Mechanical Seals

Why Mechanical Seals Replaced Soft Packing in Modern Pumps

May 12, 2026

Soft packing was historically common in pumps, but modern process pumps usually use mechanical seals because they provide better leakage control, safety and reliability.

Packing rings

Mechanical seal faces

Simplified comparison: packed gland vs mechanical seal arrangement.

What is soft packing?

Soft packing uses braided rings compressed around the shaft or sleeve. It is simple and cheap, but it normally requires controlled leakage for lubrication and cooling.

Why mechanical seals became standard

much lower leakage,
better safety for hazardous liquids,
lower product loss,
cleaner operation,
better environmental performance,
less shaft/sleeve wear when correctly applied.

Modern cartridge seals

Today, many mechanical seals are available as cartridge units. They are easier to install, reduce assembly errors and are often cost-effective even for non-API industrial pumps.

When packing may still be used

simple water service,
dirty liquids where leakage is acceptable,
low-cost utility pumps,
applications where maintenance staff prefer packing.

Why packing is often avoided

Packing can cause leakage, sleeve wear, maintenance work and housekeeping problems. In many modern plants, even relatively cheap mechanical seals are preferred because leakage expectations are stricter than before.

Engineering recommendation

For most process applications, select a mechanical seal and define the seal plan, materials and leakage expectations clearly in the datasheet or material requisition.