© Edwards Limited 2009. All rights reserved.
Page 55
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Operation
B800-00-880 Issue A
Note:
If you are using the Controller to control a TAV solenoid valve, there is a 2-second delay between either a
Stop command being received or a fault condition being detected and the vent valve opening. This delay
allows time for gauges, valves and other equipment to be switched off before venting occurs.
The green indicator LED on the Controller will extinguish as rotational speed drops below Normal speed. At very low
speeds you will see the yellow indicator LED flashing – it will extinguish when the pump has stopped.
4.9
Operation at extreme conditions
4.9.1
Operation with high inlet pressure
If the nEXT pump inlet pressure rises, the power supplied to the pump-motor will increase to counteract the gas
frictional load. The pump rotational speed will remain constant until the peak power level is reached; beyond this
level, the speed of the pump will start to reduce.
If the pump speed falls to below 50% of full rotational speed, the Timer will start if it is enabled. If the speed does
not recover to above 50% speed before the timeout period expires, the pump will shut down and display a Fail signal.
If the Timer is disabled, the pump will immediately shutdown and display a Fail signal if the speed drops below 50%
of full rotational speed. Refer to
for the maximum power delivered to the pump and to
Table 4
, for
maximum allowable inlet pressure.
4.9.2
Operation at high temperatures
Temperature sensors within the pump mechanism and electronics are monitored by an internal system. If the system
detects that any internal temperatures are too high, the power supplied to the pump-motor is reduced; the pump
may not therefore be able to maintain full rotational speed if it is too hot.
If the pump speed falls to below 50% of full rotational speed, the Timer will start if it is enabled. If the speed does
not recover to above 50% speed before the timeout period expires, the pump will shut down and display a Fail signal.
If the Timer is disabled, the pump will immediately shutdown and display a Fail signal if the speed drops below 50%
of full rotational speed. Refer to
for pump operating ranges and
for advice on pump-cooling.
4.9.3
Operation at over-speed
Control software within the Controller regulates the pump rotational speed and prevents the pump operating above
its normal full rotational speed. In the unlikely event of a failure of this control software, the Controller has a built-
in safety circuit that checks whether the pump is running at over-speed. If an over-speed condition is detected, the
Controller automatically shuts down power to the pump-motor and slows it down to rest. The Controller will signal
a Fail condition if over-speed has been detected.
If you suspect that your pump may be running at over-speed you should switch it off and consult Edwards or your
supplier.
4.9.4
Electrical supply failure
WARNING
If the power supply fails when the pump is running, the impeller could continue to spin for
approximately 30 minutes. The control circuit may not give any indication that the impeller is still
running.
WARNING
If the parallel start control signal on the logic interface connector is set to start, the pump may
automatically restart when the electrical supply is restored after an electrical supply failure.
Ensure that people cannot be injured by the rotating blades of the pump.
Summary of Contents for nEXT240
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