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GENERAL GUIDELINES FOR O-RINGS AND U-CUP SEALS
Sizes and materials of construction for O-rings and U-cup seals are selected by Graco based on compatibility with
the chemicals to which they will be exposed. Solvents that may remove residual chemicals often have negative
effects on the mechanical properties of O-rings and seals.
O-Ring Guidelines
Always replace an O-ring with the identical one in size, durometer hardness, type and material of
construction. Always be alert to the location and size of each O-ring as many look alike and be careful not to
mix them. Often similar sizes may be used in various locations on the equipment and if replaced incorrectly,
the equipment may not function properly. Refer to the Machine Operation and Service Manual for the correct
part number of all O-rings used throughout the equipment and replace them with factory approved parts only.
Re-use of O-rings is not recommended. Only re-use O-rings as a last resort. If you must re-use them, be
sure that they are clean, have no cuts or flat spots and contain NO foreign material. Also, be sure not to soak
them in solvent for extended periods as this can cause deterioration of the O-ring. Always replace O-rings
that are cut, nicked, or distorted in shape or cross-section.
Always apply a very thin film of Krytox 203GPL lubricant, item 84/0200-K3/11, to the entire surface of the o-
ring before installation. Avoid excessive lubrication. If installing O-rings over threads on a shaft or across
sharp edges, roll or push the O-ring carefully into place being careful to avoid cutting or nicking it.
Avoid stretching the O-ring too much as it may not return to the proper size.
Do not use any sharp tools or objects to install O-rings
U-cup Seal Guidelines
Always replace a U-cup seal with the identical one in size, durometer hardness, type and material of
construction. Always be alert to the location and size of each U-cup seal as many look alike and be careful
not to mix them. Often similar sizes may be used in various locations on the equipment and if replaced
incorrectly, the equipment may not function properly. Refer to the Machine Operation and Service Manual for
the correct part number of all U-cups used throughout the equipment and replace them with factory approved
parts only.
Always apply a very thin film of Krytox 203GPL lubricant, item 84/0200-K3/11, to the inner and outer lips of
the seal before installation.
Re-use of U-cup seals is not recommended. Only re-use U-cups as a last resort. If you must re-use them, be
sure that they are clean, have no cuts or flat spots and contain NO foreign material. Also, be sure not to soak
them in solvent for extended periods as this can cause deterioration of the seal. Always replace U-cups that
are cut, have flat spots, are distorted in shape or are damaged in any manner.
Always be alert to the proper orientation of the sealing lips and re-install them in the same direction as shown
on the specific equipment assembly drawing. The U-cup seals are intended to seal in only one direction and
if installed incorrectly, chemical leakage through the U-cup can occur.
Whenever possible, push the back side of the seal over the shaft to protect the inner and outer lips. If this is
not possible, carefully tuck the lip in to avoid rolling it back or cutting it.
If installing over sharp edges, slide the seal carefully into place to avoid cutting it.
Do not use any sharp tools or objects to install U-cups.