Edwards ATEX 1 EHR, Instruction Manual

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A750-04-880 Issue F
Page 30 © Edwards Limited 2012. All rights reserved.
Edwards and the Edwards logo are trademarks of Edwards Limited.
OPERATION
7. Slowly open the flow regulating valve (12) until the required sealing liquid flow rate is obtained. Refer to
Tables 6 and 7 . Edwards recommend that a flow meter is installed.
4.3 Cavitation and fluid hammer
Under cavitation conditions, the pump will be unusually noisy during operation. Cavitation conditions occur when the
process inlet pressure is close to the vapour pressure of the sealing liquid (see
Section 2.6 ), and can result from:

Operation of the pump with an insufficient non-condensable gas load. (For example, operation of a pump
which is over-sized for the application, or operation of the pump when an isolation valve in the process inlet
pipeline is closed).

Operation of the pump with insufficient sealing liquid in the pump.

Operation of the pump with the sealing liquid supply temperature too high.
However, the pump may also be unusually noisy during operation due to fluid hammer. Fluid hammer is a pressure
surge or wave resulting when a fluid in motion is forced to stop or change direction suddenly. This can occur when
the flow rate of sealing liquid into the pump is too high.
Refer to Figure 1 . If the pump is unusually noisy during operation, slowly close the sealing liquid supply flow
regulating valve (12):

If the pump quietens down, the noise was due to fluid hammer. You can now continue to operate the pump
as normal.

If the pump continues to operate noisily, or if the noise level increases, the pump is operating under
cavitation conditions:
Immediately shut down the pump (refer to Section 4.4 ). Do not continue to operate the pump, or it may be
severely damaged.
4.4 Shut-down
1. Refer to Figure 1 . Fully close the sealing liquid supply valve (16).
2. Close any isolation valves in the process inlet pipeline.
3. Immediately stop the pump.
4. Close any isolation valves in the process outlet pipeline.
5. On ATEX Category 1 and 2 pumps configured for external seals flush supplies only: close the seals flush supply
valve (2).
WARNING
Do not operate the pump without sealing liquid in the pump. If you do, there may be a risk of
explosion.
WARNING
Ensure that it is safe to shut down the pump before you use the following procedure.