Yokogawa RAKD - Manual (Page 25)

<6. SERVICE>
6-1
IM 01R01B30-00E-E 5th edition January 01, 2013 -00 All Rights Reserved. Copyright © 2003, Rota Yokogawa
6. Service
6.1.1 Function test
Checking free movement of pointer:
- Remove housing cover (4 screws).
- After deflecting the pointer by hand, it must return to measurement value. If the pointer pivots to different
values upon repeated deflections, there is too much friction in the bearings. In this case, send indication unit
to service.
Checking free movement of float:
- First, free movement of pointer has to be ascertained.
- Check visually if pointer follows each flow rate change. If not, clean float and measuring tube.
Unit with electronic transmitter:
- Without flow, the output current must be 4 mA. At a flow rate of 100% the current must be 20 mA.
If only the pointer is moved to 100%, the current may not exeed 17mA.
6.1.2 Measuring tube, float
The Rotameter does not normally require any maintenance. However cleaning is necessary if the measuring
cone or flat has been contaminated by the process. To clean, the Rotameter must be removed from the
pipeline.
For all kind of intervention in the Rotameter like tightening the packing of the valve the pressures in pressurized
pipelines has to be reduced. Take care that the counter screw is tighten after screwing the valve.
Disassembling the tube
Please perform the following steps to clean the measuring tube and the float:
• Disassemble the Rotameter from the pipe
• Unscrew hollowed top threaded bolt (6) (for cone 31 – 43)
resp. remove top snap ring and socket (for cone 44 – 51)
resp. only top snap ring (for cone 52 – 53)
• Remove top float stop (3)
• Disassemble float – Attention: Do not bend the float
• For version with valve in the inlet remove first the top head pipe plug (8)
• For version with valve in the outlet remove first the lower head pipe plug;
in that case the disassembling of all parts start from down to top
• Cleaning of metering tube and float
• To clean the valve loose screw nut (10) in the head. Afterwards you can unscrew spindle (12) with PTFE
packing box plus thrust collar (9)
Please don’t expose the float to any strong magnetic alternating fields. The floating body and particularly
its measuring edge may not be damaged.
Assembling the tube
Mounting starts in opposite sequence.
Assembling the float take care that the lower guide bar of the float is fixed in the middle boring of the lower
stop. The guide bar should not be bended.
IMPORTANT
6.1 Maintenance