Control_Valve_maintenance and calibration.pdf

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CONTROL VALVE
AN OVERVIEW

CONTENT -
• WHAT IS A CONTROL VALVE ?
• CONTROL VALVE ACTUATOR
•STANDARDS APPLICABLE FOR CONTROL VALVE
•FLASHING
•CAVITATION
•CONTROL VALVE SELECTION & INTERCHANGEABILITY
•VALVE GLAND PACKING & MATERIAL OF CONSTRUCTION
•CONTROL VALVE LEAKAGE CLASS
• CONTROL VALVE CHARACTERISTICS
• ARDUOUS SERVICE VALVE
• NOISE REDUCTIONS PRACTICES
TODAY’S DISCUSSION
CONTENT -
• WHAT IS A CONTROL VALVE ?
• CONTROL VALVE ACTUATOR & ACCESSORIES
•STANDARDS APPLICABLE FOR CONTROL VALVE
•FLASHING
•CAVITATION
•CONTROL VALVE SELECTION & INTERCHANGEABILITY
•VALVE GLAND PACKING & MATERIAL OF CONSTRUCTION
•CONTROL VALVE LEAKAGE CLASS
• CONTROL VALVE CHARACTERISTICS
• ARDUOUS SERVICE VALVE
• NOISE REDUCTIONS PRACTICES

WHAT IS A CONTROL VALVE ?
CONTROL VALVE
This is a device used to modulate flow of process fluid in line by
creating a variable pressure drop in the line .
Normally the pressure drop is made with respect to the control signal
received towards flow condition correction required.

WHAT IS VALVE FLOW COEFFICIENT ?
VALVE Cv - No. Of US gallon [ USG = 3.7 Ltrs] of water per minute
passing through the valve in full open condition with 1 PSI pressure
Drop across the valve at 15 deg C temp.
So essentially valve Cv is capacity of valve in terms of water which
helps us to identify suitable size required for any fluid in any pressure /
temp. condition.
VALVE Kv - Quantity of water in M3/Hr. at temperature between 5 to
40C that will flow through the valve at a specified travel with a pressure
drop of 1 Bar.
Kv = 0.856Cv

TYPE OF CONTROL VALVE
Also valves may be further subdivided as shown below
BY SHAPE BY INTERNAL BY CHAR. BY GUIDING
GLOBE PLUG EQ% TOP
SINGLE SEAT
DOUBLE SEAT
BUTTERFLY CAGE LINEAR CAGE
ANGLE FULL BALL QUICK OPEN TOP & BOTTOM
SLANT SLEEVED PARABOLIC BUSH/BEARING
Y TYPE V BALL
All Control valve can be divided in two category.
1. Sliding stem ( Globe valve) 2. Rotary shaft ( Quarter turn )

VALVE ACTUATOR
Actuator - Mechanism which
operates the valve by receiving the
control signal.
Type of Actuator
Pneumatic - Spring Diaphragm
Piston Cylinder
Electrical - Not discussed
Hydraulic- Not discussed

VALVE ACTUATOR

VALVE ACCESSORIES
• VALVE POSITIONERS
• PNEUMATIC
• ELECTRONEUMATIC
• SMART DIGITAL
• PROXIMITY SWITCHES
• INDUCTIVE TYPE
• PNEUMATIC CAM OPERATED
• SOLENOID VALVES
• LATCHING/ NON-LATCHING
• WITH MANUAL OVERRIDE
• SIGNAL BOOSTERS
• PRESSURE
• VOLUME
• SIGNAL INVERTERS
• HANDWHEEL
• AIR VOLUME TANK

CONTROL VALVE STANDARDS
ANSI :- AMERICAN NATIONAL STANDARDS INSTITUTE
B16.34 :- STEEL VALVES
• DEFINES CRITERIA FOR VALVE WALL THICKNESS REQUIREMENTS
• DEFINES PRESSURE / TEMPERATURE RATINGS
• DEFINE HYDRO-TEST REQUIREMENTS
Example :-
A351 CF8M ( Material :- 316SST; Temp range :- -425 °F to 1500 °F)
A216 WCB ( Material :- Carbon Steel; Temp range:- -20 °F to 1000 °F )
B16.37 :- HYDROSTATIC TEST PROCEDURE
• DEFINES REQUIREMENT FOR HYDRO-TEST = 1.5 X MWP
MWP = MAXIMUM WORKING PRESSURE
B16.104 :- CONTROL VALVE SEAT LEAKAGE CLASSIFICATION
• ESTABLISHES TEST PROCEDURES AND SEAT LEAKAGE CLASSES
API :- AMERICAN PETROLEUM INSTITUTE
SPEC 6B :- DEFINES PIPELINE VALVE
SPEC 600 :- STEEL GAGE VALVES, FLANGED BUTT WELDING ENDS

