Term denoting a mechanical seal's closing pressure. The sliding pressure is the pressure of the spring backing added to the product of the load factor k and the differential pressure between the outside and inside of the mechanical seal.

Sliding pressure p_g is defined
as p_g = p (k - k₁) + p_f

with p= pressure differential to be sealed

k = hydraulic load ratio

k₁ = factor describing the distribution of pressure across the sealing width (mostly taken as k₁ = 0.5)

p_f = the spring force as a function of the sliding face area A

With unfavourable deformation of the sliding face (e.g. a "V-gap" in an externally pressurized seal, sealing gap forms), the value k₁ can be so big that p_g becomes negative, a circumstance that can lead to the sliding faces separating.