CONCENTRATION
Coolant Conditioners and Filters
All 3400 Series direct injection Engines require the use of a chemical coolant condi- tioner. The conditioner reduces potential cylinder block and liner pitting and corrosion. A. Consult the factory for suitable coolant conditioners which should be applied and maintained in accordance with published instructions.
B. If a dry charged additive water filter is selected, the following plumbing rec- ommendations should be followed. 1. The filter inlet and outlet are ordinary
0.375 in (9.5 mm) inside diameter rubber hoses. Connect the hoses to obtain the highest possible coolant pressure differential across the unit. Heater hose connecting points at the coolant pump inlet and the tem- perature regulator housing are rec- ommended. If uncertain, plumb the inlet to a point on the discharge side of the water pump and the outlet to a point near the water pump inlet. 2. The outlet should be orificed with a
0.125 in (3.2 mm) internal diameter orifice. This will prevent excessive coolant flow through the filter which can bypass the radiator core and reduce effectiveness of the cooling system. Inlet and outlet lines should include shutoff valves so the filter can be serviced without draining the cooling system.
PLUMBING
Piping between the engine and radiator should be flexible enough to provide for relative motion between the two. Hoses less than 6 in (15.24 cm) in length provide little flexibility and are difficult to install. If the hose is more than 18 in (45.7 cm) in length, it is susceptible to failure from vibration or coming loose at the connec- tions. Support the piping with brackets, when necessary, to take weight off a verti- cal joint. High quality hose, clamps, and fit- tings are a prerequisite for long life and are necessary to avoid premature failure. It is also necessary to “bead” pipe ends to reduce the possibility of a hose blowing off. Double clamps are desirable for all hose connections under pressure. Vent lines and shunt lines must slope downward without high or low areas that may trap air and cause an air lock. In order to maintain the correct flow relationship in a baffled radiator top tank, it is recommended that no lines tee into the shunt or vent lines. FAN RECOMMENDATIONS
A. Fan Diameter and Speed
As a general rule, the most desirable fan is one having the largest diameter and turning at the lowest speed to deliv- er the required air flow. This also results in lower fan noise and lowest fan horse- power draw from the engine. Blade tip speed, while being only one of the ele- ments of cooling fan design, is an item easily changed with choice of fan drive pulley diameter. An optimum fan tip velocity of 14,000 fpm (7112 cm/s) is a good compromise for meeting noise leg- islation requirements and cooling system performance requirements. Maximum acceptable tip speed is 16,000 fpm (9144 cm/s) for Caterpillar fans.
B. Fan Performance
Proper selection and placement of the fan is critical to the efficiency of the cooling system. It requires careful matching of the fan and radiator by determining air flow needed and static air pressure which the fan must over- come. This must be done since most discrepancies between cooling system calculated performance and test results are traceable to the “air side” and direct- ly related to items affecting fan air flow. There are two major considerations for proper fan selection:
1. Air flow needed to provide the required cooling.
2. Select a fan that provides the required air flow, and one that is rela- tively insensitive to small changes in static pressure. This desired design point is where a small change in sta- tic pressure does not cause a large change in air flow. Selecting a lower pressure point is not recommended as it could be in the unstable “stall” area where a small change in static pressure causes a large change in air flow. Performance curves for available Caterpillar fans are shown as air flow (cfm), static pressure head, (inches of water, gauge) and horsepower in TMI. The Caterpillar curves are based on standard air density, an efficient fan shroud, and no obstructions.
This is a theoretical air flow which is seldom possible because of some obstruction. Theoretical air flow some- times can be approached with the fan in a properly designed close fit- ting shroud with no more than 0.0625 in (1.6 mm) blade tip clear- ance. Such a close fitting shroud is
not practical, and tip clearance is increased; a 0.5 in (12.7 mm) clear- ance is generally recommended. When a fan speed different from those shown in the curves is needed, the additional performance data can be calculated using these fan rules:
For Speed Changes cfm2= cfm1 ____rpm2 rpm1 Ps2= Ps1
(
rpm2)
2 ____ rpm1 hp2= hp1(
rpm2)
3 ____ rpm1For Diameter Changes cfm2= cfm1
(
Dia2)
3 ____ Dia1 Ps2= Ps1(
Dia2)
2 ____ Dia1 hp2= hp1(
Dia2)
5 ____ Dia1For Air Density Changes
Ps2= Ps1 ___r2
r1
hp2= hp1 ___r2
Ambient Capability Adjustments (Air Flow or Fan rpm Changes)
nT2= nT1
(
cfm1)
0.7 ____0. cfm2. nT2= nT(
rpm1)
0.7 ____0. rpm2.Maximum Ambient Capability = 210 – nT2
cfm = Air flow in cubic feet per minute. rpm = Fan speed in revolutions per
minute.
Ps = Stack pressure in inches of water.
hp = Fan horsepower.
Dia = Fan diameter in inches.
r = Air density in pounds per cubic
foot.
nT = Coolant top tank temperature
minus ambient air temperature. C. Fan Shrouds and Fan Location
Two desirable types of shrouds are: venturi and box.
Maximum air flow and efficiency is pro- vided by a tight fitting venturi shroud with sufficient tunnel length to provide straight air streamlines. Small fan clearances require a fixed fan or an adjustable shroud. Although they are somewhat less efficient than the ven- turi shroud, box type shrouds are most commonly used because of lower cost. Properly positioned, a simple orifice opening in the box shroud is practical. Straight tunnel shrouds are usually less effective than venturi or box shrouds.
The fan tip clearance should be 0.5 in (12.7 mm) or less. A properly designed shroud will:
1. Increase air flow.
2. Distribute air flow across core for more efficient use of available area. 3. Prevent recirculation of air.
As a general rule, suction fans should be no closer to the core than the pro- jected blade width of the fan. Greater distance gives better performance. Consider also that engine-mounted items close to the back side of the fan can introduce vibrations into the fan to cause fan failure, increase fan noise, and reduce air flow. Suction fans should be positioned so that two-thirds of the projected width is inside a box shroud orifice plate while a blower fan position is one-third inside the shroud.
D. Air Flow Losses and Efficiency Obstructions
Particular attention should be given to items restricting air flow, both in front of the radiator and to the rear of the fan. The additive affects of guards, bumpers, grills, and shutters in front of the radiator, pulleys, idlers, engine-mounted acces- sories, and the engine itself behind the fan can drastically reduce air flow.