Butterfly valve

The highly corrosion resistant GEMÜ 490 butterfly valve is fitted with a TFM liner and PFA-encapsulated stainless steel disc as standard. The design of the butterfly valve, and especially the liner, the shaft seal and backing has been optimised to reduce actuation torques, while providing increased tightness at the same time. The valve therefore uses smaller actuators, this being reflected in reduced purchase and operating costs. TFM is a further development of the classic PolyTetraFluorEthylene (PTFE) material. It is highly resistant to chemicals and can therefore be used almost universally. The gas permeability is significantly less than with conventional PTFE. The cold flow properties with TFM are significantly lower than with PTFE. The surface quality  is considerably improved, thus the smoother surface reduces the mechanical friction and hence wear by the butterfly disc. The backing behind the actual liner consists of two parts. Both backing parts are fully inserted in the space between the body and the TFM liner and centred with the shaft bushing. The backings are sufficiently strong in design, so that their flexibility is better transferred to the TFM liner. At the same time, the tolerances of the backings have been further reduced. The spindle seal has also been optimised further. The transition from shaft disc to liner is positive and edge-free in design. Every shaft bushing has dual protection against overload, so that the butterfly valve fulfils the leakage in the Technical Guidelines on Air Quality Control (TA Luft) VDI 2440 paragraph 5.2.6.4.