PLC logic for Bijur single shot lube pump with pressure switch?

[RTech]

My lathe has a fairly standard Bijur brand, single shot lube pump and a lube pressure switch. The pump runs off a gear motor that is energized by PLC logic when running a program or in MDI mode.

However, the lube pump does not have a lube level switch.

I would like to edit the PLC to include logic that looks at the pressure switch every so often to make sure there is lube in the tank. I'm guessing the logic would involve setting up a timer to watch the pressure switch and throw an error if there is X number of minutes of running without seeing the switch change state.

Does anyone out there have an example of the required PLC logic they can share?

Thanks,
Jim

[cncsnw]

Here is code I use with that type of pump.

In the plcmsg.txt file:

Code: Select all

41  9041 Lube Pressure-Up Failure
42  9042 Lube Pressure-Down Failure

And in the PLC program source:

Code: Select all

LUBE_UP_FLT                             IS 10497;(1+256*41)
LUBE_DOWN_FLT                           IS 10753;(1+256*42)
;...
LubePressure                  IS INP8   ; PS1, way lube pump output
;...
Lube                          IS OUT2   ;
;...
LubePrevTime_W                IS W26
LubeTotalTime_W               IS W27
;...
LubeOffPD                     IS PD38
;...
LubeRunning_T                 IS T11
LubePressure_T                IS T12
;...

; Monitor the way lube pressure switch:
;  After some accumulated time of lube pump power, the switch should close.
;  Failure to close indicates pump failure, low lube, or open lines.
;  After some shorter time, pressure should bleed down and the switch
;  should open.  Failure to open again indicates clogged lines or faulty switch.
;
IF Lube THEN SET LubeRunning_T,
             LubeTotalTime_W = LubePrevTime_W + LubeRunning_T
IF !Lube THEN (LubeOffPD)
IF LubeOffPD THEN LubePrevTime_W = LubePrevTime_W + LubeRunning_T
IF !Lube THEN RST LubeRunning_T
IF LubePressure THEN RST LubeRunning_T,
                     LubePrevTime_W = 0,
                     LubeTotalTime_W = 0
IF LubeTotalTime_W > SV_MACHINE_PARAMETER_721 * 1000
  THEN FaultMsg_W = LUBE_UP_FLT,
       SET LubeFault_M,
       RST LubeRunning_T,
       LubePrevTime_W = 0

IF LubePressure THEN LubePressure_T = SV_MACHINE_PARAMETER_722 * 1000,
                     SET LubePressure_T
IF !LubePressure THEN RST LubePressure_T
IF LubePressure_T THEN FaultMsg_W = LUBE_DOWN_FLT,
                       SET LubeFault_M

Parameter 721 is set to the maximum number of seconds that we expect to power the pump, before the plunger should drop and the pressure switch should close (e.g. P721 = 1200 for a 20 minute interval).

Parameter 722 is set to the maximum number of seconds that we expect for the pressure to bleed back down (e.g. P722 = 60 for one minute).

[RTech]

Thank you!

[aamir]

Marc which stage I write those codes
Also where we set LUBE output ?

[cncsnw]

I usually put the pressure-monitoring logic in MainStage, along with other logic specific to the particular retrofit machine.

I usually use that logic in conjunction with the usual "LubeUsePumpTimersStage" and "LubeUsePLCTimersStage" logic, which will control the Lube output based on Parameter 179 settings.

For the type of pump Jim describes, you would set P179 = 0, and "LubeUsePumpTimersStage" would turn it on whenever a program cycle is active.