Brooks Instrument BM02 - Manual (Page 18)

3-2
Installation and Operation Manual
X-PD-BM01-02-eng
Part Number: 541B042AHG
March, 2008
Brooks ® Models BM01 and BM02
Operation
3-3 Pulse Generator Principle of Operation (See Figure 3-1)
A magnet is installed in one end of oval gear “A”. As this magnet passes by
the metal contacts of the reed switch or MR Sensor contained in the cover,
it will cause the switch to close. Each time the reed switch or MR Sensor
closes, it completes the circuit representing one pulse to the counting circuit.
3-4 Operating Instructions
At initial operation, carefully operate in the following sequence, allowing the
flow within the flow range specified. (Refer to Figures 2-3 and 2-4).
1. Shut off the valve (A) on the inlet side and the valve (B) on the outlet
side and then open the bypass line valve (C) to allow the fluid in the
bypass line, thereby removing weld chips, scales and other foreign
matter left in the piping assembly.
NOTE: This is particularly important on new installations.
2. Carefully and slightly at first, open the valve (A) upstream of the meter
progressively and then, slightly at first, open the valve (B) downstream
progressively.
3. Slowly close the bypass line valve (C) and make sure that the total
counter in the receiving instrument advances in response. Maintain a
flowrate 10 to 20% of the maximum flowrate at this time, allow the flow
for more than 15 minutes and make sure that air in the piping assembly
has totally escaped.
NOTE: In applications where temperatures exceed 60° C (140° F), run the
system at least for 30 minutes in this state to ensure uniform heat
distribution in the measuring chamber.
4. Following the break-in operation (preheating), shut off the bypass line
valve (C) completely. Open the upstream valve (A) progressively until
fully open then slowly open the downstream valve (B) until the rated
flow is reached.
5. Flowrate should be regulated with the downstream valve (B) and should
be held within the rating.
6. The strainer should be inspected for condition and cleaned on a regular basis.
3-5 Operating Precautions
Periodic inspections should be made during flowmeter operation. The
following points should be checked and the flowmeter shut down if any
discrepancy is found.
1. When changing flowrates
In applications where the flowrate varies or where shut-off valve
opening and closure takes place in batch operation, avoid rapid
changes in flowrate across the meter.