BS EN ISO 8659:2020 pdf free.Thermoplastics valves – Fatigue strength – Test method.
BS EN ISO 8659 The endurance test, using water, air or gas as the fluid medium, at the temperature, pressure and velocity specified in the particular product standard, shall be carried out, at the ambient temperature specified in the product standard, as follows: a) Open the valve for multiple-turn valves to the fully open position at a hand-wheel speed of 40 r/min土10 r/min for valves of nominal size up to DN 50 and 20 r/min土10 r/min for valves of nominal size greater than DN 50.  for quarter-turn valves, the opening time shall be not less than 2 s for valves of nominal size up to DN 50 and not less than 4 s for valves of nominal size greater than DN 50. The valve shall be left in the open position for at least 5 s, but not longer than 20 s. During opening and closing, there shall be no visible leakage at any seal. b) Close the valve for multiple-turn valves at a hand-wheel speed of 40 r/min土10 r/min. for quarter-turn valves, the closing time shall be not less than 1 s. Closing shall be performed using the torque specified in the particular product standard. During opening and closing, there shall be no visible leakage at any seal. c) After the valve has been closed, an internal pressure shall be applied as specified in the particular product standard. The valve shall be left in the closed position for at least 5 s, but no longer than 20 s. d) The valve shall be opened as described in 5.2 a). e) The test procedure described in 5.2 a) to d) shall be repeated for as many cycles as required by the particular product standard.The opening torque is generally higher in ball, butterfly and gate valves as it is influenced by the wear between obturator and seats and by the maximum pressure difference between upstream and downstream side of the valve; the opening torque is lower in diaphragm and globe valves as the upstream pressure, acting on obturator, reduces the effort exerted to operate the valve. BS EN ISO 8659 pdf download.