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Find great deals on site for Fluid Power in Books About Nonfiction. Shop with confidence. Fluid Power Basics Practical knowledge about hydraulic and pneumatic components and systems Written by: Bud Trinkel, Certified Fluid Power. Featuring easy-to-understand explanations of theory and underlying mathematics principles, this book provides readers with a complete introduction to fluid.
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No notes for slide. Fluid power-data-book 1. For expanded educational material on fluid power, see textbook listings on the back cover. Ask your Catching Inside Sales Person for a printed copy.
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Revolution Motor Unidirect. Hydraulic Troubleshooting Many of the failures in a hydraulic system show similar symptoms: In fact, the cylinders may stall under light loads or may not move at all.
Often the loss of power is accompanied by an increase in pump noise, espe- cially as the pump tries to build up pressure.
Any major component pump, relief valve, directional valve, or cylinder could be at fault. In a sophisticated system other components could also be at fault, but this would require the services of an experienced technician.
By following an organized step-by-step testing procedure in the order given here, the problem can be traced to a general area, then if necessary, each com- ponent in that area can be tested or replaced.
This can happen on a new as well as an older system. It produces the symptoms described above: If the strainer is not located in the pump suction line it will be found im- mersed below the oil level in the reservoir point A. Some operators of hydrau- lic equipment never give the equipment any attention or maintenance until it fails. Under these conditions, sooner or later, the suction strainer will probably become sufficiently restricted to cause a breakdown of the whole system and damage to the Pump.
The suction strainer should be removed for inspection and should be cleaned before re-installation. Wire mesh strainers can best be cleaned with an air hose, blowing from inside Out. They can also be washed in a solvent which is compat- ible with the reservoir fluid. Kerosene may be used for strainers operating in petroleum base hydraulic oil.
Do not use gasoline or other explosive or flamma- ble solvents. The strainer should be cleaned even though it may not appear to be dirty. Some clogging materials cannot be seen except by close inspection. If there are holes in the mesh or if there is mechanical damage, the strainer should be replaced. When reinstalling the strainer, inspect all joints for possible air leaks, particularly at union joints points B, E, G, H, J, and K.
There must be no air leaks in the suction line. Check the reservoir oil level to be sure it cov- ers the top of the strainer by at least 3- at minimum oil level, with all cylinders extended. If it does not cover to this depth there is danger of a vortex forming which may allow air to enter the system when the pump is running. STEP 2— Pump and Relief Valve If cleaning the pump suction strainer does not correct the trouble, isolate the pump and relief valve from the rest of the circuit by disconnecting at point E so that only the pump, relief valve, and pressure gauge remain in the pump circuit.
Cap or plug both ends of the plumbing which was disconnected. The pump is now deadheaded into the relief valve. Start the pump and watch for pressure build-up on the gauge while tightening the adjustment on the relief valve. If full pressure can be developed, obviously the pump and relief valve are operating correctly, and the trouble is to be found further down the line.
If full pressure cannot be developed in this test, continue with STEP 3. STEP 3— Pump or Relief Valve If high pressure cannot be obtained in STEP 2 by running the pump against the relief valve, further testing must be conducted to see whether the fault lies in the pump or in the relief valve. Proceed as follows: If possible, disconnect the reservoir return line from the relief valve at point H.
Attach a short length of hose to the relief valve outlet. Hold the open end of this hose over the reservoir filler opening so the rate of oil flow can be observed. Start the pump and run the relief valve adjustment up and down while observ- ing the flow through the hose. If the pump is bad, there will probably be a full stream of oil when the relief adjustment is backed off, but this flow will dimin- ish or stop as the adjustment is increased.
If a flowmeter is available, the flow can be measured and compared with the pump catalog rating. If a flowmeter is not available, the rate of flow on small pumps can be measured by discharging the hose into a bucket while timing with a watch. For example, if a volume of 10 gallons is collected in 15 seconds, the pumping rate is 40 GPM, etc.
