Electric Power
Application
and
Installation
Guide
Crankcase Ventilation
LEBX0029-01
W H E R E T H E W O R L D T U R N S F O R P O W E R
Table of Contents
Crankcase Emissions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5
Crankcase Ventilation (“Ingestive”) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6
Low Pressure Ingestive System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6
High Pressure Ingestive System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7
Water in Engine Oil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7
Introducing Fresh Air into Crankcase . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7
Crankcase Pressure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8
Crankcase Ventilation (“Non-Ingestive”) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8
Crankcase Emission’s Affect on Oil Life . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10
Crankcase Emission Amount . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10
Measuring Engine Blow-by and Diluting Crankcase Emissions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11
LEBX0029-01 3
Crankcase Ventilation However, due to piston ring tolerances, the
crankcase Hydrocarbon emissions can become
as much as 20% of the total Hydrocarbon
emissions. The amount of NOx present in the
Crankcase Emissions blow-by decreases depending on the air/fuel
Crankcase emissions or “Fugitive Emissions” ratio of the engine. The more lean the
result from piston ring blow-by. The volume intake, the less NOx that should be present.
of blow-by varies due to cylinder pressure, The sulfates and aldehydes will change
piston ring pressure and component wear. depending on the fuel. An engine running
Crankcase emissions contain essentially exhaust on diesel fuel, landfill gas or digester gas
gases, wear particles and oil/air/gas/fuel will have more sulfides present in the blow-by
emissions. The proportions of these elements than an engine running on natural gas.
vary due to fuel type, engine type, engine
speed, load and maintenance history. Blow-by As blow-by forms it builds pressure inside
is made up of Hydrocarbons (HC), Carbon the crankcase; hence, it is important that
Monoxide (CO), Carbon Dioxide (CO2), the pressure is relieved. To prevent pressure
Nitrogen Oxides (NOx) and traces of sulfates buildup within the crankcase, vent tubes
and aldehydes. Crankcase, Hydrocarbon are provided to allow gas to escape (see
emissions are normally 3% of the total exhaust Figure 1). Removing the blow-by from the
emissions tested at the mid-life of the engines. crankcase is not very difficult, but the
Figure 1.
LEBX0029-01 5
question of what to do with the blow-by There are a number of hazards that can occur
once it leaves the crankcase is challenging. when applying an “ingestive” PCV system to a
Basically, there are two techniques used in turbocharged engine, including:
dealing with blow-by: “Ingestive” and “Non-
Ingestive.” “Ingestive” involves placing the • Reduced spark plug life
blow-by back into the combustion process • Fouled or damaged turbocharger or
and “Non-Ingestive” is using some method aftercooler
of venting the blow-by to the atmosphere. • Reduced detonation margin, engine
detonation, damaged pistons
The following paragraphs outline the benefits • Reduced load capability and operation
and drawbacks of each type of system. • Reduced efficiency
• Reduced component life
Crankcase Ventilation
(“Ingestive”) Additionally, most tests have shown that no
As emission laws become more stringent, it is matter how effective the blow-by filter, over
inevitable that crankcase emissions (or blow- time, enough oil will be adsorbed to coat the
by) will be included in total system emission aftercooler. This oil will act as an insulator,
values. Certain parts of Europe and California reducing the cooling capabilities of the
are already counting blow-by in the emission aftercooler.
numbers. In the future, ventilating crankcase
The G3516B packages offer an optional low-
emissions to the atmosphere will be
pressure ingestive PCV system in the price
discouraged or prohibited.
list. This system is specially designed for
To eliminate the worry of crankcase emissions, use with Caterpillar Gas Engines. Caterpillar
the blow-by can be returned to the combustion highly recommends that this system be
process. This method is commonly known as used if a PCV is going to be applied on this
Positive Crankcase Ventilation (PCV) in the engine. This system complies with the design
automobile industry. On naturally aspirated recommendations listed below (including a
engines, like most cars, the blow-by can easily standard cleanable aftercooler.)
be returned to the combustion process without
If a non-Caterpillar supplied system is going to
much added cost or engine component
be applied, extreme care should be observed
concern. The addition of a turbo-charger
to make sure the system design complies
makes PCV a much more challenging task.
with the following list of recommendations
There are two ways of re-introducing the for designing a low pressure, ingestive,
blow-by fumes back into the combustion PCV system:
process on a turbo charged engine. The blow-
• A cleanable aftercooler should be used
by can be put in the system at low pressure
and cleaned regularly.
