The atlas
Drag the opening and watch how the closure member gets out of the way and what the flow does. Keep an eye on the flow readout: at the same 50% open, different valves pass wildly different amounts of water. That is the line between a valve you can throttle with and one you cannot.
Same opening, different flow
Every curve here is sampled from the animation below it, not drawn by hand. Drag the opening and read across: a gate valve has given you half its flow by the time a ball valve has given you a twentieth. The shape of each curve is the whole argument about which valves can throttle.
Check valves, in detail
Every check valve does the same job, so they get specified almost at random. What actually separates them is a race: how fast the closure member shuts against how fast the flow reverses. Lose that race and the disc is slammed onto its seat by a column of water already moving backwards, and you get the bang that cracks pipe supports.
Pump trip: which one slams
The pump trips and the flow decelerates. How fast it decelerates depends on the pipeline — a long, flexible main with a flywheel on the pump reverses slowly; a short discharge line against high static head reverses almost instantly. Drag the slider and watch the ranking change.
Illustrative model only. Each valve has a typical closing time; spring-assisted types complete part of that travel while the forward flow is still slowing, so only the remainder happens after reversal (nozzle about three-quarters before, dual plate over half, sprung lift under half, the gravity types none). Reverse velocity at seating is deceleration × that remaining time, converted to head with Joukowsky at a wave speed of 1000 m/s. Every real pipeline needs a proper transient analysis — what this is for is the ranking, and how the ranking moves when the system changes.
Side by side
Where they sit in a plant
Two plants, twenty-two valves. Click a symbol on the line to see why that type was chosen for that spot. The symbols are drawn P&ID style, the same as on your drawings.
Pick a valve symbol on the line.
Quick selection guide
Five questions to point you in the right direction. Real selection still needs temperature, material compatibility, face-to-face length and budget — this only answers which types you should be looking at first, and what to check before you order.
How you drive it
The same valve body with a different actuator is a different piece of equipment. Get this wrong and the valve still works — right up until the night something goes wrong and nobody can close it.
Field troubleshooting
Things that actually happen on plant, indexed by symptom.