Have worked on lots of past projects, it looked that many piping experts be inclined to stereotype the term “extreme service “on their control valve needs.
In a given system or process, only few can be considered as such, but they are ones that pose the biggest design challenge. Each kind of valve has different parameters to consider.
Top temperature is general to energy generation and steam service. It needs temperature ratings from 400 C to even up to 900 C. As such, it needs unique focus when it comes to material and design selection that conforms the permissible thermal stress.
An alert thought of the ASME B16.34 quality is a must. Allowable working force relative to the material and temperature. Standard links like flange as per B16.5 also sets limitations and ratings.
Due to the inherent restriction of non-metallic materials like PEEK or PTFE, it is extremely general to find a metal-to-metal seated control device on top temperature application.
Corrosion is inevitable in the most procedure industry but more so in the midstream & upstream gas & oil applications. H2S and other corrosive substances can be qualified but the industry can just lessen corrosion in a piping structure, https://www.kp-lok.com/product/double-block-and-bleed-valves.
High nickel alloys such as C275 or 625, or Alloy 400, called to be corrosion-resistant alloys, are the typical-go- stuffs for such corrosive atmosphere and applications. Weld overlays and cladding on the control device are now becoming more familiar in the industry and are used for bigger control devices.
A unique design known as “Atmospheric Sealing” is a proprietary design introduced to the offshore market. Here corrosion is also mitigated from the exterior atmosphere. For example, CSCC is a general issue on offshore platforms in the Middle East. Besides that, top salinity from the sea can influence extreme corrosion outside the control device body and sealing elements.
This may have to perform with flow features such as fluid velocity, pressure drop and turbulence which can quick up the erosion. But a Double Block and Bleed Valve is used as a off-on valve or isolation, abrasive media is the general suspect that causes this issue.
Abrasive media can lead to scratches on the ground ball and on the soft typical adds. Once these stretches are overstated from closing/opening operations, a costly and serious leakage cannot be rejected. Metal-to-metal seated isolation control devices are more perfect for this application.
Also keep in mind, there are 2 general differences when picking the right DBB design for your application.
Plant operators and managers generally know the control devices performance history. For existing installation, it is vital that data sheets and operating situations/parameters be reviewed and matched against experienced or actual-based data. From this exercise, an extreme service application can be identified and then the right valve design applied.
End user may then take into considerations the commercial uptime, aspect, safety, reliability, fugitive emission needs and most vital the TCO or Total Cost of Ownership.