Metal Bellows Mechanical Seals Design Features
1.  Wide service range from cryogenics to heat transfer liquids and corrosive chemicals.
2.  Long MTBR(Mean Time Between Replacement) since there is one moving part, metal bellows.
3.  Flexible bellows construction eliminates seal hang-up due to solids or dirt in pumpage.
4.  Metal sealing wedge eliminates temperature restrictions of elastomers or plastics.
5.  Built-in hydraulic balance eliminates step in shaft or sleeve.
6.  Available for either inside or outside mounted.
7.  Stabilizer tabs prevent possible damage due to vibration and excessive shaft run-out.
Metal bellows mechanical seals will not fret the shaft or sleeve because it has no dynamic (sliding) 0- ring. All pusher seals (seals with springs) have dynamic 0-rings. This means that you can mount either metals bellows mechanical seals directly on the shaft and save the cost of sleeve. Because the bellows that act as spring does not have to overcome 0-ring friction drag, as does the  pusher seal, the spring load can be lighter than in the pusher seal design. Some common pusher seals have spring loads about 50 psi, while the metal bellows load is approximately 25 psi. This can result in up to 50% decreased seal face wear rate. The metal bellows produces even face loading, superior face tracking and less frictional heat.

Metal bellows mechanical seals feature a metal bellows core made of one of several types super alloy or steel.   The most common are AM350, Inconel 718 and  Hastelloy C-276.   Usually with Alloy 42(Carpenter 42), Stainless Steel (SS 316) end fittings permits these metal bellows mechanical seals to be used for services beyond the range of mechanical seals with elastomer as secondary sealing element.
Typical applications include: cryogenics, heat transfer fluids, severe chemicals, slurry and corrosives at temperatures from —350° to +800°F (—212° to +425°C) with standard seal construction.