E-MAIL: [email protected]
DATE: March 11, 2002
TO: Users of Record FROM: Gary Lazarre
RETURN TO: Diane Schnauder, Service Dept.

SUBJECT: PLATEN ATTACHMENT BOLTS, MEMBRANE LIFE & PROPER GOODS TRANSFER INTO THE SINGLE STAGE PRESS

We've seen a situation where the bolts broke that hold the membrane hub to the main shaft. This means that the diaphragm and platen were no longer attached to the shaft.

Sometime ago, we told some of you about an issue related to poorly manufactured bolts in this application and have since actually failed one set of the properly manufactured bolts.

There are a few concepts that you absolutely must understand and comply with in order to successfully operate your single stage press.

These are as follows:
1. Press Forces - The press creates a tremendous amount of force in the pressure cycle. For example, the 31-bar press creates approximately 600,000 pounds of force (enough to lift up a large airplane) and the 47-bar press creates over 850,000 pounds of force.

Obviously, these are tremendous numbers and need to be respected because with this much force, sheet metal and even the can of the press can be damaged when forcing pieces and parts together.

Decisions made while manually operating the press could cause significant damage to the press!

2. Membrane - The membrane is mounted on a platen, bolted to a hub and the hub bolted to the shaft. Obviously, the membrane is bigger in diameter than the shaft. The bolts that retain the hub onto the shaft essentially see no stress if the goods are perfectly flat in the can. The membrane hits these perfectly flat goods and it pressed them straight down to the bed. However, if the goods are not flat and are higher on one side than the other, the stresses on the bolts are tremendous because the platen is trying to be twisted off of the shaft. We're sure that no bolts that we can install in the shaft from the hub are large enough to withstand this tremendous force on a repetitive basis.

3. Water in the Membrane - If the membrane is not full of water, the force on the platen is extremely uneven. If the membrane is full of water and goods are not evenly distributed in the can (goods higher on one side than the other) then the water in the membrane actually evenly loads the platen. When there is air in the membrane, then the side walls of the membrane will apply most of the force to the side of the cake in the can and torque the platen severely. We are convinced this is part of the reason for failure of the bolts at the hub.

4. Water Transferring with the Goods - We have actually blocked all of the perforations in the last module scoop of the CBW in order to transfer more water into the press can. The idea is to sluice the goods into the can as evenly as possible to create a flat cake profile. This obviously prevents uneven loading of the platen, a reduction in forces on the bolts at the hub and a better extraction of the goods.

5. Hub & Platen Bolts - We suggest that you have one set of bolts that attach the hub to the shaft and platen to hub on hand at all times. If an operator makes a bad judgment call in manual operation or for some reason a small load transfers unevenly, this could lead to broken bolts and a down press. You need to be able to make a response with new bolts immediately.

The bolt type has been changed from a socket head cap screw to a hex cap screw with a change in the platen construction. Presses manufactured before date code 99323 use (24) 15K231A (socket head cap screw). Presses manufactured on or after 99323 use parts (12) 15K303 hex bolts, (12) 15K295 hex bolts and (24) 15U393 flatwashers.

The bolts must be tightened properly. As the press works, the bolts will "dig into" the mating surface under the head of the bolt. This will work the material and force it to flow from under the head of the bolt. The result is a fastener that is no longer tight. If the force on the bolt at press time exceeds the stress on the bolt from it being tightened, then the bolt will fatigue and fail. So, tighten the bolts to the proper specification shown in your manual for the fastener you use.

We ask that you confirm the type of fasteners you need and order as needed from Milnor.

If you need any further information to better understand this issue, please contact me directly at [email protected], or by fax at 504-469-9777. We will surely work through any situation to guarantee the successful performance of the your press and your entire MILNOR laundry system.

Best regards,

PELLERIN MILNOR CORPORATION
Gary Lazarre
Gary L. Lazarre
Manager
Customer Service

GLL/das