Several criteria are taken into consideration when choosing the best valve technology for a specific process.
For instance, a fire extinguisher in a refinery or an airport, where it is critical that putting out a fire is achieved as quickly as possible, means quarter-turn valves, such as butterfly or ball valves, are most likely to be used, owing to the single 90º rotation, they open fully in the shortest time possible. Even in processes that require a high switching frequency, quarter-turn valves are an advantage.
Where solids, slurries or media containing solids in suspension are involved, mechanical wear, or abrasion, and deposits in the system are often a cause of failure.
A full-bore design and, where possible, no moving parts in the valve are important features when considering how best to deal with these types of operating conditions. Suitable valve types to be considered here include diaphragm valves(in the full-bore or step-valve design), knife gate valves and pinch valves.
all valves are also sometimes used in these applications, for example, when slurries need to be conveyed over long distances or at high pressure. Common areas of application for valves used with solids include handling cement, ashes and residues from incineration procedures, ores, coal dust and mineral products, such as lime or fertiliser.
However, despite all their features and advantages, with full-bore, the above valve types can quickly reach their limits. As soon as additional requirements, such as control ability, versatility in the choice of materials, installation size, space requirements and investment costs of the valve need to be considered, it is often necessary to compromise and use alternative technologies.
Diaphragm valves, ball valves and pinch valves are now rarely used above a nominal size of diameter nominal (DN) 300, either because they are no longer available, or because they are very bulky and expensive. Only knife gate valves can still keep up, owing to their narrow installation width.