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Brand: John Crane
John Crane Type 2 Elastomer Bellows Seal
Description
A multi-purpose elastomer bellows seal in balanced and unbalanced forms
The John Crane Type 2 and Type 2B elastomer bellows seals are, according to John Crane, specified in more original equipment than any other seal from any other manufacturer. They suit water, refrigeration, oils and chemicals in pumps, mixers, blenders, agitators and compressors, and they fit confined spaces and limited seal chamber depths. Type 2B is the balanced version for higher pressures, offering greater operating speeds and reduced face wear.
Technical specifications
| Parameter | Specification |
|---|---|
| Seal type | Single elastomer bellows seal; Type 2 unbalanced, Type 2B balanced |
| Temperature | -40 to 205 degC (-40 to 400 degF), depending on materials |
| Pressure | Type 2 up to 29 bar g (425 psig); Type 2B up to 83 bar g (1,200 psig) |
| Speed | Per the speed-limit chart in the datasheet (standard or welded-end coil spring) |
| Seal sizes | 1.000 to 4.000 in. in the datasheet dimension tables |
| Face / primary ring | Carbon standard; antimony-impregnated carbon, tungsten carbide or silicon carbide optional |
| Bellows | Buna-N standard; Aflas, fluoroelastomer, ethylene propylene or neoprene (chloroprene) optional |
| Retainer, drive band, disc, spring holder | 18-8 stainless steel standard; Monel, Alloy 20 CB-3 or 316 stainless steel optional |
| Springs | 18-8 stainless steel standard; Monel, Alloy 20 CB-3 or 316 stainless steel optional |
| Shaft surface finish | 1.00 to 3.125 in. diameter 63 Ra; above 3.125 in. 32 Ra |
| Shaft ovality | 0.002 in. (0.051 mm) |
| End play / axial float | Plus or minus 0.005 in. (0.13 mm) |
Design features
A mechanical drive prevents overstressing of the elastomer bellows. The seal is self-aligning, so it compensates for shaft end play, run-out, face wear and equipment tolerances. Special balancing on the 2B allows operation at higher pressures, and the non-clogging single-coil spring is not affected by solids build-up. The datasheet gives basic pressure ratings with multiplier factors for speed, fluid lubricity and temperature, plus hydrostatic limits.
What to confirm before ordering
Choose between Type 2 and Type 2B from the operating pressure, then state the shaft or sleeve diameter, equipment, fluid, specific gravity, box pressure, temperature and speed. Type 2/2B can be customised for specific installations after review by John Crane. Compare with the simpler John Crane Type 1; more are listed under Pumps.
Documents and quotation
The attached John Crane technical specification (8 pages) covers both Type 2 and Type 2B with dimensions, ratings and materials. Send the shaft size and duty for a quotation.
Datasheets & Documents
- Datasheet John Crane Type 2/2B elastomer bellows seals technical specification Download
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About brand
Mechanical seals for pumps and other rotating equipment are a core John Crane product, and the company dates from 1917. The company is based in Slough, United Kingdom, and its seal type numbers are quoted on pump datasheets around the world. Seven Star LLC, an independent supplier in Oman, lists the John Crane Type 1 elastomer bellows mechanical seal and the Type 5610 cartridge mechanical seal.
John Crane seal types listed here
The two listed seals represent two ways of fitting a seal. The Type 1 is a component seal: an elastomer bellows head that grips the shaft, running against a separate stationary seat, and assembled into the pump piece by piece. The Type 5610 is a single cartridge seal of the O-ring pusher type, delivered as one preassembled unit with sleeve and gland plate that slides over the shaft and bolts to the seal chamber. Cartridge seals take the setting measurements out of the fitter's hands.
Ordering John Crane seals: what we need
A seal is defined by more than its type. Send the seal type, shaft or sleeve diameter, the material code for faces, elastomers and metal parts, and any drawing or part number from the old seal or its box. Add pump make and model, liquid, temperature, pressure and speed. Refineries and water plants in the GCC usually also quote the flush plan, which we pass on with the inquiry.
Browse John Crane products by category: Pumps.
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Frequently Asked Questions
What is the difference between Type 2 and Type 2B?
Type 2B is the balanced version for higher pressures, with greater operating speed and reduced face wear.
What pressure can each version handle?
Type 2 up to 29 bar g (425 psig); Type 2B up to 83 bar g (1,200 psig).
What temperature range applies?
-40 to 205 degC (-40 to 400 degF), depending on materials.
Which seal sizes are listed?
1.000 to 4.000 in. in the datasheet dimension tables.
Which face materials are offered?
Carbon as standard, with antimony-impregnated carbon, tungsten carbide or silicon carbide optional.
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