Answer: Good Question. You should pay attention to the following:

EXCESSIVE CLEARANCES - When excess gland clearance exists, either on the inside or outside diameter of the gland lip or between the piston and cylinder wall, the seal will be subjected to deformation by extrusion.

Hydraulic pressure will cause the seal to extrude through the excess clearances. Constant pressure fluctuations will result in loss of sealing material through the clearance causing eventual seal failure. Prevent this problem by adhering to recommended clearances. NOTE: Care should be taken to properly centre or align assemblies so that clearance is equal all around.

SCORED RODS, STUFFING BORES OR CYLINDER WALLS - Severe scoring can prevent sealing lips from conforming to the entire surface to be sealed, resulting in leakage. Rings may never offer a positive seal if scores are excessively deep, but even if some service is obtained, optimum seal life cannot be attained. The solution is to refinish the scored rod, stuffing box bore or cylinder wall.

FOREIGN MATERIAL IN HYDRAULIC SYSTEM - Foreign matter in the hydraulic system (dirt, metal shavings, etc.) can cause many problems with seals, resulting in weepage and premature failure along with associated equipment damage. Proper filtration and preventative system maintenance solves this condition.

FAILURE TO MAKE INITIAL SEAL - This is caused by damage to sealing lips during installation. Care should be taken during insertion, and the use of sharp tools should he avoided. To facilitate installation, seals may be lubricated with a compatible medium.

EXCESSIVE FLUID TEMPERATURE - Built in interference and/or pressure on the packing is needed to maintain a positive seal throughout the pressure range. Excessive fluid temperature can cause seal to lose memory, resulting in fluid leakage, proper seal compound selection and maintenance of nominal fluid temperature will prevent seal failure.

CHEMICAL ATTACK OF SEAL - Chemical attack to seal is sometimes experienced when using exotic fluids as hydraulic mediums. Proper compound selection will prevent seal failure.

EXCESSIVE WEARING OF RINGS IN V-PACKING - Premature or excessive wear, particularly on the dynamic side of V-packing usually indicates that the seal has not been properly seated in the stuffing box or the piston. This results in the seal set rolling in the box short service life. Proper seating and/or adjustment will prevent this condition.

WEAR ON ONE SIDE OF SEAL - Conditions exist due to worn bearings or wear rings or rods that cause misalignment or improper guidance, resulting in excessive wear on one side of the seal. Correction is attained by rebushing the assembly for proper guidance.

FAQ