Special mechanical seal is the products designed by specific condition and usage. Special seal includes mechanical seals used in high density of impurities conditions and split seal. Mechanical seals used in high density of impurities uses rubber coated metal dish spring, the dish spring has the function of elastic element and secondary seal. The disc spring can effectively avoid the failure of spring block caused by the impurities. Also the structure of this seal is very compact, has very small requirement of the install space. The metal parts and sealing face of the split seal are take apart into two pieces, this structure will be very convenient to install on the pump, no disassembly of the pump and coupling is needed.