Ch 15: Fluid Power System Maintenance and Troubleshooting
clear or semiclear polyurethane (plastic) tubing without reinforcement layers or cords
Many modern pneumatic systems use what type of tubing?
False, improper heat transfer
T/F: Excessive coats of paint applied to a component can increase insulation and provide proper heat transfer.
False, they do
T/F: Springs, seals, and O-rings do not need to be replaced every time a component is serviced.
True
T/F: When testing an actuator, it must be deenergized and disconnected from the load.
breather/ filler cap
The ______ filter is used to keep contaminants out of the hydraulic system and allow air to flow freely in and out of the reservoir.
hydraulic filters
The most important routine maintenance for hydraulic equipment is replacing ______ according to the manufacturer's recommendations or when indicated by devices such as pressure gauges, flow meters, or filter indicators.
- trained fluid power technicians - safety
Troubleshooting fluid power systems should only be performed by who? What should always be the first priority?
higher
Typically, the more layers in a hose, the higher or lower the minimum bend radius?
wear on couplings or the deterioration of seals or O-rings
What are 2 common reasons for internal leaks?
- reduces the amount of troubleshooting - many future problems can be avoided
What are some advantages of a routine maintenance program?
contamination and breakdown of hydraulic fluid
What are the 2 most common reasons for hydraulic system maintenance problems?
1. Follow all safety regulations that are in place to protect the personnel and equipment. (can result in serious injury or death); 2. Understand normal equipment operation. This will help narrow down the list of potential problems. (read all literature associated with equipment); 3. Gather info concerning the specific equipment failure. (best source for specific equipment info is the equipment operator, help reduce the amount of time required for troubleshooting); 4. Operate the equipment. Equipment is operating erratically, or part is malfunctioning, watching the equipment operate may reveal the malfunction; 5. Perform a sensory inspection of the system. Read pressure gauges, temperature gauges, and flow meters, listen for unusual sounds, or smell; 6. List possible causes of equipment failure. Compile a list of the components that could be causing the malfunction. List them in order from the most probable to the least probable. From that list, form another list of the probable causes in order of which malfunctions are the easiest and quickest to troubleshoot and repair; 7. Verify the conclusion for probable malfunction; 8. Verify that all power sources are locked and tagged out before repairing the cause of the malfunction. (In a hydraulic system, verify that there is no pressure from the two possible sources, the accumulator or the load attached to the rod. In a pneumatic system, verify that all pressure in the system was safely released after the power was locked out) Residual pressure in the pneumatic lines must be released; 9. Repair or replace the device that is causing the equipment to malfunction. Reconnect pipes and hoses and properly tighten the device to its subplate. After all connections have been securely tightened and all lockouts have been removed, start the equipment to verify that replacing the malfunctioning component has corrected the problem. (If the problem has been successfully corrected, continue to step 10. If the problem persists, repeat steps 7 through 9); 10. Clean the work area after the problem is corrected. Follow facility procedures when removing and disposing hydraulic fluid. Remove tools from the equipment area and secure the safety doors or entryways. Once the cleanup is done, complete any required written reports as soon as possible.
What are the steps within the procedure for troubleshooting a fluid power system?
part replacement, beginning-to-end, and end-to-beginning
What are the three most commonly used methods for troubleshooting fluid power systems?
Tachometers
What are used to measure electric or hydraulic motor speed?
hydraulic tester
What can be used to isolate internal leaks from hydraulic components?
clamps
What can be used to prevent abrasions on the hose?
elbows
What can be used to reduce the strain on a hose?
- damage hydraulic fluid and system components - unclean reservoir and system components because it can't dissipate heat well, kinked lines, relief valves not set properly, over-speeding, overloading,
What can overheating damage within hydraulic systems? What can cause overheating?
if the cause is an unusual problem or could logically be a number of components, this will help to isolate the problem.
What is an advantage of the half-back troubleshooting method?
a schematic diagram
What is one of the most useful tools to troubleshoot fluid power equipment?
Slack
What is required for hose length change due to hydraulic fluid pressure change?
The basic method is to ask the question "why?" five times. This will typically allow a technician to find the root cause of a problem
What is the 5 "whys" troubleshooting method?
part replacement trouble- shooting method
What is the least accurate trouble shooting method?
half-back troubleshooting method
What is the most common and practical approach when a problem occurs that could have multiple causes?
- insufficient air pressure or airflow - air leaks from worn, disconnected, or kinked hoses or tubing lines
What is the most common problem in pneumatic systems? How is this problem usually caused?
replacing hydraulic filters
What is the most important routine maintenance in hydraulic systems?
that the supply of air is clean and dry
What is the most important task when performing pneumatic system maintenance?
in lengths of 3′ or less
What lengths of hoses should be used in fluid power systems?
- clog an actuator, cause environmental hazards, and mask other problems - premature wear of components and heat build-up
What problems can too much lubricant cause in a pneumatic system? What happens if it is too little?
leaks and clogged filters and lubricator oil levels
What should pneumatic systems be inspected routinely for?
the rod must be retracted because contaminants can settle on the exposed metal and enter the system when the rod is moved Coat it in grease
When a hydraulic cylinder is not in service, what must be done to prevent contaminants? How does this prevent contamination? If the rod must be exposed, what must you do?
