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December 14, 1999


SUBJECT: M7E/M9E BASKET REPAIR

We've seen a couple of occasions where cracks began to form in the rear of the M7E/M9E extractor baskets. These cracks may appear on the cylinder back in up to five different locations.

The basket is fabricated using a hub and spoke methodology. To the center hub of the basket are attached five spokes on which is formed the cylinder back. There are two weld seams in the cylinder back that are visible while looking into the extractor basket. One of these weld seams is likely on top of one of the five "spokes" that makes up the structure of the cylinder back.

Cracks may appear where the spoke ends, very close to the outer diameter of the cylinder back. This is where the cylinder back meets the cylinder side sheet. The cylinder side sheet is the perforated outer wrapper of the cylinder.

If cracks begin to form in this location, these should be repaired by drilling out the end of the crack and grinding the cracks to enable a full penetration weld repair. After the cracks have been repaired, an overlay should be put on top of this area which will reinforce the cylinder back cover sheet.

When the centrifugal extractor basket is operating with an out-of-balance load, the cover sheet is in compression on the "heavy side" of the basket and in tension on the "light side" of the basket. The addition of these reinforcing plates will prevent future cracking of the cylinder back cover sheet.



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The MILNOR part number of these stiffener plates is 03-16018. You need five of these in order to make a repair. The basket is made of 304 stainless steel and 304L welding rod/wire should be used.

Teflon Coating: If the basket is Teflon coated, the welding of these extra pieces will burn the Teflon off in this area. Since this is on a vertical cylinder back, we are sure that it is not necessary to re-Teflon coat the added reinforcing plate. The basket will continue to work fine in the Teflon coated perforated area if so equipped.

Gary Lazarre

GLL/das

Attachment: 03 16018 DWG