RA-4 Low Flow Error

RA-4 Low Flow Error

If you are getting a "Low Flow Error" on your RA-4300A system there are three main likely causes.  A leak, a restriction, or a problem with the air pump.

It should be noted, if you have recently changed and parts, or have done any maintenance to any part of the instrument you most likely have a leak at or near that part.

Listed here in order of easiest to check and change are: Disc filters, carrier pump tube, carrier pump rotor. 

These are all items we recommend changing on an annual basis as a preventative measure to keep from getting this error.
 
In its basic form this error means the flow sensor is not reading the appropriate amount of flow.  This could be due to a leak, a restriction, or the source of the flow itself (in this case the carrier pump tube, rotor, or motor)  

To troubleshoot a "Low Flow Error": 

(1) Run a leak check from the maintenance screen and follow the onscreen instructions.  If it passes leak check, proceed to the second step.  If it fails the leak check, first ensure that the cap is correctly aligned on the top of the sample tube.  If it is not, follow this procedure before continuing. Assuming the cap is correctly aligned, exit the maintenance screen and proceed to put 5 mL of DI water into a sample tube and place in position 11 and simulate a sample run with the software for position 11.  You will now be watching for bubbles throughout the entire run.
      (a)     If bubbling occurs during the "Purge"  step before measurement.  
              --> There is a leak between the V1 valve and the Yellow marked tube, check the connections at both ends.  Or the V3                        valve is not working.  The V3 valve can be checked in the maintenance screen, listen for actuation as you toggle it                      on and off.

      (b)      If bubbling does not occur in the waste station during the "Rinse" step
                  -->  There is a disconnection between the discharge side of the air pump and the yellow-marked tube.

      (c)      If bubbling does not occur in the sample tube during measurement
                  -->  (i) There is a crack in the sample tube; (ii) foreign material on the sealing gasket of the cap; (iii) leak where the                         tubing enters the cap, make sure all the tubing is fully inserted into the cap and do not slide easily; (iv) leak at the                         dehumidifier, dehumidifier drain tank, flowcell, or any lines inbetween; or (v) faulty V3 valve.


(2) Check the disc filters. 
      --> The disc filters are teflon and thus hydrophobic, they are designed to block moisture from getting further into the             system.  Moisture can accumulate in the filter, blocking or restricting the carrier flow.  These are an easy replacement             and should be done on a semi-annual basis as a preventative measure.  If the filters are good, or changing them does             not resolve the error then the source of the carrier flow may be the problem. 

(3)  Check the pumptube of the air pump. 
      -->  The pump tube will wear out, and should be changed once a year to maintain optimal flow. 

(4)  Check the rotor of the air pump
      -->  If the pump tube is good then the plastic rotors that the pump tube rolls on may be starting to wear out, or start to             develop a groove in the plastic where the pump tube sits.  It is recommended to change the rotor every 2-3 years as a             preventative measure to keep this from happening.

(5)  Change the air pump assembly

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