- whether the problem is with the electrical control circuit or the fluid power system - most electrically controlled components have an LED light up if power is present at solenoid
When a problem occurs with an electrically controlled fluid power system, what is the most important factor to determine? What is the easiest way of doing this?
at the air compressor and move towards the actuators
When checking for pressure or airflow problems, troubleshooting should begin where?
1. Determine if there is voltage to the electrical circuit with a DMM; 2. Refer to the ladder diagram to determine which switches must be closed to activate the component's solenoid; 3. Verify that there is voltage to the solenoid with a DMM; 4. Verify that each switch is in proper working order by doing a voltage measurement or a continuity test across each switch with a DMM.
When checking for voltage and continuity within an electrically power fluid power system, what are the steps within the procedure?
the pump and flow control valve operation
When equipment speed for a hydraulic system is incorrect, what should be checked?
soft, nonabrasive, manufacturer-approved cleaning pads
When preparing metal surfaces for use in fluid power systems, they should be polished with what?
at connection points of hoses, tubing, and fittings
Where do air leaks within pneumatic systems commonly occur?
hydraulic tester
a device that measures the pressure, flow rate, and temperature of hydraulic fluid in a system
packing nut
a mechanical device on a pneumatic actuator that applies tension to the seals or packing to prevent air leaks around the circumference of a rod or shaft.
half-back troubleshooting method
a method for testing for problems in the middle of a hydraulic circuit and working backward or forward on the system.
plug-in pressure gauge
a pneumatic device that can be added to or removed from a pressurized pneumatic system without removing pressure from the system
digital multimeter (DMM)
a portable meter that can measure more than one electrical property and display the measured properties as numerical values.
minimum hose bend radius
a standard given by the manufacturer that indicates the least amount of bend that can be used for a specific type of hose
Polyethylene spiral wrapping
an inexpensive method of covering hoses and tubing that can extend their operational lifetimes
- 400 to 600 - 3
mobile hydraulic equipment typically should be inspected every _____ hr to ____ hr or every ____ months.
Maintenance
the practice of periodically inspecting and repairing equipment.
- part replacement trouble- shooting method - When technicians troubleshoot the same equipment
- a fluid power system troubleshooting method that replaces parts without the use of equipment diagnosis tools - When is this beneficial?
- beginning-to-end trouble- shooting method - for fluid power systems that have completely stopped operating, the problem is most likely at the beginning b/c nothing is working
- a fluid power troubleshooting method that traces problems from the beginning of the fluid power system (prime mover, hydraulic pump, or air compressor) to the end (actuator) - When is this system prefered? Why?
- end-to-beginning trouble- shooting method - when actuators are not operating, but the gauges at the beginning of the system indicate normal levels
- a fluid power troubleshooting method that traces problems from the end of the fluid power system (actuator) to the beginning (prime mover, hydraulic pump, or air compressor) - When is this prefered?
air compressor controls
A common cause of pneumatic system problems is ________ that are at incorrect pressure settings.
compressor oil
A pneumatic system uses ______ for lubrication.
25
Air leakage can waste up to ___% or higher of the pneumatic system energy.
The exterior should be cleaned
Before dismantling a hydraulic system, what should be done?
low-pressure, clean, dry compressed air
Components that have been dismantled from a hydraulic system and cleaned are dried with ________.
leak
Fluid stains or puddles under hydraulic equipment and hoses indicate the presence of a(n) ______ in the line.
linear reinforcement cords
High-pressure pneumatic hoses have what along the inner layer of the hose?
maintaining the correct hydraulic fluid level in the reservoir
How can air be kept out of a hydraulic system?
By listening or applying soapy water to see bubble come up
How can someone locate an air leak?
coats their components with protective paint.
How does a manufacturer prevent corrosion damage and efficiently dissipate heat in a pneumatic component?
in a cool, dry area not in direct sunlight, never hung on nails/hooks, coiled to avoid kinking, if kept below 32 degrees gradually warm up
How should hoses be stored?
slowly
How should someone start a hydraulic system when it is cold?
internal leakage and poor lubrication
Hydraulic fluid that has lower viscosity than that recommended by the manufacturer can cause what?
the results of routine inspections of equipment and systems within a specific period of time
Hydraulic system maintenance should be performed based on what?
the force or speed of the actuators.
Hydraulic system problems are usually related to a malfunction in what?
a lack of pressure
If the hydraulic system is not producing enough force, what is the problem most likely related to?
dye and a "black" light can be used
If there is an external leak for a hydraulic system, what should be done to find it?
efficient heat dissipation
In addition to the prevention of hose ruptures, pneumatic components must be kept clean and damage free to provide efficient ________.
the layers can collapse and are not seen on the surface
In pneumatic hoses that have reinforcement layers rather than cords, what is a problem that can occur?
operating temperature, pressure, accessibility, operating time, and environmental factors such as shock, vibration, operating time, and cleanliness.
Inspection intervals for hydraulic systems are based on conditions that include what?
pressure and fluid flow
Internal and external leaks can affect what?
