Which valve should I use: gate, butterfly or globe?
Each of these three is built for a different job, and using one outside its purpose shortens its life.
Gate valve — isolation
Fully open, the gate withdraws from the flow path, leaving an unobstructed bore and almost no pressure drop. Designed strictly for open or shut. Running one partly open causes vibration and accelerated seat wear.
Globe valve — regulation
The disc moves perpendicular to the seat, giving fine, repeatable throttling control. The trade-off is a higher pressure drop even when fully open.
Butterfly valve — compact isolation and throttling
A single disc rotates 90° within the bore. Short face-to-face length, light weight and fast quarter-turn operation. Handles both duties, which makes it the practical choice on larger lines where a gate valve would be too heavy or too tall.
And the others
Ball valves for fast, tight shut-off. Check valves to prevent reverse flow. Strainers to catch debris before it reaches a pump or meter.
What is cavitation and how do I prevent it?
Cavitation happens when pressure at the pump inlet drops below the vapour pressure of the liquid. Vapour bubbles form, travel into the higher-pressure part of the impeller, and collapse violently. Each collapse removes a tiny amount of metal.
How to recognise it
A distinctive rattling sound, often described as pumping gravel. Alongside it: vibration, fluctuating flow and pressure, and falling performance. Left running, it pits the impeller, damages seals and bearings, and eventually destroys the pump.
The root cause
Available NPSH is lower than the NPSH the pump requires. In practice that usually means the suction line is too long, too narrow, partially blocked, or the pump sits too high above the water source. Hot liquids make it worse, because vapour pressure rises with temperature.
Prevention
Keep the suction line short, straight and generously sized. Fit a strainer and keep it clean. Reduce the static lift where possible. And at selection stage, confirm available NPSH exceeds the pump requirement with a margin — not just barely.
