PRODUCTS | Failure Causes and Countermeasures

1. Valve fails to operate

No signal nor supply air pressure

Presumed causes	Corrective action
Air pressure source (compressor) fault	Check compressor
Large leakage on Air piping	Check air piping

No supply Air pressure

Presumed causes	Corrective action
Clogged or leaking on Air piping	Check air piping
Pressure Regulator Valve fault	Check and repair of Pressure Regulator

No signal Air pressure

Presumed causes	Corrective action
Controller fault	Check controller
Clogged or leaking on signal Air piping	Check air piping

No Positioner output

Presumed causes	Corrective action
Pilot Valve in Positioner fault	Check and repair Pilot Valve
Large leakage on Actuator	Check Actuator (Diaphragm)

Valve no movement even Air press is working on Actuator

Presumed causes	Corrective action
Valve Stem or Guide stick	Disassemble Body and check, repair or replace
Bend or breakage on Valve Stem	Repair or replace Valve Stem
Foreign matter entrapped on Seat or between Guide clearances	Disassemble and check valve port

2. Vibration or Noise

Vibration and noise in all range of opening

Presumed causes	Corrective action
Large clearance between Guide and Plug	Repair or replace Valve Plug and Guide
Loose connections (Valve Stem and Valve Plug, Valve Stem and Top Stem, Top Stem and Diaphragm)	Re-tighten connection
Poor de-aeration of fluid	De-aerate fluid
Flashing at outlet of the Valve Plug	Change valve type

Valve vibrates at middle to maximum openings

Presumed causes	Corrective action
Natural vibration (double sealed valves except for cage type generate when unbalanced force of Valve Plug reverses)	Change valve type. (ex. cage type)

Plug chatter at almost fully closed position

Presumed causes	Corrective action
Fluid flow to close Valve Plug (flow close)	Change valve Cv or Plug and control position

Shock waves occur at valve outlet

Presumed causes	Corrective action
Valve size too small (steam)	Enlarge valve size

3. Valve fails to operate

Supply air pressure fluctuates

Presumed causes	Corrective action
Insufficient Air source capacity	Add compressor
Pressure Regulator fault	Repair or replace pressure Regulator Valve

Signal Air pressure fluctuates

Presumed causes	Corrective action
Inappropriate resistance or volume of Controller	Install valve or volume tank in signal circuit
Controller fault	Check controller

Neither supply Air nor signal Air pressure fluctuates, but valve hunts

Presumed causes	Corrective action
Positioner fault	Check Pilot Valve Tighten Positioner connections
Large friction on Valve Stem	Check and repair Valve Stem and Guide
Large friction on Gland Packing	Replace Packing
Resonance with fluids turbulent wave motion (fluctuations in stem's thrust due to changes in fluid pressure)	Reduce differential pressure; Change Actuator, higher rigidity; Install rectify straight pipe on upstream

4. Too Slow Action

Too slow stroke both direction

Presumed causes	Corrective action
Clogged guide with slurry or solids	Disassemble and clean Change valve type (Angle type)
Deteriorated and hardened gland Packing	Change packing and grease Change packing material

Too slow stroke, one way

Presumed causes	Corrective action
Thrust by large differential pressure to Plug	Install Positioner Install big Actuator
Actuator Air volume is big	Install Positioner or booster
Air leakage from Actuator	Check Actuator

5. Large hysteresis error

Large hysteresis error

Presumed causes	Corrective action
Valve Stem and Guide, no alignment	Check Valve Stem alignment
Deteriorated and hardened gland Packing	Change Packing
Foreign matter entrapped in Valve Plug	Disassemble and clean up
Clogged Valve Stem or Guide with slurry or solid	Disassemble and clean up

6. Valve no move beyond certain travel

Valve no move beyond certain travel

Presumed causes	Corrective action
Manual Handle position is not set at “NEUTRAL”	Set Handle position “NEUTRAL”
Lack of supply air pressure	Check supply air pressure

7. Large Leakage

Valve Stem fully closed position

Presumed causes	Corrective action
Corrosion, erosion or damage on Valve Seat	Check Seat and repair or lap
Cavity in Valve Body	Repair or replace Body
Corrosion or erosion of thread in Valve Seat	Change Seat-Ring or Body

Impossible to move to fully closed position

Presumed causes	Corrective action
Large differential pressure	Large differential pressure
Foreign matter entrapped in Valve Plug	Disassemble and clean up
Guide or port seizure	Repair or replace damaged parts

Control position changed, range ability decreased

Presumed causes	Corrective action
Corrosion or erosion of Valve Plug or Cage	Change Valve Plug or Cage

8. Leakage from Gland Packing

Leakage from Gland Packing

Presumed causes	Corrective action
Loose Gland Nut	Re-tighten uniformly
Deteriorated and hardened Gland Packing	Change Packing. Change Packing material
Incorrect insert of Gland Packing	Re-insert correctly
No Grease	Add Grease
Corrosion, erosion, or damage of Valve Stem	Repair or change Valve Stem

FAQFailure Causes and Countermeasures