John Crane Type 1 Elastomer Bellows Mechanical Seal

Overview

John Crane Type 1 is a full convolution, industrial-duty elastomer bellows shaft seal that John Crane describes as the industry workhorse. Its single coil spring and elastomer bellows have a long record of reliable service in water, steam, chemicals and many corrosive fluids, and the design is used in pumps, mixers, blenders, agitators, refrigeration compressors, blowers, fans and other rotary shaft equipment. Because the bellows acts as the secondary seal and also drives the seal head, the John Crane Type 1 is simple to fit, tolerant of shaft end play and economical, which is why it remains a standard choice for general process duties.

Seven Star LLC supplies the John Crane Type 1 to plants in Oman and the GCC, with engineering support in Muscat. Typical customers include power, water and wastewater operators, food and chemical processors and maintenance workshops that need a dependable single seal for centrifugal pumps. We can help you collect the shaft size, seal chamber dimensions, fluid and speed data that John Crane lists as the basis for confirming an application before an order is placed.

Operating Principle

The John Crane Type 1 is a rotating, non-pusher mechanical seal. A primary ring, normally carbon, is held against a stationary seat by the force of a single stainless steel coil spring and by the pressure of the sealed fluid. The two lapped faces run with a thin fluid film that keeps leakage very low while preventing contact wear. A moulded elastomer bellows grips the shaft or sleeve and also seals between the shaft and the primary ring, so no sliding O-ring is needed and there is no fretting of the shaft at the secondary seal position.

The bellows is not stressed by the transmission of torque. A drive band and drive notches carry the breakout and running torque from the shaft to the face assembly, which prevents overstressing of the elastomer and eliminates slippage that could score the shaft or sleeve. The seal is self aligning, compensating automatically for abnormal shaft end play, run-out, primary ring wear and equipment tolerances through uniform spring pressure. Special balancing allows higher pressure and speed duties with lower face wear, and the non-clogging single coil spring is not affected by build-up of solids from the pumped liquid.

Engineering Design of the John Crane Type 1

The Type 1 assembly consists of a face or primary ring, a spring, an elastomer bellows, a retainer, a drive band, a spring holder and a disc. In the standard configuration the face is carbon, the retainer, disc, drive band, spring holder and springs are 18-8 stainless steel, and the bellows is Buna-N. Options include antimony-impregnated carbon, tungsten carbide and silicon carbide faces, Monel, Alloy 20 CB-3 and 316 stainless steel metal parts, and Aflas, fluoroelastomer, ethylene propylene or neoprene bellows. This material range lets the same seal envelope cover clean water, hot water, mild chemicals and many hydrocarbons once the correct combination is selected.

John Crane publishes dimension tables for shaft sizes from 1.000 to 4.000 inches. For a 1.000 inch shaft the Type 1 seal outside diameter D3 is 1.500 inches, the minimum bore D4 is 1.750 inches and the working length L3 is 1.562 inches. For a 2.000 inch shaft the corresponding values are 2.625, 2.937 and 2.125 inches. The balanced Type 1B version shares the same family and is rated to higher pressure. Installation requires a chamfered lead-in on the shaft or sleeve, a surface finish of 63 Ra for 1.00 to 3.125 inch shafts and 32 Ra above that, shaft ovality below 0.002 inches and axial float within plus or minus 0.005 inches.

Key Features of the John Crane Type 1

The John Crane datasheet and product page highlight these design features of the John Crane Type 1.

• A mechanical drive through a drive band and notches eliminates overstressing of the bellows and slippage on the shaft.
• Self-aligning automatic adjustment compensates for shaft end play, run-out, primary ring wear and equipment tolerances.
• Special balancing allows higher pressure applications and greater operating speed with less wear.
• A non-clogging single coil spring is not affected by the build-up of solids.
• Low drive torque improves performance and reliability.
• The temperature range is minus 40 to 205 degrees Celsius depending on the materials used.
• The Type 1 is rated up to 29 bar g and the Type 1B up to 82 bar g under the datasheet basic conditions.
• A wide choice of face, metal and elastomer materials suits water, steam, chemicals and corrosive services.

Industrial Applications

The John Crane Type 1 is widely used on process pumps and other rotating equipment. In the Sultanate of Oman it fits well on water transfer and circulation pumps in power and desalination plants, on cooling water and utility pumps in oil and gas facilities, and on general service pumps in industrial zones such as Sohar and Salalah. John Crane lists the pulp and paper, petrochemical, food processing, wastewater treatment, chemical processing and power generation industries as frequent users. The seal also suits mixers, agitators, blowers, fans and refrigeration compressors where the shaft is accessible and the duty is moderate.

Selecting the right pressure rating is important. The datasheet explains that the basic pressure rating assumes stable operation at 1800 rpm in a clean, cool, lubricating, non-volatile liquid, and it supplies multiplier factors for speed, fluid lubricity and temperature. For example, water and aqueous solutions use a multiplier of 0.75 and flashing hydrocarbons 0.60. Seven Star LLC can help you work through the application data for the John Crane Type 1 with these factors and refer unusual duties to the manufacturer.

Technical Specifications

The table summarises published data for the John Crane Type 1 family from the John Crane Type 1/1B technical specification.

Related Sealing and Pump Products

If you are comparing seal types, see the John Crane Type 5610 cartridge mechanical seal. For the pumps that commonly use a seal like the John Crane Type 1, review the KSB Etanorm centrifugal pump and the Goulds 3196 i-FRAME ANSI process pump.

How to Order

To order the John Crane Type 1, send an RFQ to Seven Star LLC with the shaft or sleeve diameter, the equipment make and model, the shaft rotation direction, the fluid and its temperature and pressure, and the operating speed. We will confirm availability and lead time, share the John Crane technical specification and arrange delivery across Oman and the GCC. Our team in Muscat can also advise on spare seal faces, bellows and springs for scheduled maintenance.