Hydraulic Drive & Controls

Lesson 28 Hydraulic circuit diagrams and troubleshooting

Hydraulic Circuit Diagrams

The circuit diagrams are used in hydraulics to show the components along with their interaction. It a useful tool for the manufacturers and assemblers so that they can come to know  how  the components are to be connected. Mechanics or technicians will be helped with it, that  how the system works, what each component does and what is the flow of  the fluid . It helps them in repairing and also in maintenance of the system. There are various types of hydraulic circuit diagrams which are as follows-

Block Diagram

This type of  diagram indicates  the various components and the lines between the blocks, which indicate connections and/or interactions.

Cutaway Diagram

This type of  diagram indicates the internal construction of the components along with the flow paths. This diagram uses colors, shades, or various patterns in the lines thus it can depict the flow and pressure conditions.

 Pictorial Diagram

This type of  diagram indicates a circuit piping arrangement. The components are usually having similarity  of their actual shapes and sizes.

Graphical Diagram

This type of  diagram indicates  is usually preferred for design and troubleshooting. It uses simple geometric symbols for various components and their controls and connections.

Troubleshooting in hydraulic system

Troubleshooting procedure is required to be performed in a proper manner so that no component is being changed illogically. Hence systematic approach for correcting a hydraulic problem is  a must in the hydraulic circuits. Before starting any troubleshooting operations get informed about the problem. Make out the possible  causes and their suitable remedies of different hydraulic problems occurred during hydraulic system operation. Take care to check that the proper drawings and diagrams are always available of the system or circuit .A convenient table is given for probable cause and suitable remedies-

Fault	Probable causes		Remedies
Noisy Pump	Hydraulic pump may have  cavitations  and taking air into the system.		Remove cavitations
	Low fluidl level		Fill fluid
	To heavy of flud		Use light fluid
	Cold fluid		Raise temperature
	Suction filter clogged		Clean it
Fluid does not come	Fluid level in the reservoir is low.		Add the recommended fluid
	Fluid  inlet hose  or inlet filter is clogged		Clean the filter
	Air leak in the inlet line prevents priming		Repair the leaks
	The  viscosity of fluid  is too high		Use a lighter oil viscosity
	Pump has dirt in it		Clean the pump
Overheating of fluid	Contaminants present  in relief valve
	Viscosity is low
	fan not running
	Dirty oil
	Low fluid level
	Excessive pump wear
Low pressure in the system	Air in the fluid e		Fill the tank nearly full or recommended level
	Pressure relief valve  set too low		Reset valve
	Defective or worn out pump /actuator		Repair or replace pump / actuator
	Pressure relief valve not properly seated		Rectified, adjust the relief valve.
	Leak in the hydraulic line		Tighten leaky  connections.
Foaming of fluid or  air in the fluid	Air leak in hydraulic pump suction side	Tighten leaky connection
	fluid level low	Fill fluid
	Wrong fluid put in tank	Use proper fluid
	Pump shaft seals or access plates could be drawing air into the system	Check for leakage
Excessive Wear	Viscosity of fluid  is too low .	Use appropriate recommended fluid
	High pressure occurs above the maximum pump rating	Check the relief
	Misaligned in the drive or belt drive is tight	Check the parts and rectify the problem.
	Air recirculation is causing a chatter in the system	Remove the air from the system
	Abrasive matter in the hydraulic oil is being circulated	Put a proper filter to check dust particles
Control valve sticky or working hard	Misalignment in control valve	Align it
	Valve is broken	Repair or replace it