Ramén Ball Sector Valves
Ramén Ball Sector Valves are used as isolating and control valves for fluids, gases, turbid media and sludge, especially in the mining industry, pulp and paper industry and chemical industry. Abrasive slurries of iron ore, coal, lime and fly ash are also controlled with this type of valve.
Ramén Ball Sector Valve – Construction principle
Ramén Ball Sector Valve is made from a half ball sector which via two shafts is journal led in the valve body. One part of the ball sector sphere is used for shut-off. The other part does the regulation and has a hole with a diameter of about 80% of the nominal valve size. This is the optimal size to get excellent regulating characteristics.
The ball sector is turned through about 90° on operation from fully open to closed. The shape of the valve opening (flow area) is thereby changing from fully circular to elliptical. The circular opening reduces the risk of blockage and is less subject to wear in throttling position than the more slot-like flow in certain other types of control valves.
Size overview of the Ramén Ball Sector Valve, DN25-300
A versatile valve suitable for most control tasks
The valve characteristic maintains almost the same percentage value with constant differential pressure. The modified equal percentage operating characteristic (in operation, the differential pressure increases as the valve closes) combined with the outstanding rangeability of 300:1 mean that the valve can be used for most control tasks. The special connection of the valve body ensured that the differential pressure on the valve has little effect on the actuating torque.
Throttling control characteristics
For ball sector valves it is important to observe the difference between inherent valve flow characteristic at constant pressure drop and valve flow characteristic at varying pressure drop. Figure 1 presents the inherent flow characteristic of Ramén KS ball sector valve for air and water when pressure drop is constant. It is near to equal percentage. Shown also for comparison is the characteristic of a linear valve.
Figure 2 presents the installed characteristic for the same ball sector valve when installed in a control loop where the valve pressure drops increases when the valve is closing. An equal percentage characteristic becomes more like a linear. A linear characteristic becomes more like quick opening.
The more the pressure drop is changing for a certain change of flow, the more the installed characteristic is altered. The comparison shows that the installed flow characteristic of Ramén KS is very suitable for most of all control valve installations with its equal percentage characteristics.