Inlet and Exhaust Valves

INLET AND EXHAUST VALVES
The exhaust valves open against pressure within

the cylinder at the end of the working stroke. This
pressure is considerably higher than against which
the inlet valves have to open. Furthermore, the
pressure of the exhaust gases assists, once the
valve is open, in expelling the gasses through the
open valve. Because of this consideration it is not
unusual to find that exhaust valves are designed to
be of a smaller diameter than the inlet valves.
Being smaller also assists with keeping them cool
which is important as exhaust valves often give rise
to thermal problems.
Both the inlet and exhaust valves may seat against the
flame plate of the cylinder head. These valves seats
become damaged during the operation and from time
to time they have to be reconditioned by grinding-in
the valves. This is required much more often in the case
of the exhaust valves because they operate at higher
temperatures and because the gases flowing through
may contain particles of carbonaceous matter. These
occasionally get trapped under the valve seat and cause
pitting. The life of an exhaust valve between
reconditioning can be extended if the thermal loads to
which it is subjected can be evenly distributed around
the valve. This is accomplished by the rotating the
valves slowly as the engine is working.
Valve rotators which carry out this movement have a
type of ratcheting mechanism (the best known is the
Rotocap type as in Fig.7.3.) which indexes the valve
round a small amount every time it is operated by the
rocker gear. In more recent designs the exhaust valves
are rotated by the vanes fitted to the stem and driven by
the gases expelled from the cylinder (see Fig.7.2.) The
main advantage of this rotator is that the valve has still
sufficient momentum to turn as the head comes to
touch the seat, thus scraping off the deposit formed
particularly in heavy oil fuel operation. Valves may be
assembled in cages which are removable from the
cylinder head as separate units. Each valve cage, in
addition of the valve itself, carries the seat ring, stem
guide, and spring.
When the seat ring wears, it may be renewed at low cost. The
condition of the exhaust valve is influenced greatly by the
temperature at which it operates. To reduce its temperature the
cage is cooled in the upper part near the guide and round the
seat region aswell. Fig.3. shows how water is conducted down an
annular passage immediately behind the valve seat and back
again. Cylinder heads are fitted with relief valves in order to draw
attention to any abnormally high firing pressure. The setting of
the spring is such that the pressure required to open the valve is
10% to 20% above the maximum combustion pressure. Provision
is also made in the cylinder head to connect an indicator for
measurement of cylinder pressures. Frequently this passage is
combined with that of the relief valve. The starting air valve is
also accomodated in the cylinder head. This is a non-return valve
which will admit the compressed air required for starting
purposes. It also prevents the high pressures which occur inside
the cylinder during the normal operation getting back into the
starting air system.

Why are exhaust valves sometimes of a smaller diameter
then the inlet ones ?
What should be done when the valves are damaged ?
What causes pitting and where does it occur ?
How can the life of an exhaust valve be prolonged ?
Describe the two system commonly used today for rotating
the valve.
What is a valve cage and what is the advantage of using it ?
Describe the cooling of the valve following Fig.7.3..
What is the cylinder cover relief valve provided for ?
How does pressure refief valve operate ?
What are two functions of the starting air valve ?
What other devices are generally fitted on to the cylinder
head ?

I Fig.7.4. illustrates an exhaust valve.
Complete the labeling and describe it.

Both types of diesel engines, two and four cycle, employ air inlet and
exhaust valve.
The exhaust valves are arranged to open outwards ( i.e. towards the
outside of the cylinder ) in order to avoid opening against the high
pressure within the cylinder at the end of the power stroke.
In order to facilitate overhaul of the valves without removing the cylinder
cover, valves together with their springs, stems, etc. may be fitted in
separate casings.
The air inlet valves are fitted with an automatic rotating device causing
the valve to rotate slowly, thereby avoiding local overheating.
The air inlet valves operate under less difficult condition than the
exhaust valves and the period between their maintenance is longer.
In larger engines, owing to the larger dimensions of the exhaust valves
and the consequent slower rate of cooloing by conduction,
arrangements have to be made to conduct the heat rapidly away from
them.
Compressed air is admitted to the cylinder through the relief valve and
the engine is made to rotate by this means until sufficient momentum is
attained to obtain the necessary compression to fire the fuel.

III Replace the boldface word in the sentences
with the expressions similar in meaning from
the list below using the correct form of the
verbs.

ACCOMMODATE, ADMIT, DEPOSIT, EXPELL
FROM, EXTEND, REMOVE, ROTATE, SCRAPE,
STEM, VANES, FIT, FLOW, GIVE RISE TO,
PITTING, MAINTAIN, RECONDITION.

