COMMON VALVE TYPES
Gate Valves
The families that appear on first RFQs and Chinese export quotes. Shared names are not interchangeable designs.
Choosing Gate Valves
A gate valve lifts a wedge or sliding disc out of the flow path. Its main purchasing role is line isolation with a relatively unobstructed passage when fully open. Wedge gates and parallel-slide designs solve different seating and thermal-movement problems; the family name alone does not identify the offered construction.
What to include in the RFQ
- State whether the valve will remain fully open or closed, or whether intermediate-position operation is required.
- Request the gate construction, seat materials, rising or non-rising stem, and clearance needed above the bonnet.
- Compare face-to-face length, end standard, full-open flow coefficient and pressure-temperature rating.
- Specify seat-leakage acceptance, flow direction and the differential pressure against which it must close.
Selection scenario
For isolation beside a water-transfer pump, compare the open-valve pressure loss and available handwheel clearance. If the same position must regulate the flow continuously, prepare a separate control-valve specification before requesting a quote.
Common selection mismatch
An ordinary isolation gate should not be selected merely because its bore matches a throttling line. Ask for a design explicitly rated for that operating duty.