SEVERE SERVICE
Severe service generally refers to applications that feature heavy particle involvement, high-frequency cycling, extreme temperatures, corrosion, erosion, or any combination of these factors. Metal-seated ball valves are required for these demanding conditions.
By Flowserve
Ball valve hard coating in severe service applications
Image 1: Pre-coating treatment
The success of a metal-seated ball valve largely depends on the selection of a suitable hard coating and whether that coating is manufactured correctly. Hard coatings can protect vulnerable parts and enhance a valve’ s performance. However, it is much more difficult than most valve end users would imagine to obtain a satisfactory hard coating. This is why it is still common to see a variety of coating issues in ball valves on-site, such as galling, cracking and even delamination.
Why do ball valves require coatings?
Soft seated ball valves have their limitations when it comes to high temperatures or severe conditions. To handle the loads between the ball and seats, and to ensure a reliable and long lifetime, a suitable coating is required between the moving contact areas. Additionally,
Table 1. HVOF and Spray & Fuse coating applications
Advantages
Applications
HVOF coating
• Applicable to any metallic base material
• Highest hardness and wear resistance
• Severe service
• General service, moderate operating cycles
• High-pressure, high-temperature
Spray & Fuse coating
• Closed porosity and metallurgical bond
• High impact resistance
• Corrosion resistance to a variety of liquids and gaseous media, especially bases and oxidising acids, even at higher temperatures
• Severe service( abrasion, erosion, corrosion)
• High-pressure oxygen, hydrogen and critical gases
• Demanding low-leakage classes
• Thermal cycling / shock
• High and ultimate operating cycles
38 Valve World August 2025 www. valve-world. net