Sealing effect of pneumatic shut-off valve

The sealing effect of a pneumatic shut-off valve is better than that of a ball valve. For example, for corrosive media containing particles, the valve core must be considered to avoid direct erosion by high-speed media. Straight stroke valves and butterfly valves do not have this function, but cut-off ball valves have this feature.

Of course it is a ball valve. Ball valves with soft seats can achieve complete shutoff without leakage. However, the leakage of eccentric butterfly valves is also very small. Hard seals generally only have 3 Cv values.* 10^-6

Ball valves have better sealing effects than butterfly valves. For valve sealing, they are designed according to needs and have a leakage level requirement.

Both ball valves and butterfly valves have good sealing effects. It mainly depends on the occasion where they are used. If the diameter of the pipeline is large, butterfly valves are recommended. Ball valves can be used in ordinary occasions! Control valve leakage standard national standard GB/T4213.92 Leakage level test medium test pressure Maximum valve seat leakage 1/h Ⅰ Determined by user and manufacturer Ⅱ Water, air or nitrogen A 5×10-3×valve rated capacity Ⅲ 10-3×valve rated capacity Ⅳ water A or B 10-4×valve rated capacity air or nitrogen A Ⅳ-S1 water A or B 5×10-4×Valve rated capacity Air or Nitrogen A Ⅳ-S2 Air or Nitrogen A 2×10-4×△P×DV Water B 1.8×10-7×△P×D VI Air or Nitrogen A 3×10-3×△P (Leakage amount continues) Valve seat diameter continues: 20 25 40 50 65 80 100 150 200 250 300 350 400 Leakage volume ml/min 0.1 0.15 0.3 0.45 0.6 0.9 1.7 4.0 6.75 11.1 16.0 21.6 28.4 Bubble number/min — 1 2 3 4 6 11 27 45 — — — — Note: 1. The number of bubbles per minute is measured using a pipe with an outer diameter of 6mm and a wall thickness of 1mm that is vertically immersed in water at a depth of 5~10mm. The surface of the pipe end should be smooth. 2. If the valve seat diameter differs by more than 2mm from one of the values ​​listed in the table, the leakage coefficient can be obtained by interpolation method assuming that the leakage amount is proportional to the square of the valve seat diameter. American standard ANSI B16.104-197 Leakage level maximum allowable leakage test medium test pressure II 0.5%Cv Maximum working pressure difference of air or water at 10~52℃ △P or 501b/in2 pressure difference, whichever is lower III 0.1%Cv The maximum working pressure difference of air or water at 10~52℃ △P or 50lb/in2 pressure difference, whichever is lower IV 0.01%Cv The maximum working pressure difference of air or water at 10~52℃ △P or 50lb/in2 pressure difference, whichever is lower V When nominal diameter per inch and pressure difference per pound/in2, Water leakage of 0.0005ml/min is allowed. Maximum working pressure difference △P for water at 10~52℃ Ⅵ Nominal diameter of valve ml/min Number of bubbles/min Maximum working pressure difference for air or nitrogen at 10~52℃ △P or 501b/in2 pressure difference, whichever is lower in mm 1 25 0.15 1 1.5 38 0.30 2 2 51 0.45 3 2.5 64 0.60 4 3 76 0.90 6 4 102 1.70 11 6 152 4.00 27 8 203 6.75 45 You can also refer to GB/T4213-2008, many forums can download it for free!

The sealing performance of ball valves is better than that of butterfly valves. The current technical sealing performance is good, and the leakage can reach V level. However, the economical performance of large-diameter butterfly valves depends on your pipe diameter.