FLUID POWER MODULE:02 ~ HYDRAULIC SYSTEM COMPONENTS
FLUID POWER Sources of Hydraulic Power ◦ Pumps ◦ Actuators ◦ Fluid motors Control Components: Direction control valve Flow control valves Electrical control -- solenoid valves. Relays, Accumulators and Intensifiers. MODULE:02 ~ HYDRAULIC SYSTEM COMPONENTS
FLUID POWER HYDRAULIC PUMPS MECHANICAL ENERGY HYDRAULIC ENERGY It is the heart of any hydraulic system.
Hydraulic pumps can be classified using three basic aspects: Displacement - Non-positive displacement pumps - Positive displacement pumps Pumping motion - Rotary - Reciprocating Fluid delivery - Constant Delivery - Variable Delivery FLUID POWER HYDRAULIC PUMPS
Non-positive displacement pumps FLUID POWER HYDRAULIC PUMPS Working: Features: High Flow rate Low Pressure Not self-priming type Advantage & Disadvantage: Fewer moving parts Smooth continuous flow Not self-priming and hence they must be positioned below the fluid level. Discharge is a function of output resistance
Pumps used in FLUID POWER SYSTEM:~ Positive displacement types PUMPING ACTION / THEORY: FLUID POWER HYDRAULIC PUMPS
Pumps used in FLUID POWER SYSTEM:~ Positive displacement types ADVANTAGES : - They are self-priming. - Can be operated at very high pressure (up to 800 bar ) - High volumetric efficiency of up to 98%. - Highly efficient and efficiency is almost constant throughout the designed pressure range - Small, compact unit, having a high power-to-weight ratio - The flow rate does not change with head - They have a great flexibility of performance. They can be made to operate over a wide range of pressures and speeds. FLUID POWER HYDRAULIC PUMPS
Positive displacement pumps External Gear Pump ~ constructional features: FLUID POWER HYDRAULIC PUMPS - Uses two identical gears - One gear is driven by a motor - Each gear is supported by a shaft with bearings on both sides of the gear - Oil chamber formed between gear teeth, pump housing, and side wear plates.
FLUID POWER HYDRAULIC PUMPS 1. As the gears come out of mesh, they create expanding volume on the inlet side of the pump. Liquid flows into the cavity and is trapped by the gear teeth as they rotate. Positive displacement pumps External Gear Pump ~ working principle:
Positive displacement pumps External Gear Pump ~ working principle: FLUID POWER HYDRAULIC PUMPS 2. Liquid travels around the interior of the casing in the pockets between the teeth and the casing -- it does not pass between the gears.
Positive displacement pumps External Gear Pump ~ working principle: FLUID POWER HYDRAULIC PUMPS 3. Finally, the meshing of the gears forces liquid through the outlet port under pressure...\video\Edited\Gear Pump(ipad).wmv
Positive displacement pumps Gear Pump ~ volumetric capacity: FLUID POWER HYDRAULIC PUMPS Flow Rate: Volumetric Efficiency: Flow vs speed curve Flow vs pressure curve at const. pump speed
Positive displacement pumps External Gear Pump ~ features: FLUID POWER HYDRAULIC PUMPS Popular pumps in low-pressure ranges (140bar). Max pressure rating is very important. Long operating life, high efficiency and low cost They give constant delivery for a given speed. The liquid to be pumped must be clean, otherwise it will damage pump. Variable speed drives are required to change the delivery. If they run dry, parts can be damaged because the fluid to be pumped is used as lubricant. Can not be reversed always.
Positive displacement pumps External Gear Pump ~ problems: FLUID POWER HYDRAULIC PUMPS Problem:01 A hydraulic pump delivers 12 L of fluid per minute against a pressure of 200 bar. Calculate: (a) The hydraulic power. (b) If the overall pump efficiency is 60%, what size of electric motor would be needed to drive the pump? Answer: 4 kW, 6.67 kW
Positive displacement pumps External Gear Pump ~ problems: FLUID POWER HYDRAULIC PUMPS Problem:02 A gear pump has an outside diameter of 80mm, inside diameter of 55mm and a width of 25mm. If the actual pump flow is 95 LPM and the rated speed is 1600 RPM what is the volumetric displacement and theoretical discharge. Also find volumetric efficiency. Answer: 6.627x10 -5 m3/rev, 0.106m3 /min, 89.6%