USPS 955 Practice EXAM (LATEST 2026) || MOST RECENT
EXAM ACTUAL COMPLETE REAL EXAM QUESTIONS AND
CORRECT ANSWERS (VERIFIED ANSWERS) ALREADY
GRADED A+ | NEWEST EXAM | JUST RELEASED!!!
Screw-type joints
There are external threads on the ends of pipes and internal
threads in the joint fittings. These are connected by screwing
the pipe into the fitting. Generally, a tapered thread is used for
piping, which makes the joint seal itself sufficiently. Even
though high-precision tapered threads can achieve a good seal,
sealing cement or sealing tape is used for a much better
connection.
Flange joints
A flange is formed or welded at the end of a pipe and is then
connected to the flat surface of another flange. Flanges are
usually welded to
piping but sometimes brazing or bolts are used. Since flange
joints can be easily connected or disconnected and sealed with a
gasket, they are commonly used for piping around compressors
and very large diameter pipes.
,Directional-Control Valve
Directional control valves ensure the flow of air between air ports
by opening, closing and switching their internal connections. Their
classification is determined by the number of ports, the number of
switching positions, the normal position of the valve and its
method of operation. Common types of directional control valves
include 2/2, 3/2, 5/2, etc. The first number represents the
number of ports; the second
number represents the number of positions.
Two-Way Directional Valve:
A two-way directional valve consists of two ports connected to
each other with passages which are connected and
disconnected. In one
extreme spool position, port A is open to port B; the flow path
through the valve is open. At the other extreme, the large
diameter of the spool closes the path between A and B; the
flow path is blocked. A two way directional valve provides an
on-off function.
,Three-Way Directional Valve
A three-way directional valve consists of three ports connected
through passages within a valve body that are shown here as port
A, port P, and port Ex. If port A is connected to an actuator, port
P to a source of
pressure and port Ex is open to exhaust, the valve will control
the flow of air to (and exhaust from) Port A. The function of this
valve is to
pressurize and exhaust one actuator port. When the spool of a
three-way valve is in one extreme position, the pressure
passage is connected with the actuator passage.
, Four-Way Directional Valve
Perhaps the most common directional valve in simple pneumatic
systems consists of a pressure port, two actuator ports, and one
or more exhaust ports. These valves are known as "four-way
valves" since they
have four distinct flow paths or "ways" within the valve body. A
common application of the four-ported four-way directional
valve is to cause reversible motion of a cylinder or motor. To
perform this function, the
spool connects the pressure port with one actuator port. At the
same time, the spool connects the other actuator port with the
exhaust port. This is a four-ported four-way valve.
Five-Port / Four-Way Directional Valve
Four-way valves are also available with five external ports, one
pressure port, two actuator ports, and two exhaust ports. Such
valves provide the same basic control of flow paths as the four-
ported version but have
individual exhaust ports. In the fluid power field, this is
referred to as a "five-ported, four-way valve." This type of
valve brings all flow paths to individual external ports. The
pressure port is connected to system
pressure after a regulator. Actuator ports are connected to inlet
and
outlet ports of a cylinder or motor. Each exhaust port serves an
actuator port.
EXAM ACTUAL COMPLETE REAL EXAM QUESTIONS AND
CORRECT ANSWERS (VERIFIED ANSWERS) ALREADY
GRADED A+ | NEWEST EXAM | JUST RELEASED!!!
Screw-type joints
There are external threads on the ends of pipes and internal
threads in the joint fittings. These are connected by screwing
the pipe into the fitting. Generally, a tapered thread is used for
piping, which makes the joint seal itself sufficiently. Even
though high-precision tapered threads can achieve a good seal,
sealing cement or sealing tape is used for a much better
connection.
Flange joints
A flange is formed or welded at the end of a pipe and is then
connected to the flat surface of another flange. Flanges are
usually welded to
piping but sometimes brazing or bolts are used. Since flange
joints can be easily connected or disconnected and sealed with a
gasket, they are commonly used for piping around compressors
and very large diameter pipes.
,Directional-Control Valve
Directional control valves ensure the flow of air between air ports
by opening, closing and switching their internal connections. Their
classification is determined by the number of ports, the number of
switching positions, the normal position of the valve and its
method of operation. Common types of directional control valves
include 2/2, 3/2, 5/2, etc. The first number represents the
number of ports; the second
number represents the number of positions.
Two-Way Directional Valve:
A two-way directional valve consists of two ports connected to
each other with passages which are connected and
disconnected. In one
extreme spool position, port A is open to port B; the flow path
through the valve is open. At the other extreme, the large
diameter of the spool closes the path between A and B; the
flow path is blocked. A two way directional valve provides an
on-off function.
,Three-Way Directional Valve
A three-way directional valve consists of three ports connected
through passages within a valve body that are shown here as port
A, port P, and port Ex. If port A is connected to an actuator, port
P to a source of
pressure and port Ex is open to exhaust, the valve will control
the flow of air to (and exhaust from) Port A. The function of this
valve is to
pressurize and exhaust one actuator port. When the spool of a
three-way valve is in one extreme position, the pressure
passage is connected with the actuator passage.
, Four-Way Directional Valve
Perhaps the most common directional valve in simple pneumatic
systems consists of a pressure port, two actuator ports, and one
or more exhaust ports. These valves are known as "four-way
valves" since they
have four distinct flow paths or "ways" within the valve body. A
common application of the four-ported four-way directional
valve is to cause reversible motion of a cylinder or motor. To
perform this function, the
spool connects the pressure port with one actuator port. At the
same time, the spool connects the other actuator port with the
exhaust port. This is a four-ported four-way valve.
Five-Port / Four-Way Directional Valve
Four-way valves are also available with five external ports, one
pressure port, two actuator ports, and two exhaust ports. Such
valves provide the same basic control of flow paths as the four-
ported version but have
individual exhaust ports. In the fluid power field, this is
referred to as a "five-ported, four-way valve." This type of
valve brings all flow paths to individual external ports. The
pressure port is connected to system
pressure after a regulator. Actuator ports are connected to inlet
and
outlet ports of a cylinder or motor. Each exhaust port serves an
actuator port.
