1ST FAA

1. A fluid, by definition, is any substance that is able to flow if it is not in some way confined or restricted. _____ and ____ are both classified as fluids, and often act in a very similar way.

 

1. Liquids

2. gases__

1. One significant difference comes into play when a force is applied to these fluids. In this case, liquids tend to be ______ and gases are highly __________

1. incompressible

2. compressible_.

1. A solid body submerged in a liquid or a gas weighs less than when weighed in free space. This is because of the upward force, called ________., which any fluid exerts on a body submerged in it.

1. Bouyant force.

1. When will an object float?

If the upward force of the fluid is greater than the weight of the object.

1. The pressure exerted on the bottom of a container by a liquid is determined by the _____. of the liquid and not by the _______. of the container.

1. height_

2. shape_

1. Pressure based on the column height of a fluid is known as:

Static pressure

1. When a fluid is in motion, and its velocity is converted to pressure, what pressure is it known as?

Ram

1. What is total pressure?

It is the sum of ram pressure and static pressure.

Pressure set up in a fluid acts _______. in all directions. This pressure acts at ______ . to containing surfaces

equally

right angles

1. What is the Pascal’s law formula?

Force=pressure x area

he purpose of a hydraulic system is to generate a ______. output force, with a _____ input force.

large

less.

1. Since work is equal to force times distance, if we gain   _____ with a hydraulic system, we must lose  ______.

1. force_.

2. distance

1. Seals are used to prevent fluid from __________, as well as to keep ____. and ____. out of the system in which they are used.

1. passing a certain point.

2. air

3. dirt

No one style or type of seal is satisfactory for all installations. Some of the reasons for this are:

: (1) pressure at which the system operates, (2) the type fluid used in the system, (3) the metal finish and the clearance between adjacent parts, and (4) the type motion (rotary or reciprocating), if any.

1. Seals are divided into three main classes:

1) packings, (2) gaskets, and (3) wipers.

1. They can be referred to as running seals, what does this mean?

It means that these seals that are used in units that contains moving parts.

 

1. Packings are made in the form of:

O-rings, V-rings, and U-rings

1. What two types of leakage do O-rings prevent?

Prevent both internal and external leakage.

1. What is used with O-rings above 1500 psi to prevent extrusion?

Backup rings

1. When an O-ring packing is subjected to pressure from both sides, what must be used?

two backup rings must be used (one on either side of the O-ring).

When an O-ring is subject to pressure on only one side, what side is the single backup ring installed?

In this case, the backup ring is always placed on the side of the O-ring away from the pressure.

1. An O-ring designed specifically for use as a static (stationary) seal probably will not do the job when installed on a  _______

1. moving part__.

An O-ring is useless if it is not compatible with the  ________. and __________

system fluid_

operating temperature_

Hydraulic O-rings were originally established under ______.  specification numbers

The standard specification numbers now replacing these is the _______. series.

AN

MS28775

1. Is the colour coding a reliable or complete means of identification?(O-RING)

No

1. Because of the difficulties with colour coding, O-rings are available in ___________. labelled with all pertinent data.

 

1. individual hermetically sealed envelopes

When selecting an O-ring for installation, what is the most reliable identification?

the basic part number on the sealed envelope

1. O-rings should be rejected for  _______. that will affect their _________.

1. flaws

2. performance_

1. What power magnifier do some manufactures recommend using to inspect O-rings?

4 power magnifying

1. How can I inspect the inner diameter of an O-ring?

By rolling the ring on an inspection cone or dowel

1. What will help to reveal some defects not otherwise visible when the ring is rolled inside out?

The slight stretching of the ring

1. Backup rings are made of ________. They do not deteriorate with ______., are unaffected by any _______. or ______. and can tolerate _________. extremes in excess of those encountered in high pressure hydraulic systems.

1. Teflon™

2. age

3. system fluid_

4. vapor

5. temperature

1. What do their dash numbers indicate?

Their size and to the dash number of the O-ring for which they are dimensionally suited.

1. How can a backup ring be positively identified?

It can be identified from the package labels

1. The inspection of backup rings should include a check to:

ensure that surfaces are free from irregularities, that the edges are clean cut and sharp, and that scarf cuts are parallel.

1. When checking Teflon™ spiral backup rings, what should you make sure?

make sure that the coils do not separate more than 1⁄4 inch when unrestrained.

V-ring packings are ______ seals and are always installed with the open end of the “V” facing the _______

One way

pressure

1. What must be either side of a V-ring packing?

V-ring packings must have a male and female adapter to hold them in the proper position after installation.

What is also necessary during installation of a V-Ring seal or the seal may not give satisfactory service?

It is also necessary to torque the seal retainer to the value specified by the manufacturer of the component being serviced

1. The U-ring will seal pressure in _________.; therefore, the lip of the packing’s must face ________the pressure.

 

1. only one direction

2. toward.

1. What type of pressure are U-ring packing’s used in?

low pressure packings to be used with pressures of less than 1,000 psi.

1. Gaskets are used as static (stationary) seals between two flat surfaces. Some of the more common gasket materials are:

asbestos, copper, cork, and rubber.

1. Gaskets are used in fluids systems around the ________. of actuating cylinders, valves, and other units.

1. end caps

The gasket generally used for this purpose is in the shape of an _____

O-ring.

1. What are wipers used for?

Wipers are used to clean and lubricate the exposed portions of piston shafts.

What do wipers prevent?

They prevent dirt from entering the system and help protect the piston shaft against scoring.

What material are wipers made from?

Metallic or felt

If both material types are used together how are they installed?

a felt wiper installed behind a metallic wiper.

1. What is the purpose of a seal?

Seals are used to prevent fluid from passing a certain point, as well as to keep air and dirt out of the system in which they are used.

To withstand pressurization by air, to prevent leakage of fuel, to prevent passage of fumes, or to prevent corrosion by sealing against the weather.

1. Prior installation what must be done to a seal?

No one style or type of seal is satisfactory for all installations. (not sure)

1. How are gaskets used?

used as static (stationary) seals between two flat surfaces.

1. What are common gasket materials?

common gasket materials are asbestos, copper, cork, and rubber