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Speed Control Governors
For GME Cadets
A governor maintains the average speed
of an engine whereas the flywheel
controls the cyclic fluctuations in speed.
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– Second level
• Third level
– Fourth level
» Fifth level
Anglo-Eastern Maritime
Maritime Academy
Anglo-Eastern
Academy
ajit / Tr Sup (Engg) 29/06/12
© 2010
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Contents
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Governor classification
U Tube Video on Diesel Engine Governors
A. Classification of Speed Governors as per the control media used
B. Classification of Speed Governors as per the functions they carry out
C. Classification of Speed Governors as per the speed setting arrangement
Further classification of Speed Governors based upon their operating principles
Dead Weight type basic centrifugal governor
Mechanical / Hydraulic, Relay or Indirect acting type Governor
Speed droop (Permanent) , Feed back
Speed droop (Transient) , Compensation
Woodward governor nomenclature SG, UG8, UG40, PG200, PGA200 etc.
Controls on Woodward UG8
Speed droop Knob, Synchronizer Knob, Load limit Knob, Synchronizer indicator Knob
Woodward UG 8 Internals
UG 8 Governor Operation
Load Reduction 1
Load Reduction 2
Load Reduction 3
Load Increase 1
Load Increase 2
Load Increase 3
Initial set up & Adjustments of Governor
Speed droop & Steady state speed regulation
Isochronous Governor
Droop and its relation to load division
Methods of speed setting
The A/E governor
The M/E governor
Equilibrium position of governor flyweights and balancing of forces
Speeder Spring rate and its effect on governor stability
Over speed governor & Speed regulating governor spring rate selection
conical or trumphet shaped spring as the SPEEDER SPRING
Some important features & terms in governors
Anglo-Eastern Maritime Academy
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– Second level
• Third level
– Fourth level
» Fifth level
ajit / Tr Sup (Engg) 29/06/12
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Index
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A. Classification of Speed Governors as per the control media used.
1. Mechanical or Direct acting type
When the movement of the flyweights directly operate the engine fuel control rack, it is
called a direct acting governor.
They need huge fly weights so that enough power can be obtained for moving the racks.
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– Second level
2. Mechanical / Hydraulic, Relay or Indirect acting type
This type has the movement of the flyweights operating a pilot valve plunger only.
The operation of the rack being through a power piston operated by hydraulic pressure
controlled
by the pilot
valve.
– Fourth
level
• Third level
3. Electronic governor » Fifth level
The speed governor can considered to be of three main parts,
1. Speed sensing
2. Control function
3. Actuator.
An electronic governor may have its speed sensing and the control functions
electronically carried out.
The actuating of the rack may be done by an electric motor or by a pneumatic
actuator.
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ajit / Tr Sup (Engg) 29/06/12
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Index
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B. Classification of Speed Governors as per the functions they carry out.
1. Regulating governors
They are constantly positioning the fuel rack at all speeds.
Two kinds of regulating governors are possible,
Constant speed Where the set speed of the governor cannot be altered.
Variable speed Where the set speed can be varied to control load.
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– Second level
• Third level
2. Speed limiting governors
Which act only to keep speed within the normal range, not allowing over speeding or under
– Fourth level
speeding.
They are not»acting
when
speed is in normal range.
Fifth
level
These type of governors are found in vehicle engines.
3. Overspeed governors (overspeed trip / shutdown)
They act only in case of an overspeed.
An overspeed governor shuts down or trips the engine as compared to the others which
regulate the fuel rack.
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ajit / Tr Sup (Engg) 29/06/12
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Index
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C. Classification of Speed Governors as per the speed setting arrangement
1. Lever type
• Lever
Click
to edit
text
type governor
is one Master
in which the speed
settingstyles
is carried out by a lever which
adjusts the speeder spring tension.
– Second level
2. Dial type
• Third level
Dial type governor is one in which the speed setting is done by turning a dial on the
governor.
– Fourth level
» Fifth level
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Index
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Further classification of Speed Governors based upon their operating principles.
