When deciding on the best type of seal for a particular application, it is best to consider all aspects of the environment and its purpose. If the application requires a spring- loaded seal, that does not eliminate either the rotary shaft seal or the mechanical seal. If the equipment is operating in extreme temperatures, including situations where the rapid movement of the equipment creates extreme heat, a mechanical seal will hold up better than an oil seal.
Oil seal vs. mechanical seal is not always an easy decision. In some cases, one is the obvious choice because you are replacing a worn out seal with the same type. But in other situations, either type would work and the question is which will enhance productivity the most. At Abbey Seals, we have ample experience with a full range of seal types. We are happy to discuss the specifics of your application and advise you on the optimum type of seal for your equipment. The decision between a rotary shaft or oil seal vs. mechanical seal involves many factors, and we are here to help you make the best choice for your specific needs.
You can find our contact information here or please fill in the product information request form here for information on either type of seal
We just discovered that one of the seals on our pumping system is leaking. Do you have any ideas as to what could have caused this, and can you offer some advice for selecting a good seal?
The main causes of external lubricant leakage from pumping systems, hydraulic machines, gearcases and sumps are the wrong selection, improper application, poor installation and inadequate maintenance practices that are applied to sealing systems.
These problems can be overcome through a better understanding of the types of sealing materials available, redefined selection procedures and the consistent application of sound replacement and maintenance practices.
A number of variables must be considered when selecting oil seals. There are nine factors that designers and maintenance engineers must evaluate when oil seals are specified:
The maximum allowable shaft speed is a function of the shaft finish, runout, housing bore and shaft concentricity, type of fluid being sealed and the type of oil seal material.
The temperature range of the mechanism in which the seal is installed must not exceed the temperature range of the seal elastomer.
Most conventional oil seals are designed only to withstand very low-pressure applications (about 8 psi or less). If additional internal pressure is present or anticipated, pressure relief is necessary.
Longer seal life can be expected with shafts having a Rockwell (RC) hardness of 30 or more. When exposed to abrasive contamination, the hardness should be increased to RC 60.
Most effective sealing is obtained with optimum shaft surface finishes. The sealing efficiency is affected by the direction of the finish tool marks and the spiral lead. Best sealing results are obtained with polished or ground shafts with concentric (no spiral lead) finish marks. If you must use shafts with spiral finish leads, they should lead toward the fluid when the shaft rotates.
When the bore and shaft centers are misaligned, seal life will be shortened because the wear will be concentrated on one side of the sealing lip.
The best seal performance is achieved when close shaft and bore tolerances are present. Other factors include shaft eccentricity, end play and vibration.
Runout must be kept to a minimum. Movement of the center of rotation is usually caused by bearing wobble or shaft whip. When coupled with misalignment, this problem is compounded. Contrary to popular belief and common practice, the installation of flexible couplings cannot correct or compensate for misalignment.
Seals perform much better and longer when they are continuously lubricated with an oil that has the correct viscosity for the application and that is compatible with the seal lip elastomer material. The consideration of seal incompatibility, particularly with certain additives and some synthetic lubricants, should not be ignored, but unfortunately very often is.