터보차저고장에 대하여 - 터보고장정보<명준 Tutbo ATD>

 

터보차저 고장에 대한 기본적인 글입니다.

터보관련문의: 010 6294 3481

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정품신품터보와 터보엑츄에이터

중국산터보, 중고터보는 취급하지 않습니다.

차대번호로 문의을 하면 보다 상세한 정보를 제공할 수 있습니다.

 

터보차저고장을 일으키는 요인은 매우 다양하나 주된 요인으로 5가지 항목으로 나눌 수 있습니다.

(1) Lack of lubricating oil or oil delay.  오일윤활부족 또는 오일공급 지체
(2) Foreign material or dirt in the lubricating system. 윤활시스템에 이물질유입이나 오염
(3) Oil break-down. 오일 break-down
(4) Foreign material in exhaust or air-filtration systems. 흡배기시스템에 외부물질 유입
(5) Material and workmanship.

 

터보차저는 매우 고속으로 회전(기본적으로  분당 100,000 r.p.m이상이며 최신의 터보차저는 300,000 r.p.m:초당 6,000회전)하기 때문에  터보차저에서 가장 중요한 것은 엔진오일입니다.

 

(1) Lack of lubricating oil or oil delay

올바른 터보차저의 작동을 위해서는 각각의 터보차저가 요구하는 오일유량과 압력으로 공급되어져야 합니다.

1. Lubricate the thrust and journal bearings.
2. Stabilise the rotating shaft and journal bearings.
3. Act as a coolant before high Turbocharger speeds are reached.

 

As the Turbocharger speed and the engine load increases, so the need for oil both as a lubricant and as a coolant increases.

If there is a delay for a short period of time in the oil reaching the Turbocharger then bearing failure will occur. Oil delay can be
recognised very simply by the blueing of the bearings or the shaft. The blueing is simply the colour of the shaft when it has
been exposed to excessive heat.

(2) Foreign material or dirt in the lubricating system

Many operators assume, quite wrongly, that if they operate the engines with dirty or contaminated oil, the oil filters will
remove any foreign matter before the oil reaches the engine and, in our case, the Turbocharger bearings. IT CAN BE A VERY
COSTLY MISTAKE. All of these materials can cause damage to the bearings when the amount is sufficient to cause bearing
wear and bearing-housing bore wear or if the particles of dirt are large enough to block the internal oil passages of the
Turbocharger so causing the unit to become starved of oil. The Turbocharger bearings are most likely to fail before the main
engine bearings, simply because the Turbocharger rotates at much higher speeds than the engine. A unit with 80,000 r.p.m.
will have a blade tip speed on the compressor wheel of 700 miles per hour. New designs of Turbochargers have blade speeds
of over 1,000 miles per hour.

(3) Oil break-down

Diesel lubrication is a very important part of the engine and although modern oil technology has gone a long way in providing
good oils, we still have two basic problems to contend with

(a) Oil deterioration.
(b) Outside contamination.

(a) Oil deterioration
The high temperatures that are present in modern diesel engines can cause oils to crack or break-down. This action
produces carbonaceous (tarry) materials, which stick to the engine rings and cause other troubles.
Oxidisation is caused by the hydrocarbons in the oil mixing with the oxygen; this produces organic acids of which there
are two main types: those with low boiling points and those with highly corrosive.
These products are responsible for several of the problems on diesel engines and Turbochargers. If the acids are allowed
to become concentrated, they will attack the bearings etc., causing pitting and subsequent failure. Also they
react to the remaining oil to form sludge, this is then deposited throughout the engine, particularly in the filters aggravating
the Turbocharger oil supply. Heavier oxidation causes hard varnish to appear.
Where sludge is allowed to accumulate in the oil systems, as this passes through the Turbocharger it is thrown by centrifugal
force from the rotating shaft against the walls and internal surfaces of the bearing housing where it can stick
and impede the free oil flow. In time the build-up will cause problems with oil drainage, resulting in oil leaking from the
turbine end of the unit. If this matter is allowed to accumulate on the turbine side, the heat will cause a baking to take
place and the result is usually unbalance in the Turbocharger system.

 

(b) Outside contamination

So far we have briefly looked at oil break-down caused by changes in the oil, usually caused by its exposure to heat and
air. However, we must also consider other agents.
Amongst these are the products of fuel combustion, such as ash, soot, the un-burnt heavy ends of the fuel and water.
All these elements cause oil contamination. The engine itself contributes to oil break-down in that tiny metal particles
produced by wear and tear will either pass through the oil ways into the Turbocharger or oxidise and hasten deterioration.
Finally, foreign matter from outside the engine, such as dust and dirt, enters the cylinders through the air intake system.

(3) Foreign material in exhaust or air-filtration systems

Any material, which enters these systems is, without doubt, going to damage the Turbocharger and could damage the
engine. As a Turbocharger is a precision instrument its vulnerability will become instantly apparent the first time any particles
go into the casings; damage will be to the wheels which could cause pieces of aluminium to go into the engine, resulting in
engine piston, valve, liner and, possibly, crank shaft damage.
This type of material will vary tremendously from dust in the air system to engine valve fragments in the exhaust system. It
should also be noted that if any foreign body stays in these systems, the Turbocharger will react with possible loss of power,
black smoke, excessive oil usage and leakage and damaged wheels.