If the gauge pressure does not rise above a low value, say PSI, and if the volume of flow does not substantially decrease as the relief valve adjustment is tightened, the relief valve is probably at fault and should be cleaned or replaced as instructed in STEP S. If the oil substantially decreases as the relief valve ad- justment is tightened, and if only a low or moderate pressure can be developed, this indicates trouble in the pump.
Proceed to STEP 4. As- suming that the suction Strainer has already been cleaned and the inlet plumb- ing has been examined for air leaks, as in STEP 1, the oil is slipping across the pumping elements inside the pump. This can mean a worn-out pump, or too high an oil temperature.
High slippage in the pump will cause the pump to run considerably hotter than the oil reservoir temperature. In normal operation, with a good pump, the pump case will probably run about 20F above the reser- voir temperature.
If greater than this, excess slippage, used by wear, may be the use. Check also for slipping belts, sheared shaft pin or key, broken shaft, broken coupling, or loosened set screw. The faulty valve may later be disassembled for inspection and cleaning. Pilot-oper- ated relief valves have small orifices which may be blocked with accumulations of dirt. Blow out all passages with an air hose and run a small wire through or- ifices. Check also for free movement of the spool.
In a relief valve with pipe thread connections in the body, the spool may bind if pipe fittings are over-tight- ened.
If possible, test the spool for bind before unscrewing threaded connections from the body, or screw in fittings tightly during inspection of the valve.
STEP 6— Cylinder lithe pump will deliver full pressure when operating across the relief valve in STEP 2, both pump and relief valve can be considered good, and the trouble is further downstream. The cylinder should be tested first for worn-out or defec- tive packings by the method described on page 7.
Although it does not often happen, an excessively worn valve spool can slip enough oil to prevent build-up of maximum pressure.
Symptoms of this condition are a loss of cylinder speed together with difficulty in building up to full pressure even with the relief valve adjusted to a high setting.
This condition would be more likely to occur with high pressure pumps of low volume output, and would develop gradually over a long period of time. Four-way valves may be tested by the method described on page 7. Other Components Check other components such as bypass flow controls, hydraulic motors, etc. Solenoid 4-way valves of the pilot-operated type with tandem or open center spools may not have sufficient pilot pressure to shift the spool.
Cylinder and Valve Testing On an air system, if air is detected escaping from a 4-way valve exhaust while the cylinder is stopped, this air is either blowing by worn-out piston r Cylinder is leaking the inseals, or across spool Piston the 4-way valve.
These two leakage Leakage paths are shown in the figure to the right. Most air cylinders and valves have soft seals and should be leak-tight. Valve However, those air valves having a Cylinder metal-to-metal seal between spool and ports body may be expected to have a small amount of leakage.
If leakage is noted, it is more likely to be coming through the cylinder than Spool across the valve spool, and the cylinder should be tested first.
Crack the fitting Two Leak Paths on the same end of the cylinder to check for fluid leakage. After checking, tighten the fitting and run the piston to the opposite end of the barrel and repeat the test.
Occasionally a cylinder will leak at one point in its stroke due to a scratch or dent in the barrel. Check suspected positions in mid stroke by installing a positive stop at the suspected position and run the piston rod against it for testing. Once in a great while a piston seal may leak intermittently.
This is usually caused by a soft packing or O-ring moving slight- ly or rolling into different positions on the piston, and is more likely to happen on cylinders of large bore. The open line from the valve should be plugged or capped since a slight back pressure in the tank return line would spit from the line if not plugged.
Pistons with metal ring seals can be expected to have a small amount of leakage across the rings, and even leak- tight" soft seals may have a small bypass during new seal break-in or after the seals are well worn. To make the test, disconnect both cylinder lines and plug these ports on the valve. Start up the system and shift the valve to one working position. Any flow out the exhausts or tank return line while the valve is under pressure is the amount of leakage. Repeat the test in all other working positions of the valve.
Sate Inlet Vacuum, In. Hg 10 4to6 4 The auction strainer should be cleaned or replaced when inlet vacuum on a hydraulic pump reaches these values.
