All mechanical seals need to keep the mechanical seal faces closed in the absence of hydraulic pressure.Different types of springs are utilized in mechanical seals.

Single spring mechanical seal with an advantage of comparatively heavy cross section coil can resist a higher degree of corrosion, and does not get clogged by viscous fluids The single spring mechanical seal has a disadvantage which doesn't provide uniform loading characteristics for the seal faces. Centrifugal forces may tend to unwind the coils.Single springs tend to require more axial space and mechanical seals with different sizes require springs with different sizes.

 Multiple springs are usually smaller than single springs,supplying a more uniform load at the seal faces. Many mechanical seal with different sizes can use the same springs only by changing the number coils of springs.Multiple spring resist unwinding from centrifugal force than a single coil spring with the forces working differently.But the small cross section wire.of the small springs causes the smaller springs not to resist corrosion and to be clogged

A wave spring mechanical seals requires even less axial space than the multiple spring design. But special tooling must be made to reach the best manufacturing results,besides the tempering required on this design limits materials to the high grade stainless steel and Hastelloy groups.Thirdly,a greater change in loading for a given deflection must be tolerated.A great deal of force loss or force gain with comparatively small axial movement must be expected.

A washer is a very stiff spring;in fact,the normal problem with a washer is that the spring rate is too high. To reduce the spring rate,the washers are stacked.

bellows：A combination of a spring and secondary sealing element is a metal bellow.There are welded edge metal bellows and formed bellows.The formed bellows are used to reduce the quantity of welding with formed bellows being a much higher spring rate than welded bellows.Selection of the bellow thickness is made according to the resistance to pressure without an excessive spring rate.It is important to select the welding technique and bellows shape for maximum fatigue life.