Replacing the throttle valve components: To replace the valve disc and seat, first relieve the pressure in the valve chamber and remove the bonnet bolts; then, lift out the valve disc along with the bonnet assembly. Remove the slotted round nut, switch pin, hex screws, and the front and rear stop caps to replace the cylindrical valve disc and the valve seat. Clean the valve chamber, paying special attention to the sealing surfaces. When installing the new valve disc and seat, fill the gap between the valve disc and the bonnet boss with sealing grease, and fill the interior of the bonnet with calcium-based grease to lubricate the bearings.
Replacing the lip-type seal packing: First, relieve the pressure in the valve chamber; then, remove the protective cover, round nut, handwheel, bearing gland, bearings, and packing gland before replacing the lip-type seal packing.
Replacing the bearings: Remove the protective cover, round nut, handwheel, and bearing gland to access and replace the bearings. To replace the lower bearing, the valve stem nut must be removed. Bearing clearance is adjusted via the bearing cap; after adjustment, the handwheel should operate smoothly without binding.
