It can be electrowelded to optimize the compactness and the execution versatility. The constructive versions are those mentioned on page 3.
Seat in the body:
The seat in the valve body is obtaine executing a carryover of 21 degree Stellite, through welding. This carryover is executed both on the bodies of steel to the carbon and those of stainless steel. The place of business is worked at digital control machine with CAD-CAM technology to obtain his special elliptical form which marries exactly the estate ring.
This particular shape, together with the stem double eccentricity, allows it not to be subject to creeps, during the disc rotation, with the relevant sealing ring.
It is compact and shaped in such a way to offer the lowest possible resistance to the medium passage as well as a low dynamic torque.
The construction is suitable for housing both the shaft in double accentric position vs. the seat and the sealing ring with its retaining ring held on the disc by means of screws.
The fixing to the shaft is carried out using conic pins and keys; the first for small sizes, both for bigger sizes.
Seal lamellar ring:
It is built intercalating metal rings with gasket materials (graphoil, AFM, or similar) absolutely free of elastomers and PTFE.
It is positioned on the disc in a loose housing and held by a bolted ring; nevertheless it has the possibility to move for centering and fitting itself to the body seat.
Its eliptical shape, obtained by machining, perfectly fits the seat in the body and, joined to a suitable shut-off torque, the perfect sealing, also bi-directional, is reached.
The shaft is made of one-piece and passes across the whole valve.
This allows the better distribution, all over the disc, of the shut-off torque. It is mounted on wide-band bushings and has a bottom of an adjustable thrust bearing that the perfect disk centering allows in axial sense.
In standard version they are made of stainless steel with an surfacing anti-friction hardening; for more exacting applications they are made of high quality alloys.
In the most cases it is made of graphoil pre-compressed rings inserted into a stuffing box in the body and kept under compression by a gland with adjustament rods. For particular operating conditions other materials can be used.