(before the turbocharger) or at high pressure
• The blow-by MUST be sent through
(after the turbo charger).
a filtering system prior to entering the
turbocharger.
Low Pressure Ingestive System
• The system must ensure the draw on the
A low pressure, ingestive system involves
crankcase does not exceed 26 mm H2O
piping the crankcase emissions into the
(1.0 in. H2O). (i.e. A pressure relief valve
low pressure side of the turbo charger
should be placed between the turbocharger
(see Figure 2). The blow-by is drawn from
and the filtering system)
the crankcase through the vent tubes, into
• Blow-by filters should be replaced or cleaned
the oil condensing device (or blow-by filter)
every oil change.
and “sucked” back through the air cleaner
• System must be designed to handle two
by the turbo charger.
times the engine blow-by measurements
to account for normal engine wear.
6 LEBX0029-01
• A minimum oil removal rate of 99.97% is
required. Oil removal rate can be calculated
as follows:
Blow-by concentration
% Removal = (before PCV – after PCV)
Blow-by concentration before PCV
• Caterpillar’s recommendation is that the oil
should NOT be returned to the crankcase
for a non-approved system. If oil is planned
to be returned to the crankcase, trend
S•O•S samples of recovered oil every
100 hours of engine operation up to Figure 3. Ingestive, high pressure system.
800 hours to certify that the recovered
oil does not reach condemning limits.
If oil exceeds condemning limits, Water in Engine Oil
DO NOT return oil to the crankcase. Crankcase emissions are essentially
concentrated exhaust fumes; therefore, they
• System must have a bypass to eliminate the
contain a considerable amount of water vapor.
possibility of crankcase over pressurization
When oil is separated from the blow-by and
if the filter element clogs.
filtered back into the oil sump, there is the
risk of water condensing. Engines have a
considerable amount of water in their exhaust,
which has resulted in many PCV suppliers
recommending that the excess oil be drained
into a separate container.
When water is introduced to the engine oil, it
forms an emulsion that clogs oil filters. As the
amount of water increases, the ability for the
additives to disperse the water in the oil
decreases. The heat of the oil usually burns
off water particles, but condensed blow-by
contains so much water that the water can
Figure 2. Ingestive, low pressure system. actually cool the oil and form sludge. Cooler
oil temperatures may cause water and oil to
combine to form dangerous acids that can
High Pressure Ingestive System corrode metals, thus reducing the lubricating
A high pressure PCV system involves qualities of the oil.
removing the blow-by from the crankcase and
pumping it directly into the intake plenum
Introducing Fresh Air into Crankcase
Removing blow-by out of the crankcase may
(see Figure 3). This type of system removes
not be enough to ensure an emission free
the risk of coating the aftercooler and turbo,
crankcase environment. It may be necessary
but the crankcase fumes should still be
to add fresh air directly into the crankcase in
filtered to reduce the amount of oil going
order to distill the air inside the crankcase.
into the intake stream.
The quantity of this air should be about two
The limiting factor of this type of system is times the volumetric flow rate of the blow-by.
cost. An extra pump would be expensive and
One risk of adding fresh air might be the cold
difficult to mount. Therefore, this type of system
ambient air cooling off the crankcase, resulting
has been bypassed for the less effective, but
in water condensing from the existing
more economical low pressure system.
crankcase fumes. Therefore, it may be
necessary to heat the air before introducing
it to the crankcase.
LEBX0029-01 7
Crankcase Pressure engine. The addition of moisture into an
The conventional wisdom of internal combustion engine can cause corrosion and buildup
engines is that the engine should operate at a of harmful deposits.
slight positive pressure in order to keep any
“engine surrounding” contaminants out of Crankcase vent pipes must be large enough
the engine. The effect of a PCV system tends to minimize back pressure. Normal blow-by
to create a slight vacuum on the crankcase on a new engine will be approximately
[0.25 kPa (1 in. H2O) MAXIMUM]. The 0.02 m3/hr bkW (0.5 ft3/hr bhp). Adequately
negative crankcase pressure is accepted in size the pipes to accommodate a worn engine,
order to have fugitive emissions removed with a blow-by rate of 0.04 m3/hr bkW (1 ft3/hr
from the crankcase. bhp). Size the vent pipe with a maximum of
13 mm H2O (0.5 in. H2O)pressure drop at
Under no circumstances should crankcase full load.
pressures vary more than 25.4 mm (1.0 in.)
