Hi All,

I recently saw some reports that one of our plants recieved from an outside lab. There was a line on the report that listed a "PQ index". I'm not quite sure how to interpret this number and it's magnitude. Does anyone know about this and how it compares to using other data (ex. particle counts).

To give a little more background, most of our plants use an in-house lab that does TAN, Moisture, Spec., FTIR, Viscosity, Particle Counts, and ferrography. I'm used to seeing this data already...I'm just not sure how useful this PQ index is with regards to other information available.

Thanks for any insight you can provide.

Hi,

The PQ measures all magnetic/ferrous material in a sample. Its advantage is that all metal in the sample regardless of size is measured (a problem with ICP and sometimes the Spectroil M).

In my experience the PQ mimics the Fe (from the Spectrometer) almost exactly.

What if the PQ and Fe don't match?? An example - PQ is high and Fe is low we can assume in this case that the Ferrous metal in the sample is comprised of large metal pieces which the ICP or Spectrometer have not picked up but are being read by the PQ. This scenario might occur at the onset of failure e.g. a chipped gear tooth results in large metal particles not picked up by the ICP immediately.

The PQ should not be used as a substitute for the Spectroil M / ICP.

Anyone correct me if I'm wrong but I think measurement is in miligrams per litre. Or PPM.

I echo Andrew's info except that the PQ Index can be considered unitless. It is an index and thus has no units. It is very useful to trend and use to determine if further analysis is required i.e. an actual visual debris analysis. But keep in mind it only measures "magnetic" metals so one could have a low PQ but still a lot of non-magnetic metallic particles present i.e. aluminium, brass, bronze etc. The good thing is that this is a rare occurence as most systems have at least one iron-based wearing part.

This message has been edited. Last edited by: Michelle,

To confirm, PQ(Particle quantifier) Index as the name implies is an index ie has no units. The larger the index the greater the ferrous content.
My experience with PQ is that it is quite a coarse measurement unlike ICP, but is helpful in picking up indications of large ferrous particles in conjuction with ICP and also useful in trending ferrous wear.