YOKOGAWA vigilantplant DM8, User Manual

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<4. OPERATION>
4-7
IM 12T03A01-02E
4.3 Preparation for Measurement
4.3.1 Check for Piping
Check the following points.
• Is the pressure difference 100 kPa or more between both sampling tap?
• Is the diameter of the sampling pipe appropriate? Is length of the inlet pipe too long?
(Note): The sample inlet pipe is usually JIS 15A or Sch 40 to 80 stainless steel pipe.The pipe length between sampling tap and the
detector should be 10 m or less.
• Are valves and meters (pressure gauge, thermometer) provided in the sampling pipe for
normal operation and maintenance?
• Is air for cleaning the detector provided?
(Note): Dried 0.3 to 0.5 MPa G air is requires for cleaning the detector.
• Can heating steam for the density detector be stopped during operating time?
4.3.2 Check for Wiring
Check that whole wiring of the measuring system including a receiving unit (for example,
recorder) is completed.
When the detector is explosion-proof type, place the terminal box cover as completely as before
if it is once released.
4.3.3 Measuring Liquid Flow
Operating procedure for introducing sampling liquid is explained here, assuming the piping in
Figure 3.5 in Section 3.1.2 is equipped. When pipe arrangement is different from that of Figure
3.5, carry out corresponding operations described here. It is important that air bubble does not
remain in the pipe.
If calibrating is to be made with standard solution, conduct the measuring liquid after calibration
work to omit cleaning the vibrator. However, if pressure compensation is to be made (see Section
4.3.6), conduct the measuring liquid to obtain compensation value beforehand.
(1) First, set each valve in the sampling unit as follows.
Ball valve “BV1”: Fully closed
Needle valve “NV1”: Fully closed
Needle valve “NV2”: Fully closed
Needle valve “NV3”: Fully closed
Needle valve “NV4”: Fully closed
* ‘Stop’ valve “V1” *: Fully closed
* ‘Stop’ valve “V2” *: Fully closed
(Note): V1 and V2 marked by * are used only for steam tracer.
(2) For the sampling conduit with the steam tracing pipe, open the steam main valve to heat the
sampling conduit.
Keep the ‘stop’ valve “V1” closed, not heat the detector if it is not remarkably cooled.
(3) Prepare a sample receptacle (liquid pan) just under the ‘drain’ valve provided in the sample
conduit. First, fully open the ‘drain’ valve, then gradually open the ‘tap’ valve.
When the sample liquid begins to flow out of the drain valve, close the ‘tap’ valve.
(4) The same procedure as (3) should be made for the sample return conduit. Prepare a
sample receptacle (liquid pan) just under the drain valve. First, fully open the ‘drain’ valve,
then gradually open the ‘stop’ valve. When the sample liquid begins to flow out of the ‘drain’
valve, close the ‘stop’ valve.
5th Edition : Dec. 11, 2015-00