In industrial pumping systems, sealing reliability directly affects plant safety, operating cost, and equipment life. Among different sealing technologies, the bellow mechanical seal is widely used because it compensates for shaft movement, absorbs vibration and helps maintain consistent sealing pressure.
However, not all bellow seals are the same.
In this article, we explain the four most commonly used types of bellow mechanical seals:
- Welded metal bellow mechanical seal
- Rubber bellow mechanical seal
- Elastomer bellow mechanical seal
- PTFE bellow mechanical seal
This guide is written for maintenance engineers, purchase managers and plant operators who want to select the right seal and avoid repeated seal failures.
Table of Content
What is a Bellow Mechanical Seal?
A bellow mechanical seal uses a flexible bellow element instead of conventional springs to generate closing force on the seal faces.
The bellow also acts as a secondary seal, preventing leakage along the shaft or sleeve.
Because of this design, bellow seals are especially suitable for:
- misalignment and shaft deflection
- thermal expansion
- applications where springs can clog or corrode
Welded Metal Bellow Mechanical Seal
A welded metal bellow mechanical seal uses multiple thin metal diaphragms that are welded together to form a flexible bellow assembly.
Unlike elastomer-based designs, this seal does not rely on rubber components for flexibility.
Key features
- Excellent resistance to high temperature
- Suitable for high vacuum and high pressure services
- No dynamic O-rings or rubber parts
- Very stable face loading
Common materials
- Stainless steel
- Inconel
- Hastelloy
Typical applications
- hot oil pumps
- chemical processing pumps
- hydrocarbons and solvents
- refinery and pharmaceutical services
Why choose welded metal bellow seals?
If your pump operates at elevated temperature or handles aggressive chemicals that attack elastomers, a welded metal bellow seal provides long-term reliability and stable performance.
Rubber Bellow Mechanical Seal
A rubber bellow mechanical seal uses an elastomer bellow as the flexible and secondary sealing element. It is one of the most widely used and cost-effective bellow seal types.
Key features
- Simple construction
- Good flexibility and vibration absorption
- Easy installation
- Economical solution for standard pumps
Common elastomers used
- NBR
- EPDM
- Viton (FKM)
Typical applications
- water pumps
- cooling systems
- HVAC circulation pumps
- light chemicals and utility services
Why choose rubber bellow seals?
Rubber bellow seals are ideal when operating conditions are moderate and cost efficiency is important without compromising basic sealing reliability.
Elastomer Bellow Mechanical Seal
Although rubber bellows are elastomers, elastomer bellow mechanical seals generally refer to advanced polymer or specialty elastomer bellows that are designed for improved chemical and temperature resistance.
Key features
- Better chemical compatibility than standard rubber bellows
- Improved fatigue life
- Enhanced sealing reliability in variable operating conditions
Typical applications
- pharmaceutical and food processing pumps
- mild corrosive fluids
- process water containing additives
Why choose elastomer bellow seals?
When standard rubber bellows show swelling, cracking or premature ageing, elastomer bellow seals provide a more stable alternative while maintaining installation simplicity.
PTFE Bellow Mechanical Seal
A PTFE bellow mechanical seal uses a chemically inert PTFE bellow instead of rubber or metal.
This design is preferred where chemical resistance is more critical than mechanical flexibility.
Key features
- Outstanding chemical resistance
- Non-stick and contamination-free design
- Suitable for highly corrosive fluids
- Low friction characteristics
Typical applications
- acids and alkalis
- chemical transfer pumps
- pharmaceutical and specialty chemical industries
Why choose PTFE bellow seals?
If elastomer components fail due to aggressive media, PTFE bellow seals offer a reliable solution with superior corrosion resistance and long service life.
Looking for the Right Bellow Mechanical Seal for Your Pump?
At Mechanical Seal India, we supply and support rubber bellow, elastomer bellow, PTFE bellow and welded metal bellow mechanical seals for a wide range of centrifugal and process pumps.
Our technical team helps you:
- match the correct seal type to your operating conditions
- select suitable materials
- avoid unnecessary trial-and-error replacements
👉 Send your pump model, shaft size and application details to request a quotation or technical recommendation.