Basic classification of mechanical speed governors based on operating principle are
1. Inertia governors
2. Centrifugal governors
a. Gravity Controlled / Dead Weight type
1. Watt
2. Porter
2. Proell
b. Hartnell (Spring controlled)
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– Second level
• Third level
In the former type the centrifugal force is relied on for operation. The flyballs or flyweights responds to
– Fourth level
change in rpm.
» Fifth level
In the latter type the inertia force is relied on for operation. The inertia of rotating weights causes a shifting
of weights when acceleration or deceleration occurs. This rate of change in rpm is detected by inertia
governors and hence they are more sensitive that centrifugal governors. It should be noted that it only
detects rate of change of speed and hence cannot be used independently for speed control.
A centrifugal governor can be dead weight type also called gravity controlled, in which the gravity force is
what acts against the centrifugal force. Watt governors fall in this category, Porter and Proell are of same
type with some modifications. These governors are inherently stable.
The centrifugal governor that is used today is of Hartnell type where the gravity force is replaced by spring
force. The spring rate can be varied as necessary and the spring rate decides the stability of the governor.
Linear or non linear springs (trumpet / conical) can be used.
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Index
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Dead Weight type basic centrifugal governor
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– Second level
• Third level
– Fourth level
» Fifth level
Draw Backs
Torque output low, depends on flyweight size
Large flyweights required to reduce static friction effects
Large flyweights leads to
inertia effects
low rpm, less sensitive
Speed droop inherent
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Index
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Mechanical / Hydraulic, Relay or Indirect acting type Governor
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– Second level
• Third level
– Fourth level
» Fifth level
Advantages
Output no longer linked to fly weight size
Smaller flyweight size lead to
no inertia effects
higher rpm, more sensitive
Drawbacks
Over sensitive
Will hunt
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Index
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Speed droop (Permanent) , Feed back
A mechanical negative feed back arrangement is provided
Feed back is having the movement of the power piston transmitted to the speeder spring
Negative feed back is so as to reduce its tension as the fuel in increased
Negative Feed back introduces stability
But introduces a permanent speed droop.
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– Second level
• Third level
– Fourth level
» Fifth level
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Index
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Speed droop (Transient) , Compensation
A hydraulic negative feed back arrangement is provided by the compensation system
The compensation system consists of the Compensating spring, actuating piston and receiving piston.
A compensating needle valve setting decides the rate of oil flow in or out of the compensation system
Provides a transient speed droop
As the fuel is being increased, the speed setting is reduced temporarily. which is set back to normal
slowly as the engine rpm recovers.
Compensation gives stability without introducing droop, it enables isochronous operation.
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– Second level
• Third level
– Fourth level
» Fifth level
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ajit / Tr Sup (Engg) 29/06/12
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Index
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Woodward governor nomenclature SG, UG8, UG40, PG200, PGA200 etc.
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SG - Simple Governor Simple Proportional governor, without compensation. Has adjustable droop, cannot
operate isochronously. Pressure oil has to be supplied from the engine, no attached pump or sump.
– Second level
UG - Universal Governor Governors with Adjustable compensation & Adjustable droop. Can operate
isochronously or with droop. Has attached pump and sump.
• Third level
PG - Pressure compensating hydraulic Governor No adjustment of droop or compensation. Has limited
– Fourth level
compensation.
» Fifth level
PGA - PG + Air speed setting PGA/EG - PGA + Electric Actuator PGA/TL - PGA + Torque Limiter
The number "8/40/200" indicates the maximum torque that the terminal shaft can apply, called the "stalling
work capacity". It is the torque specified in "foot pounds".
Woodward UG8 Specs Rated for drive from 375 to 1500 rpm on drive shaft. Ratio of 1 : 2.2.
