Mechanical seals can operate for many years without issue, as long as they've been properly selected for their application. One must identify the application data (or operating conditions) to properly select the type of seal and materials of construction to ensure maximum performance from the seal over its lifetime. Below we define the operating conditions and discuss what material characteristics to consider for preventing improper material selection.
**Please note: There are many things to evaluate when selecting a seal, so be sure to speak with an experienced engineer before your final selection is made.
Identifying the exact liquid being handled is the first step in the seal selection process. Seal material must be able to withstand the fluid being processed. All seal materials must be chemically compatible with the fluid, or there is an increased risk of seal failure.
Pressure in the seal chamber and seal size determines the type of seal required, balanced or unbalanced.
Seal materials must be selected to appropriately handle the liquid’s temperature. Temperature is important because different seal materials are rated for certain termperatures and you should not exceed the temperature limit of these materials.
Knowing the viscosity of the liquid is important to ensure appropriate seal life. Abrasive liquids can create excessive wear and will ultimately shorten the seal's life. Double seals or use of an external flush plan give operator's the option to use mechanical seals on these difficult fluids.
RELIABILITY & EMISSION CONCERNS
Every company has their own standards and operating procedures when it comes to reliability and emission concerns for an application. The seal type and arrangement selected must meet the desired reliability and emission standards for the pump application. Since environmental safety has become a hot topic among manufacturing companies, double seals are peaking as the solution of choice.
After understanding the seal's exact operating conditions, you can select the seal's overall construction material and its face and component materials. When selecting the seal's material of construction, be sure to consider the following characterstics of the material:
- Temperature constraints
- Chemical resistance properties
- Wear resistance
- Thermal expansion and conductivity properties
And, when selecting the face and other component materials for the seal, consider these material characteristics:
- Wear resistance
- Low leakage & friction properties
- Good thermal properties
- Corrosion resistant
For more information on elastomer guidelines and compatibility for metals and typical face materials, check out the resources below:
As you work with your local seal supplier, remember that a mechanical seal recommendation is not complete without a seal support plan, such as a seal flush piping plan. And, if you are new to mechanical seals and are considering making the switch from packing to the mechanical seal, read more about it on our blog, Understanding the Basics of Mechanical Seals vs. Packing.