NACE :- NATIONAL ASSOCIATION OF CORROSION ENGINEERS
NACE MR-01-75
• DEFINES SULFIDE STRESS CRACKING RESISTANCE MATERIAL
• MATERIAL COMPLY TO NACE STANDARD ARE
CARBON STEEL WITH HEAT TREATMENT
SST 302,304,316,17-4PH
ALLOY STEEL MONEY, HASTELLOY C
• MATERIAL NOT SUITABLE FOR NACE ENVIRONMENT IS
CAST IRON

ISA :- INSTRUMENT SOCIETY OF AMERICA
• DEFINES STANDARDS FOR CONTROL INDUSTRY
Example :-
VALVE SIZING EQUATIONS.
NOISE PREDICTION TECHNIQUE
CONTROL SIGNAL 3 - 15 PSIG, 6 - 30 PSIG
OSHA :- OCCUPATIONAL SAFETY AND HEALTH ACT
DEFINES CRITERIA FOR PERMISSIBLE DURATION FOR EXPOSURE OF NOISE LEVEL

SHELL REFERENCES
Control Valves –Selection , Sizing and Specification
• DEP 32.36.01.17- Gen July 1987 &
• Basic Process control & Instrumentation Shell
M114-1999
• Shell Best Practice –[Ref Process Measurement
and Control Devices –Shell Canada Ltd
Standard 16-1.2]

CONTROL VALVE LEAKAGE
ControlValve Leakage -
This is basically the fluid which passes through the valve when the valve is fully closed.
This value however should not be considered as the valve Cv at NIL Opening.
So this leakage shall depend on the contact of valve plug & seat with the seating force
applied for holding the plug over the seat.

CONTROL VALVE LEAKAGE
ANSI/FCI 70-2 Test Medium Pressure and temperature
Class II
Class III
Class IV
Class V Water Service DP at 10 to 52deg C
Port dia.
Bubbles per
Min.
mL per Min.
1 1 0.15
1 - 1/2 2 0.30
2 3 0.45
2 - 1/2 4 0.60
3 6 0.90
4 11 1.70
6 27 4.00
8 45 6.75
Maximum Leakage
0.5% valve capacity at full travel
0.0005ml/min/psid/in. port dia
Class VI
Service DP or 50 PSID
whichever is lower at 10 to
52deg C
Water / Air
Service DP or 50 PSID
whichever is lower at 10 to
52deg C
Air

VALVE CHARACTERISTICS
Equal % - Rate of change of flow due to change of valve
travel is proportional to earlier flow.
Linear - Rate of change of flow is same to rate of
change of valve travel
Quick Open - Full capacity attaining without change of
travel after initial opening
On/Off- Used mainly as Isolation valves (Pump suction and
ESD valves)

1. CHARACTERISING FLOW
• Linear Cage
• Quick Opening Cage
• Equal Percentage Cage
• Modified Equal percentage flow
2. NOISE ABATEMENT
3.ANTI CAVITATION
TRIM AND CAGE DESIGN

CHARACTERIZING FLOW BY CAGE
TYPE

CHARACTERIZING FLOW
% Valve Travel
0 20 40 60 80 100
100
80
60
40
20
0
Cv
Design
Cv
% Quick
Opening

VALVE SELECTION PROCESS FOLLOWED
IN RELIANCE
• If valve sizing does not give warning of cavitation, flashing or Noise level ( >85dBA) then
select standard trim valve.
• If valve sizing gives warning of cavitation, flashing or Noise level ( >85dBA) then select
arduous service trim valve.
Example:- For cavitation select CAVITROL III stage 1 to 5 valve or CAVITROL 4 valve.
For noise select WHISPER I ,III or WHISPERFLO valve trim.
• Select the suitable Approved vendor suiting the product .
Example:- ABB - Introl design or CCI - DRAG design.
• In case of very high DP ( DP*100/P1 > 50%) or Noise select ABB or CCI valves.
Example:- Compressor Anti - surge control valves - CCI- DRAG design.

