Service Bulletin: SB 038.1
Subject: Main Drive Lubricant
All PMC machine main drives incorporating a Griesen type oil filter assembly, with an electrical oil pressure differential switch, to insure continuous filtration of lubricant and positive pressure lubrication should be modified as cautionary maintenance.
As with automobiles, the cup machine filter must be inspected periodically, and cleaned or replaced under an established local maintenance program. Intervals vary due to local lubricants, and operating conditions, and are best established at the plant of operation. General initial recommendation is to clean the filter element monthly, and replace every six months.
It has come to our attention that an isolated domestic incident was incurred when this practice was not followed. The filter assembly when blocked by contamination has an automatic by pass valve which will allow oil to be continuously circulated through the oil feed lines and ultimately could block the lines with contaminates, losing lubrication to many areas of the main drive.
To protect the drive from this operation/maintenance oversight we are advising all customers to modify the oil filter housing as shown on enclosed print 26570-A. Remove the incorporated bypass valve plug and spring and close off the by-pass chamber with a commercial expansion plug or equivalent. With this modification, if the filter element is dirty no oil will pass through. The drop in pressure will automatically stop the machine and require corrective maintenance action to be taken.
With the above modification completed it is necessary to modify the electrical pressure sensitive switch to insure at least minimum lubricant pressure passing through the filter at all times. Here again, there have been two reported incidents where a machine had the pressure switch differential set at zero and therefore negated the automatic safety.
To protect against this happening, the switch should be modified as shown on print 26392-A enclosed. The spacers described will insure at least a fifteen pound pressure differential at all times and can only be increased as required by local conditions.
The described modifications to two commercial assemblies in the PMC machine are strongly recommended. But even these safeguards are no substitute for regular preventive maintenance inspection of the machines complete lubrication system. As with modern automobiles when the gauge lights come on it is generally too late, and therefore a responsible operator must routinely check all vital functions of his machine.
The changes described will be incorporated on all PMC machines manufactured from January 1977.