OPERATING LENGTH OF THE MECHANICL SEAL O012
The operating length of the seal is measured after the seal has been set to the proper compression. When the seal is at its correct operating length it will have the proper face load of approximately 30 psi. (2kg/cm2).
The installation measurement is different. It tells us where to attach the seal to the shaft or sleeve. The measurement is usually made from the face of the stuffing box to the back of the rotating part of the mechanical seal. In most seal installations you have a tolerance of about ± 0.030 inches (± 0.8 mm) to stay within the proper face loading.
When properly installed the seal will maintain the correct spring load over the wear length of the carbon face.
The wear length is usually in the order of 0.125 inches (3 mm).