Hygienic Seal Material | Hygienic Rubber | Seal & Design

Hygienic Seal Material

Hygienic seal materials are elastomers or perfluorocarbons utilized in high purity sanitary hygienic seals where critical pure water, process fluids (both ambient and hot), and SIP environments exist.

Download the Hygienic Seal Material brochure (PDF).

The following criteria is used in determining correct hygienic seal materials:

  • U.S. Pharmacopeia Class VI Certification
  • Cytotoxicity Criteria
  • CFR Title 21 Section 177.1550
  • CFR Title 21 Section 177.2600
  • Traceability: Lot and Batch
  • Certification: Lot and Batch
  • ASME-BPE Standards
  • USDA Standards
  • 3-A Sanitary Standards
  • Current Good Manufacturing Practices (CGMP)
  • Manufacturer data and specifications
  • Consultation with various pharmaceutical users
  • Animal Derived Ingredient Free

The gasket materials considered are Tuf-Steel® (PTFE/Stainless Steel), Tuf-Flex®, PTFE, Silicone (platinum), FKM Fluoroelastomer, EPDM and Buna.

 

Exposure Limits

It is important to define the operating parameters of a new or existing processing sanitary system. The user specifications for exposure limits and reactivity to process fluids are compared with process operating parameters. All materials are acceptable for steam excluding Buna. All materials should meet process fluid reactivity parameters. Even though all compound exposure limits fall within operating parameters, the service life of some compounds will be different under certain conditions. This must be considered when selecting a compound.

 

FDA & USP Qualifications

CFR’s define the criteria for extractables and for compounds used in the manufacture of rubber and plastic articles. The two applicable categories are; rubber articles (Buna, EPDM, FKM Fluoroelastomer, Silicone) and perfluorocarbon resins (PTFE). USP defines the criteria for testing biological reactivity and the amount/type of extractables. The hygienic seals in service must meet USP Class VI specifications, and be manufactured using the proper compounds as stated in the CFR, Title 21, Sections 177.1550 and 177.2600 respectively. Certificates are available from Rubber Fab Technologies Group verifying compliance with regulatory requirements, traceability lot and batch and certification lot and batch. Note: Not all hygienic seals meet these requirements.

 

Curing Methods

Curing agents have an affect on the amount and type of extractables a material will emit. Typically, the hygienic seal group in service uses three methods; sulfur cured*, peroxide cured and platinum cured. When dealing with elastomers, peroxide cured is the most favorable method. When dealing with silicone, platinum curedis the most favorable. All gaskets shall be post cured. Using these methods minimize potential reactions with the respective process fluid applications and can uphold pure water and process fluid standards.

 

Hygienic Seal Material Usage Guidelines

1 = Excellent       2 = Good       3 = Acceptable       4 = Marginal       5 = Poor       X = Do Not Use

Gasket

     Comments

Continuous
Stream
Intermittent
Stream
Pure Water
Ambient
Pure Water
Hot
Process
Fluids
Ambient
Process
Fluids
Hot
Process
Fluids Variable
( <0C> 100C )
Temp.
Range

Tuf-Steel
Maintains seal with wide
temp. variations. Has
extended service life.*

1 1 1 1 1 1 1 -100°F
to
500°F

Tuf-Flex
Maintains seal with wide
temp. variations. Has
extended service life.*

1 1 1 1 1 1 1 -100°F
to
350°F

PTFE
Wide temperature
variations and may cause leakage at ΔT.

1 1 1 1 1 1 3 -100°F
to
500°F

Silicone (Platinum)
Very flexible low temperature.

2 2 2 2 2 2 1 -40°F
to
450°F

FKM Fluoroelastomer
Acceptable for steam applications.

3 2 2 2 2 2 2 -30°F
to
400°F

EPDM (peroxide cured)
Low pressure steam only.

3 3 3 3 3 3 3 -30°F
to
300°F

Buna
Not recommended for strong
acids and ozone

0 0 5 5 5 5 5 -30°F
to
200°F
* Application dependent
  • Tuf-Flex: Tuf-Flex is the world’s only unitized gasket, setting new standards for purity, performance and flexibility. A Tuf-Flex Gasket’s contact surface is a layer of PTFE unitized to an EPDM rubber inner core. This totally bonded construction provides a PTFE gasket with the mechanical characteristics, including memory, of an elastomer gasket. Designed to meet critical requirements in biopharmaceutical, ultra-pure water, WFI (water for injection) and difficult food and beverage processing, Tuf-Flex out performs other gaskets while eliminating costly process interruptions. Achieves higher performance under SIP/CIP conditions.
     
  • Tuf-Steel: A unique 50/50 blend of nonpigmented PTFE and 316L, water atomized and passivated, delivers leak-proof performance . Tuf-Steel is the choice for leak-proof, perfect surface performance and outstanding durability in SIP (steam in place) and WFI (water for injection) applications. Tuf-Steel is ideal for sanitary steam pipe   connections in extreme temperatures ranging from -20°F to 500°F. The superior strength of Tuf-Steel eliminates cold flow and creep to prevent maintenance problems and system downtime.
     
  • PTFE is the material of choice whenever low temperature flexibility or gasket memory is not required (not recommended where large temperature variations occur frequently, leakage can occur). PTFE has almost no extractables, has a low absorption rate and excellent resistance to process fluids. It can remain in service for longer periods of time in both water and steam for continuous use, high pressure clamps are recommended to prevent leakage resulting from temperature variations. PTFE envelope gaskets with a FKM Fluoroelastomer inner core should be used if slight misalignment is observed.
     
  • Platinum Cured Silicone is the material of choice in sanitary water systems when PTFE is not feasible due to severely misaligned fittings, or if the cost of high pressure clamps does not outweigh the benefits of PTFE (extended service life).
     
  • FKM Fluoroelastomer and EPDM compounds are specified by many of our process equipment manufacturers. They are generally suitable for these applications, however, service life must be considered and a preventative maintenance program be implemented to mitigate degradation. They are acceptable, but not recommended for  continuous use in SIP procedures.
     
  • Buna is the last choice in most applications due to temperature limitations and does not pass U.S. Pharmacopeia Class VI Certification and Cytotoxicity.