GE Masoneilan 4700E, Maintenance Manual

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Masoneilan 4700P/E & 4800P/E Positioners Manual =
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WARNING
When a valve (because of high pressure drop) uses a supply
pressure higher than 20 psig, the 3-15 psig instrument signal may
not be sufficient to operate the valve when the positioner is
bypassed. Moreover, if the positioner with a high supply pressure
is bypassed suddenly, the high pressure in the actuator may
damage the diaphragm and/or the control instrument. Therefore,
the bypass valve should be used only if the positioner supply
pressure is 20 psig (140 kPa or 1, 4 bar), or at most 35 psig (240
kPa, or 2, 4 bar), or if the controller is capable of operating the
valve directly. When bypassing a positioner, ensure that the
controller output is equal to supply required to operate valve.