1. When the maneuvering handle is moved to the start position, compressed air is let in to
turn the engine in the disered direction.
2. Improper on board fuel treatment may cause troubles to the combustion chamber
components.
3. The valve plate of the exhaust valve is turned by means of the propeller fitted to the valve
shaft acted upon by the outgoing exhaust gases stream.
4. The gas rotator is simple an efficient since it provide sufficient rotating torque when the
valve seats down the rub of the thin layer accumulated mainly in heavy oil operation.
5. The cylinder head is equipped by the inlet and exhaust valves designed for the cross flow gas
exchange principle, i.e. air intake is opposite to exhaust gas outlet.
6. The inspection of the valves revealed clean seats with only shallow indentation from carbon
deposits.
7. With modern grinding equipment valves can be quickly restored.
8. For engines of larger size, valve cages for the inlet exhaust valves are considered an
advantage as they can be replaced without dismantling the cylinder head.
9. The aplication of new maintenance methods may increase service life of the engines
components by 30%.
10. The pressure of the exhaust gases assists, when the valves open, to drive the gases out of
the cylinder.

The power developed within the engine cylinder can be
measured by an ____________ . It is fastened onto the
indicator cock provided in the cylinder head by a
_______________ . The engine indicator consists of a small
______________ of known size which operates in a cylinder
against a specially _____________ . A magnifying
_________________ transfers the piston movement to a
_____________ on which is mounted a card. The drum moves
backwards and forewards under the pull of a _______________
. The cord is moved by a reciprocating mechanism which is
proportional to the engine movement in the cylinder. A
diagram which represents the gas pressure on the engine
piston at different points of the stroke is drawn by means of
the _______________ .
U tehnikom su jeziku vrlo esti primjeri kazivanja uzroka ili
razloga, te uzrono posljedinih veza unutar reenica ili meu
vie reenica. Evo primjera iz VII lekcije.

This is required much more often in the case of the exhaust
valves because they operate at higher temperatures and
beacause gases flowing through may contain particles of
carbonaceous matter.
Because of these considerations it is not unusual to find that
the exhaust valves are designed to be of smaller diameter
than the inlet valves.
Being smaller also assists with keeping them cool which is
important as exhaust valves often give rise to thermal
problems.

Uzrok (Razlog) izreen je istaknutim dijelovima gornjih reenica. U
prvoj reenici uzrok je izraem dvjema zavisnim (uzronim) reenicama,
u drugoj predloenom grupom (Because of ), u utreoj putem glagola
sa nastavkom -ing
(Being smaller ) i zavisnom reenicom ( as exhaust valves often
give rise to thermal problems.). Evo jo nekoliko primjera izricanja
uzroka ili razloga itavom nezavisnom uzronom reenicom:

Because the castings are not so big and heavy, the column and cylinder
block may be
made in one piece.
As no repair was possible, the auxiliary pump had to be replaced.
For installation intended to burn only Diesel oil, only a simple supply
system is used since the fuel will flow under gravity at all times.
Since new system of chocking was introduced, there was no more
movement or bolt breakage.
Uzrok (razlog) se najee izraava zavisnim reenicama
because, since i as a njihovi su ekvivalent u Hrvatskom jer,
budui da, zbog toga to, stoga to, zato to, itd. Kada se
zavisne reenice uvode sa since i as onda one najee
prethode glavnoj reenici (5), (7), dok uzrona navedena sa
because obino slijed iza glavne reenice (1). No to ne mora
biti i vrsto pravilo to potvruju primjeri (2), (4), za because,
te (3) i (6). za as i since. U primjeru (3) upotrebljen je oblik na
ing (Particip sadanji) glagola be (being) umjesto svrenog
oblika be u reenici koja bi glasila:

3a. As (since) exhaust valves are smaller, this also assists in
keeping them cool.
Ex. a. The damage to the hull appeared to be serious. The ship was
drydocked in the
shipyard.

As (since) the damage to the hull appeared to be serious, the ship
was drydocked in the nearest shipyard.

Ex b. In oil burns the bunker space is reduced. Fuel oil is stored in
double bottom tanks.

In oil burns the bunker space is reduced, because oil is stored in
double bottom tanks.

1. The bolts have not been accurately tightened . The flange leaks.
2. The friction in bearing surfaces increases. The wrong lubricant
was chosen.
3. The pipe in the main feed line had burst. Steam was lost in both
boilers.
4. This type of liner is called the wet liner. The cooling water is in
direct contact with the outer surface of the liner.
5. The temperature rose. The cooling of the engine was poor.
6. The Engine Cadet had very little training. His work was not quite
satisfactory.
7. The needle lifts of its seat. The upward force on the needle
exceeds the force of the compressed ring.
8. The aperture in the frame for the water jacket is much larger
than the cylinder bore. The connecting rod large end has much
more room to pass.

Ex. Last night the Second Engineer did not join in the conversation, because he
was angry
with us.

Last night the Second Engineer did not join in the conversation, being
angry with us.

