Reference Manual
00809-0100-4696, Rev AA
September 2004
Rosemount 848L
E-14
Redundant Motors -
Switch on Failure
Again, there are redundant pumps. There is a pressure switch in the common
discharge line. If the pressure falls then the other pump is started. If the
pressure does not recover, possibly because a flammable liquid is pouring on
the ground from a broken pump housing, then the alternate pump is stopped.
The push button controls are Stop (input 1) and Start (input 2). An auxiliary
contact is required from each starter (inputs 3 and 4). The pressure switch is
linked into a DO that is true when the pressure is low.
| |
| 3 4 2 +-----+ L1 |
+--|/|-----|/|-----| |---|Set |------( )--+ EQ1
| 1 | | |
+--|/|--+----------------|Reset| |
| T | +-----+ |
+--| |--+ |
| |
| DO P |
+--|^|--+-----------------------------( )--+ EQ2
| L1 | |
+--|^|--+ |
| |
| DO L1 T |
+--| |-----| |------------------------( )--+ EQ4
| |
| P L2 +-----+ L2 |
+--|^|----|/|------------|Set |------( )--+ EQ4
| P L2 | | |
+--|^|----| |------------|Reset| |
| +-----+ |
| |
| L1 P L2 Out2 Out1 |
+---------| |--+--||--+--|/|---|/|----( )--+ OUT1_EQ
| | 3 | |
| +--||--+ |
| |
| L1 P L2 Out1 Out2 |
+---------| |--+--||--+--| |---|/|----( )--+ OUT2_EQ
| | 4 | |
| +--||--+ |
| |
Instantiate a DO block and set the channel number to 9.