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Index
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Controls on Woodward UG8
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text styles
Controls on Woodward UG8
– Second level
• Third level
– Fourth level
» Fifth level
Speed droop Knob
Synchronizer Knob
Load limit Knob
Synchronizer indicator Knob
Speed setting motor and friction drive
Shut down solenoid
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Index
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Speed droop Knob, Synchronizer Knob, Load limit Knob, Synchronizer indicator Knob
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Speed droop Knob
The graduations are from 0 to 100, this does not indicate percentage droop.
For stand alone engines, speed droop can be set to zero. For engines interconnected electrically (AC
busbar) or mechanically, the speed droop is to be set at the lowest setting which gives stable load
division. Normally 30 to 50 on the dial.
If speed droop is set to zero, the governor operates isochronously.
– Second level
• Third level
Synchronizer Knob – Fourth level
This knob is free to turn for many rotations. This changes the speeder spring tension, thus changing the set
speed of the governor. » Fifth level
Load limit Knob
This scale is graduated from 0 to 10. A pointer below the knob indicates the power piston position over this
scale. The knob can be put to any postion and the rack movement is limited to that position. This limits
hydraulically the maximum possible movement of the terminal shaft. The load limit can be used to, limit fuel
during a start, Shut down a running engine, Limit the maximum load on the engine.
Synchronizer indicator Knob
This knob is coupled by gears to synchronizer knob. The gear ratio is in such a way that the indicator
turns one division for every one revolution of the synchronozer knob. This indicates the position of the
synchronizer knob over its range of movement.
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Index
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Woodward UG 8 Internals
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– Second level
• Third level
– Fourth level
» Fifth level
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Index
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1.
Load Reduction 1
2.
Load is decreased and speed
increases
As speed increases, FLY BALLS move
out raising SPEEDER ROD and inner
end of FLOATING LEVER, thus raising
PILOT PLUNGER and uncovering
REGULATING PORT in PILOT VALVE
BUSHING
Uncovering of REGULATING PORT
opens bottom of POWER CYLINDER
to sump and will allow oil pressure in
top of POWER CYLINDER to move
POWER PISTON down
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– Second level
3.
• Third level
– Fourth level
» Fifth level
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Index
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1.
Load Reduction 2
Oil pressure moves POWER
PISTON down rotating TERMINAL
SHAFT in the direction to decrease
fuel
2. As the POWER PISTON moves
down, ACTUATING
COMPENSATING PISTON moves
up and draws RECEIVING
COMPENSATING PISTON down
compressing COMPENSATING
SPRING and lowering outer end of
FLOATING LEVER and PILOT
VALVE PLUNGER
3. Movement of POWER PISTON,
Fourth level
ACTUATING COMPENSATING
» Fifth level
PISTON, RECEIVING
COMPENSATING PISTON and
PILOT VALVE PLUNGER continues
until REGULATING PORT in
BUSHING is covered by land on
PLUNGER
4. As soon as REGULATING PORT is
covered, POWER PISTON and
TERMINAL SHAFT are stopped at
a position corresponding to
decreased fuel needed to run
engine at normal speed under
Anglo-Eastern Maritime Academy decreased load.
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– Second level
• Third level
–
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Index
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Load Reduction 3
1.
2.
As speed decreases to normal,
FLYBALLS return to normal position
lowering the SPEEDER ROD to
normal position.
RECEIVING COMPENSATING
PISTON is returned to normal
position by COMPENSATING
SPRING at the same rate as
SPEEDER ROD thus keeping
REGULATING PORT in PILOT
VALVE BUSHING covered by land
on PILOT VALVE PLUNGER. Flow
of oil through COMPENSATING
NEEDLE VALVE determines rate at
which RECEIVING
COMPENSATING PISTON is
returned to normal.
At completion of cycle, FLYBALLS,
SPEEDER ROD, PILOT VALVE
PLUNGER, and RECEIVING
COMPENSATING PISTON are in
normal position. POWER PISTON
and TERMINAL SHAFT are
stationary at a position
corresponding to decreased fuel
necessary to run engine at normal
speed under decreased load.
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– Second level
• Third level
– Fourth level
» Fifth level
3.
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Index
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Load Increase 1
1.
2.