Note the omission of the subject and the position of the -ING form: the very
beginning, preceding all other words. This occurs when the subject of both
clauses ING form must follow its noun / pronoun as in the example:

As the pressure was too low, we could not start the engine

The pressure being too low, we could not start the engine

The greaser cannot talk with you now, because he is busy.
As Saturday was a holliday, all shops were closed.
Because the fixing studs were loosely tightened, the safety of operations
was not guaranteed.
As they saw that they could not fight the fire the left the engineroom.
The fuel is being atomised properly, because it has been preheated at
the correct temperature.
As the last bus has gone we had to walk home.
Since the temperature has risen too high, it will be impossible for the
lube oil to maintain its viscosity.
As none of those present had any questions to ask, Master closed the
meeting.
The Engine Cadet applied to the Donkeyman for advice, because did not
know what to do.
The large end bolts withstand any load since they are strongly made.

ACCOMMODATE THE VALVES, ADMIT THE AIR, CAUSE PITTING, CONDUCT
WATER, COOL THE CAGE, DISTRIBUTE THE LOAD, EXPELL THE GASES,
EXTENT THE LIFE, FIT THE HEAD WITH VALVES, GRIND THE VALVES, SET THE
SPRING, MEASURE THE PRESSURE

Nakon sagorijevanja goriva u cilindru dio ispunih plinova se tjera u zrak
kroz dimnjak.
Bojim se da emo u slijedeoj luci morati brusiti ventile.
Budui da je podmazivanje bilo slabo, to je uzrokovalo ljutenje zupanika u
reduktoru.
Kako da produimo vijek trajanja ventila ?
Morat emo osigurati bolje hlaenje sjedita ventila.
Voda se cijevima odvodi u izmjenjivae topline.
Ventili nisu bili dobro podeeni, jer nismo obratili panju na knjigu sa
uputstvima.
Nakon to se regulira pritisak zrak se puta u cilindar.

1. DEFINITION
A device used to regulate or control the flow of fluids ( liquid, air or gas ), in
pipeings, systems and in machinery.
1. DEFINITION
2. VALVE OPERATING GEAR
1. DEFINITION
Cam
1. DEFINITION
Cam
Roller
1. DEFINITION
Cam
Roller
Tapet
1. DEFINITION
Cam
Roller
Tapet
Push rod
1. DEFINITION
Cam
Roller
Tapet
Push rod
Rocker arm / lever
1. DEFINITION
Cam
Roller
Tapet
Push rod
Rocker arm / lever
Valve spring
1. DEFINITION
Cam
Roller
Tapet
Push rod
Rocker arm / lever
Valve spring
Valve
3. PARTS
Valve cage - valve housing.

3. PARTS
Valve stem / valve spindle the rod by means of which the disk or plug is
moved to open or close a valve.

3. PARTS
Valve head / valve lid disk part of poppet valve that gives a tight closure on
the valve seat.

3. PARTS
the valve seat.
Valve seat the circular metal ring on which the valve head / valve disk /
valve plug of a poppet valve rests when closed.

3. PARTS
the valve seat.
Valve guide a channel which supports the stem of a poppet valve for
maintanance and alignment.

3. PARTS
the valve seat.
Valve rorator a device rotating the valve stem.

Adjusting valve clearance
3. PARTS
the valve seat.
POPPET VALVE is a cam-operated or spring loaded reciprocating engine
mushroom type valve used for control of admission and exhaust of working
fluid. Its direction of movement is at right angle to the plane of its seat.

3. PARTS
the valve seat.
POPPET VALVE is a cam-operated or spring loaded reciprocating engine
mushroom type valve used for control of admission and exhaust of working
fluid. Its direction of movement is at right angle to the plane of its seat.
OHV engine means overhead valve engine, i.e. an engine having valves in the
head.
4. MATERIALS
Valve stem / valve spindle of heat resistant steel
4. MATERIALS
Valve seat steel with stellite welded on it ( 65% Cobalt, 32% Chromium,
3% Tungsten )
4. MATERIALS
3% Tungsten )
Valve cage cast iron
4. MATERIALS
3% Tungsten )
5. STRESSES
4. MATERIALS
3% Tungsten )
5. STRESSES
High pressure and temperature due to combustion.
4. MATERIALS
3% Tungsten )
5. STRESSES
6. REQUIREMENTS
4. MATERIALS
3% Tungsten )
5. STRESSES
6. REQUIREMENTS
Strong, sturdy construction / manufacture.
4. MATERIALS
3% Tungsten )
5. STRESSES
6. REQUIREMENTS
Carefully cooled
4. MATERIALS
3% Tungsten )
5. STRESSES
6. REQUIREMENTS
Carefully cooled
7. COOLING
4. MATERIALS
3% Tungsten )
5. STRESSES
6. REQUIREMENTS
Carefully cooled
7. COOLING
Is executed by F.W. circulation, as excessive temperature may give rise
to damage by cracking.
8. MATERIAL
Cast or forged steel
Special cast iron

Inlet and Exhaust Valves

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INLET AND EXHAUST VALVES

The exhaust valves open against pressure within

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