Type 1 Mechanical Seal Replacement

Type 1 replacement: confirm the fit before ordering

This single-spring, unbalanced mechanical seal uses an elastomer bellows and supports either direction of rotation. It is offered for Type 1 replacement enquiries where the rotating assembly, stationary seat and pump installation dimensions can be matched. Start with the seal fitted in your pump: a model name and shaft diameter alone do not describe the complete assembly.

Specifications for this replacement range

• Standard shaft sizes: 12–100 mm
• Temperature range: −10 to +160 °C
• Pressure limit: 10 bar
• Sliding speed limit: 20 m/s
• Construction: single spring, unbalanced, elastomer bellows
• Rotation: bi-directional

These are the listed limits for this supplied range, not the ratings of every original-brand Type 1 seal. The permitted duty depends on size, face combination, elastomer and liquid. Do not assume that maximum temperature, pressure and speed can be used together; include the actual operating conditions in your enquiry.

Four checks for a Type 1 seal replacement

1. Identify the shaft or sleeve. Record the diameter at the seal position and the measurement units. Include the pump model and any markings on the old seal.
2. Confirm the working length. Compare the installed axial space with the proposed seal drawing. A loose seal’s free length does not establish its required working length.
3. Match the stationary seat. Check the seat outside diameter, thickness, mounting recess and retention details. Show both faces of the seat in photographs; a similar-looking rotating assembly does not confirm that the seat will fit.
4. Check the complete assembly. Compare the rotating assembly envelope and available chamber space as well as the shaft size. Resolve drawing differences before ordering or installation.

The drawing and size chart below are useful starting references. If a dimension cannot be read clearly, send a marked sketch or request a drawing for the proposed size rather than estimating it from a photograph.

Materials to specify in your enquiry

• Seal faces: carbon, silicon carbide (SiC), sintered silicon carbide (SSiC) and tungsten carbide (TC) options.
• Elastomer: NBR, EPDM and FKM (listed as Viton in the original specification) options.
• Spring and metal parts: 304 or 316 stainless steel.

Specify both mating face materials if known. Include the liquid name, concentration, temperature and any solids so the face pair and elastomer can be checked together. If the old bellows is swollen, hardened or cracked, mention that condition instead of simply requesting the same material.

Model references and interchangeability

Our catalogue references John Crane Type 1, Burgmann MG901, AES P05U, Flowserve 51 and Vulcan A5 for replacement enquiries. Treat these names as identification leads. Interchangeability requires confirmation of the particular size, working length, seat arrangement and materials. Brand names identify the seal being replaced; this page offers a replacement product rather than an original-brand seal.

For other model families, see our John Crane replacement selection guide or browse pump mechanical seals.

Questions before purchase

Is the shaft diameter enough to select a seal?

No. Also confirm the installed length, stationary seat dimensions and chamber clearance. Two assemblies with the same shaft size can require different fitting dimensions.

Can I order from a photograph of the old seal?

A photograph helps identify the construction, but it does not establish dimensions or materials. Add measurements, markings and operating details. Photograph the stationary seat separately if possible.

What should I send for a quotation?

Send the pump make and model, seal reference, quantity, shaft size, working length, seat measurements, liquid, temperature, seal-chamber pressure and operating speed in rpm. Attach the old seal drawing or clear photographs and identify any dimensions that are still unknown.

Request a Type 1 replacement quotation with these details so the proposed dimensions and material combination can be confirmed before supply.