Australian Pipeline Valve - Installation, Operation and Maintenance Manual 25 API6D THROUGH CONDUIT EXPANDING GATE VALVE - AP400-405 SERIES Emergency sealant injection on seats Provision of seat injectors with integrated check valve provides emergency back up sealing. Additionally, an inner check valve is installed in front of the seat injector to prevent blow out in case of wrong operation. If a seal surface is damaged by foreign matter, valve leakage can be eliminated by using a sealant injected into a specially designed groove in the seat ring assembly. The secondary seat sealant injection backup provides a peace of mind to users who demand reliable block valve service until the valve can be properly serviced. Seats may be lubricated by injecting lubricant to enhance service life and reduce operating torque. API6D EXPANDING GATE VALVE