VALVE SELECTION PROCESS
Carbon steel WCB
Carbon steel NACE
Stainless steel 316 or 316L
Standard Materials :
ANSI rating class 150
Standard Ratings :
Is it
standaard
material
Yes
No
Is it standard
flange rating
Yes
No
0 deg. C
+ 420 deg. C
Standard Temp. Rangge
Is
temperature
withing
standard
range
Yes
No
Choke Flow
Cavitation
Severe Service :
Noise above 85dbA
Oxygen service
Low temperature service
HF service
Ethylene oxide service
Vacuum service
HP steam service
Hydrogen service
Chlorine service
Is it sever
service
No
Yes
Standard valve design
and application.
Ref DEP 32.36.01.17
All Section except 6
and 7
Special valve design
and application
ref DEP 32.36.01.17

POPULATION OF CONTROL VALVES
AT RELIANCE JAMNAGAR.
• Based on above criteria RIL complex has following Installed quantity of
valve
• Fisher direct supply ( Through Bechtel ) :1800+ valves.
• Fisher package supply valves :800+
•Masoneilan package supply : 180 +
• ABB UK direct supply :150+
• CCI USA direct supply :40+
• Fisher Gulde package supply : 190 +
• Linde Mepag package supply : 120 +
•Copes Vulcan package supply : 50 +
•Keystone Biffi direct supply : 300 +
•Neles Jamesbury direct supply : 630 +
•Rotork MOVs direct supply : 2100 +

VALVE INTERCHANGEABILITY
• Body pressure rating and certification ( e.g. IBR )
• End connection ( Ex:- Screwed or welded flange connection )
• Valve Size and type.
• Trim Size - Cv
• Leakage classification
• Body and trim material and certification ( e.g. NACE )
• Plug and cage characteristics.
• Actuator bench setting / spring range.
• Actuator action ( AFC/ AFO )
• Process temperature ( For gland packing and body - trim material )

FLOW PATH THROUGH A CONTROL VALVE
- ANALOGY
Minimum
Geometrical
Flow Area
Streamlines Contract as
Flow Approaches Restriction
Vena Contracta
(Minimum Flow Area)

VARIATION IN PRESSURE AND VELOCITY
Valve
Inlet
Trim
Exit Vena
Contracta
Valve
Outlet
Trim
Inlet
Velocity
Variation
DP
Pressure
Variation
P1
P2

PRESSURE RECOVERY
Valve
Inlet
Trim
Exit Vena
Contracta
Valve
Outlet
Trim
Inlet
DP
Low
Recovery
High
Recovery

FLASHING
Flashing :
The formation of vapor bubbles in liquid flow streams at vena contracta.
As liquid passes through a restriction (vena contracta) in a control valve the liquid velocity
increases and liquid pressure decreases. And if the pressure at this point falls to or below
the vapor pressure of the liquid, vapor bubbles form in the flow stream. Flashing results if
this pressure remains below vapor pressure of liquid.
When a liquid flashes into vapor, there is a large increase in volume. Due to increase in
volume velocity will increase and hence high velocity will erode the surface.
Flashing damages can be identified by smooth polished appearance of eroded surface.
Flashing damages is usually at or near seat line of the valve plug and seat ring.
Vapor pressure :- The pressure at which liquid begins to vaporize.

FLASHING DAMAGE ( TAG NO.
241FV040 )

CAVITATION
Cavitation : The formation and subsequent collapse of vapor bubbles in liquid flow
streams.
As liquid passes through a restriction in a control valve the liquid velocity increases, while
the liquid pressure decreases. The pressure reaches a minimum at a point called the vena
contracta, and if the pressure at this point falls to or below the vapor pressure of the liquid,
vapor bubbles form in the flow stream.
Downstream of the vena contracta, flow area increases, velocity de-creases, and pressure
increases.
If this recovered pressure is sufficient to raise the pressure above the liquid vapor pressure,
the vapor bubbles will collapse. The collapsing bubbles generate significant noise and
vibration, and can mechanically attack pipe walls and valve components.
Cavitation damages can be identified by rough and pitted surface. Cavitation damage may
extend to the downstream pipeline if that is where the pressure recovery occurs.
Phenomenon of Cavitation is experienced in CV and PUMPS

CAVITATION
Valve
Inlet
Trim
Exit Vena
Contracta
Valve
Outlet
Trim
Inlet
DP
P1
P2
PV
PVC’

