AIR SERVICE UNIT :

This unit (ASU) can take the form of three separate units, filter, regulator, lubricator. In later units the filter and regulator are combined and on machines using lap spool valves and special cylinder, no oiler is necessary. This fact should be remembered if alternative components are fitted which require an oil mist.

In order from air supply :-

Filter . This unit filters the air supply and allows water vapour to condense and be trapped in the bowl. If it is not a self draining type this should be emptied regularly.

Regulator . Because of fluctuating air supply pressures and differing weld pressure requirements, it is necessary to fit a regulator to the air supply.

Weld pressure for soft pliable PVC should be 50-75 PSI and 100-150 PSI for rigid material, and where PVC has to flow through tontine or fibre 150 PSI is desirable.

These figures of PSI refer to square inches of weld area i.e. a die with 38 linear inches of weld ¼" wide would have an area of 9½ square inches.

As units of pressure have changed from PSI to Kilo-pascals the conversion table is :-

1 PSI = 6.9 KPA

= .07 Kg/cm²

= .07 bar

100 PSI = 700 KPA

= 7 Kg/cm²

= 7 bar

A 140mm dia cylinder operating on an air line pressure of 6 bar (600KPA) = 924 Kg - ram force (less friction losses). So for ordinary soft material allow 6 Kg for every one square cm. of weld.

This information is only a guide , in fact it is very rare to adjust air pressure when you change dies.

NOTE: Because of air valve pilots most machines should not be operated below about 300 KPA.

Lubricator . Most new machines don't require this unit, it is designed to inject an oil fog into the air stream. Most are adjustable. A sight glass is provided to see oil drops falling from a tube.

One drop every third press operation is ideal. Only a fraction of this drop is atomised so oil usage is minimal. As previously mentioned some machines with lap spool valves do not use a lubricator.

Recommended lubricants :-

Amoco Rycon 22

BP HPL 32 or THB 32

Ampol Ardea 32 or Tecoma 32

Caltex Rando HD 46

Castrol Hyspin VG 32

Esso Teresso 32

Shell Tellus 22

The lubricator lubricates all cylinders and valves but the press guide rods are to be greased separately.