Skid, left isometric — Inzonex Modular Insulation, hot-water skid
Ball valves / Types
Ball valve types
Four choices, and only one of them is the size.
A ball valve is described by its bore, its body, its ends and how it is operated. Get those four right and the size follows from the pipe. The one that costs people money is the bore. A reduced-bore valve is cheaper and smaller, and it puts a restriction in a circuit that was balanced without one.
Bore
Full against reduced
Full bore
The hole through the ball matches the pipe, so the valve adds almost nothing to the resistance of the run. Anything that fits down the pipe goes through it. It is what an isolating valve on a main should be.
Reduced bore
The hole is one size down. Cheaper, lighter and perfectly adequate on a branch. It becomes a genuine restriction once several of them sit in series on a circuit designed without them.
Body
One, two and three piece
One piece
A sealed body that cannot be opened. Cheap and disposable: when it fails it is cut out and replaced.
Two piece
The body splits into two, which allows manufacture but not much service. It is the common industrial pattern.
Three piece
The centre section comes out between two end caps that stay welded or bolted to the pipe. The valve can be serviced or replaced without touching the pipework. It earns its cost where access is bad.
Ends and operation
How it joins and how it turns
Threaded, flanged, welded
Threaded on small bore, flanged from around DN50 where the valve has to come out, welded where nothing should ever leak. The flanged pattern is the one on this skid, and its flanges are counted in the bare area.
Lever, gearbox, actuator
A lever is a quarter turn, and it tells you the state of the valve at a glance. Along the pipe is open, across is shut. Above about DN150 the torque wants a gearbox. An actuator puts it under control, and it puts a motor on top of a hot valve.
Against other valves
Where a ball valve is the wrong answer
Gate valve
Lifts a wedge clear of the flow over several turns. It seals well when fully open or fully shut, and it is slow. That is the point on a large main, where a quarter turn would slam the system.
Butterfly valve
A disc that turns in the flow, compact and cheap in large sizes, with the disc always in the stream. It is the usual choice above the size where a ball valve becomes a lump of metal.
Neither of them throttles
A ball valve half open is not a regulating valve. The seat wears at the edge of the ball and the valve stops sealing. Regulation is a globe or a double-regulating valve, and isolation is the ball valve.
Reference
Choice against consequence
| Option | What it is | What it costs you | Where it belongs |
|---|---|---|---|
| Full bore | Bore matches the pipe | Negligible resistance | Isolating a main |
| Reduced bore | One size down | A restriction, cumulative in series | Branch work |
| Three piece | Centre section removable | Serviced without cutting pipe | Poor access, long life |
| Actuated | Motor or air on the stem | Control, and a motor on hot metal | Automated isolation |
Option · What it is · What it costs you · Where it belongs
Asked about ball valve types
Questions.
Answers distinguish modelled heat-loss estimates from equipment selection and service guidance.
What is the difference between full bore and reduced bore ball valves?
In a full-bore valve the hole through the ball is the same size as the pipe, so it adds almost no resistance. A reduced-bore valve is one size down. It is cheaper and smaller, and fine on a branch. It becomes a real restriction once several of them sit in series on a circuit balanced without them.
What is a three-piece ball valve?
One where the centre section lifts out between two end caps that stay attached to the pipe. The valve can be serviced or swapped without cutting or unbolting pipework, which is what makes it worth the extra cost where access is difficult.
Should I use a ball valve or a gate valve?
A ball valve for isolation you want quick and certain: quarter turn, and the lever shows the state. A gate valve where a quarter turn would slam a large main and the slower several-turn close is the safer action. Neither is a regulating valve.
Can you use a ball valve to control flow?
No. Held part open, the flow concentrates at the edge of the ball and the seat wears there. The valve then stops sealing when you eventually want it shut. Regulation belongs to a globe or double-regulating valve. The ball valve is there to be fully open or fully closed.
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More on ball valves
The node page carries the heat-loss figures and the size table.