Mechanical seals are inspected to determine whether they need to be repaired or replaced. The inspection procedure is the same in either of the cases. Identifying discharge sizes, suction, impeller, and pump can help improve the inspection.
Pumps are used in several applications, so the seal must be designed accordingly. Pump manufacturers may place multiple configurations of seals into pumps.
Numbers of the Seal
Getting part numbers off of the seal is the first step in a mechanical seal inspection. Major manufacturers often place part numbers on the seal representing the elastomer, seal faces, and seal metallurgy. If you can’t find the service wears any part number or the part number, you can still identify some components.
Check the Components
Start with the weakest link elastomer and assess the rubber components. Check whether they look melted, chemically attacked, brittle or hard. If they’re flexible and in optimal condition, it can help you determine that the elastomer was compatible with the service. If not, you may need a different elastomer. Considering the application and temperature can help you narrow down the compatible elastomers.
Check the Seal Faces
You can evaluate the seal faces with colors. If the seal face is white, it’s ceramic. On the other hand, a metal seal face looks more like bronze, brass, or aluminum bronze. Grey color and light in weight properties represent silicon carbide – the same family as ceramic.
Moreover, grey to silver grey color means it is tungsten carbide. A spray-on coating is an exception in these seals that are rarely found because they tend to fail faster and fall out of favor.
Consider the Types of Springs
Each seal uses a method of energizing the seal faces together with a spring. There are three types of spring sets – single spring, multiple springs, or wave spring. Wave springs are rarely found but are used if there’s minimal space in the pump. Single springs are most commonly used in approximately 80% of seal applications. Bellows are used as an alternate to springs but can be more costly.
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