VCS Very Critical Service Flange Insulation Gasket by Pikotek
Description
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
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.
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.
