CONSTRUCTION DETAILS

Body
The body geometry is designed as the result of stress calculations to achieve the most regular distribution of the internal forces dues to pressure action. The body material is high quality cast steel. The seats surface is covered by a wear resistance stainless steel. On request the seat surface can be covered also with stellite or other special material overlays.

Bonnet
The bonnet is the bolted type, or pressure seal type (for higher pressures), designed to achieve the minimum turbulence and flow resistance. The bonnet material is the same or similar to the body material. Beside, the bonnet is designed and manufactured in order to ensure a perfect seal, as well as to allow an easy disassembly and reassembly work.

Wedge
All RT's gate valves have a full bore and in the open position the wedge is fully retracted to ensure the lowest pressure drop. RT's gate valves can be provided with the following gate systems:

• Split wedge (double disk wedge): this type is the best solution for small valves with frequent operation. The normal wear is easily recovered by the automatic adjustment of two disk and a perfect tight can be obtained with low torque.
• Flexible wedge: this is the most used and well known type of wedge. Owing to his low weight and the flexibility due to his particular construction can be employed in medium and large size valves with very good result also in high and low temperature services.
• Solid wedge: this type is generally used in larger size where due to small space between the two body seat other types can't be used (typically in short face to face valves).

Yoke and handwheel
The standard valves are provided with yoke sleeve and handwheel for manual operation. On request the yoke can be provided with a connection flange according to ISO that allow the mounting of other operation devices (actuator, gear box, etc.).

Gasket
The standard gasket is in pure graphite stainless steel reinforced. This type of gasket is suitable for many different applications.
On request RT can supply special gaskets designed for the specific application or according to customer specifications.

Stem
In all outside screw valves the stem is provided with integral backseat for emergency leak repairing. The stem is produced whit special turning machinery for a high resistance and durability. The stem thread is metric type according to ISO standard with trapezoidal section. The tread is left hand type in the way that the valve opens rotating clockwise the handwheel.

Packing
The standard packing is made of four or more pure graphite rings with square section with anti-extrusion system. Other materials like PTFE are available on request.