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SP80 / SP80H air purge option

SP80 and SP80H units built after September 2010 have the ability to fit the air purge option. From this date all new probes have been supplied with a suitable push fit connector as part of the standard probe kit.

The SP80 and SP80H probes are supplied with a blanked off air purge hole.  If the probe is to be operated in an environment where oil mist or other heavy vapours are present it is essential that an air supply is used to maintain positive purging of any contamination from the interior of the probe.


SP80 air filter system diagram

The air purge system requires an air filter.  This can be purchased directly from Renishaw (Renishaw part number A-3060-0070) or a suitable alternative can be used.

WARNING: It is vital that the air filters used for SP80 and SP80H air purge meet the specification detailed below and that the filter unit is maintained to the manufacturer's specification.

1. Ensure the air provided to the filtration system meets the specification given.

Incoming air supply specification:

Air pressure1 to 2 bar*
Air consumption15 to 25 litres per minute
Particle size
Dirt concentration
Dew point

Class 4
15 μm
8 mg/m3
+3 °C
5 mg/m3


* NOTE: The exact values are dependent on the inherent characteristics of the air pipe between the air filters and the SP80 / SP80H.  Higher flow rates should be avoided as this could impair metrology.

Please ask the installer for the specification.

It is important that the air supply to the probe is maintained to ensure that the positive purging is effective.

2. Regularly monitor the dew point indicator (see image below) and follow the instructions given in the table.

Maintenance of the REVO air filters

For more information please visit the air filtration manufacturer's website and search for IDG5 filters. (Please refer to the section Air filter service kits for details on air filter service kit part numbers).

Dew point indications and maintenance instructions

Grain colour




NOTE: The grains may be pink on delivery and can take up to 1½ hours to turn blue when air is connected. 

Normal operation.

No action required.

Pink, white or brown

NOTE: If the grains are brown, then both indicator and membrane must be replaced. 

Water and oil flow into membrane air dryer.

1) Check and replace filters if necessary.
2) Check condition of inlet air for excess oil or water.

Pink or white

Input air temperature is too high.

Lower input temperature. Install in-line air coolers if necessary.

Pink or white

Purging air exit obstructed.

Check outlet of air purge port.


Membrane dryer near end of useful life.

Replace dew point checker.

Grains crushed

Water flow into membrane air dryer.

Replace dew point checker.


NOTE: Allow a minimum of 1 hour from start of air flow for the dew point indicator to change colour.