What is the difference between a gate valve and a ball valve in terms of flow control?

The main difference is temperature resistance versus elasticity. Graphite is relatively soft and deformable, so under pressure it conforms to the sealing faces. A graphite/stainless steel seal offers good resistance to high temperatures and chemicals, but is less elastic than rubber. This seal is therefore suitable for steam and hot liquids. An example is the ORANGEPACK® OP61, a graphite gasket sheet with a perforated 316 stainless steel insert.

A rubber/metal seal combines the elasticity of rubber with the strength of metal. Rubber seals well, but has a more limited temperature range. For higher temperatures and aggressive media, special elastomers are available: FKM (Viton®) is resistant up to approximately 200 °C, and FFKM combines flexibility with very high chemical resistance, but is considerably more expensive.

In short: choose graphite/stainless steel for high temperatures and steam, and rubber/metal when elasticity is the priority within a moderate temperature range.

A butterfly valve is often the better choice when installation space, weight and cost at larger diameters are important. A butterfly valve has a round disc that turns a quarter turn. It is lightweight, has a short face-to-face length and can be installed between two flanges. At larger diameters, a butterfly valve is also generally more economical than a ball valve.

A ball valve has a bored ball that rotates 90 degrees. In the open position, the bore is in line with the pipeline, giving you a fully unobstructed flow path and a very tight seal. With a butterfly valve, the disc remains in the flow even when open. Ball valves are also available with a straight bore or an L-port, so that the flow can be diverted in another direction.