Some valve bodies can be adapted for low flow rates retaining the standard
size valve body but using smaller valves and seats. These are known as restricted
trim valves and may be contoured, Vee ported or fluted (Fig. 100(b)). The
capacity of the valve using this trim style is usually about 40 per cent that of the
full body size. Such designs are used when it is not economical to reduce pipe line
size to fit a smaller valve and with certain vapour liquid conditions.
The valve body may be of cast iron (-29°C to 350°C), carbon steel (450°C),
stainless steel (corrosion resistant) (-100°C to 560°C) chrome molybdenum steel
620°C)
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