MECO AH Type-2

The MECO AH Type-2 seal is a fully-custom, pneumatically loaded shaft seal that can fit in limited axial space. In most cases, split components can be used, which makes replacing parts easy and minimizes maintenance downtime.

The AH Type-2 features a stack of adjusting gaskets that allows for field adjustments. It uses an elastomer to drive two polymer rotary seal faces (rotors). The rotors are kept in full contact with two stainless steel stationary seal faces (stators) by the elastomer and a compressed gas purge. The AH Type-2 seal can be designed to fit most shaft sizes.

The MECO AH Type-2 seal model is used on a wide variety of conveying and process machines, often with limited axial clearance. This seal model can be used on horizontal, inclined, and vertical shafts. This seal is appropriate for applications with infrequent thermal expansion or pressure changes. It can be adjusted to extend the life of the seal. The AH Type-2 is frequently used where an air or an inert gas barrier is needed to isolate the process from the atmosphere. It can also be designed for some explosive environments.

AH Type-2 seals are used on a variety of machines:

• Screw conveyors
• Blenders
• Bucket elevators
• Mixers

AH Type-2 seals are best suited in the following applications:

• Dry bulk conveying
• Dry chemical processing
• Plastic powder blending and colorizing
• Dry food conveying
• Dry and wet food mixing and cooking
• Explosive environments

The AH Type-2 seal is one member of MECO’s wide range of sealing solutions. Other shaft seal models may be considered for faster speeds, higher pressures, and thermal cycling. MECO Seals team evaluates the parameters of each application individually and provides a custom engineered solution. Contact us for a design to suit your specific application.

The MECO AH Type-2 seal model incorporates separate inboard and outboard stator housings acting as the stationary seal faces. Between the stators is a rotating seal face assembly, consisting of two rotors with a driving elastomer between them. By completely tightening the stators together to compress against the two rotors and squeezing the drive elastomer to the shaft, we form an interlocking, airtight seal. As the drive elastomer interlocks with the shaft and rotors, a dynamic contacting face seal, behaving mechanically as a thrust bearing, is created. The low-friction rotor seal faces are at right angles to the shaft and in full contact with the stators, forming the rotating seal plane between the rotors and stators.

The seal cavity is typically charged with compressed gas, which acts as a barrier fluid to provide pneumatic seal face loading. The two stator housings are typically separated by a stack of 1/64″ (0.40mm) thick shims to provide a method of adjustment.

A pressure regulator is included with the seal to set seal cavity pressure. A pressure gauge is attached to the inboard stator to monitor actual seal cavity pressure.

The seal cavity is charged with low pressure air or inert gas, which acts both as a barrier fluid and provides pneumatic seal loading. An access port is typically provided so the seal can be blown free of contaminants. A drop in seal cavity pressure indicates a need to inspect the seal. Pressure can be restored to normal by removing an adjusting shim, replacing the drive elastomer, or, if rotating faces are worn, by rebuilding the seal.

The MECO AH Type-2 seal model is custom-designed and built to order. Typically, assemblies are fully-split. Shaft diameters range from ¾” (18mm) to 18.5″ (470mm) and all sizes in between. Our typical space requirement is 2.5″ (65mm) around the shaft and 4″ (100mm) along the shaft for an easy split seal installation. Much smaller values are possible. Fig.1 is a design following USDA manufacturing guidelines; Fig.2 is a design meeting application-specific requirements for explosion protection following the European ATEX directive. The seal can be built into modified equipment components or simply swapped with existing seal housings, eliminating the need for equipment modifications, see Fig.3.

The MECO AH Type-2 seal is manufactured in several housing-stator combinations. The standard is an AH Type-2S, using 300-series stainless steel housings with integral stators. The AH Type-2A consists of aluminum housings with replaceable 300 series stainless steel stators attached. Other stainless steel or high-nickel alloys are also available.

The AH Type-2AP (not shown) uses one or two 1/8″ (3mm) thick stainless steel stator(s) with an extra-thick central housing or stator. Space, assembly and equipment restrictions dictate the need for the AH Type-2AP approach.

Rotor materials include a variety of filled PTFE and PBT materials, UHMW-PE, and PET. The different elastomer options available are Silicone, Viton®, EPDM and Nitrile, all available as FDA-compliant compounds.

Since Woodex Meco manufactures many custom MECO shaft seal models, we have the capacity to fabricate from many materials. If looking for an “off-the-shelf” version of the sealing approach, please check our HB model seal as a viable option.

Viton® is a registered trademark of E.I. Dupont de Nemours & Company.

Specifications

Results vary with conditions – call for discussion.