The mechanical seals were leaking in a horizontal split case centrifugal pump. A horizontal split case centrifugal pump has two mechanical seals installed; one inboard and one outboard side. The seals started to leak approximately two week after installation. Talking to maintenance people the seals in this pump always leak because the installation is difficult. The diameter of the shaft is approximately 5 inches and the seal needs to be installed in several steps. One time I witnessed the seal replacement and understood why maintenance is complaining. The seal needs to be installed onto the pump sleeve in several step and pushed along the sleeve until it reaches the final destination. If the maintenance people push the seal at the wrong piece the seal falls apart and it needs to be removed from the pump sleeve and the assembly and installation process goes back to the first step. The solution was to design a cartridge seal that does not need to be assembled because it is assembled at the seal manufacturers including the sleeve and the gland plate. Therefore, no assembly at the site is required. The complete assembly can be installed onto the pump shaft as a unit. In order to add a sleeve to the cartridge seal the outside diameter of the pump sleeve had to be remachined. The pump manufacturer gave us the allowable dimensions. The pump sleeve was remachined and reinstalled onto the shaft. The cartridge seal was installed onto the pump sleeve without any problem and final assembled to the pump. The seal did not leak statically or after startup.
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