Valve guide

Know your valve.

Four valve types cover most of what you'll find on site. Before you scan, a few quick checks tell you a lot: look at the handle (handwheel or lever?), watch the stem (does it rise when opened?), note the body shape, and read any markings cast or stamped into the metal — DN size, PN pressure rating and material codes such as GG25 or CF8M.

Gate valve

A gate valve opens and closes by raising or lowering a flat gate (a wedge or slab) across the flow. It is fully open or fully closed — never used to regulate flow part-way.

How to spot it

• A round handwheel on top — you turn it many times to open or close.
• A rising stem: on many gate valves the threaded stem visibly rises out of the bonnet as you open it.
• A tall, bulky bonnet (the housing above the body) because the gate needs somewhere to go when open.
• Flanged or threaded ends in line with the pipe — flow goes straight through.

Typical uses

Isolation duty on water, steam, oil and gas lines — sluice/gate valves on mains, ship systems and plant pipework where the valve stays open or shut for long periods.

Ball valve

A ball valve uses a drilled ball that rotates a quarter turn. When the hole lines up with the pipe the valve is open; a 90° turn of the handle closes it completely.

How to spot it

• A lever handle, not a handwheel — a single quarter turn is enough.
• Handle direction shows the state: in line with the pipe = open, across the pipe = closed.
• A compact, chunky body — often much shorter than a gate valve of the same size.
• Common in small sizes with threaded or compression ends; larger ones are flanged.

Typical uses

Fast shut-off on fuel, air, water and chemical lines — anywhere quick, tight isolation matters. Very common in marine and process plant in sizes up to about DN100.

Globe valve

A globe valve moves a disc down onto a seat, and the flow inside takes a Z-shaped (S-shaped) path up and over the seat. That makes it ideal for throttling — controlling how much flows, not just on/off.

How to spot it

• A rounded, globe-shaped body with a clear bulge in the middle.
• A handwheel that screws the disc down onto a horizontal seat — several turns to open or close.
• The stem usually does not rise; the wheel stays at the same height.
• Often an arrow cast into the body showing the required flow direction.

Typical uses

Flow control and throttling on steam, cooling water and process lines — bypass lines, gauge and vent connections, and any duty where the valve is adjusted regularly.

Butterfly valve

A butterfly valve rotates a thin disc inside the bore. A quarter turn takes it from fully open (disc edge-on to flow) to fully closed (disc across the bore).

How to spot it

• A very slim body — a flat ring sandwiched between pipe flanges, much thinner than any other valve type.
• A lever handle or a small gearbox with a handwheel on larger sizes — always a quarter turn.
• The disc is visible edge-on down the bore when open, like a butterfly wing — hence the name.
• Lugs or bolt holes around the rim instead of full flanges.

Typical uses

Large-diameter isolation and control on seawater, cooling water, HVAC and ballast systems — anywhere space and weight matter. Standard on ships from DN50 upwards.