There are two reasons:

*1. PTFE is a hard material which allows minimum flexibility. In the shape of the straight through design the travel of the diaphragm is quite long and under this degree of travel the PTFE would crease, buckle or even rupture during operation.

*2. The Straight Through Diaval Diaphragm Valve has been specifically designed to handle mainly slurries and abrassive fluids. PTFE's resistance to abrasion is poor and hence would not offer an economic choice whereas a elastomeric diaphragm would. If you have any further queries on this topic or a specific application then please contact Diaval on email at scorreas@diaval.com

PTFE moulding is not a 'strong structure' and as the stud is moulded into the PTFE facing the fixing point into the compressor must be such that it offers minimum torque on the area of the study fixing in the PTFE. A screw stud has a VERY high torque and will quite often shear from the PTFE face. The bayonnet (90 degree turn) has virtually no torque effect on the PTFE moulding and hence is the prefered fixing method.

Definitely not! Each diaphragm grade has its own chemical resistance characteristics and has been formuated to handle specific catagories of fluids. An example of this is with Butyl (D30) and Viton(D70). Viton is much more expensive than Butyl but Viton has NO CHEMICAL RESISTANCE to acetone which will destroy Viton in a very short time. Butyl on the other hands has excellent resistance to acetone and can be used safely on this application. If there is any doubt which diaphragm grade to use consult the Diaval Technical Handbook or email info@diaval.com for assistance.