Brooks Instrument BM50 - Manual (Page 26)

3-2
Section 3 Operation Installation and Operation Manual
X-PD-BM-Ovals-eng
Part Number: 541B031AAG
January, 2009
BM Oval Series
3-3 Pulse Generator Principle of Operation (See Figure 3-1)
Pulse Generator:
When fluid passes through the meter, rotors turn. The magnets which are
located in the rotors will pass across the pulser circuit board (containing
either Reed Switches or Hall Effect sensors). A signal is received which is
then sent by the Pulse Circuit Board (PCB) to the relevant LC display or
receiving instrument.
Mechanical Display:
When fluid passes through the meter rotors turn. The gear located on top
of one of the rotors drives the mechanical registers gear train which
provides an accurate readout.
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.