an actuator that will cover the maximum valve torque or the average. If the maximum torque is selected, the actuator is overworking for 95% of the actuation cycle. If the average torque is selected, the actuator is underperforming when the disc is closed and could lead to accelerated actuator wear.

Advantages of our Garlock Actuator

  • 60% more efficient (energy savings)
  • 30% lighter
  • Guaranteed 2,000,000 cycles over lifetime

Actuator Accessories

Butterfly Valve Performance

Primary Areas for Valve Leakage


“Bubble Tight”

  • This is where the disc and liner do not form a tight seal.
  • It can be caused from poor quality manufacturing – more details are in the next section.
  • There are two main tests for disc/liner leakage:
    • Bubble Tight is an API 598 or EN 12266-1 test, where the valve is closed and attached on one side to a flange. Water is put poured onto the open side of the valve, and air pressure is applied from the other side. If air bubbles come through the water, then the valve is not considered ‘Bubble Tight’.
    • Spark Test shows the density of the liner. A certain voltage is applied to the liner, and, if it goes through the liner, the density of the liner is not good, and media can permeate it. The higher the voltage test, the better quality the liner is.
      • Garlock Spark Tests every single disc and liner at 35,000 volts.
  • Valves that are not bubble tight could be leaking process media when the valve is supposed to be closed.

Stem Leakage

  • This is where the media leaks inside the valve and comes out the stem.
  • It can be caused from a poor quality liner or stem seals (more details in the next section).
  • There are two main tests for stem leakage, and one test which shows the overall quality of a valve:
    • ISO 15848-1: A global test for stem leakage (fugitive emissions) over 4,000 actuation cycles.  There are 3 grades of leakage: A (best), B, and C (worst).
    • The GAR-SEAL® valves meets Leakage Rate A.
    • TA-Luft: A German pass/fail test for stem leakage. To pass, you must meet x10-4 leakage.
      • The GAR-SEAL® valve meets Leakage Rate 5x10-8—10,000 times better than requirement!
    • EN 51508: A European test for the overall safety of the valve. It is a very comprehensive and time-consuming test which ultimately shows how likely the valve is to fail. There are 4 Safety Ratings: SIL 1 through SIL 4, with SIL 4 being the best.
      • The GAR-SEAL® valve meets SIL 3 (mean probability of failure ≥10-4 to <10-3).
  • Stem seals are important because they prevent the media from escaping up and out the stem. If the media escapes out the stem, it can be a safety issue; it can contribute to fugitive emissions, and it can damage actuators or the equipment running the valve.

Valve Manufacturing

There are three main molding processes to create a non-metallic disc and liner: Compression Molding, IsoStatic Molding, and Injection Molding.

Compression Molding

This is a less expensive process which presses the PTFE from the top and bottom. This can result in irregular mechanical properties and uneven densities which affect sealing, reliability, and permeation resistance.

IsoStatic Molding

With this process, the mold is surrounded by water, and the water is pressurized, which creates equal pressure in all directions. The result is a homogenous structure with lower porosity. The product has a consistent density with improved permeability, resulting in a better-sealing, longer-lasting valve. The below pictures show the different methods and microscopic pictures of what the PTFE looks like after molding.

All Garlock PTFE valves are IsoStatically Molded.

Injection Molding

This process is used for PFA disc and liners. PFA is more difficult to mold, and this can result in thinner materials or uneven densities.

PFA has a slightly lower temperature rating than PTFE, 320⁰F vs. 400⁰F (160⁰C vs. 200⁰C), and the chemical resistance isn’t quite as good. Permeation resistance is very close–it will depend on the quality of the molding process.

The quality of the disc and liner will affect how well the disc seals against the liner (bubble tight) and permeation through the liner resulting in stem leakage.

Stem Seal

The weakest spot in a valve is where the stem goes through the liner and disc.

Most valves have multiple ways to seal off this area:

Alternate Stem Seal: O-Rings


O-rings or encapsulated o-rings. O-rings can wear over time or be abraded if abrasive media gets past the primary seal.


Alternate Stem Seal: Spring-Loaded Seals

Spring loaded (similar to Belleville Washers). Springs press elastomeric seal against either the liner or the stem. The result of this is a thicker neck and base on the valve.

With this stem seal, disc and liner repairs can also be more difficult and expensive. If the spring is damaged, you can lose all of the load on your stem seal; plus, the bottom of the valve is not solid, so if there is stem leakage, it can escape out the bottom of the valve.

Alternate Stem Seal: Dynamic Seals

Dynamically self-loaded three-part stem seal that combines compression, labyrinth, and rotary seal concepts into one unique system. This patented stem seal uses a PTFE carrier ring energized by two Viton o-rings.

Garlock valves use the primary stem seal (disc against liner) plus the patented dynamically self-loaded stem seal.

Additional Seals

Some valves have additional stem seals in the valve neck for added protection. Additional stem seals are important, because they add an extra layer of protection in case the media gets past the primary and secondary stem seals. They also prevent external contaminants from getting inside the valve.

Single O-Ring Seal

One o-ring pressing against the stem and body.

Multiple O-Rings

O-rings in different positions to press against multiple sealing surfaces.

Garlock valves use multiple o-rings in various positions to seal against both the stem and the body.

This concludes the Garlock Pipe, Valve, and Pump Sealing Solution Training: Valves, Level 2 course. You may proceed to the testing portion.

Take the Garlock PVP Training - Valves, Level 2 Test