When installing butterfly valves, you want to have the disc open slightly (Garlock recommends 10° open) to reduce the pressure on the valve body.
Generally zero offset valves can be installed in either direction. With double and triple offset valves, it is important to install the valves correctly.
For abrasive applications, it is recommended that zero offset valves are installed horizontally to minimize the abrasive media contact with the stem seal.
For lined valves, you normally do not need to use a gasket, because the liner acts like a gasket on both sides; however, if your flange surface finish is rough, we recommend using a softer PTFE gasket to prevent damage to the liner. Otherwise, the use of a gasket is not recommended.
The liner on the valve essentially turns the valve flange into a raised face. If installing against a flat face pipe flange, it is recommended to use a flange spacer to protect the flat face pipe flange. Most flat face flanges are meant to butt up against another flat face–when butting up to a raised face, it can create bending stresses on the flange as it is tightened against the raised face valve. A flange spacer is like a gasket with a big inner diameter (ID)–it will sit outside of the liner, turning the raised face valve flange into a flat face.
If attaching a metallic valve to a non-metallic pipe, please check with your piping engineers to ensure that the non-metallic pipe will not be damaged with the weight of the metallic valve. The same guidelines apply if the non-metallic pipe is flat face or has limited torque recommendations.
If your pipe schedule is very low (i.e. your pipe wall is very thick), please consult with engineering; depending on the size and thickness, the disc of the valve could hit the pipe wall ID.
When installing a valve into a pipeline, be sure to use the recommended bolt installation torques, which are listed in the Operating and Installation Manual that comes with every valve. Please ensure that your pipe and bolts are capable of meeting these recommended torques. (The lug valves have threaded holes, which are offered in US or DN standards.)
More commonly when discussing torques, people refer to the torque needed to open or close the disc; these torques are used to determine which actuator to use and are located in the technical manual.
KV or CV rates give the amount of fluid (water) that will flow through a valve with a pressure difference of 1 bar given the opening angle of the disc. In a pipeline with an open butterfly valve, as the fluid goes through the valve, the flow rate will decrease, because the open disc is blocking part of the passage. The KV or CV rates will show you exactly how much of a reduction in flow rates you will have, including the flow rate loss as the disc is at different open/closed angles. (KV rates in are m3/hr, and CV rates are in G/h. Tables are listed in the technical manual.)
