ISO 12238 pdf download – Pneumatic fluid power一Directional control valves一Measurement of shifting time

ISO 12238 pdf download – Pneumatic fluid power一Directional control valves一Measurement of shifting time.
5.3 Pressure transducers
5.3.1 Install a pressure transducer directly into each outlet port to be tested, as well as into the inlet pressure measuring tube.
5.3.2 When a pneumatically-operated valve is tested, mount the control pressure transducer into the pilot pressure measuring tube.
5.3.3 Use pressure transducers, amplifiers and recording devices that together have a system frequency response of within —3,0 dB at 2 000 Hz and a reference time to a known base resolvable to less than 0,1 ms.
5.3.4 Changes in the shifting time caused by limitation of the negative voltage peaks due to the test equipment should not exceed 0,1 ms.
5.4 Supply reservoir
5.4.1 Use a supply reservoir of sufficient capacity so that the pressure drop in the flow tube during the test does not exceed 3 % of the supply pressure. A larger pressure drop is permissible but will increase the shifting time and result in a less favourable rating for the product under test. Connections from the supply reservoir should be several times larger than the pressure measuring tube and as short as possible. to minimize the pressure drop.
5.4.2 Use a supply reservoir that provides for measuring of the internal air temperature of the reservoir.
5.4.3 Locate the optional shut-off valve, and the control valve when applicable, as close as possible to the reservoir outlet. Use a valve whose flow area is larger than that of the pressure measuring tube, because a smaller valve can restrict flow and increase shifting time.
5.5 Control signal
5.5.1 For solenoid pilot-operated valves (see Figure 1). maintain pilot supply pressure at either the pressure supplied to the valve or the maximum rated pilot supply pressure, whichever is less.
5.5.2 For a.c. solenoid-operated valves, generate the control signal with a trigger device set to trigger at the zero voltage crossover point. Maintain voltage to within + 5 % of the rated voltage.
5.5.3 For d.c. solenoid-operated valves, maintain steady-state voltage to within ± 5 % of the rated voltage.
5.5.4 For pcieumatically-operated valves (see Figure 2). maintain the pilot pressure at the same pressure as in the
supply reservoir or at the maximum permitted pilot pressure, whichever is less.
5.6 Data recording system
During a test run, record the pressure variations with time for all transducers in the system. Figure 3 gives exampies of how data from an analogue recorder would appear. Other data recording techniques, including digital methods, which do not produce data in this form, may be used.
time lapse between the initiation point of an operation and its point of completion, these points being defined for each type of component
4.0.7.1
valve response time
the initial point is the moment when the pilot pressure rises/tails past a given point; the completion point is when a given value of the outlet pressure or flow has been reached
4.0.7.1.1
dead time of a pneumatic directional control valve with pneumatic control
the initial point is the moment when the pilot pressure riseslfalls past a given level; the completion point is the moment when the outlet pressure reaches a specified percentage of its maximum, the outlet being connected to zero capacity (outlet port closed)
4.0.7.1.2
dead time of a pneumatic directional control valve with electrical control
the initial point is the opening (or closing) of the electrical circuit; the completion point is the moment when the outlet pressure reaches a specified percentage ot its maximum, the outlet being connected to zero capacity (outlet port closed)
4.0.7.1.3
switching time
switch-on time for an output going from the 0-state to the 1-state; switch-off time for an output going from the 1-state to the 0-state
4.0.8.1
switching pressure
minimum pilot pressure necessary to cause a change of state at an output port
4.0.8.2
switching time
time the initial point is the moment when the control or pilot pressure reaches the level of switching pressure; the completion point is when a given value of the outlet pressure has been reached
A.2 From CETOP RP111P – 1989-11-01
3.1.3
switching threshold
the joint effect of two limiting values, rising or falling, on the one hand the signal pressure and on the other signal voltage, which causes or allows switching
switching time
the complete transition from an initial to a final state under the normal operating conditions foreseen by the manufacturer (no oscillations, correct sealing, normal flow values, etc.).