GESTRA Flowserve DK 47L Instructions De Montage Et De Mise En Service page 17

Maintenance / Exchanging Valve Plate
The DK 47 and DK 57 do not require any special maintenance.
1. Unscrew and remove cap A.
2. Clean body seat C and valve plate B.
3. Insert cleaned valve plate (with grooved side down).
4. Apply heat-resistant lubricant to cap thread.
5. Tighten cap with a torque of 150 Nm (DN 1": 250 Nm).