Sustained operation at these vacuums may damage the pump. To select a replacement for a broken or worn out hydraulic pump or motor which has no nameplate or has no rating marked on its case use the formulas below after making internal physical measurements. When replacing a pump, catalog ratings will usually be shown in GPM at a specified shaft speed.
On a motor, catalog ratings will usually be in C. Use the formula which is appropri- ate. Make all measurements in inches, as accurately as possible. Convert fractional dimensions into decimal equivalents for use in the formulas.
Make sure the catalog pressure rating is adequate for your application, and in the case of a pump, be sure direction of shaft rotation is correct. Gear Pumps and Motors 1. Measure gear width, W. Measure bore diameter of one of the gear chambers: Measure distance across both gear chambers; this is L. Measure width of rotor. This is W. Measure shortest distance across bore; this is D.
Measure longest distance across bore: Find piston area from piston diameter; this is A in formula. Measure length of stroke; this is L in formula. Count number of pistons; this is N in formula. If one with lower GPM is used, the system will have plenty of power but cylinders will move more slowly than originally.
If a motor with greater displacement is used, it will deliver more torque at a reduced RPM, but will require no more fluid HP from the pump. If it has less displacement it will rotate faster with less torque. Fluid Power Formulas Torque and horsepower Relations: Hydraulic fluid power horsepower: Velocity of oil flow in pipe: Charles' Law for behavior of gases: Boyle's Law for behavior of gases: Circle formulas: Heat equivalent of fluid power: Force or thrust of any cylinder: Force for piercing or shearing sheet metal: Side load on pump or motor shaft: Effective force of a cylinder working at an angle to direction of the load travel: Heat radiating capacity of a steel res- ervoir: Burst pressure of pipe or tubing: Relationship between displacement and torque of a hydraulic motor: Rules-of-Thumb Horsepower for driving a pump: Horsepower for idling a pump: Compressibility of hydraulic oil: Compressibility of water: Wattage for heating hydraulic oil: Flow velocity in hydraulic lines: Pump suction lines 2 to 4 feet per second; pressure lines up to PSI, 10 to 15 feetper sec; pressure lines to PSI, 15 to 20 feet per Sec.
Fluid Power Abbreviations abs absolute as in psia ipm inches per minute AC alternating current ips inches per second Bhn Brinell hardness number lb pound Btu British thermal unit max maximum C degrees Centigrade Celsius mm minimum cc closed center mtd mounted ccw counter clockwise NC normally closed cfm cubic feet per minute NO NPT normally open threadcfs cubic feet per second national pipe cir cubic inches per revolution NPTF dryseal pipe threads cim cubic inches per minute oc open center corn Common OZ.
Ounce cpm cycles per minute P. Vehicle Drive Calculations The force to drive a vehicle is composed of the sum of I road resistance, 2 force necessary to climb a grade 3 force needed to accelerate to final velocity in the allowable time, 4 force to overcome air resistance, on fast moving vehi- cles. Each of these forces can be calculated or estimated from the formulas on this page, then added together. In selecting an engine, allow enough extra pow- er to make up for losses in the mechanical transmission system including gear boxes, clutches, differentials, chain or belt drives.
Travel Speed in M. Axle Torque for driving the vehicle Acceleration of a vehicle is ex- pressed in this formula involving weight, accelerating force, and time. V is final velocity in feet per second. W is vehicle weight in pounds. The gravity acceleration sym- bol, g, converts weight into mass.
F is drawbar pull in pounds. Drawbar Pull to keep the vehicle in steady motion on level ground de- pends on the road surface. The follow- ing figures are pounds of drawbar pull per lbs.
Grade, in mobile work, is usually expressed in percentage rather than in degrees. Grade Resistance is the drawbar pull needed to keep the vehicle in con- stant motion up a grade.
This is in ad- dition to the drawbar pull to overcome road resistance as expressed by anoth- er formula. W is gross vehicle weight in pounds. Additional HP is required at the engine to overcome transmission system losses.
