Liner Wiper Plug

The Liner Wiper Plug may be shear-pinned on the bottom of the setting tool. The conjunction with pump down plug keeps mud to be separated from cement and removes the cement from the inside of the liner.

The Saigao latch-in liner wiper plug is similar in design to the standard liner wiper plug and has the same function of wiping the liner of excess cement. The primary difference is that it has a latch-in nose assembly located at the bottom of the plug. After wiping the liner the plug lands in a landing collar located near the bottom of the liner. The plug nose has a snap ring that latches into the landing collar, thus locking the wiper plug and drill pipe dart tandem in place. This ensures that the plugs will not move during subsequent operations. The landing collar serves a second purpose in that it has a function similar to that of a float collar. The float collar contains a valve that allows the cement to flow to the bottom of the liner and through the float shoe. Once the cement job is complete the valve in the float shoe closes so cement doesn’t come back up the liner. If the float shoe fails the valve in the float collar acts as a back up to the float shoe. Once the plug assembly latches into the landing collar it effectively closes off any pathway for fluid flow. Therefore a wiper plug landing collar can effectively be used in place of a standard float collar. The landing collar is an additional item that is used only with the latch-in wiper plug. All materials in the wiper plug and landing collar can be easily drilled out later.