week 4 pneumatics Flashcards
flared fittings are not used where in pneumatics?
where vibration is present.
how do you tighten a flare nut?
finger tight, then for nuts under 5/8 use a flare tubing wrench for a 1/4 turn and over 5/8 diameter use 1/8 of a turn.
how do you tighten flareless fittings?
hand tight then 1/6 to 1/3 more with a wrench.
true or false use the bursting pressure to select a hose
false, always use the working pressure.
how are pressures measured for pressure hoses?
standard in psi, metric in MPA. mega pascals 1 MPA = 145 psi
how are vacuum hoses rated?
inches of mercury
how is hose size measured?
by inside diameter, which determines the velocityof the fluid that flows through it.
on what is the diameter of tubing based?
the outside diameter
which type of tubing is best suited to flared fittings?
thin walled tube
which type of tubing are flareless fittings most suited for?
thick wall tube
how is the wall thickness of tubing specified in the imperial system?
the wall thickness is in thousandths of an inch.
what is the most important property of the material of the inner tube in a hose?
compatibility with the fluid
which part of a hose determines its pressure rating?
the reinforcing
which type of hose should should you use on the inlet to a pump?
vacuum hose
what does a excess flow valve do?
the valve is normally open, but excess flow surges push the poppet against a spring, causing flow to be cut off.
what is the purpose of the safety relief valve?
to bleed off excess system pressure before it becomes to extreme.
possible causes of why an actuator cylinder is drifting…
the piston seal is leaking.
the operating valve is leaking.
the lines are leaking.
possible reasons why the cylinder is sticking or binding
the packing on the cylinder rod is over-tighten.
the cylinder is misaligned.
the seals are defective.
the pilot pressure is low.
possible causes why the cylinder body deal is leaking
the tie rods are loose.
the pressure at the cylinder is excessive.
the cylinder body seal is pinched or extruded.
possible causes why the rod gland seal is leaking
the seal is deteriorating
possible causes why a pneumatic valve is blowing to exhaust when actuated.
the valves seals are faulty.
the valve-to-base gasket is faulty.
the spool is damaged
possible cause why a pneumatic valve is blowing to exhaust when not actuated
the inlet poppet is not sealing.
possible causes why the pilot section is blowing exhaust
the pilot cover is loose.
the poopet is not sealing
possible cause why the poppet is chattering
the air supply pressure is too low.
the pilot pressure or signal pressure is too low.
in pneumatic systems environmental pollution occurs in what two forms mostly?
noise and oil mists
in operating pneumatic cylinders under clamping conditions the system should be designed to avoid accidental operation through the use of what
control interlocks or manually operated switching devices with protective covers
to avoid hand injuries caused by pneumatic clamping conditions what precautions should you use
pressure transducers or sequence valves to ensure the second operation does not occur until the clamping is confirmed.
where should air intake occur on a pnuematic system?
coolest place possible
air recievers are classified as
unfired pressure vessel
what must a pressure vessel have
gauge, drain, safety relief valve, fusible plug,
air reservoirs have two functions, what are they
first to accommodate any fluctuations in the system’s supply. this dampens pulsations and creates a steady pressure to the system.
second to reduce the velocity of the air, this allows moisture to settle out.
what are the three most common piping systems for compressor systems?
the grid (dead end or trunk), the decentralized, the loop system.
if an FRL is installed backwards what would happen?
the lubber would clog the regulator and the filter would remove the oil
all air hoses larger than what should be equipped with excess flow vavles to limit pressure in the event of fitting or hose failures.
1/2 inch
Name three factors to affect control of speed in pneumatic systems
Uniformity of the applied load Friction forces Acceleration forces
Name an example of 2/2 valve?
Air tools trigger.
Name an example where 3/2 valves are used?
Single acting cylinder
Name what examples a 4/2 dcv is used in
Reversible motion of a cylinder
What are 4/3 valves used in?
Reversible motion cylinder with a center position, that always a float or exhaust to happen in the center position.
What is the difference between the operation of a 4/2 dcv and a 5/2 valve
The dcv on a 5/2 allows exhaust.
5/3 dcv have what common center positions?
Block, exhaust, pressure, tandem.
Explain shuttle valve
A shuttle moves back and forth to allow flow in one Direction compared to the pressure highest.
Name three type of flow control valves?
Ball, globe, needle. Needle being the most common.
What are causes of low air pressure in the receiver?
Leaky compressor valves, stuck piston rings, faulty unloading valve, break in the line.
You have excessive air pressure in the receiver what could cause this?
Faulty unloading valve, faulty safety valve.
Your pneumatic circuit has low air pressure why
Pressure regulator sweet too low Damaged line
Your pneumatic circuit has excessive pressure why?
Pressure regulator set too high
Your pneumatic circuit has sticky valves why?
Excessive carbon deposits on the valve components, insufficient lubrication, valve packing to tight.
Your pneumatic circuit has incorrect delivery of lubrication why?
Excessive oil discharge, no oil discharge.
Your pneumatic circuit has a cylinder moving inconsistently why
Scored piston or liner, bent piston rod, damaged piston seals, insufficient air pressure
Your pneumatic circuit has a motor moving inconsistently why
Scored rotor casing, worn bearing, insufficient air pressure.
Name three devices to measure vacuum
Barometer, manometer, bourdon tubes.
name four ways to contol maximum pressure
unloading devices, throttling the air intake, using variable speed drive, using a pressure switch.
in a fingers unloading device the finger is control by what
the pilot air provided the compressor output
when using a variable speed drive such as a gas or diesel engine power unit your doe this control maxiumum pressure from the compressor?
by having the centrifugal clutch disengaging, allowing the engine to run at low rpm with no load.
oil is not add to the compressor intake air why
because the overheating of the oil would take away the lub properties.
what is this symbol?
lubricator
what is this symbol?
cooler