CAVITATION DAMAGE

CAVITATION CONTROLS
•SYSTEM DESIGN
1. LOCATION OF VALVE
2. CASCADING
•MATERIAL SELECTION
HARDEN MATERIAL,
LIKE 17-4 pH, 440C, 420SST HT
AND 316/COLMONOY 6 / ALLOY 6

CAVITATION CONTROLS
• ANTI - CAVITATION PRODUCTS
• CCI DRAG DESIGN, UP TO 380 BAR PRESS. DROP.
• FISHER CAVITROL - III DESIGN
CAVITROL - III WITH 1 STAGE- UP TO 99 BAR.
CAVITROL - III 2-3 STAGES- 99 TO 207 BAR.
CAVITROL -4 , ABOVE 200 BAR, SIZE LIMIT 2” TO 6”.
• ABB INTROL DESIGN

CAVITATION CONTROLS :- FISHER
CAVITROL DESIGN
CAVITROL - III CAVITROL - III
STAGE - 2 STAGE - 3

CAVITATION CONTROLS :- FISHER
CAVITROL DESIGN
CAVITROL - 4

CAVITATION CONTROLS :- ABB
INTROL DESIGN
INTROL CAGE

CAVITATION CONTROLS :- CCI DRAG
DESIGN
CCI DRAG CAGE

CAVITATION CONTROLS :- CCI DRAG
DESIGN

CHOKED FLOW
Choked flow :-
Formation of vapour bubbles in the liquid flow stream cause a crowding
condition at the vena contracta which tends to limit flow through the valve.
If valve pressure drop is increased slightly beyond the point where
bubbles begins to form, a choked flow condition is reached. With constant
upstream pressure, further increase in pressure drop will not produced
increased flow through the valve.

NOISE FUNDAMENTALS
Noise :- A random mixture of sound pressure waves of various amplitudes and frequency. Which
people do not like to hear.
Sound Wave :- A pressure wave with a fixed frequency and amplitude traveling through a medium.
Unit of Noise :- dBA ( Decibels )= 20 Log( Existing sound pressure level / 0.0002 microbars )
Source of valve noise:
• Mechanical Noise :- It produces high mechanical stress - fatigue failure of vibrating part.
Mechanical noise can be solved by improved design to suppress vibration
by good guiding and rugged construction.
• Vibration of valve components :- This is due to lateral movement of valve plug relative
to guide surfaces. The sound level produce normally will have frequency less then
1500Hz and is describe as metallic rattling.
• Fluid impingement upon the movable of flexible part ( Metallic chattering )
• Components resonates at its own natural frequency ( single tone 3KHz to 7KHz)
• Hydrodynamic Noise :- It is due to cavitation. It is because of implosion of vapor bubbles and
is relatively low.

NOISE FUNDAMENTALS
Aerodynamic Noise :-
Highest energy component at same frequency where human ear is most sensitive. Large
amount of energy converted to aerodynamic noise.
• High intensity noise resulting due to turbulent flow of gas, are due to high relative
velocity.
This can be classified as non-periodic or random noise with occurring frequency between
1 KHz to 8 KHz.
• Valve pressure drop ( Main source ),
• Obstruction in flow path,
• Valve style , having more flow directional changes,
• Degree of turbulence varies with valve style1,
• Valve size.

PERMISSIBLE EXPOSURE DURATIONS
NOISE LEVEL
OSHA :- OCCUPATIONAL SAFETY AND HEALTH ACT
DEFINES CRITERIA FOR PERMISSIBLE EXPOSURE DURATIONS NOISE LEVEL
IN JAMNAGAR COMPLEX MAX. 85 dBA IS CONSIDERED AS A VALVE SELECTION
CRITERIA.
DURATION IN HOURS PER DAY SOUND LEVEL IN DBA
8 90
6 92
4 95
3 97
2 100
1-1/2 102
1 105
1/2 110
1/4 OR LESS 115

NOISE CONTROL
• PATH TREATMENT
• INSULATION OF PIPE
• HEAVY WALLED PIPE
• SILENCER
• SOURCE TREATMENT
• VALVE CAGE STYLE ( TRIM )
• WHISPER - I ( DP/P1 <= 0.65 ), Noise reduction up to 18 dBA.
• WHISPER - III ( 0.6 <= DP/P1 <= 0.99 ), Noise reduction up to 30 dBA.
• WHISPERFLO (NEW DESIGN), Noise reduction up to 10 dBA.
• BY INLINE DIFFUSER
• BY WHISPER DISK

