Matching Type to Function: A Swagelok Valve Tutorial
by Katie Dennis, on Wed, Apr 23, 2014 @ 15:04 PM
We'll walk you through the steps, starting with 'What do I want the valve to do?'
When you need a valve for an instrumentation system, the choices may seem overwhelming: ball valves, check valves, excess flow valves, fine metering valves, multi-port valves, needle valves, relief valves -- the list just keeps going. And each of these valves comes in many sizes, configurations, materials and actuation modes.
There's an article in a recent issue of PROCESSWest magazine that can help you sort through options and make the best choice for your particular needs. Not surprisingly, the author is from Swagelok. Mike Adkins is an industry expert when it comes to valves and regulators.
Adkins says the best place to start is with the most basic question: What do I want the valve to do? Is it simply an on-off function, or do you need to control the flow? Some fine metering valves are not designed to shut off at all. Do you need to control a thick fluid, a thin fluid or a gas? Do you need to make sure the fluid goes in only one direction?
On/off (ex: 60 Series)
|60 Series Ball Valve|
On-off control is the most basic valve function. Valves in this category stop and start system fluid flow. Primary on-off valves are ball, gate, diaphragm, and bellows valves. Perhaps the most common of all valve types, ball valves can turn the flow on and off with just a quarter-turn of the handle. The ball has a large hole through its centre. When the hole is lined up with the flow path, it's wide open. Turn it 90 degrees, and the flow is completely stopped. Swagelok's 60 series ball valves are designed for reliability and low maintenance. They feature a unique coned-disc, spring-loaded seat; live-loaded, two-piece chevron stem packing; and three-piece, swing-out design, 3-piece process/instrumentation.
(ex: 26 Series)
|26 Series Needle Valve|
Sometimes you need the flow to be somewhere between fully on and fully off. For that function, a needle valve is a great option - and we are a needle valve supplier. A needle valve has a long stem with tip in the shape of a thin V, or needle. The fine thread means you can turn the handle to get a precise desired flow, and it will stay there reliably. Swagelok's 26 Series is one of many Swagelok needle valves that can fit the bill.
(ex: CH Series)
|CH Series Check Valve|
Some applications require a valve that ensures flow in only one direction. Those are called check valves. Did you know Swagelok is a check valve supplier? In most designs, the upstream fluid force cracks open a poppet, allowing flow. When there's an increase in downstream of back-pressure force, the poppet is forced back into its seat, preventing reverse flow. Swagelok's CH Series valves come with a variety of end connections, and with cracking pressures of one-third PSI to 25 PSI. That's 0.03 bar to 1.8 bar.
(ex: R Series)
|R Series Relief Valve|
Too much pressure can damage a fluid system. Overpressure protection valves do exactly what the name says, preventing the build-up of pressure beyond a certain setting. They come in two types, rupture discs and relief valves. Rupture discs are used primarily on sample cylinders. A metal diaphragm ruptures when pressure gets too high, venting to the atmosphere. Obviously, it's good for only one use. A relief valve is more sophisticated, using a spring-loaded poppet for measured release of fluid, and closing back up when pressure falls back below the set level. Swagelok R Series proportional relief valves can be set at pressures from 10 psig (0.68 bar) to 6000 psig (413 bar).
(ex: XS Series)
|XS Series Excess Flow Valve|
If a downstream line ruptures, the fluid can flow out uncontrolled unless the system includes an excess flow valve. Under normal conditions, a spring in the valve holds a poppet open. When there's excess flow downstream, it trips the poppet into a closed position, stopping almost all the fluid flow. When the system is corrected, the valve returns to its open position. Swagelok's XS Series stainless steel valves have spring loaded actuation, allowing them to work in any orientation. They can handle pressures up to 6000 psig (413 bar) and temperatures up to 204 C degrees.
You can read the Adkins entire tutorial online. Once you have matched the valve type to the function you need, there are still many details to work out. There are installation issues, maintenance schedules, safety code requirements and more. And, of course, you need the valve in the correct size for the pressure, flow rate and temperature of the fluid in your system. To discuss the answers to those questions, call us at 780-437-0640.