VCS Gaskets - Very Critical Service VCS Gaskets

VCS / Lineseal

The Pikotek VCS gasket is a high reliability gasket used for both isolating and general sealing purposes in Very Critical Services. The gasket has a proven track record of integrity in aggressive sealing situations. The VCS is suitable in all services up to and including ANSI 2500# and API 15,000# classes. The VCS is designed for service where the cost of gasket failure cannot be tolerated. The VCS gasket consists of a PTFE (Teflon) spring-energized face seal, or an elastomeric o-ring, seated in an isolating laminate, which is permanently bonded to a high-strength metal gasket core.

Due to its unique pressure activated sealing mechanism, the gasket requires far less bolt stress to seal than any other gasket. The VCS gasket inner diameter is exactly matched to the flange bore to eliminate turbulent flow and flange face erosion/corrosion. The seal elements are replaceable in the reusable gasket retainer.

  • Flange isolation in conjunction with cathodic protection.
  • Isolation between dissimilar metals to prevent galvanic corrosion.
  • Wellhead isolation from inter-connected flowlines.
  • Mating mismatched ring-joint to raised-face flanges (VCS will seal in ring-joint, raised-face and flat face/slip-on flanges).
  • Eliminate fluid trap corrosion between ring-joint (RTJ) flanges where high concentrations of CO2, H2S and other aggressive hydrocarbon media are present.
  • Eliminate turbulence and flow-induced erosion between ring-joint (RTJ) flanges.
  • Protect against coating impingement on coated flange faces.
  • To seal between flanges subjected to vibration/cavitation (i.e., compressor stations).
  • Flange Specification (ANSI/ASME, API, MSS, BSI or DIN standard)
  • Nominal Pipe Size, Pressure Rating and Bore Size
  • Operating Pressure, Temperature and Media
  • Required Seal Material
  • Isolating Sleeve Material and length if a custom size
  • Isolating Washer Material

VCS Metallic Core

The core of each gasket is made of annealed 316 stainless steel. Other metals, including Duplex and Inconel are available upon special order. 

vcs-kit

Gasket Isolating Material Options

1) G-10

  • NEMA grade G-10 Glass-Reinforced Epoxy (GRE) laminate – STANDARD
    • Compressive Strength: 65,000 PSI
    • Dielectric Strength: 750-800 VPM
    • Max. Continuous Operating Temp: 302° F (150° C)
    • Minimum Continuous Operating Temp: (minus) – 200º F
    • Water Absorption: .05%
    • Flexural Strength: 65,000 PSI
    • Tensile Strength: 50,000 PSI
    • Bond Strength: 2,600 lb.
    • Shear Strength: 22,000 lb.

2) G-11

  • NEMA grade G-11 Glass-Reinforced Epoxy (GRE) laminate material:
    • Compressive Strength: 50,000 PSI
    • Dielectric Strength: 500 VPM
    • Max. Continuous Operating Temp: 392° F (202° C)
    • Minimum Continuous Operating Temp: (minus) -50 Fº
    • Water Absorption: .085%
    • Flexural Strength: 57,700 PSI
    • Tensile Strength: 41,000 PSI
    • Bond Strength: 2,200 lb.
    • Shear Strength: 21,200 lb.

Seal Material

The sealing elements are intended to provide an impervious barrier through which no contained media or other substance can penetrate. Consequently, the composite retainer backing material behind the seal remains uncontaminated and thus permanently holds the seal in place in a static, fully encapsulated manner.
 

Seal Material Options

  • Teflon (Spring-Energized) STANDARD

    Recommended for all environments. Helical wound spring provides radial load. Encapsulation in the seal groove eliminates creep or cold flow. This sealing system truly distinguishes Pikotek gaskets from all other flange sealing systems.
    Temperature Range: -250° F to +392° F (note: gasket material is limiting factor)

  • Viton

    General-purpose oilfield elastomer. Excellent resistance to aliphatic hydrocarbons, glycols and H2S. Good resistance to aromatic hydrocarbons.

    VCS Tech7.8 Final.indd 4 7/9/09 1:38 PM

    Not recommended for: Systems with amine inhibitors and in piping systems containing significant partial pressures of polar gases (i.e. CO2) where radical pressure drops (i.e., 2000 PSI to 0 PSI) commonly occur.

    Temperature Range: -15° F to +392° F

Isolating Sleeve Options

  • GRE STANDARD

    GRE (Glass-Reinforced Epoxy) tubing is suitable for continuous exposure to 302° F. This material is an epoxy laminate that offers excellent resistance to crushing, cracking, breaking and thread pinch.

  • NOMEX

    Nomex is a high temperature sleeve material manufactured from solid organic polymer and is suitable for temperatures up to 425 degree F.

  • Mylar

    Spiral wound Mylar is a general-purpose material recommended for bolting applications with flange temperatures below 250° F. This material has generally fair resistance to crushing, cracking, breaking and thread pinch.

Isolating Washers Options

  • HCS WASHERS Hardened Coated Steel Isolating Washers
  • RE STANDARD WASHERS 1/8” (.125) thick washers

Steel Washer Options

  • ZPS STANDARD Zinc-Plated Steel Washers
  • SS Stainless Steel Washers

Three primary cross-sections of the Pikotek VCS

  • ½” thru 5” = .245” (.250” nominal) for all flange types including RTJ
    This cross-section is used for all small diameter flanges (less than 6” ID) in all pressure classes except API 10,000 PSI. This cross-section is thicker than conventional flange isolation for added flange separation. Further, the gasket thickness coincides closely to the flange separation (standoff) found with standard small diameter “R” and “RX” RTJ connections.
  • 6” thru 72” = .308” for all flange types including RTJ
    This cross-section is used for all large diameter flanges (equal to and greater than 6” ID) in all pressure classes except API 10,000 PSI. This thicker cross-section accommodates larger cross-section seals and further increases flange separation. Further, the gasket thickness coincides closely to the flange separation (standoff) found with standard large diameter “R” and “RX” RTJ connections.
  • API 10,000 PSI = .250”
    This cross-section is designed for elevated pressures. The core is thicker with redundant seals seated deeper into the metal core for greater sealing integrity. This cross section is standard for all API 10,000 PSI flanges. VCS Tech7.8 Final.indd 5 7/9/09 1:38 PM

vcs-chart

Notes:

  • Recommended bolt torque is based on deriving a minimum gasket seating stress of 7,500 psi
  • Bolt torque values listed assume a lubricated stud bolt resulting in a friction factor of 0.16
  • Recommended torque values are based on using weld-neck (integral) flanges with standard bores and ring grooves

ANSI B16.5 Bolt Torque (ft.-lbs) for 7500psi Gasket Seating Stress for RTJ FlangesPressure Classes

Notes:

  • Recommended bolt torque is based on generating a minimum gasket seating stress of 7,500 PSI arrived at using API 6A Annex D recommended flange bolt torque.
  • Bolt torque values listed assume a lubricated stud bolt resulting in a .16 friction factor.
  • Recommended torque values are based on using weld-neck (integral) flanges.
  • The torque figures above are based on a flange surface finish between 125 -250 rms finish, surface flatness within 0.020” tolerance and no misaligned flanges.
  • Deviation from these specific requirements may affect product performance or longevity
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