Why the body is forged, and where that matters
ASTM A105 is a forging specification, not a casting grade. In a ball valve the pressure boundary is a bolted or welded assembly — a side-entry body and closure, or a fully welded shell — and every bolt-up face carries the full closure load. A forged billet has a worked, directional grain structure and no risk of shrinkage porosity at those thick flange transitions, which is why ASME B16.34 special-class ratings and API 602 Class 800 and above are written around forged bodies. Below roughly NPS 2, a forged A105 body is also simply more compact than the cast equivalent for the same rating.
The seat, not the body, usually sets your temperature limit
The -29 °C to +425 °C range above is the body material limit. A soft-seated ball valve will not reach it. Virgin PTFE seats are normally limited to about 200 °C, reinforced PTFE and PEEK extend that to roughly 250–290 °C, and only a metal-seated design will follow A105 to its upper limit. If your line runs above 200 °C, specify the seat material explicitly — quoting the body grade alone is the most common cause of a mis-supplied ball valve. At the cold end, A105 is supplied without Charpy impact testing by default, so service below -29 °C requires a different grade such as LF2, not an A105 body with a low-temperature extension.
Sour service and corrosion allowance
A105 is an accepted base material for wet H2S service, but only under controlled hardness — NACE MR0175 / ISO 15156 caps the base metal and welds at 22 HRC, which constrains heat treatment and any weld overlay. State sour service on the enquiry; it is a manufacturing requirement, not a coating option. Carbon steel also carries no inherent corrosion resistance, so for wet CO2 or produced-water duty either budget a corrosion allowance or move the wetted parts to a stainless trim.
What to include on the enquiry
- Seat and seal material — this, not the body grade, sets the real temperature and fire-safe envelope
- Bore style: full bore for pigging and minimum pressure drop, reduced bore where torque and weight matter
- Floating or trunnion-mounted — trunnion above roughly NPS 6 or Class 600 to keep operating torque sensible
- Sour service (NACE MR0175 / ISO 15156) and any Charpy requirement, stated at enquiry stage
- Actuation: required break-to-open torque and fail position, if the valve is not lever-operated
Material behaviour and standard references on this page are general engineering guidance for grade selection. Confirm the final specification against your line list and the applicable design code for the project.
