Innovation: Pre-cartridge mechancial seal for tubular pumps. The pre-cartridge structure of this design makes sure the mechanical seal component can be installed or uninstalled easily by final end users. Comparing to other traddional tubular pump seals, this component can be installed within 30 minutes. Also improved design is applied into the seal such as inserted O-ring, rubber blanket under rotating and stationary rings, slot under the ends of the shaft sleeve, multi-spring design, stop ring for easy uninstallation etc. This mechanical seal component has much longer life-time (over 16,000 operating hours) than tradditional tubular pump seals (8,000 or 12,000 hours).