Unit Two Force Transmission through a Fluid

Force Transmission through a Solids, Liquids, and Gases Solids transmit force in only one direction but fluids transmit force in ALL directions.

Force Transmission through Solids, Liquids, and Gases(Continued) Whereas liquids are relatively incompressible, gases will compress.

Force Transmission through a Solids, Liquids, and Gases(Continued) Gases compress until their pressure is equal to the force applied.

Fluids take the shape of their container The fact that fluids will take any shape gives them the property of unlimited conductive geometry.

Pascal’s Law “Pressure set up in a fluid is transmitted equally and at right angles to all containing surfaces”

Pressure = Force/Area Applying Pressure An object at rest on the ground will develop pressure between itself and the point, or area, where it meets the ground.

Area of a Circle The area of a circle is equal to the diameter squared multiplied by .7854

Fluid pressure to Mechanical Force A fluid under pressure is converted into another energy form at the point of operation.

Fluid Power Cylinders The actuator is where pressurized fluid is converted into mechanical force for performing work.

How Cylinders Work By allowing the fluid to contact a movable area, usually a piston, cylinders use the piston and rod to move a resistive object.

Mechanical Force Multiplication Actuators multiply force by applying pressurized fluid against a movable area that acts like a “lever.” Force = Pressure x Area

Intensifier and Intensifier Operation In operation, a intensifier is very much like a transformer. It “steps” up pressure but reduces movement because of a difference in volume.

How Intensifiers Work In practical operation, the intensifier is used for momentary need of high pressure.

Movement Sacrificed You generally do not get something for nothing so when Force is increased, something must decrease and that will usually be movement.

Pressure Scales For measuring pressure we have two different scales. One, PSIA, takes into account the weight of the atmosphere.

Measuring Atmospheric Pressure The idea of the barometer is based on the observation of a liquid with a specific weight being held back by the atmosphere. Every cubic inch of mercury exerts a weight of .491 pounds per inch.

Absolute Pressure Scale Since the weight of atmosphere is based on altitude at sea level, any increase in land height will have a corresponding decrease in atmospheric pressure.

Vacuum Pressure Scale Vacuum is any pressure below “atmospheric” conditions.

How Vacuum is Measured Vacuum is measured on a gauge calibrated in inches of mercury so it matches the barometer scale.

Pressure Gages and Design Plunger design Bourdon tube design