Parts in Oil & Gas Valve Applications

Oil and Gas Valve Applications

DuPont™ Kalrez® perfluoroelastomer and Vespel® polyimide parts provide improved solutions for valve applications, in wide operating temperature ranges and valves exposed to rapid gas decompression.

Theoretical Example of the Combined Effect of Modulus & Friction

Vespel® Polyimide Parts

DuPont™ Vespel® SP & SCP polyimide parts provide improved solutions for Ball Valves allowing for improved sealing, ease of design and less force required to achieve sealing. They have a very wide operating temperature range from -273°C to 350°C on a continuous basis.

However, what is truly remarkable about Vespel® SP valve seats is that they stay near constant modulus between room temperature and cryogenic temperatures such as liquid nitrogen (-195°C). This means the plastic stays relatively malleable, making it much easier to form a bubble tight seal in cryogenic conditions when compared to others plastics or metals that can be used in such applications.

The same material, Vespel® SP can operate without creep at very high temperatures, up to 300°C continuous with excursions to 480°C. Vespel® SP does not exhibit a detectable glass transition (Tg). Vespel® SCP grades can operate at 350°C continuous with excursions to 600°C

Lastly, the combination of ease of sealing and low friction means with appropriate design, an actuation torque on a for example a ball valve can be reduced by approximately 30%.

The high wear resistance, consistent properties vs temperature and high compressive strength of Vespel® SP and SCP allow for easier sealing, operating torque reduction and ease of design for a wide range of uses. They are used in:

  • Liquid natural gas (LNG) valve seats
  • High temperature valve seats
  • Backup rings
  • Piston rings in reciprocating compressors
  • Liquid oxygen and liquid hydrogen sealing systems for space applications

Vespel® SP-21 is specified by Total for use in cryogenic and high temperature valves over the temperature range -196°C to +260°C and appears in standard P.V.V. 1.4.2.

Vespel® Composite Parts

In addition to polyimides offerings, the DuPont™ Vespel® CR series are a range of composite materials designed for use in hostile chemical environments. In particular, Vespel® CR-6100 carbon-fiber filled thermoplastic fluoropolymer parts have shown their ability to perform in a range of high-pressure pumps and valves used in hydrocarbon processing and refining.

Vespel® CR-6100 offers higher wear resistance and near universal chemical resistance.

However what can set Vespel® CR-6100 apart, is its ability, with correct design, to expand and contract at the same rate as the surrounding metallic parts. This allows consistent clearances to be maintained between stationary and rotating parts in high energy applications such as large centrifugal pumps.

Due to its low creep and high thermal resistance, Vespel® CR-6100 often excels where other chemically-resistant plastics fall short. This makes Vespel® CR-6100 particularly well suited for seals, wear rings and other components used in a variety of devices and operating conditions.

Kalrez® Perfluoroelastomer Parts

Kalrez® perfluoroelastomer parts (FFKM) combine chemical resistance which is similar to PTFE, with thermal stability up to 327°C, extrusion resistance and excellent rapid gas decompression (RGD) performance. Whether for O-rings, custom shapes or Kalrez® KVSP™ valve stem packing, Kalrez® seals can help improve productivity, control fugitive emissions and reduce costly seal failures.

Low temperature performance is increasingly important in oil and gas valve applications. Kalrez® Spectrum™ 0040 can achieve a static seal at -42°C with back up rings when cooling the valve first and then applying pressure. Lower temperatures are possible when pressurising first.

In particular, Kalrez® 0090 has exceptional mechanical properties and with proper design is able to resist extrusion damage even at 15,000 psi (103MPa) and 232°C without the use of back up rings. The extrusion gap being 0.2mm diametrically measured in this case. Using these remarkable properties enables seals to be designed that can seal at -25°C when cooled first and then pressurised and lower if pressurised first. Removal of the backup rings reduces costs, part count, simplifies assembly and makes the sealing system more robust as fewer components are involved.

 Kalrez® seals are used in:

  • Sealing in valves of all types
  • Improving control valve emissions and hysteresis when used in valve stem packing