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– Second level
3.
• Third level
– Fourth level
» Fifth level
Load is increased and speed
decreases.
As speed decreases, FLYBALLS
move in lowering the SPEEDER
ROD and inner end of FLOATING
LEVER, thus lowering the PILOT
VALVE PLUNGER and uncovering
the regulating port of the PILOT
VALVE BUSHING.
Uncovering of REGULATING
PORT admits pressure oil to the
bottom of the POWER
CYLINDER. Since bottom area of
POWER PISTON is greater that
the top area, oil pressure will move
PISTON up
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Index
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Load Increase 2
1.
2.
Oil pressure moves POWER PISTON up
and rotates the TERMINAL SHAFT in
direction to increase fuel.
As POWER PISTON moves up,
ACTUATING COMPENSATING PISTON
moves down and forces the RECEIVING
COMPENSATING PISTON up
compressing COMPENSATING
SPRING and raising outer end of
FLOATING LEVER and PILOT VALVE
PLUNGER
Movement of POWER PISTON,
ACTUATING COMPENSATING
PISTON, RECEIVING
COMPENSATING PISTON and PILOT
VALVE PLUNGER continues until
REGULATING PORT in PILOT VALVE
BUSHING is covered by land on
PLUNGER
As soon as REGULATING PORT is
covered, POWER PISTON and
TERMINAL SHAFT are stopped at a
point corresponding to increased fuel
needed to run engine at normal speed
under increased load
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– Second level
• Third level
– Fourth level
» Fifth level
3.
4.
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Index
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Load Increase 3
1.
2.
As speed increases to normal,
FLYBALLS return to normal position
raising SPEEDER ROD to normal
position.
RECEIVING COMPENSATING
PISTON is returned to normal position
by COMPENSATING SPRING at the
same rate as SPEEDER ROD, thus
keeping REGULATING SHAFT in
PILOT VALVE BUSHING covered by
land on PILOT VALVE PLUNGER.
Flow of oil through COMPENSATING
NEEDLE VALVE determines rate at
which RECEIVING COMPENSATING
PISTON is returned to normal
At completion of cycle, FLYBALLS,
SPEEDER ROD, PILOT VALVE
PLUNGER and RECEIVING
COMPENSATING PISTON are in
normal positions, POWER PISTON
and TERMINAL SHAFT are stationary
at a position corresponding to increase
fuel necessary to run engine at normal
speed under increased load.
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– Second level
• Third level
– Fourth level
» Fifth level
3.
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Index
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Initial set up & Adjustments of Governor
Initial adjustments after setting up, or after overhauling, oil change (air bleeding).
Procedure of adjustments to the compensating system.
Compensation lever adjustment
Compensation needle adjustment
Hunting, high overspeeds and underspeeds and slow return to normal speed following load
changes are results of incorrect compensation adjustment.
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– Second level
• Third level
Adjustment should be done when the engine has been operating for some time and the governor
and its oil has attained
operating
temperatures. The engine is to be off load, at the normal operating
– Fourth
level
rpm.
» Fifth level
The compensating lever is put to maximum upward position and the needle valve opened four to
five turns outward. This will cause the engine to hunt which will bleed trapped air form passages.
Then the lever is put to minimum and the needle valve closed gradually till hunting stops. If hunting
doesn't stop at all till full closing of the needle valve, the compensating lever can be raised by two
graduations and then procedure repeated. The needle valve should be ideally open from closed
position only by about 3/4 th turn, maximum.
If the needle valve is closed more than needed, slow return to normal speed will result following a
load change. If the compensation lever is moved more towards maximum than needed, excessive
speed change upon load change will result.
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Index
Speed droop & Steady state speed regulation
Speed droop is the drop in rpm that occurs as with full travel of the power piston, expressed as a
percentage of full load rpm.
Steady state speed regulation is percentage change in speed from no load to full load expressed as a
percentage of the full load rpm. If N1 (720, 60 Hz for 10 poles) is the no load rpm and N2 (690, 57.5
Hz for 10 poles) the full load rpm, then speed droop is (N1 - N2)/ N2 * 100. (4.3%).
