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/
3
-Port Solenoid Valves
Precautions 1
Be sure to read this before handling products.
Design/Selection
Warning
1. Confirm the specifications.
Products represented in this catalog are designed only for use
in compressed air systems (including vacuum).
Do not operate at pressures, temperatures, etc., beyond the
range of specifications, as this can cause damage or malfunc-
tion. (Refer to the specifications.)
Please contact SMC when using a fluid other than
compressed air (including vacuum).
We do not guarantee against any damage if the product is
used outside of the specification range.
2. Actuator drive
When an actuator, such as a cylinder, is to be driven using a
valve, take appropriate measures (such as the installation of a
cover or the restricting of access to the product) to prevent
potential danger caused by actuator operation.
3.
4.
5.
Holding pressure (including vacuum)
Since valves are subject to air leakage, they cannot be used
for applications such as holding pressure (including vacuum)
in a pressure vessel.
6.
Not suitable for use as an emergency shut-
off valve, etc.
The valves listed in this catalog are not designed for safety
applications such as an emergency shutoff valve. If the valves
are used in such applications, additional safety measures
should be adopted.
7.
Release of residual pressure
For maintenance and inspection purposes install a system for
releasing residual pressure.
8.
Ventilation
Provide ventilation when using a valve in a confined area,
such as in a closed control panel. For example, install a
ventilation opening, etc., in order to prevent pressure from
increasing inside of the confined area and to release the heat
generated by the valve.
Do not disassemble the product or make any
modifications, including additional machin-
ing.
Doing so may cause human injury and/or an accident.
Resumption after a long period of holding
time
When resuming operation after a long period of holding time,
there are cases in which, regardless of whether the product is
in an ON or OFF state, there is a delay in the initial response
time due to adhesion. Conducting several cycles of running-in
operation will solve this problem. Please consider implement-
ing this before resumption.
-4-
Caution
1.
2.
Leakage voltage
3.
Valves with a power-saving circuit (PWM circuit
built-in type)
Valves with a power-saving circuit (PWM circuit built-in type)
perform the high-speed switching operation with the PWM
control circuit inside the valve after the rated power has been
applied for several tens of ms to reduce the power consump
-
tion. The problems shown below may occur in this type of
valve due to the switch or drive circuit system by the PWM
control. Be sure to check the operation with the customer’s
machine sufficiently when selecting the product.
1) The valve does not turn ON.
1. If the PWM circuit built-in type valve is driven by a
mechanical relay, etc., and chattering occurs during the
several tens of ms necessary for the valve to reach its
rated voltage, the valve may not turn ON correctly.
2. If a filter, etc., is connected between the power supply
and the PWM circuit built-in type valve, the current
necessary to drive the valve lowers due to the effects of
the filter, and then the valve may not turn ON correctly.
R
SOL.
OFF
Switching element
C
P
ow
er
supply
Leakage v
oltage
Leakage current
2) The valve does not turn OFF.
If the PWM circuit built-in type valve is driven by the photo
coupler, the photo coupler cannot turn OFF and the valve is
kept in an ON state. Therefore, take great care when using
the photo coupler built-in SSR (solid state relay) or drive
circuit.
Surge voltage suppressor
1)
I
f an overvoltage or overcurrent is received from an external
peripheral device, the surge voltage protection element inside
the valve is overloaded, causing the element to break. In the
worst case, the breakage causes the electric circuit to enter
short-circuit status. If energizing continues while in this state, a
large current flows. This may cause secondary damage to the
output circuit, external peripheral device, or valve, and may
also
cause a fire. So, take appropriate protective measures,
such as
the installation of an overcurrent protection circuit in
the power
supply or a drive circuit to maintain a sufficient level
of safety.
2) If a surge protection circuit contains nonstandard diodes,
such as Zener diodes or varistor, a residual voltage that is
in proportion to the protective circuit and the rated voltage
will remain. Therefore, take into consideration the surge
voltage protection of the controller.
In the case of diodes, the residual voltage is approximately 1
V.
Take note that the leakage voltage will increase when a
resistor is used in parallel with a switching element or when a
C-R circuit (surge voltage suppressor) is used for protecting a
switching device because of the leakage voltage passing
through the C-R circuit. The suppressor residual leakage
voltage should be as follows.
Keep it at 2% or less of the rated voltage.