Recent developments in API standards now allow the distinction between Double Block and Bleed and Double Isolation and Bleed valves. Check out this interview and transcript with Fred Turco from Omni Valve, at Valve World.
Wednesday, 3 July 2013
Tuesday, 2 July 2013
Chevron packing is a valuable resource for industrial valves owing to its specific features like durability, high elasticity, tough resistive power and above all the ability to withstand high/low pressures.
Crane’s Xomox Tufline severe service valves, for example, use Chevron packing, particularly in valves designed for alkylation service. These particular valves are made of carbon steel or monel body and monel trim which are required to withstand the corrosive nature of hydrofluoric acid (HF acid). Given the highly corrosive nature of HF acid service, alkylation valves require reliable packing making Chevron packing a reliable choice.
|Xomox Tufline sleeved plug valve. Source: cranecpe.com|
Designing the seal
The Chevron packing seal consists of a base ring, V-ring and a pressure ring. All three rings are come together to form a seal that reacts to the pressure changes. The base ring is made of a cotton fabric mixed with nitrile rubber that ensures complete safety from the extrusion problems. This ring is then backed up by the V-rings which are also made from the cotton fabric as well as the nitrile elastomers, combined as per industry standards. The overall purpose of the packing is to increase the sealing efficiency and balance the load which is crucial for better performance. The third and last element of the packing are the pressure rings whose function is to distribute the pressure equally among the rings and protect its different, integral elements from disproportionate wear and tear.
Usually one base rings is combined with one or three V-rings followed by one pressure ring. The Chevron seals find their use in industrial applications as well as other robust and high-alloy valves.
Benefits of using Chevron seals
There are several advantages of using Chevron seals in monel valves or other packing solutions:
- It has the ability to adjust to a broad range of demanding industrial applications.
- Durability and lasting performance reduces down-time, cost-of-ownership and increases worker safety.
- Despite wear and tear, the Chevron sealing and packing system will work well without adversely affecting performance.
- Flexible to bear even the severe temperature and pressure conditions.
Chevron packing can be found in many different types of valves, but are of particular use in corrosion resistant valves designed for alkylation service and made of monel. Other industrial purposes of such seals include pumps, marine hydraulics, and injection molding machines.