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– Second level
The term steady state speed regulation is mostly used to mean the same as speed droop. It does
mean the same as speed droop, when the fuel rack and governor linkage is such that, full travel of
governor power piston occurs as the engine goes from no load to full load.
• Third level
– Fourth level
Supposing only 50 % of the governor terminal shaft movement is utilized for the engine to change from
no load to full load and »
theFifth
governor
is set to speed droop of 4 %, then in this case the steady state
level
speed regulation is only 2 %.
It is generally reccommeded that only about 2/3 rds of the power piston travel is utilized for full load /
speed range of the engine. In such a case speed droop and steady state regulation would be different.
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Index
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Isochronous Governor
A governor which maintains a steady speed at the set value irrespective of load changes is called an
isochronous governor.
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A constant speed or variable speed governor can be isochronous.
– Second level
Isochronous operation deals with the ability of the governor to maintain the set speed whereas constant
& variable speed deals with the provision in the governor to change the set speed.
• Third level
Isochronous operation
is obtained
if speed droop is set to zero.
– Fourth
level
» Fifth level
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Index
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Droop and its relation to load division
Stable load division between two engines feeding power into a common system
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– Second level
• Third level
– Fourth level
» Fifth level
Supposing the system is running initially with load L1 on both machines and at an rpm of r1. When
additional load in imposed, the system rpm has to drop since droop is there in both machines. If the
system rpm drops to r2, the corresponding load changes will have to follow the curves. It can be seen
that Engine 1 having lower droop will take up more load than the other.
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Index
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Methods of speed setting
(Adjustment of SPEEDER SPRING tension)
•Manual
Click
Master
text
styles
turn ofto
knobedit
which adjusts
speeder spring
directly.(A/E
governor).
– Second level
Turning the speed set mechanism by an electric reversible motor from remote. (A/E governor).
• Third level
Remote speed set pneumatic signal, through a pneumatic positioner controlling the speed set lever.
(lever type governor)
– Fourth level
Remote speed set pneumatic signal acting on the speeder spring directly through the pneumatic /
» into
Fifth
hydraulic positioner built
thelevel
governor.
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Index
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The A/E governor
It is a constant speed governor, within a narrow range, speed variation is possible for synchronizing of
alternators.
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– Second level
Speed droop setting is needed since generators have to run in parallel. If stable division of load is to be
achieved, isochronous operation is not possible.
• Third level
The remote speed setting is by an electric motor driving the speeder spring setting mechanism.
– the
Fourth
level
The power output of
governor
is less since the engine is small.
» Fifth level
The generator governor should be able to maintain engine speed during load changes as laid out by
rules. (see below)
Requirements of A/E governor
With a load change of 25 % of the full rated load, the speed change is not greater than 2.5 %. Within two
secs the speed should remain within one % of the final steady state speed and within four secs, the
speed should be within half % of the final steady state speed.
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Index
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The M/E governor
The main engine governor is a variable speed governor which allows speed to be controlled form
lowest to the maximum limit.
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Speed droop setting is not needed other than for twin engined vessels which feed into a common shaft
for driving the propeller. Twin engined vessels where there is no mechanical coupling between engine
do not have to have speed droop setting.
– Second level
• Third level
The remote speed setting is pneumatic, either through a positioner with a lever type governor or by
pneumatic / hydraulic built in arrangement. Being used on large engines, the power output is higher and
an amplifier is used–inFourth
case thelevel
power output is not sufficient to move the rack.
» Fifth
Scavenge air pressure fuel
limiter level
This system senses the scavenge air pressure from the scavenge air box and releases fuel as a
function of the scavenge air pressure. This ensures no more fuel than that which can burn fully is
released, which ensures proper combustion during load increase.
Speed setting fuel limiter or Torque limiter
This is a system which releases fuel as a function of the speed set air signal to governor. This prevents
engine overloading and also lower fuel admission at start.
