Valve does not work upon installation
Valve fails after a period of successful usage
Valve not operating
Valve not operating linearly
Whether the air supply is normal.
The positioner power supply is normal or not.
Check the air filter regulator working condition.
Check the volume booster, airlock relay and solenoid value condition if installed additionally.
Check all the tube line free from the choke.
Check the i /p converter working condition.
Check the output of the positioner.
Excessive Tightening of Compression Tube Fittings
Use of Insufficient Torque/Improper Tools
Mounting of Instruments on Vibration Source
Use of Nonstandard Leak Test Agent
Improper Storage/Handling of Tube
Inadequate Design of Tubing Clamp Support Systems
Incorrect improper process hook-up installation
Tube Fitting Failures
Safety Related Breakdown
Non-Safety Related Breakdown
Use of Proper Tools
Leak Test Agent
Proper Handling & Storage
Jacketed or Shielding of Tubing
Detailed Engineering Design for Clamp Supports
Understanding the Connections
The Pump Elements
The Process Elements
Determine the amount of energy each element in the piping system model should use based upon the system's "as designed" parameters
Determine the amount of energy each element in the physical system is consuming based on the plant's operation data
Get the control loop function test performed and get the logic verified. If some malfunction in the control loop or logic, then get it corrected.
Get the original design calculations and rated Cv information
Check the current operating conditions and try to locate current situation between original design cases.
If the current operation is too far from original design cases then perform the sizing (Sizing of valve) to estimate the current Cv. Compare the calculated Cv against the design cases and find out the current Cv represents how much opening. If current opening is in between 10% and 90% (ideal healthy range is 15-85% for design cases for installed control valve, it can be relaxed little bit) then valve can still function look for other mechanical damage like
Check for suitability of valve for selected for service or even service has changed over period from clean service to fluid with solids content.
Wear and tear in the trim (are common phenomena observed), this can alter the characteristic of the selected valve. Look for the damage to the valve plug, cage and seat for any damage. If damage is observed then get the repair done from the valve supplier.