(4) Material and workmanship

Only quality assured materials are used and constant quality checks are made on both material and workmanship to meet
the stringent O.E. specifications.
The Turbocharger is probably the most misunderstood component on the engine, and it is this lack of knowledge by the
owner that makes Turbocharger service a very difficult area to work in. As we have seen, a Turbocharger will increase a given
engine power by about 30%; it will not change any operating characteristics of the engine, it will only do what the engine tells
it to do. The source of power for the Turbocharger is exhaust gases produced by the engine and this power is controlled by
flow, pressure and temperature. If there is an engine malfunction or an abnormal working condition in the engine, the
Turbocharger will not overcome this, it is more likely to emphasize the problem. From this it follows that replacing a faulty
unit with a new one will not always solve the problem. If we are in any doubt at all, we should consult the original equipment
engine manual.

 

IDENTIFICATION OF FAULTS

 

(1) Lack of lubrication oil

Lack of lubricating oil shows itself in excessive shaft movement in the bearings. It can be identified by the presence of the
following defects:-
(a) Wear on the inside and outside diameters of the bearings.
(b) Heat discolouration near the outside diameters of the piston ring carrier at the compressor end.
(c) The back face and intake section (inducer) of the compressor wheel shows signs of rubbing. The face of the wheel will
show signs of rubbing 180° from the area of contact on the back of the wheel.
(d) The turbine wheel will show similar signs as the compressor wheel.
(e) one section of the turbine end seals (piston rings) will show heavy rubbing.
(f) Heat discolouration and rubbing on one area of the face of the thrust ring.
(g) Wear pattern on the thrust bearing.
All these symptoms will vary in degree dependent upon the length of time that the Turbocharger has been run without
adequate lubrication.

 

(2) Foreign material in the lubrication system

As we have already stated, the fault will result in excessive bearing wear and a possible blocking of the oil inlet channels in
the Turbocharger causing oil starvation. This fault should show itself in the form of scratches, either light or extreme on the
outside diameter of the bearings or on the bearing housing bore. The extent of damage depends upon the amount and size
of foreign bodies present in the lubrication system.

 

 

(3) Oil oxidisation

A hard deposit of baked oil builds up at the turbine end. Turbine seal leakage can occur; if the hard carbon flakes away,
damage can be caused to the bearings. Sludge will be apparent in the Turbocharger, particularly round the bearing housing
outlet bore.

 

(4) Foreign material in either the exhaust or air induction systems

This is fairly obvious to detect, the turbine or compressor wheel could have sections of a blade of blades broken off there
may be indentations at the entrance to the compressor cover. Rubbing of the compressor wheel, due to the unbalance of the
rotating assembly caused by any broken blades. At the turbine end, damage can be caused by broken valves, pistons or fuel
injector tips. Small particles, such as sand, erode the leading edges of the blades. Large hard particles tend to rip or tear the
blades. Soft materials, such as shop towels or rubber, roll the blades back in the opposite direction of the wheel rotation.

 

 

TROUBLE-SHOOTING PROCEDURES – CAUTION!

Do not place hands or fingers near the Turbocharger air inlet bore while the engine is running. Air pressure drop at this
location can draw fingers onto the compressor wheel blades and cause injury. Every Turbocharged engine system when
operating has its own distinctive sound or noise level. In many cases malfunction can be detected when the noise level
changes. If the noise level changes to a higher pitch, it can indicate an air leak between the air cylinder and the engine or a
gas leak in the exhaust system between the Turbocharger and the engine.
Noise level cycling from one level to another can indicate a blocked air cleaner or restriction in front of the Turbocharger air
inlet or heavy dirt built-up on the compressor housing or on the compressor wheel. Sudden reduction in a noise level, with a
resultant black or blue smoke and excessive oil leakage, indicate a complete failure.

 

 

NOISE AND AIR LEACK CHECK
With the engine running, check the Turbocharger for uneven noise and vibrations (this can indicate a malfunction in the shaft
and wheel assembly). If suspicious conditions are apparent, shut down immediately to protect the Turbocharger and engine
form further damage. Examine the Turbocharger as per the recommended inspection procedures. If any damage is evident,
the Turbocharger will have to be removed.

If the Turbocharger is assumed to be functional, check the air system as follows:-
With the engine not running, check the air cleaner for restricted condition. Check all the hose clamps for tightness. Check
that the intake manifold gasket is fitted and is in good condition. Check the air hoses for cracks or deterioration. A pin hole in
the air hoses can lose 10% of the Turbocharger’s power.

 

WITH THE ENGINE RUNNING AT IDLE

1. Where starting fluid is used on the engine, spray lightly the air tubes and connections between the
air cleaner and Turbocharger. Leaks will be indicated by an increase in engine speed, this is caused
by the air pressure drop in this part of the air system causing the starting fluid to be drawn through
the compressor wheel into the engine.
2. Air leaks between the Turbocharger and the engine can be checked by feel and by application of a
light-weight oil or soap suds on the cross-over tubes connections or hoses.
Exhaust gas leakage between the engine block and turbine inlet flange will also create a change in
the noise level and reduce Turbocharger performance.

