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AH Type-2

Eliminate Setting Seal Face Pressures

The MECO AH Type-2 model is the best choice for fitting a split seal in limited space on small to large shaft diameters. The configuration is a double mechanical seal using an elastomer drive to rotate bearing-grade synthetic seal faces against fixed, stainless steel seal faces. The AH Type-2 uses a barrier fluid to pneumatically load the seal faces and isolate the process from the atmosphere. The AH Type-2 is suited for MRO and OEM equipment.

What Is MECO’s AH Seal?

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.

When Are AH Seals The Best Option?

The MECO AH Type-2 seal model is the answer to the question, “How can we fit a seal in the existing space?” 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 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 MECO models may be considered for faster speeds, higher pressures, and thermal cycling. MECO evaluates the parameters of each application individually and provides a custom engineered solution. Contact MECO for a design to suit your specific application.

This seal can be designed to fit between the gear reducer and trough end of a screw conveyor, as shown below.

How Does The AH Seal Model Work?

he 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, watertight 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.

How Is The AH Seal Maintained?

A pressure regulator is included with the seal to set inlet 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 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.

What Sizes Are Available?

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 20" (500mm) 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.

What Construction Is Available?

The MECO AH Type-2 seal is manufactured in several housing-stator combinations. The standard is an AH Type-2S, using integral 300-series stainless steel stators. The AH Type-2A consists of aluminum housings with replaceable 300 series stainless steel stators attached. Hardened stainless steel is also a stator material option.

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.

The common rotor seal face material is MECO 3000, a high-performance, bearing-grade, polymer-filled PTFE with FDA approval. Other options are: bearing grade PEEK; ceramic filled PTFE; virgin PTFE & UHMW. The different elastomer options available are Silicone, Viton®, EPDM and Nitrile, with all having an FDA-compliant option.

Since Woodex’s MECO Seal division manufactures many custom shaft seal models, we have the capacity to fabricate from any material required. If looking for an "off-the-shelf" version of the sealing approach, please check our MECO HB model seal as a viable option.

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

Specifications

Mechanical Capabilities
TEMPERATURE	-60° to 500° F (-50° to 260° C) Less on large shafts.
PRESSURE	Vacuum to +20 psig (140 kPa)
Shaft Speed	Up to 600 SFM (200 m/min) without cooling. Less on small shafts
Total Indicator Runout (TIR)	1/4" (6mm) standard; greater runout can be accommodated
Barrier Fluid Options	Air or Inert Gas, grease, Occasional water flush.

Results vary with conditions - call for discussion.

Literature

AH Type-2

The MECO AH Type-2 model is the best choice in split sealing technology, fitting a seal in limited space on small to large shaft diameters.

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Dairy Seals

A variant of MECO’s popular AH model seal, the Dairy Seal is specially designed to meet the needs of dairy product manufacturers

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Custom Shaft Seals for Food Processing

Originally developed for sealing dry powders in screw conveyors, MECO seals have evolved to fill sealing needs for a wide variety of food process machinery

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AH Type 2

AH Type-2

Eliminate Setting Seal Face Pressures

What Is MECO’s AH Seal?

When Are AH Seals The Best Option?

How Does The AH Seal Model Work?

How Is The AH Seal Maintained?

What Sizes Are Available?

What Construction Is Available?

Specifications

Results vary with conditions - call for discussion.

Literature

Industries

Resources

Partners