Valves, Actuators & Pump Control


Ball sector valve from Schubert & Salzer

May 2015 Valves, Actuators & Pump Control

The type 4040 ball sector valve is used everywhere where conventional valves break down under severe operating conditions. They are ideal for providing precise control and the safe shut-off of difficult media, such as:

• Suspensions in the pulp and paper industry.

• Pasty media.

• Abrasive suspensions of ores, coal or ash.

• Effluents contaminated with solids or containing fibrous matter.

• Alkalis and acids.

• Oxygen, air or gaseous ammonia.

The ball sector

The key element at the heart of the new ball sector valve in the 4040 range is the ball sector. One part of the ball sector acts as the shut-off, while the other contains a hole whose diameter is normally about 80% of the nominal size of the valve. As the valve is closing, the cross section of the opening changes from completely round to elliptical. This change in shape reduces the risk of the ball sector valve becoming blocked when the valve opening is small or draining water from suspensions, or wearing out the valve at high flow speeds. At the same time, the ball sector seals off the medium even under harshest operating conditions by means of a seat ring against the valve body. The seat ring can be exchanged easily.

Outstanding control characteristics

The characteristic curve of the ball sector valve has an almost equal percentage profile. This curve represents the optimum for most operating conditions, in particular during operation if the differential pressure across the valve decreases over-proportionally as the degree of opening increases. Furthermore, this characteristic shape is more tolerant where the valve is oversized, since the valve, with its flat characteristic curve at the lower end of the opening range, provides an ample control range when only a portion of the Kvs value is being utilised. Additionally, the rangeability is an impressive 300:1, substantially underpinning the properties described above regarding control behaviour.

Special design features

The shafts for the ball sector in the Type 4040 valves are positioned centrally. As a result, any deposits on the surface of the ball are wiped off by the seat ring. Also, when the valve is being closed, no solid parts can become trapped between the seat ring and the ball sector.

By positioning the O-rings in the TA Luft-certified shaft guide in front of the bearing location, no abrasive substances in the medium can penetrate the bearings. Thus, the smooth operation and, therefore, the high control performance of the valve cannot be impaired.

In order to avoid the effects of thermal or mechanical stresses, the bearings and the shaft seals are housed in swivelling bearing bushings in the body.

Schubert & Salzer Control System’s ball sector valves in the 4040 range are supplied in nominal sizes from DN 25 to DN 300. Up to DN 250, the valves are wafer types, in DN 300 with flanges. The pressure stages available start at PN 16 and go up to PN 40 (ANSI 150 to ANSI 300). Depending on the nominal size, Kvs values from 12,5 up to 3840 are possible. These ball sector valves are produced in stainless steel 1.4408 as well as in special materials. Based on the sealing material selected, the ball sector valves can be used at temperatures up to 230°C.

For more information contact Keith Hedges, Macsteel Fluid Control, +27 (0)82 575 9354, keith.hedges@macfluid.co.za, www.macsteel.co.za



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