H2O from ambient barometric pressure for These formulas allow the crankcase ventilation
3300, 3400, and 3500 diesel and gas engines designer to calculate a pipe diameter which
as well as 3600 diesel engines. The shutdown will give a back pressure less than 13 mm
or maximum value for G3600 engines is H2O (0.5 in. H2O).
102 mm H2O (4.0 in. H2O). Restrictions
Calculate back pressure by:
higher than the limit on passive systems
will worsen any oil leaks. A powered system
L 2 S 2 Q2 23.6 2 106
should draw no more than a 25.4 mm (1.0 in.) P (kPa) =
D5
H2O vacuum, or dirt and dust could be
drawn into the engine past the main seals.
L 2 S 2 Q2
Measurement should be made at the engine P (in. H2O) =
dipstick location with the engine at operating 187 2 D5
temperature, speed and load.
P = Back pressure (kPa), (in. H2O)
Crankcase Ventilation psi = 0.0361 2 in. water column
kPa = 6.3246 2 mm water column
(“Non-Ingestive”) L = Total Equivalent Length of pipe (m) (ft)
Most areas do not include crankcase emissions
Q = Exhaust gas flow (m3/min), (cfm)
as part of the total emissions for an engine.
D = Inside diameter of pipe (mm), (in.)
In order to save cost and potential engine
S = Density of gas (kg/m3), (lb/ft3)
hazards, it may benefit the customer to vent
S (kg/m3) = 1.08
the blow-by to the atmosphere. The following
S (lb/ft3) = 0.067
discussion explains how venting an engine’s
blow-by should be performed. To obtain equivalent length of straight pipe
for various elbows:
When ventilating the crankcase, it is important
not to vent crankcase fumes directly into L = 33D Standard Elbow
the engine room without filtration. Fumes X (Radius of elbow = pipe diameter)
may clog air filters and increase air inlet
temperature, possibly causing engine damage. L = 20D Long Elbow
X (Radius > 1.5 diameter)
Problems in electrical equipment can be
caused by exposure to the fumes. The fumes L = 15D 45° Elbow
can also be a health hazard if discharged in a X
poorly ventilated room. Therefore, crankcase
emission should be ventilated to the L = 66D Square Elbow
atmosphere, by means of a venting system. X
When there are multiple engines at a site, a Where X = 1000 mm or 12 in.
separate vent line is required for each engine
to prevent fumes and moisture produced by Calculate the pipe diameter according to the
a running engine from entering an idle formula, then choose the next larger
commercially available pipe size.
8 LEBX0029-01
As can be seen, if 90° bends are required, a Crankcase fumes must not discharge into the
radius of two times the pipe diameter helps air ventilation ducts or exhaust pipes. They
lower resistance. will become coated with oily deposits creating
a fire hazard.
Loops or low spots in a crankcase vent pipe
must be avoided to prevent condensation from Vent the crankcase pipe directly into the
building up in the pipe and restricting the atmosphere and direct it to keep rain or spray
normal fumes discharge. Where horizontal from entering the engine. Give consideration
runs are required, install the pipe with a to equipment located near the discharge area
gradual, 41.7 mm/m (1/2 in/ft), slope from as well as to the building itself. If not handled
the engine (see Figure 4). The weight of the properly, very small amount of oil carry-over
vent pipes will require separate off-engine can accumulate and become unsightly and
supports as part of the installation design. even harmful to auxiliary equipment.
Any horizontal or vertical run of pipe that
cannot be disassembled for cleaning should A drip collector installed near the engine will
have clean-out ports installed. minimize the amount of oil discharge through
the vent pipe. It is necessary to provide
Crankcase some type of trap that will prevent crankcase
breather line gases from venting into the engine room,
Clean- (see Figure 5). If a trap as in Figure 5B is
Correct slope
out used, the designer must be sure the drip
port
collector can be removed or drained for
Low disposal. Another alternative is to install a
X spot
valve on the end of the drip pipe and
periodically drain it.
