Control Valve Erosion Problems
A problem common to control valves used in slurry service (where the process fluid is a liquid containing a substantial quantity of hard, solid particles) is erosion, where the valve…
What is Control Valve Cavitation ?
Fluid passing through a control valve experiences changes in velocity as it enters the narrow constriction of the valve trim (increasing velocity) then enters the widening area of the valve…
What is Control Valve Flashing ?
When a fluid passes through the constrictive passageways of a control valve, its average velocity increases. This is predicted by the Law of Continuity, which states that the product of…
Control Valve Trim Characteristics
The root cause of the problem – a varying pressure drop caused by frictional losses in the piping and other factors – generally cannot be eliminated. This means there is…
Control Valves Mechanical Friction Problems
Control valves are mechanical devices with moving parts, and as such they are subject to friction, primarily between the valve stem and the stem packing. Some degree of friction is…
Choked Flow of Control Valves
Both gas and liquid control valves may experience what is generally known as choked flow. Simply put, “choked flow” is a condition where the rate of flow through a valve…
Instruments Calibration Procedures
Calibration refers to the adjustment of an instrument so its output accurately corresponds to its input throughout a specified range. The only way we can know that an instrument’s output…
Relative Flow Capacity of a Valve
The flow capacity of a valve (Cv) is a quantitative rating of its ability to pass a fluid flow for a set of given pressure and fluid density conditions, defined…
Gas Valve Sizing
Sizing a control valve for gas or vapor service is more complicated than for liquid service, due to the compressibility of gases and vapors. As a gas or vapor compresses…
Process Safety and Instrumentation
Here we discuss about instrumentation related to industrial process safety. Instrumentation safety may be broadly divided into two categories: how instruments themselves may pose a safety hazard (electrical signals possibly…
