Emerson Copeland Scroll, Introduction Manual

Page: 41 / 52

37 38
Figure 6: Tubing recommendation
Compressors Ident Number Characteristics Drawing
ZB15K* to ZB45K*
ZF09K* to ZF18K*
ZF13KVE to ZF18KVE
ZS21K* to ZS45K*
8030450
527-0157-00
60-70
Durometer
ZB56K* to ZB11M*
ZF24K* to ZF48K*
ZF24KVE to ZF48KVE
ZS56K* to ZS11M*
8522911
527-0168-00
Variation = 8516741
Hard
steel
6. Tubing and mounting considerations
6.1 Starting pulse
The standard mount for the scroll compressor is a soft rubber mount. It is designed to transmit the lowest possible disturbance
to the mounting frame. Because of the flexibility of this mount, it is essential that tubing to each compressor be designed to
accommodate the movement which will occur, particularly upon start-up.
The three phase motors used in the refrigeration scroll compressors exhibit a high starting torque characteristic. The reaction of
the stator is directly on the shell because there are no internal spring mounts. This reaction causes easily observable movement of
the shell when the standard mounts are used and this is normal. However, if the suction and discharge tubing of the compressor is
closely clamped to the frame or linked to another compressor, the tubing will restrain the movement and the motor reaction force
will be taken by the tubing. This may cause excessive stress and premature failure of tubing joints.
6.2 Resonance
The discharge pulse can in some configurations give rise to resonance of tubing. It is advisable to avoid a natural frequency of
between 45 and 55 Hz for the section of tubing between the compressor and the first clamp. It is often not possible to determine
this in advance but in the unlikely event of a resonance problem arising a change in tube configuration will usually resolve it.
6.3 Recommendations for tubing and mounting
Always allow some flexibility in the tubing to the suction and discharge connections. If the standard mounts are used there should
be at least two bends and a vertical section before the tube joins a header. Test the finished assembly by rocking the compressor on
its mounts. Vibration eliminators may be used but are not essential if the tubing has sufficient flexibility. Vibration eliminators should
be fitted in the vertical plane.
An alternative harder mount as detailed in Figure 7 is recommended. This will allow more loads to be transmitted via the feet,
and the very small additional vibration transmission is not usually a problem in refrigeration applications. It is still advisable to
incorporate a vertical section of tube between the compressor and the first rigid mount. This will give flexibility and minimise the
risk of resonance.