Following investigations of all potential sources of fugitive emissions from a petrochemical plant (flanges, pumps, heat exchangers etc.), Flexitallic discovered around 65% of fugitive emissions emanate from the stems of control and isolation valves.
In response, it manufactured the Enviroflex™. The basic Enviroflex stem packing sets consist of five rings. The top and bottom rings are produced from braided (scarf cut), with the remaining three rings being die-formed graphite rings. Additional carbon /metal brushing can also be installed to make up the depth of the stuffing box.
However in recent years there has been a change in the way the industry operates, with higher process temperatures being used. This resulted in more-rapid oxidation of the graphite, leading to a poor seal. In order to prevent this from occurring Flexitallic developed the new Enviroflex HOT.
The Enviroflex Hot is a low-emission valve stem-sealing system for high-temperature applications. It is supplied as a seven-ring set, consisting of three moulded rings and two braided ‘header’ and ‘footer’ rings. All of the moulded rings and the central low-density ring (olive) are made from high-purity phosphate-inhibited graphite. The braided header is made of exfoliated Thermiculite® tape reinforced with inconel wire, whereas the braided footer ring is manufactured from high-purity, low-sulphur graphite foil containing corrosion inhibitors and reinforced with inconel wire.
The oxidation barrier afforded by the CEV-based sealing components imparts exceptional long-term high-temperature sealing performance compared to traditional ‘graphite only’-based valve stem-sealing systems.
The key features of the Enviroflex HOT are:
- Excellent seal integrity
- Low stem friction
- Easy to install
- Suitable for all types of stem movement
- Suitable for isolation and actuated valves
- Minimal sensitivity to dimensional clearances
- Effective across a wide range of stem finishes
- Cryogenic to high temperature service
Enviroflex HOT provides many benefits to the user, including:
- Easy installation
- Fewer leaks
- Reduced maintenance cost
- More efficient processing in critical applications
- Class B emission performance
The Enviroflex HOT can work at a pH range of 0-14, temperatures up to 650°C (1,200°F), and a service pressure up to 860bar (12,470psi) or 80MPa.
The unique geometry of the sealing elements ensures a much more efficient conversion of compressive load to sealing stress than is achievable with traditional square section rings. This enables a high-quality seal, reducing the level of emissions.
In high-temperature applications, Enviroflex HOT valve stem seals assist in complying with fugitive emissions legislation by reducing the thermal degradation of conventional graphite-sealing technology.