Valve assemblies

For process applications, valve assemblies (body, seats, suction and discharge valves) are made of different valve type, i.e. up-guided, wing, single or double ball, axial with or without spring guidance. Valves are chosen according to the available NPSH, operating pressure, fluid viscosity and the solid particles hardness, size and percentage. The axial type valves, used since the beginning of the 80's, provide several advantages such as:

• large flow section areas and consequent low fluid velocities through the valves, allowing reduced pressure loss and wear;
• dual-seal suction valves allowing high suction capability and low NPSHR;
• easy maintenance in the field: the valves and valve seats can be pre-assembled and replaced in very short time (30 minutes approx.);
• limitation of the fatigue stress present in the hydraulic end to the valve seat block only; this reduces the possibilities of failure due to fatigue in the hydraulic end to a single component of small dimensions, easy accessibility with the ensuing economics.

For slurry service the valves are wing type with technopolymer insert and are designed by adopting:

• optimised metal plus non metal sealing surface; 
• low fluid speed under valve passage to reduce erosion wear;
• large radius and smooth fluid passages to minimise flow resistance , particles erosion and sedimentation effect;
• remote canister arrangement to make the relevant maintenance activities easy and fast.