Thursday, 20 February 2014
Valve World posted this interview with De Tomi staff regarding weld overlay cladding using corrosion resistant alloys, such as nickel alloys. A transcript of the interview follows below the video: enjoy!
Question: What is weld overlay cladding?
Response: Weld overlay cladding is a process to deposit a thin layer of material on components.
Question: When and where would this technique be applied?
Response: Weld overlay cladding is applied to improve the corrosion resistance of the material of the component.
Question: What are some of the typical cladding materials?
Response: Yes, typical cladding materials are alloy and nickel alloys and stainless steel.
Question: The overlay process, is it manual or automatic?
Response: Both—the main process is automatic but you can do some parts with manual processing.
Question: Now your company is applying the weld overlay process to ball valve components. In your experience, is there any restriction to the shape or size of components that can be cladded?
Response: From experience there is only a restriction on the holes. If the diameter of the holes is less than 13 millimeters it’s impossible to do the process.
Question: Final question, is this an easy technique to apply?
Response: No it is not an easy technique because there are a lot of technical parameters to control. For example, heat input, the speed of the filler metal and so on.
Wednesday, 3 July 2013
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.
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.