NOISE CONTROL - SOURCE
TREATMENT
WHISPER - I DESIGN
WHISPER - III DESIGN

TREATMENT
WHISPERFLO DESIGN BY FISHER

TREATMENT
WHISPER DISK AND IN
LINE DIFFUSER
DESIGN BY FISHER

NOISE CALCULATION
SPL = SPLDP + DSPLCG + DSPLDP/P1 + DSPLK + DSPLP2
SPL = OVERALL NOISE LEVEL IN DECIBLE ( 1 METER DOWNSTREAM OF VALVE OUTLET
AND 1METER FROM THE PIPE SURFACE )
SPLDP = FUNCTION OF PRESSURE DROP ACROSS THE VALVE ( MAJOR COMPONENT )
DSPLCG = GAS SIZING COEFFICIENT ( MAJOR COMPONENT )
DSPLDP/P1 = RATIO OF PRESSURE DIFFERENTIAL TO INLET PRESSURE
DSPLK = CORRECTION IN DBA FOR PIPE SIZE AND SCHEDULE
DSPLP2 = DOWNSTREAM PRESSURE
SIMPLIFIED EQUATION ( WITHOUT MUCH LOSS OF ACCURACY ) :
SPL = SPLDP + DSPLCG

CONTROL VALVE GLAND PACKING

CONTROL VALVE GLAND PACKING
Temp.
Range
Common use
Suitablity
for Oxygen
/Oxidizing
Service
Packing material Description
Stem
friction
Special
consideration
-73 to 232C Non-Radioactive Yes
PTFE impregented
composition
Split rings of braided
composition impregented with
PTFE
Low -
All chemicals ( Except
Molten alkali) Non
radioactive
No single PTFE V - Ring Solid rings of molded PTFE Low
Vacuum Pressure /
Vacuum
No Double PTFE V - Ring Solid rings of molded PTFE Low
-84 to 232C
Vacuum, All chemicals
( Except molten alkali )
Yes Chesterton 324
Split rings of braided,
preshrunk PTFE yarn
impregented with PTFE;
available with copper rings at
top and bottom of packing
box to meet UOP
specification 6-14-0 for acid
service.
Low -
-18 to 538C
Water, Stem Petroleum
products, Radiactive
and Non-radiactive
nuclear
Yes but upto
371C
Graphite/
Ribbon/Filament
Ribbon style graphite rings
and rings of braided graphite
fibers with sacrificial zinc
washer
High
Low chloride
content ( less then
100ppm) chrome
plated stem not
necessary for high
temperature service
371 to 649C
High temperature
oxidizing service
Yes
Ribbon - Style
graphite
Solid rings of ribbon-style
graphite with sacrificial zinc
washers
High -
-40 to 232C
Required 2 to 4
micro inch RMS
valve plug stem
finish

VALVE MATERIAL
Essentially material for the valve is valve assembly MOC. Standard material
commonly used can be listed as below -
Valve Body & Bonnet - As per Process
Internals - As per Process . Commonly SS316 with or w/o
stellite.
Valve Gasket - Graphite, Metallic SS 316 or SS 316L
Valve Packing - CommonlyTeflon Or Graphite
Fasteners - B7 or B8M
ActuatorYoke - Cast Iron
Actuator Spring - Spring Steel
Actuator Diaphragm - Nitrile Rubber with fabric reinforcement
Accessories - Commonly Aluminum.

TECHNOLOGY
With the advent of new technology ControlValve has
undergone rapid change in terms of change in Internals, Capacity
Increase, Guiding, Leakage Class Improvement,Treatment of
Noise And Cavitation And Finally DIGITAL.
About 30 years back control valves were only available with top
guided or top & bottom guided design with asbestos packing
and practically no solution available for Hi Pressure drop
application leading to Noise for Gas service Or Cavitation for
Liquid Service.

TECHNOLOGY
Now a days we are also having control valve with digital technology, where valve
positioner is digital in nature and able to provide PID function at the valve itself.
Digital positioner can provide the following apart from acting as interface
between controller and valve actuator -
1. Provide HART feedback.
2. Can couple with Foundation Fieldbus.
3. Can provide valve diagnostics.
4. Helps in Asset Management.
5. Provide lock, soft alarms and data logging facilities.
6. Can achieve split action, remote calibration etc.

