Figure 1: The MECO EP Type-2 Seal. Source: MECO SealsFigure 1: The MECO EP Type-2 Seal. Source: MECO SealsThe importance of seals in machinery cannot be overstated. They keep chemicals, solvents and a host of other contaminants at bay, preventing costly product loss and damage to industrial parts and machinery. They often improve product quality and consistency between batches. MECO Seals, a leader in the sealing industry, recognizes the role that seals play and develops products to ensure that this role is not undermined.

One such product capable of sealing various materials while keeping out contaminants is MECO Seals’ EP Type-2 seal, which is custom engineered for processing equipment that handles dry solids, assorted liquids, vapors and other components on small to large shafts and at low to moderate (and sometimes high) shaft speeds.

These seals are appropriate for machinery such as single- or twin-shafted extruders, compounders, blenders (plow and paddle), conveyors and other rotating equipment typically used in the plastics, metals, chemical, pharmaceutical and food processing industries.

Operation

EP Type-2 seals are fully split, with each of their 10 components divided into two halves, thereby simplifying installation. These double mechanical seals are functionally similar, at least in appearance, to stuffing boxes and gland followers. However, the difference between EP Type-2 seals from gland followers and stuffing boxes is in the seal’s configuration, where the sealing plane is perpendicular to the shaft rather than located along the shaft.

Components of the EP Type-2 seal include an elastomer drive, rotating primary and secondary seal faces and stationary primary and secondary seal faces. The double mechanical seal uses an elastomer drive to engage the synthetic seal faces to rotate against stainless steel stationary seal faces. The elastomer and rotors link to each other to form an air- and water-tight seal.

Typically, EP Type-2 seals are appropriate for use with hard-to-reach parts and machinery with predetermined speeds and feed rates as well as for small shaft vacuum service, low pressure applications and fixed applications that produce infrequent thermal expansion and pressure changes. For applications with frequent thermal cycles, pressure cycles and exposure to aggressive chemicals, MECO Seals offer Model EP Type-3 seals.

Maintenance

The EP Type-2 seals are pneumatically loaded using a compressed gas barrier fluid, which provides seal face closure and the air/gas serves as a diagnostic tool, using the pressure gauge monitoring seal cavity pressure as the indicator.

Springs accommodate small pressure changes in axial shaft motion and offer backup seal face loading when compressed gas pressure is inadvertently lost. Additionally, as seals wear, monitored pressure decreases and a noticeable drop in pressure signals that maintenance or a simple spring adjustment needs to be performed.

ConstructionFigure 2: EP Type-2 construction. Source: MECO SealsFigure 2: EP Type-2 construction. Source: MECO Seals

EP Type-2 seals are constructed of rugged components that are high quality and customizable. Custom shaft seals can be manufactured in virtually any material imaginable. For instance, rotor seal faces are typically made from MECO 3000, which is a high-performance, bearing grade polymer filled polytetrafluoroethylene (PTFE) or MECO 4001, which is a glass-filled bearing grade polyetheretherketone (PEEK). The elastomer is generally white silicone, while Viton, nitrile and EPDM are possible alternatives.

EP Type-2 vs. EA Type-2

MECO Seals’ EP Type-2 seal is essentially an upgrade from MECO Seals’ EA Type-2 seal. Both models are available split or unsplit. However, the EA Type-2 seal uses bolts to control the distance between stators and requires manual fine-tuning for proper adjustment, while the EP Type-2 seal uses spring assemblies for the setpoint.

Another feature distinguishing EP Type-2 seals from EA Type-2 seals is shaft speeds. EP Type-2 seals are appropriate for applications with higher shaft speeds, approaching 650 ft/minute (3.25 m/sec), while EA Type-2 seals are appropriate for applications with shaft speeds half of that. Flatness of the stationary seal face or stator is truer with the EP-T2 than the EA-T2, leading to higher shaft speed capability. Shaft speeds are application dependent and influenced by materials of construction, shaft size, pressures and duty cycle.

It is important to note that while most EA Type-2 seals and EP Type-2 seals are not dimensionally interchangeable, their rotating components are.

SpecificationFigure 3: Typical dimensions for a MECO EP Type-2 Seal. Source: MECO SealsFigure 3: Typical dimensions for a MECO EP Type-2 Seal. Source: MECO Seals

MECO EP Type-2 seals are built to order for a variety of processing equipment and can be designed to SAE or metric dimensions. Typically, these seals are used on shaft diameters ranging from 1.5 to 20 inches and for sizes in between. However, dimensions will vary according to application. Optimal axial clearance is roughly 9.5 inches (with 5 inches sometimes permissible). The typical mounting bolt circle is the shaft diameter plus 3 inches, while the shaft protrusion optimum is 5 inches (a minimum of 3 inches) and a typical seal outer diameter is the shaft diameter plus 6 inches.

Figure 4: Mechanical capabilities. Source: MECO SealsFigure 4: Mechanical capabilities. Source: MECO Seals

Conclusion

MECO Seals can help with a host of sealing applications with its line of seals suitable for a variety of cases. Contact them today and their skilled team of in-house engineers will help design the right seal for your application. The company can also help train maintenance staff on seal MRO.