The reversible attached oil pump The attached oil pump of the governor has to be having an
arrangement to deliver oil irrespective of the running direction, for reversible main engines.
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Index
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Balance of forces in a governor
Two opposing forces are at balance in equilibrium position
1. The centrifugal force of flyweights
2. The Gravity OR Spring force
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The centrifugal force, FC = m ω2 r (mv 2 /r as v = r ω)
The spring force , FS = spring constant × deflection
Deflection is proportional to radius r
Therefore, both FC & FS are functions of the radius ‘r’ of
flyweights for a given rpm
– Second level
• Third level
Both forces FC & FS (centrifugal & gravity / spring) can be
– Fourth level
plotted against radius ‘r’
» Fifth level
For a given rpm, the centrifugal force is a straight line
passing through the origin
Considering a linear rate spring, the spring force line too
would be straight.
The point of intersection of the two lines will be the radius of
flyweights at equilibrium.
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Index
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Speeder Spring rate & governor stability
For a governor to be stable, the rate of spring force should be higher that that of the centrifugal force at
the point of intersection of the two lines.
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– Second level
• Third level
– Fourth level
» Fifth level
In the left graph, the spring rate is higher at the point of intersection
in case of drop in rpm, the centrifugal force and spring force both drop and find a new
equilibrium position at a reduced radius
in case of rise in rpm, the centrifugal force and spring force both rise and find a new
equilibrium position at an increased radius
In the right graph, the spring rate is lower at the point of intersection
in case of drop in rpm, the centrifugal force reduces, radius also reduces, the increaseing
spring force (over centrifugal force) takes the flyweights to the inner extreme position
In case of rise in rpm, the centrifugal force increases, radius also increases, the rising
centrifugal force (over spring force takes the flyweights to outer extreme position
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Index
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Regulating governor & Over speed governor, spring rate selection
Regulating governor spring rate is as per graph shown on left.
For every rpm there is a different equilibrium position.
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– Second level
• Third level
– Fourth level
» Fifth level
Over speed trip governor’s spring rate is chosen to be in the
unstable range. There is only one equilibrium rpm and the
flyweights takes extreme positions when rpm changes.
When the equilibrium rpm is reached, the flyweights start
moving out, increasing the radius and corresponding increase
in centrifugal force over the spring force.
Since the spring rate is lower, this moving out of flyweights is
very positive and with increasing force.
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Index
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Selection of conical or trumphet shaped spring as the SPEEDER SPRING in a governor
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– Second level
• Third level
Graph on right shows how a non linear speeder
– Fourth level
spring (conical OR trumphet shaped spring) makes
the governor more stable »
at Fifth
a wide level
range of rpms.
Graph on right shows How a non linear
conical speeder spring makes the governor
more sensitive. Percentage change in load
is plotted against spring deflection. It can
be seen that the deflection for a small
change in load is high in case of a non
linear spring and the deflection at a high
load change is not correspondingly higher.
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Index
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Some important features & terms in governors
1. Speed droop (Permanent) , Feed back
2. Speed droop (Transient) , Compensation
3. Steady state speed regulation.
4. Isochronous
5. Boost air to governor (Booster)
6. Pre set air to governor
7. False scavenge air pressure to governor
(Cancellation of scavenge air pressure fuel limiter )
8. Hydraulic Amplifier
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– Second level
• Third level
– Fourth level
In a mechanical hydraulic governor, the dead band effects are reduced by,
» Fifth level
1. A conical speeder spring
2. Having the flyweights rotate at a higher rpm than the engine, which increases sensitivity.
3. Reducing static friction effects by rotating the pilot valve bushing.
Anglo-Eastern Maritime Academy
ajit / Tr Sup (Engg) 29/06/12
© 2010
32
Index
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U Tube Video on Diesel Engine Governors
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– Second level
• Third level
– Fourth level
» Fifth level
Anglo-Eastern Maritime Academy
ajit / Tr Sup (Engg) 29/06/12
© 2010
33