Figure 4. Pipe installation.
Vent to atmosphere
Engine mounted crankcase
locate higher than engine
breather
combustion or ventilation
40 mm per meter (1/2 inch
air inlet
per foot) downward slope
from engine
A B
Rubber hose flexible
fitting 25 mm (1 in.)
Condensed combustion products
25 mm (1 in.)
(May be initially filled with oil or water)
Condensed combustion products
(may be initially filled with oil)
b) Alternate Installation
Figure 5. Illustrations of traps.
9
LEBX0029-01
Figure 6 illustrates a powered fumes disposal Crankcase Emission’s Affect
system for a multiple engine installation. on Oil Life
There are two main advantages to a powered One of the goals of a PCV system is to increase
system: the fumes will become diluted with the oil life of the engine. The removal of
air for better dispersal into the atmosphere, crankcase fumes can reduce the amount
and it can improve oil life by removing the of oil degradation. It has been shown that
nitric oxides from the crankcase before they a non-ingestive PCV system can double the
can cause nitration of the oil. oil life of an engine. However, the affects of
PCV on oil life will vary with engine size,
Since a vacuum will be drawn with a powered
load, engine hours and ambient conditions.
system, the addition of a small air filter
somewhere on the engine crankcase is
required. This will filter the air entering
Crankcase Emission Amount
Normal blow-by on a new engine will be
the crankcase and prevent dirt from being
approximately 0.02 m3/hr bkW (0.5 ft3/hr bhp).
introduced into the oil. A valve connected in
Adequately size the pipes to accommodate a
the line to each engine controls the flow of
worn engine, 0.04 m3/hr bkW (1 ft3/hr bhp).
crankcase fumes out of the engine.
Size the vent pipe with a maximum of
13 mm H2O (0.5 in. H2O) pressure drop
at full load.
Pipe size selected to
provide less than
12 mm H2O (0.5 in. H2O)
Electric fan (drip tray with
line loss drain plug required to catch
condensation fluids if fan
is not oil-tight)
Sloped
Balance valve Risors should enter manifold
for fan vacuum above center line of pipe to
if required prevent drain back
Pressure relief valve
required on G3600
Condensate
drain
Valve per
engine to adjust
individual vacuum
Figure 6. Powered fumes disposal system.
10
LEBX0029-01
Measuring Engine Blow-by and This procedure will allow an equal amount
Diluting Crankcase Emissions of air to be drawn into the crankcase as is
The following is a step-by step procedure on being blown past the piston rings. This will
how to dilute the crankcase with fresh air. sufficiently dilute the fumes and increase
This will measure the blow-by of an engine. oil life.
This information is needed when designing a
This procedure should be done for each
crankcase ventilation system.
engine. Make a final check of the crankcase
To set up the system, a Blow-by/Air Flow pressure to insure the vacuum on the engine
Indicator (part number 8T2700) is required. is less than 25.4 mm H2O (1 in. H2O).
1. Measure the amount of combustion blow- Sometimes it is difficult to precisely size the
by for a given engine. This is done by blower for a powered system. If the only
closing the crankcase ventilation valve, blower available is too large, it may draw too
blocking the crankcase air filter, and much vacuum on the crankcase ventilation
attaching the Blow-by Indicator to the valves and make adjustments difficult.
oil fill spout. The reading on the indicator is To overcome this problem, a balance valve
the engine’s blow-by. All measurements are can be connected on the vacuum side of the
to be taken with the engine running at blower to allow air to be drawn in the system
rated speed, load, and temperature. and reduce the vacuum pressure on the
adjusting valves.
2. Unplug the crankcase air filter and connect
the Blow-by Indicator to it. Slowly open An optional relief valve may be used to limit
the crankcase ventilation valve until the crankcase pressure to 0.14 kPa (0.5 in. H2O).
indicator reads the same as in step 1. This is used to avoid problems if the
crankcase ventilation fan is not engaged.
LEBX0029-01 11
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LEBX0029-01 (01-02)
Replaces LEBX0029 Materials and specifications are subject to change without notice.
