The ARCA angle style control valves Series 350 and 380 are proven under critical process conditions. If used in steam or process gas applications at high pressure and temperature, in cavitation-free relaxation of liquids at high pressure differential, or in handling of fluids with high solid contents, the modular system of valve housings, bonnet and trim styles, in combination with a large range of materials, always offer an ideal solution.
The combination of high pressure ratio and solid-containing fluids, such as those found in boiler feed water control for example, is one of the most critical challenges for sizing, selection and design of a control valve.
Due to the high pressure ratio, multi-stage valves are indispensable to avoid severe cavitation damage. However, as soon as the fluid contains solid particles, besides the normal fluid-dynamic sizing (determination of the number of throttling stages and their individual flow coefficient), the grain size of the particles has to be taken into account. The cross-section area of each flow channel in the valve must then be of the size and shape that will allow all particles in the fluid (assumed to be of spherical shape) to pass.
Since the cross sectional area of each throttling stage is explicitly defined by the flow coefficient calculated from the fluid-dynamic valve sizing, only the shape of the flow channel remains to be optimised.
It is obvious, that a circular shape is the optimum with regard to the permeability of spherical particles. ARCA’s newly developed multistage trim MS4 valves, which have only one flow channel in each stage, milled as a spherical calotte into a rigid, multiple guided control rod, approximates this ideal shape and is superior to a multistage parabolic plug design in this respect.
Another special feature of this trim style is the protection of the seating surface (which is the most sensitive area in terms of erosion) by over-stroke of the valve. The rigid multiple guidance of the control rod is an effective prevention against mechanical vibrations and resulting wear, even at extremely high pressure differentials.
Series 350 and 380 are available in sizes up to 10” (DN 250) and ratings up to Class 2500 (PN 400). Depending on the process conditions, MS4 trims can be delivered in valve sizes up to 4” (DN 100).
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