Conversion Formula between torque, HP, and speed. Momentum of a vehicle is equiva- lent to that constant force which would bring it to rest in one second by resisting its movement. V is velocity in feet per second. FA is frontal area of vehicle in square feet. Axles and drive shafts must have a diameter large enough to transmit the torque without excessive deflection.
The angle of deflection for a solid round axle may be calculated from this formula: I is applied torque in inch pounds. L is shaft length in inches. E is modulus of elasticity of material.
Some authorities say that a steel shaft should be limited to an angular deflection of 0. A certain application requires a cylinder force of 25 tons. What should be the cylinder bore diameter used and at what gauge pressure? Refer to the "Hydraulic Cylinder Force" table on pages 15 and 16 which shows several combinations of piston diameter and PSI pressure which will produce 50, pounds of force or more.
For example, a 6 inch piston will produce 56, pounds at PSI; a 7 inch piston will produce 57, lbs at PSI; an 8 inch piston will produce 50, lbs at PS! So there are many combinations which could be used, and the final choice is a matter of preference or of matching the pressure and flow capability of other components, particularly the pump.
This will provide a safety allowance which will take care of pressure losses in valves and piping, and mechanical losses in the cylinder.
Refer to the "Hydraulic Cylinder Force" table on pages 15 and The chart shows 12, lbs. A solution can also be obtained by using the pis- ton area 8.
On the retraction stroke the amount of force developed on the 2. What PSI gauge pressure is required for retraction of a 50, lb. The net piston area must be found which is the full piston area minus the rod area. The actual pressure will be slightly greater due to friction of the piston in the barrel. Calculation of Hydraulic Cylinder Speed At what speed would the piston of a 4 inch bore cylinder extend on an oil flow of 12 GPM?
The table of 'Hydraulic Cylinder Speeds" on pages 17 and 18 may be used or the speed figured with the formula which says that 'speed is equal to the incoming flow of oil in cubic inches per minute, divided by the square inch area of the piston". The speed will be in inches per minute. This checks very closely with the value shown in the table on page Find the GPM flow necessary to cause a inch bore cylin- der to travel at a rate of inches per minute while extending. How fast would this cylinder retract on the same oil flow if it had a 2 inch diameter piston rod?
Flow is determined by multiplying the piston area in square inches times the travel rate in inches per minute. This gives flow in cubic inches per minute. Divide by to convert to GPM: This checks very closely with 15 GPM at inches per minute shown on the chart on page To find the retraction speed on This is the full piston area minus the rod area: The flow rate is cubic inches per minute equivalent to Note that this is faster than the extension speed on the same oil flow.
The chart on this page covers cylinder operation in the pressure range of to PSI, and the chart on the next page covers the to PSI range. Lines in bold type show extension force, using the full piston area.
Lines in italic type show retraction force with various size piston rods. Remember that force values are theoretical, derived by calculation. For pressures not shown, the effective piston areas in the third column can be used as power factors. Multiply effective area times continued on page 16 Bore Dia. Rod DIa. Area, Sq. No piston rod diameter is involved.
He is an author of several research publications and chapters in textbooks. His research work encompasses both compressible flow and incompressible flow. Compressible flow research is primarily on flow and acoustic field associated with formation of compressible vortex ring and its interaction with shock, wall or other generic shape objects. Incompressible flow research spans across different topics; transition of unsteady internal flow, free shear and buoyancy driven flows, unsteady aerodynamics of birds' and insects' flights.
In theoretical fluid dynamics, he has contributed towards an analytical solution method for unsteady internal flow when the pressure as well as the velocity is unknown. He is author of several research publications.
Rajesh Srivastava has worked extensively on numerical simulation of flow and transport through variably saturated porous media.
His work provides significant insight into the transport of reactive solutes in porous media. His research finds applications in remediation of contaminated sites as well as mining of minerals through heap leaching. His present work focuses on the effect of climate change on water resources and inverse techniques for characterization of porous media and identification of possible contaminant sources.
He is an author of several research publications and two textbooks. Previously, he was the Head of the Laser Technology Program.