Check the exhaust system as follows:-
2.1. Check the manifold gaskets for leakage.
2.2. Check manifold bolts for tightness.
2.3. Check the manifold for cracks or porosity.
2.4. Check the manifold Turbocharger inlet gasket for leaks.
2.5. Check the manifold Turbocharger inlet flange for contamination.
2.6. Check the manifold flange (Turbocharger) for contamination.
2.7. Check the Turbocharger inlet flange bolts for tightness.
2.8. An obvious sign of exhaust gas leakage is heat discolouration around the leaking part.

 

 

RECOMMENDED INSPECTION PROCEDURE (FIELD SERVICE)

1. Remove inlet and exhaust tubing from the Turbocharger.
2. Inspect both wheels for blade damage caused by foreign material. The compressor wheel is easily ex amined by looking
through the compressor air inlet opening. A light is necessary when examining turbine wheel blade tips, as they are
positioned inside the turbine housing and you must look between the turbine wheel blades from the exhaust outlet end
of the turbine housing.
3. Examine the outer blade tip edges, both wheels adjacent to their respective housing bores and check for wheel rub.
4. Rotate the shaft and wheel by hand and feel for smooth turning drag or binding conditions; push the shaft to one side and
rotate to feel for rub.
5. Lift up and down both ends of the shaft at the same time and feel for excessive bearing clearance. If clearance is normal,
very little shaft movement will be detected. If the shaft is rocked up and down at one end only in a unit having bearing
clearances of .003 to .006 inches, the movement at the opposite end of the shaft could be .015 inches to .020 inches.
6. If the shaft and wheel rotates freely, no wheel damage, binding or rubs have been noticed, it can be assumed that the
Turbocharger is serviceable.

GENERAL FACTORS AFFECTING TURBOCHARGERS - SERVICE LIFE
An analysis of Turbochargers removed from service indicates that approximately 40% of the troubles are due to foreign
material going through either the turbine or the compressor. An additional 40% are due to lubrication failures. The remaining
20% are of a miscellaneous nature.
Some of the foreign material damage is the result of pieces of burned or broken valves and combustion cups passing through
the exhaust system into the turbine. Other turbine damage is due to casting fins that may break out of the manifolds and
ports.
Occasionally improperly installed gaskets will permit pieces of the gasket to overhang a port and break off into the exhaust
system.
Damage due to nuts and washers that have dropped into the exhaust system is also altogether too frequent.
Occasionally engines suffer from scuffed and broken pistons, pieces of these pistons will damage turbine wheels.
Compressor wheel breakage also occurs due to foreign material, although not as frequently as turbine wheel damage.
Sometimes pieces of the air cleaner will break loose and go through the compressor. There have also been instances where
hose connections fail and pieces of rubber or wire reinforcing from the hose get into the compressor wheel.
Again, carelessness in allowing nuts, bolts and washers to get into the intake system, sometimes cause compressor wheel
failures.
Lubrication failure may be any one of a number of types; undersized or plugged oil lines are quite common. It is essential to
have an adequate supply of oil at full engine oil pressure for the Turbocharger bearings; the Turbocharger runs at very high
speeds and will very quickly overheat with even a momentary failure of the oil supply.
The oil supply to the Turbocharger should first pass through a good filter of adequate size so that there is always full oil
pressure at the Turbocharged bearings. With an adequate supply of clean oil, Turbocharge bearings will run for thousands of
hours with no measurable wear. Failures may occur due to extreme exhaust temperatures encountered in excessive altitude
operation. Inlet restrictions due to plugged air cleaners, collapse in hose connections or undersized air pipes, have the effect
of reducing the air supply to the engine and result in excessive exhaust temperatures.
Both inlet restriction and the excessive altitude operation can cause turbine housing cracking or even turbine wheel failures
due to excess temperature.
With any Turbocharger it is possible to accumulate enough dirt in the compressor housing to reduce the air flow capacity and
efficiency of the compressor, if the air cleaning system is not properly maintained. Reduced air flow will cause the engine to
run hotter and may result in burnt valves and pistons which in turn will cause Turbocharger failure.
Leaking gaskets or connections on either the intake or exhaust system of the engine will cause a reduction in the air supply to
the engine and will result in high exhaust temperatures.
Sometimes air connections and exhaust connections are made in such a manner that the thermal expansion of the exhaust
manifold and other parts connected to the Turbocharger will produce very high loads on the Turbocharger. These high loads
result in housing distortions that cause the compressor and turbine wheels to rub.
Excessively heavy piping that is supported only by the Turbocharger may cause housing distortion.
Turbocharger mountings that are not sufficiently rigid to prevent excessive vibrations in the Turbocharger can also cause
distortions and failures.
In conclusion, it can be stated that very few Turbocharger failures would occur if no foreign material were permitted to enter
the turbine or compressor; if precautions were taken to prevent excessive exhaust temperatures and if the Turbocharger was
always supplied with an adequate amount of clean oil.