What are the Faults in Hydraulic Circuits and Solution Suggestions?
What are the Faults in Hydraulic Circuits and Solution Suggestions?
What are the Faults in Hydraulic Circuits and Solution Suggestions?
Hydraulic;
The word is derived from the Latin word hydor, meaning water.
Hydraulic systems;
Hydraulics began to be widely used in machinery manufacturing and industrial applications in the second half of the 20th century, as it transmits forces and movements more easily and efficiently than friction systems.
Description of Hydraulic System
The structure formed by the elements that operate a mechanism with the transmission of pressurized fluid power is called the hydraulic system.
The hydraulic pump in the hydraulic system absorbs the oil from the tank and directs it to the system with effective pressure. If the System Pressure is higher than the designed value, the system is secured by returning to the tank from the Pressure Adjustment valve. The oil sent to the Direction control valve by the hydraulic pump is directed to the user elements (Hydraulic cylinder, Hydraulic Motor, etc.) from there and with the hydraulic oil flow rate and pressure. The moving user element operates the machine to which it is connected. The speed of the machine (mechanism) can be changed by the flow adjustment of the oil passing through the flow control valve.
In order to ensure the back and forth movement of the user element, the flow and return paths of the oil are alternately changed by the directional control valve.
The main parts of the hydraulic circuit are:
1- Tank (Tank)
2- Pump
3- User Elements (Cylinder – Hydraulic Motor etc.)
4- Valves
5- Accumulators
6- Pipe - Hose - Fittings
7- Sealing elements
8- Filters
9- Cooler
10- Accessories, Indicators
Description and symbol of hydraulic pump:
The element that absorbs the fluid from the tank with the mechanical energy it receives from the engine and transfers it under pressure at a certain flow amount is called a hydraulic pump.
Hydraulic pumps convert the Mechanical Energy they receive into Hydraulic Energy with the pressure and flow formation of the hydraulic fluid. The pressure and flow rate of the fluid supplied by the hydraulic pump to the hydraulic circuit fed by the hydraulic pump must be of sufficient value for the needs of the user components (also considering the combined works).
Working principle of Hydraulic Pumps:
The Hydraulic Fluid, which is sucked with the effect of vacuum at the suction mouth, works with the principle of transferring the fluid with positive transmission by creating compression at the discharge port. Thus, if there is a resistance in front of the fluid transferred by the pump, pressure is created. The hydraulic pump is the power transmission source in the circuit. The power transmitted by the pump depends on the Hydraulic Fluid Pressure and the Fluid Flow. If the cross-sectional area A, flow rate v, through which the fluid passes, is the flow rate (the amount of fluid flowing per unit time),
Q = A . It is calculated with the formula v .
Working conditions and Hydraulic pump:
Pump selections should be made in accordance with the work that will be needed in the hydraulic circuits and the need for power transmission.
In case of using more than 1 pump in a hydraulic system, the pumps are designed to work in a certain order.
Fluid flow rate for speed requirement and pressure values for force requirement should be calculated.
Features to consider when choosing a Hydraulic Pump:
1. Fluid properties
2. Working pressure range
3. Flow requirement
4. Number of revolutions
5. Operating temperature range
6. How to drive the pump
6. Ease of maintenance
7. Service life
8. Dimensions and assembly
9. Cost elements
10. Advantages and disadvantages
11. Number of flow directions
Definition of flow:
The volume of liquid flowing through a section in unit time is called flow rate. Therefore, the flow (Q) is directly proportional to the flow section (A) and velocity (v).
Fluid as long as the pump maintains the same flow rate:
Q = A1 . V1 = A2 . V2 = ... = An . vn
flows according to the rule. Although the flow rate is the same, the flow sections and velocities change inversely.
Hydraulic Valve:
It is the circuit element that determines the direction of the hydraulic fluid, changes its direction when desired, and controls the pressure and flow of the fluid.
Duty of Hydraulic Valves
It opens and closes the path of the fluid.
It changes the direction the fluid will go.
It sends the fluid to the tank.
It adjusts the operating speed of the receivers by controlling the flow rate of the fluid.
It protects circuit elements against high pressures. It sends the fluid whose pressure rises to the tank.
By controlling the pressure of the fluid, it ensures that the circuit elements operate at certain pressures.
It controls the pressure, flow and direction of the fluid at certain time intervals.
Some valves can perform one or more of the tasks listed above.
Hydraulic Directional Control Valves
It is the valves that determine when and which path the fluid should follow in hydraulic circuits. They change the flow path at will; They open and close the flow path when desired.
SCHEMATIC DESCRIPTION OF DIRECTIONAL CONTROL VALVES
Each position of the valve should be indicated by a square.
The flow directions of the fluid are indicated by arrows.
Closed roads are marked with a horizontal line.
Valve connections are indicated by dashes.
Marking of valve positions; valve positions are marked with letters from left to right. For three-position valves, the center position is indicated by 0.
Lettering of Hydraulic Valve connections;
P=Pressure line A,B,C....=Work line or work line
R,S,T=Warehouse(return) line
X,Y,Z=Pilot(warning) line
L=Leakage line
Identification of Hydraulic Directional Control Valves;
2 / 2 = Number of paths/ Number of locations
When 3 /2 valve is defined, it is understood that the valve is 3-way, 2-position.
Normal positions of Hydraulic Valves;
In hydraulic circuit drawings, valves are drawn and lettered in their normal position.
Hydraulic Directional Control Valve Malfunctions
There are some problems that occur repeatedly during operation. The most common of these are:
Bad Control Element
Excessive Oil Leakage
Broken or Broken Springs
Adhesion and Adhesion
Cracked or Broken Parts
Solid parts in the Hydraulic System
Water in the Hydraulic System
Extremely Hot Operation of the Hydraulic System
Air in the Hydraulic System
Chemical Reaction in Hydraulic Oil
Most valve failures are caused by problems elsewhere in the system. You can expect repeat failures with valves that have been repaired or replaced unless the actual failure is corrected.
General inspection of parts; includes visual inspection of defects such as protrusions, cuts, roughness, nicks, cracks, signs of wear, or bent parts.
Place it sideways on a flat surface and roll it. Visually inspect for a wobble indicating skewing.
Hydraulic Valve Failure Symptoms
Sludge: Matter formed by oxidation due to overheating of hydraulic fluid.
Scratch: Small channels formed by abrasion on the surface of a valve by high pressure fluid.
Knocking: Noise, hum, buzzing caused by the control tip hitting the solenoid body continuously due to insufficient or excessive current.
When you disassemble a valve for repair or maintenance, always install a new one, even if all sealing elements appear to be in good condition.