Introduction The ability of the elastomeric radial lip seal to adjust to a broad range of changing environmental conditions makes it the preferred design choice of user and supplier alike. However@ the interaction of the seal with its changing environment can cause leakage to occur. Figure 1 lists seal and application variables that can produce certain dynamic effects resulting in leakage. Each application should be reviewed carefully. There are three basic steps that are normally taken to ensure success. They are: 1. Determine the application parameters that appear to be most significant. 2. By working with the seal manufacturer@ determine the type of seal to be used. Try to use an existing production seal whenever possible. 3. Test the proposed seals in the application. Try to obtain a representative@ statistical sample. If actual application testing is not possible@ use the seal manufacturers' laboratory test machines to simulate actual field conditions as closely as possible. When the seal is approved for proaxtion@ it is important that blueprint specifications be agreed upon between supplier and user for purposes of quality control. Usually@ the manufacturer's customer print of the oil seal contains the essential control specifications. A useful document is the SAE seal print format. Any additional information should be mutually agreed upon. Since the oil seal is composed of many different organic and inorganic constituents@ the seal manufacture: must make adjustments when necessary for maintaining proper seal function. Shortages of raw materials make some substitutions mandatory. Occasionally@ some health standards make it necessary to alter the constituents. It is important that the manufacturer evaluate any changes made in terms of functional performance. If major adjustments must be made to the products@ the manufacturer will review the changes with his customer before making them to assure continued satisfactory field performance. The parameters that are considered important to most applications are: 1. Housing 2. Shaft 3. Fluid 4. Environmental conditions 5. Duty cycle The following discussion relates to the use of standardseal designs. Special seal designs can be developed to accommodate more severe application conditions.