Block J – Hydraulic Systems

Trends

Hydraulic systems are getting more advanced with the introduction of more electronics. Areas such as the oil industry, road maintenance and waste management are increasing their use of hydraulics in almost all applications because of convenience and simpler design.

Although these systems have not been traditionally recognized as part of the truck and transport mechanic’s scope of work, they are now commonly used with after-market accessories. Therefore, servicing, diagnosing and repairing these systems are becoming a more common practice for truck and transport mechanics.

Related Components (including, but not limited to)

Cylinders, motors, reservoirs, accumulators, controls, valves (relief, flow control, splitter), hoses, sensors, gauges, pumps (vane, piston, gear).

Tools and Equipment

See Appendix A.

Task 38 Services, diagnoses and repairs hydraulic components.

Context

Hydraulic systems pump confined fluid to transfer energy smoothly from one component to another. Advantages of using hydraulics include smooth and quiet operation, and adjustability of speed and force to prevent damage, which allows for a versatile and adaptable system.

Truck and transport mechanics must service, diagnose and repair hydraulic systems to ensure proper function and reduce down time.

Required Knowledge

• K 1 theory and operating principles of hydraulics
• K 2 primary hydraulic components such as prime mover, pump, reservoir, relief valve, control valves, hoses/fittings and actuators
• K 3 assembly procedures for hoses/fittings according manufacturers’ specifications and correct application
• K 4 pressure limits of hoses, tubing and fittings
• K 5 types of prime movers such as PTO and drop box (transfer case)
• K 6 types of positive (piston, vane, gear) and non-positive (centrifugal) displacement pumps
• K 7 types of hydraulic oils based on viscosity index rating
• K 8 types of accessories such as cement mixers, dump boxes, snow removal equipment, lift gates, arial lifts and mobile cranes
• K 9 importance of cleanliness
• K 10 hazards associated with hydraulics such as stored high pressure, skin and eye irritation, flammability and high heat
• K 11 safe work practices related to hydraulics and associated jurisdictional safety regulations
• K 12 types of failures such as intermittent, catastrophic and degradation
• K 13 common causes of failures such as contamination, improper operation, improperly designed components and poor maintenance practices
• K 14 common faults such as stuck valves, chafed or broken hoses and leaking seals
• K 15 troubleshooting techniques
• K 16 specialty tools such as pressure gauges, vacuum gauges, fittings, flow meters and temperature gauges
• K 17 specialized tests such as pressure test, flow test and leakage test
• K 18 removal, replacement and repair procedures
• K 19 inspection and testing procedures
• K 20 oil sampling procedures
• K 21 recycling and disposal methods, and jurisdictional requirements
• K 22 hydraulic schematics

Sub-task - J-38.01 Services hydraulic components.

Key Competencies

• J-38.01.01 clean hydraulic components such as inlet screen and reservoir
• J-38.01.02 perform sensory inspections of hydraulic components to identify worn, damaged or defective components such chaffed hoses, leaking gaskets, seals or hoses, low hydraulic oil levels and abnormal sounds
• J-38.01.03 release stored energy such as high pressure in a controlled manner without releasing fluid from the system
• J-38.01.04 remove and replace consumables such as filters and oil according manufacturers’ specifications
• J-38.01.05 recycle and/or dispose of consumables according to jurisdictional regulations
• J-38.01.06 record service information and inspection findings according to manufacturers’ requirements for warranty, and for future reference and tracking

Sub-task - J-38.02 Diagnoses hydraulic components.

Key Competencies

• J-38.02.01 obtain details of symptoms associated with complaint to establish a starting point for diagnosis
• J-38.02.02 release stored energy such as high pressure in a controlled manner without releasing fluid from the system
• J-38.02.03 perform sensory inspections to confirm complaint and establish a preliminary diagnosis
• J-38.02.04 perform diagnostic procedure by following schematics supplied by manufacturer to determine failure
• J-38.02.05 perform specialized testing procedures such as pressure, flow and vacuum to assess components for wear, damage or defects using tools and equipment such as pressure gauges, flowmeters, temperature gauges and vacuum gauges
• J-38.02.06 compare test results to manufacturers’ specifications or expected values to verify diagnosis
• J-38.02.07 perform failure analysis to determine root cause of failure
• J-38.02.08 record test results and inspection findings according to manufacturers’ requirements for warranty, and for future reference and tracking

Sub-task - J-38.03 Repairs hydraulic components.

Key Competencies

• J-38.03.01 release stored energy such as high pressure in a controlled manner without releasing fluid from the system
• J-38.03.02 remove and replace worn, damaged or faulty components such as damaged hoses, worn pumps, worn or damaged actuators, improperly vented reservoir, and worn damaged or faulty valves
• J-38.03.03 rebuild components such as actuators, pumps and valves, according to manufacturers’ specifications
• J-38.03.04 repair components such as actuators, pumps and valves, by replacing parts causing the failure, according to manufacturers’ specifications
• J-38.03.05 perform adjustments such as setting pressure and flow to ensure proper operation of component/equipment
• J-38.03.06 verify repair using methods such as operational tests, verifying pressures and flow according to manufacturers’ recommendations
• J-38.03.07 document that repairs and verifications have been performed for warranty, liability, future reference and tracking