TROUBLE SHOOTING IN CONTROL
VALVES.
TROUBLE SHOOTING
To Check
Gland Packing
Increase
Actuator
Check Vlv
Guiding
High Stem Friction
HUNTING
(At any vlv opening)
Reduce dP
Use Smaller
Cv valve
Oversizing
Change
Flow dir.
Flow to Close
flow direction
HUNTING
(Near to vlv close posn)
INSTABILITY CYCLIC MOTION
Poor
Piping
Increse
Support
Other
source
Find
Plug guide
wear & tear
Replace
with new
At any vlv
opening
Increase
pipe support
Throtle pump
discharge
valve
Resonance of
Vibration
Change
plug
profile
Change
Cv value
Resonance
Noise
of vlv plug
At specific
vlv opening
VIBRATION (NOISE) DULL RESPONSE NOT WORKING
ACTION LEAKAGE OTHERS
MALFUNCTION

VALVES.
Trouble Shooting
CYCLIC MOTION
Dissemble &
Clean
Enlarge
guide ring
bleeder hole
Provide
flashing port
Use jacketed
vlv body
Use rotary
or angle type
valve
Slurry/sludge
in vlv guide
Actuator
piston ring
wear & tear
Change
Piston ring
Gland pkg
hardened
Change
gland pkg
Travel Not
smooth
(In both dir)
Change
diaph.
Leak in
Actuator
diaph.
Change
stem seal
Use dust
seal bellow
Leak from
Act. stem
seal
Travel Not
smooth
(In one dir)
DULL RESPONSE NOT WORKING
MALFUNCTION

VALVES.
Trouble Shooting
CYCLIC MOTION DULL RESPONSE
Trouble in
air source
Trouble in
electric source
Leakage from
tubing
Check comp.
elec source &
Main air tubing
No signal &
supply pr.
Trouble in
controller
Check
Controller
Control sig
leakage
Check
air tubing
Act diaph
air leak
Change parts
Positioner
air leak
Change bellow
or diaph
No signal pr.
sup pr. avl
AFR
contamination
Clean
Filter
Pn tubing
Leakage
Check Tubing
(mainly air
conn.)
Trouble with
AFR
Check
AFR
No sup. pr.
Signal pr. avl
Trouble in
posn pilot
relay
Check
Act diaph
air leak
Change
parts
Posn O/P Nil
Stem/guide
galling / jamming
Disassemble
& check
Foreign particle
in vlv port
Disassemble
& check
Stem Bend Change
parts
Trouble in
Actuator
Check
Act Stroke
Actuator not
working with
air sup.
NOT WORKING
MALFUNCTION

VALVES.
Enlarge
compressor
capacity
Exclusive
compressor
Too much air
consumption
in other line
Check AFR
Trouble in
AFR
Drift of
air sup pr.
Insert vol tank
& restriction to
air signal loop
Control loop
Resistance
Check
Controller
Trouble in
Controller
Hunting of
Sig air pr.
Check posn
parts friction
Check posn
pilot relay
Positioner
loop hunting
Decrease dP
Higher size
Actuator
Shift in plug
reaction force
Hunting of
Vlv stem
CYCLIC MOTION
MALFUNCTION

VALVES.
Remachine & Lap
seat surface
Change
seat & plug
Corrosion & erosion
of vlv seating
surface
Change seat
& seat gasket
Check
seat design
Corrosion & erosion
of seat ring thread
or gasket
Tack weld
defect area
Change vlv
body
Leakage
thro' inner
vlv body wall
Valve Closed
Reduce dP
Increase
Actuator size
Too high dP
Check for
Foreign parts
Remachine
galling portion
Galling on
guide or port
Valve not
able to close
Seat Leak
Tighten
pkg. nut
Insufficient
pkg nut tight
Provide
lub or chg pkg.
Pkg Lub
missing
Change
pkg
Wear & tear
of pkg
Change parts
or remachine
Use dust seal
bellows
Damage of stem
surface
Examine part MOC
Change gasket
Corrosion/erosion
of seat gasket
surface
Gland Leak
LEAKAGE
Change seat ring
or plug
Corrosion / erosion
of plug or S. ring
Rangeability narrowed
because of
control position
changed
OTHERS
MALFUNCTION

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