The valve mid-section and the body contain the parts that interact with the fluid in question.
- The upper stem seal seat is where the seal rests and seals the stem preventing fluid migration beyond the valve cavity.
- The bonnet seal seat is home to the seal that prevents fluid migration between the bonnet and the body, ensuring fluid containment within the valve cavity.
- The upper valve stem attaches to the gate and is the linkage that raises and lowers the gate. The upper portion of this may be threaded and as such this is how it raises and lowers the gate. It can rotate freely a top the gate thus turning with the handle however as the stem is turned the threaded stem lifts the gate.
- The valve body contains all of the components, those not contained within it are mounted to it. It represents the base or chassis of the valve. The cavity is the space that is machined within to hold the gate and valve seats as well as contain the fluid. This part is particularly critical in maintaining the integrity of the entire valve as it sees the majority of the fluid pressure and flow characteristics, especially when every other part is mounted onto it.
- The valve gate is the component that physically impedes or stops the flow of the fluid through the bore. In the case of the the gate valve its motion is strictly linear, either vertical or horizontal or at an angle depending on the overall orientation of the valve.
- The gate seal seat holds the seal that presses against the valve body. This seal ensures that the gate stays centered within the cavity and that the fluid path through the valve is well aligned. It also ensures that that the gate moves easily within the cavity.
- The gate bore aligns with the bore in the valve body thus allowing fluid flow through. When said bore is not aligned then the valve is closed thus preventing fluid flow.
- The lower valve stem primarily guides the gate as it is moved preventing it from becoming mis-aligned, this too ensures that the gate bore remains properly aligned allowing for proper operation.
- This performs the same function as that of the upper, sealing the lower valve stem and the bonnet preventing fluid migration beyond the valve cavity when the stem is moved.
- The seal seat is the same as the upper to seal the lower bonnet and valve body connection.
