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VCS Flange Insulation Gasket
by Pikotek
High-reliability flange gasket for electrical
insulation & sealing
in Very Critical Service.
The Pikotek VCS Flange Gasket
is a "Very Critical Service" gasket designed for electrical
flange insulation and general sealing applications. This gasket
is suitable for use in raised-face, flat-face and RTJ flanges in
all pressure classes including API 15,000 psi service. In
addition to its superior sealing characteristics and excellent
dielectric properties, the VCS gasket is ideal for isolating
flanges made from dissimilar metals (thus mitigating galvanic
corrosion) and for mitigating localized flange face corrosion.
The VCS was originally designed
to provide a reliable sealing solution for electrical insulation
of critical flanges, particularly where phenolic ring gaskets
had been failing in RTJ flanges. The gasket was successfully
developed and tested by a major oil and gas company prior to
initial service approval. After demonstrating the VCS to be
superior to all competing products for sealing and insulating,
the VCS was placed in operational service in 1981. Since then,
hundreds of thousands of VCS gaskets have been placed into
service throughout the world. Current users include virtually
every international oil and gas company operating in every major
worldwide market.
Advantages &
Benefits
- Extreme high-reliability sealing
and insulating solution for all critical services.
- Seals and insulates at all
pressures up through ANSI 2500 class and API 15000 psi service.
- Withstands severe service
conditions including large bending moments, vibration,
temperature and pressure cycling.
- Designed to withstand corrosive
environments, including high concentrations of C02,
H2S,
produced water, etc.
- Outstanding insulation
properties for cathodic protection.
- Pressure-activated seals provide
high confidence sealing and eliminate costly leaks.
- Gasket is sized to the bore to
protect flange faces from media-induced corrosion and
flow-induced erosion.
- Prevents turbulent flow at
flanged connections.
- Mitigates galvanic corrosion in
dissimilar metal flanges.
- High-strength laminate material
resists failure due to excess compression (i.e., over-tightening
bolts).
- Available to match any flange
specification (ANSI, API, MSSP, BS, DIN, AS, others).
- Can mate mismatched RTJ with
raised-face flanges.
- Easy installation, make-up and
removal:
- Flanges do not have to be spread as with ring gaskets. The VCS
easily slips into place.
- Sealing system results in low required bolt loads.
- Less make-up force is required resulting in less flange and
bolt stress.
- Gasket is self-aligning and centering, quick to install. No
special tools are required.
- Maintenance-free,
corrosion-resistant design is resistant to deforming under load,
which makes the gasket reusable
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VCS Design
The unique and patented design of the VCS
gasket incorporates high-strength, glass-reinforced epoxy laminate
bonded to a stainless steel core. This provides the strength of a
traditional metallic gasket while maintaining complete electrical
insulation between the flange faces. Seal grooves are machined through
the laminate insulating material and into the stainless steel core. This
provides a strong base for the seal to seat into and breaks the
potential leak/weep path that is inherent in glass laminate materials.
Spring-energized Teflon internal face seals are installed in the
dovetail-shaped seal grooves to provide the trademark pressure-activated
sealing that distinguishes the VCS from all other high pressure
insulating gaskets (Viton o-rings also available if specified).
 Electrical
Insulation
In addition to its superior sealing
characteristics, the Pikotek VCS distinguishes itself by providing
electrical flange insulation in a high-strength gasket. The VCS
significantly decreases electrical potential between two flange
faces by providing a non-conducting, non-metallic interface. This
effectively eliminates corrosion resulting from dissimilar metals
contact or ground current induced corrosion of metal piping
components. When used with insulating sleeves and washers, the VCS
is particularly effective in breaking electrical conductivity in
piping systems with cathodic protection systems.
What makes the VCS unique among
insulating gaskets is its strength and durability. Traditionally,
insulating gaskets have been fragile and prone to failure because
they are often made from brittle, non-metallic materials (i.e.,
phenolic resin) and are not capable of withstanding imperfect
installation practices. The VCS's steel core and patented
construction enables the gasket to withstand far more system
pressure, pressure cycling, bending moments, over-torquing and
overall abuse than conventional insulating gaskets with zero risk of
product failure.
Sealing
Characteristics
The primary job that any gasket must
perform is to seal the pressure differential between the internal
and external environment. The VCS performs this task through the use
of its spring-energized, pressure-activated sealing elements. At low
system pressure, the spring acts to deflect the lips of the seal,
thus enabling low pressure sealing. As the pressure increases and
comes in direct contact with the sealing element, the system
pressure energizes the lips of the seal against the flange face and
the stainless steel core. The greater the pressure, the more sealing
force is applied against the flanges. This high pressure sealing is
accomplished while maintaining complete electrical flange
insulation. This high-reliability sealing system makes the Pikotek
VCS the gasket to use when gasket failure cannot be tolerated.
The fact that the VCS uses
pressure-activated sealing elements which are located inboard of the
ring groove on RTJ flanges has the additional benefit of allowing
the VCS to seal mismatched RTJ to raised-face or flat-face flanges.
This feature is very useful when replacing valves using stock
inventory that may have a different flange face than the mating
flanges.
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| VCS Gasket
Specifications
Description
The Pikotek VCS gasket is a high
reliability gasket used for both insulating 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 insulating 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.
Applications
- Flange insulation in conjunction
with cathodic protection.
- Insulation between dissimilar
metals to prevent galvanic corrosion.
- Wellhead isolation from
interconnected flow lines.
- 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).
Ordering
When ordering a complete VCS
insulating kit, the following must be specified:
- 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.
- Insulating Sleeve Material.
- Insulating Washer Material.
- Metal Washer Material.
Metalic Core
The core of each gasket is made
of annealed 316 stainless steel. Other metals, including Duplex
and Inconel are available upon special order.
Gasket Insulating
Material Options
G-10: NEMA grade G-10
Glass-Reinforced Epoxy laminate material (standard)
- Compressive Strength: 65,000
PSI
- Dielectric Strength: 750-800
VPM
- Max. Continuous Operating
Temp: 302° F (150° C)
- Water Absorption: .05%
- Flexural Strength: 65,000
PSI
- Tensile Strength: 50,000 PSI
- Bond Strength: 2,600 lb.
- Shear Strength: 22,000 lb.
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: 3502°F (177°C)
- 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 +350°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. 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 +350°F
Insulating Sleeve
Options
- GRE (standard)
GRE (Glass-Reinforced Epoxy) tubing is suitable for continuous
exposure to 350°F. This material is an epoxy laminate that
offers excellent resistance to crushing, cracking, breaking and
thread pinch.
- 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.
Insulating Washers
- GRE (standard)
1/8" (0.125") thick washers cut to standard SAE washer
dimensions.
Steel Washer
Options
- ZPS (standard)
Zinc-Plated Steel washers cut to standard SAE washer dimensions.
- SS
Stainless Steel washers cut to standard SAE washer dimensions.
Three Primary
Cross-sections of the Pikotek VCS
- 1/2" 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.
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