103U Cartridge Mechanical Seal

The product specifications give the 103U Cartridge Mechanical Seal a clearer structural identity than a generic cartridge-seal listing: it describes the seal as internal-mounted, internal-flow, unbalanced and driven by a single spring. That combination is useful for buyers because it gives four concrete checkpoints when replacing an existing seal: installation direction, flow arrangement, balance type and spring arrangement.

Instead of choosing only by shaft diameter, a maintenance or purchasing team should confirm that the existing assembly follows the same basic layout and then compare the critical installation dimensions. This is especially important when the old seal has no readable marking or when several visually similar cartridge assemblies are used in the same plant.

103U at a Glance

A Better Way to Select the 103U: Start With the Failure Risk

Media: Read the product specifications Wording Carefully

Suitable media include sewage, acid, seawater and other particle-containing neutral corrosive liquids. For acid service, seawater service or liquids with solids, confirm the actual concentration, particle characteristics and selected seal materials before production.

For accurate selection, convert a broad medium description into real operating data instead of treating "acid" or "sewage" as one fixed duty.

103U vs 104U: Why Model Numbers Should Not Be Treated as Interchangeable

The 103U and 104U have many similar shaft and diameter values, but the overall installation length L differs for several sizes. For example, 103U-16 uses L = 52 mm while 104U-16 uses L = 49 mm; 103U-20 uses L = 58 mm while 104U-20 uses L = 54 mm.

That small difference is exactly the kind of detail that can turn a "same size" replacement into a fitting problem. If a buyer is deciding between 103U and 104U, compare the full drawing and installation dimensions rather than relying on shaft diameter or visual similarity.

For Maintenance Teams: Five Measurements to Take Before You Remove the Old Seal

• Shaft diameter d.
• Primary outside diameters D3 and D4.
• Installation diameters D6 and D7.
• Overall installed length L.
• Axial reference length L3, plus L4-L8 when possible.

These measurements do not replace the complete drawing, but they create a much stronger starting point for factory matching than a model name alone. Photos should be taken before disassembly if the installation arrangement may be difficult to reconstruct later.

Factory Customization: What Qixing Can Work From

Qixing is a manufacturer and factory, so the product page should lead the buyer toward usable production information. For a standard size, send the 103U model and shaft diameter. For replacement or OEM work, also send the drawing, main dimensions, medium, temperature, pressure and speed. If the seal is already removed, clear photos of the assembly and stationary seat can help the matching process.

Customized does not have to mean a completely new seal design. In many B2B inquiries, customization starts with confirming the correct size, working condition and material configuration for the buyer's equipment.

When to Ask Qixing Before Ordering

• The working fluid is more corrosive than the product specifications description suggests.
• The liquid contains solids or granules and the particle condition is uncertain.
• Operating temperature is close to 180°C.
• Speed is close to 3000 r/min.
• The old seal looks similar to 103U but the model marking is missing.
• The shaft size matches but one or more installation dimensions do not.
• You are replacing 104U or another nearby series with 103U.

FAQ

What is the size range of the 103U Cartridge Mechanical Seal?

The product specifications list shaft diameters from 16 mm to 120 mm.

What design type is the 103U?

The 103U is an internal-mounted, internal-flow, unbalanced seal driven by a single spring.

What working limits are listed?

The product specifications list medium temperature from -20°C to +180°C, medium pressure up to 1.0 MPa and rotational speed up to 3000 r/min.

What media are listed for the 103U?

Suitable media include sewage, acid, seawater and other particle-containing neutral corrosive liquids. Final material compatibility should be checked for the actual fluid.

Can I order by shaft diameter only?

For a repeat order with a confirmed drawing, shaft diameter may identify the size. For replacement work, Qixing recommends checking the installation dimensions as well.

Is 103U interchangeable with 104U?

Do not assume direct interchangeability. The supplied tables show different overall lengths for several same-shaft-size models.

What should I send if I do not know the old model?

Send shaft diameter, main installation dimensions, photos of the seal and stationary seat, and the operating conditions.

Can Qixing make a customized 103U solution?

Qixing can review size, dimensions and operating requirements for factory matching. Any non-standard dimensional or material requirement should be confirmed case by case.

103U Dimension Table

Dimensions are shown in millimeters. Model names below use the Qixing-facing 103U designation.