Certificate Control Valve Sizing, Selection and Maintenance

Course Outline

• Selection process and formulations
• Selection steps and sizing of control valves
• Valve coefficient
• Purpose
• Pressure recovery factors
• Application of control valves
• Liquid sizing equations for determining volumetric flow rate
• Metric and SI formulae
• Valve characteristics

• Selection steps and sizing of control valves for gas
• Saturated steam
• Superheated steam
• Determination of valve coefficient
• Gaseous and vapor sizing equations for determining volumetric flow rate
• Metric and si formulae

Inherent And Installed Flow Characteristics

• valve characteristics
• butterfly disc shapes
• butterfly valve – inherent characteristic
• high performance characteristics
• flow characteristics
• globe valve characteristics
• cage valve characteristics
• various ball valve characteristics
• simple calculation data
• inherent characteristics
• installed characteristics
• overall process control loop
• closed loop control and controller
• importance of loop gain
• non-linear response conversion of gain to percentage of controller input range
• process pressure ratio and conclusion

Actuators And Positioners

• purpose
• principles of actuators for control valves
• issues of size
• force and speed matched to valve type
• control valve design considerations

• Pneumatic actuator types –piston and diaphragm
• Fixed spring, rotary
• Rack and pinion
• Rotary vane
• Electrical actuators – on/off control
• Modulated control
• Solenoid type
• Hydraulic actuators for large valves
• Actuator accessories

• Fundamental concepts on Cavitation
• Static and dynamic pressure profiles
• Multistage pressure reduction through the valve trim
• Cavitation mechanisms
• Effects of flashing
• Damage
• Velocity and noise
• Incipient cavitation
• Diffuser plate and choke
• Trim selection guide

• problem characteristics
• Types and cavitation control parameters
• Anti-cavitation trim
• Cavitation elimination

• Control valve noise Sources
• Treatment
• Prediction of noise
• Methods
• Low noise trim
• Diffuser plates
• Globe valve trim selection
• High pressure drop applications
• ED disk stack
• Low noise retainers
• Examples of noise reduction,
• Noise treatment and accessories
• Q-ball for noise attenuations and anti cavitation
• Noise source treatment
• Chokes
• Disk stack technology
• Pressure balanced trim

• Control valve materials
• Overview of material selection issues
• Standard control valve body materials
• Typical materials of construction for body and valve trim
• Recognize issues of corrosion and wear, valve trim materials
• Seating materials for tight shut off vs durability
• Problems of leaks from seals
• Applications of bellows seals for toxic materials

Maintenance Issues

• Tasks involved in valve maintenance
• Installation features relevant to good maintenance
• Recognize the setting up and testing tasks for valves
• Methods of detection of backlash and stiction in the valve drive
• Potential advantages of using smart positioners and diagnostic software tools.

• Hazards of overpressure
• Causes and consequences,
• Basic terminology
• European standards
• Pressure types
• ASME code requirements

• Requirements
• Purpose
• Relief systems
• layer of protection
• use and purpose of relief system

• Safety valves- types and performance issues
• Sizing principles and equations
• Calculations with examples
• Superimposed and built – up back pressure
• Balanced pressure relief valve operation and construction
• Balanced spindle design
• Pilot operated type
• Back pressure effects on pilot operated valve

• Outline of relief design procedure
• Sizing reliefs – determining relief rates
• Vent area
• Size of valve
• Sizing formulae and equations for gaseous and liquid flow
• Specification and installation issues
• Problem of chatter
• Rupture discs
• Rupture pins
• Prv conclusions