Forging in Control Valves

Not realy sure what information your looking for so I will toss my two cents in.

Most valves in use are casted then machined as needed, this includes most control valves, even the high priced ones. The reason for casting is for cost savings, why pay $10,000 USD for a machined tool hardened valve when your system does not require it.

Some of your smaller valves made out of materials such as brass are often machined out of bar stock, again because it is more cost effective.

The method of manufaturing while can be important at high level engineering levels it's not so at the end user level. We need to look at spec's, what is the CV, what is the pressure rating, is it chemicaly compatible, what are the flow characturistics (linear control or non-linear), ect.

Hope my rambling helped.

If you are referring to process valves such as ball, globe, gate, etc. then a cast valve will operate at lower pressure than forged. Forging metal creates a close grain structure in a particular direction giving it greater strength than a casting. Pressure dictates the choice. Give the specifications for the valve to a valve supply house, and let them recommend the right product. It doesn't cost any more.

One reason is that Casting process can be used in large parts but forging not.

Another reason is that Forging parts are more intensity than casting.

The last reason is that casting precess can be used in hollow and tanglesome parts but forging depends on moulds.

It's all depends on the valve body working pressure rating. A valve body that is cast, will have a lower pressure rating due to the casting process, just as it sounds, the valve body is made from a standard casting, pressed in a mold. A forged valve body is made from one single piece of cold stock and machined. This enables the valve body to handle alot more working pressure. As an example, a 10 story high rise building will have 150# (10.2am) valves on the upper levels, but valves on the lower levels and basement will need a higher working pressure like 300#,(20.4am) because there is a column of water sitting on the lower valves that is over 100 feet high, or (30.5m high) Be aware of your surroundings for valve placement and pay attention to system pressures. Wbburris has provided a more detailed account of the physical makeup between the two, and why forged is stronger, good job.

FORGING and CASTING are two metallurgical manufacturing processes.

In FORGING, metal heated to its plastic state ( less temp. then liquid state) and then pressed with high pressure in a hydraulic or power press. Forging can stand large pressure. Cost of the die of forging press is very costly and is affordable if production batch is large.

CASTING is produced by liquifying the metal and pouring the liquid into desired shape of mould. It is allowed to cool. As during cooling there is absence of pressure, the resultant body can stand less pressure. Now some special methods of casting create pressure and hence are very strong. This process is known as pressure die casting. Cost of Mould is low and hence small quantities of sand casting can be produced. The pressure die cast mould is costly. hence good pressure die cast valves are costly.

vipin dave, Consulting Engineer S M ASSOCIATES Ahmedabad India