Soft-Start valves; a necessary accessory for your air circuit?

Soft-Start valves; are an able accessory to help prevent cylinder / actuator damage on your equipment.

While perhaps not critical on a small, one or two air-cylinder piece of equipment, a more complex machine may have dozens or hundreds of air cylinders or other air actuators, all finely timed to ensure that they won't interfere with each other when the equipment is running.

When that machine is being set up or being repaired, it is normal for the compressed air to be dumped, and to be completely absent from the lines and air cylinders. This will allow a mechanic to move the tooling that is attached to various cylinder rods easily, as they go about their business of building, setting up, or fixing the equipment.

Most industrial mains will have an available air supply at around 100 - 120 PSI. That's commonly lowered to 80 -100 PSI to the machine actuators through the use of one or even a number of regulators in the line to the equipment.

This lowered pressure setting will help ensure that the pressure and volume to the machine stays constant as the compressor cycles on an of. As long as the pressure level to the machine is set below the "kick-in" set point on the air compressor, the actuators on the machine should see a constant pressure.

Once the installation or maintenance work is done it's time to get the machine operational.

What you do not want to do is fully crack open a main air valve and have compressed air in high volume screaming into the lines and pressurizing all of the air cylinders on the machine at full flow and at once.

Some of the air cylinders and actuators will be in the correct position. Some will be left at mid-stroke, and others will be in the extend position when they are supposed to be in the retract position on start up, or vice versa.

Remember, there's no air in any of the lines. This means that even if the cylinders have flow controls , there is no air in the exhaust side of the cylinder to allow the flow control to moderate the speed of the cylinder piston as it is driven by the high speed inflow of compressed air.

By introducing air at full line volume and pressure, any mis-positioned air cylinder will respond at high speed with possibly catastrophic results as pistons crash into end caps, and various end-of-rod toolings interfere with one another as the pistons, rods and tooling all react to the incoming air.







To prevent having to repair or to rebuild your equipment again... :-) , consider a Soft-Start valve.

A soft-start valve will first crack open the air supply to the machine only slightly, and allow a very low flow of compressed air into the entire circuit, feeding the various actuators and bringing them calmly up to full operating pressure and in so doing allow them to cycle - again very slowly and softly - to their home positions. No crashing, no banging, no damage.

Once the apparatus is up to full line pressure, the soft-start valve opens fully allowing the full volume of compressed air into the machine air lines and the machine is ready to do work.

There are a number of styles of soft-start valves.

In simple terms, a 3 ported, 2 position manual valve upstream from the filter, regulator and lubricator will allow the operator to shut off the compressed air supply to the application completely, and allow the downstream air, that's the air in the machine, to bleed back upstream and out the exhaust port on tht valve, to atmosphere.

Caution: Though the compressed air may be "dumped" from the machine through this 3/2 valve, there may still be compressed air trapped in the various pieces of equipment on the machine. Before starting work, make sure that the component you are working on is completely void of compressed air, and that no adjacent equipment is still charged. Any component with compressed air still in it might inadvertently shift or activate suddenly, with nasty results!

When it comes time to start the machine, the operator simply opens this 3/2 manual valve a small amount, and allows air to slowly bleed into the equipment until all actuators have shifted and the air circuits are full. At this point, the operator simply opens the valve all the way, and the system is ready to go.

Automatic soft-start valves are available in a variety of configurations and styles. They can be electrically solenoid operated, penumatically operated, or a combination of the above.

In either case, an integral pressure regulator "reads" the downstream pressure, and won't allow the soft-start valve to open fully until it sees the downstream pressure at the predetermined set point. Once the downstream pressure gets to the set point, the valve opens fully to allow full flow of compressed air into the apparatus as.

Whether a manual or automatic version, using a soft-start valve could save you a lot of time and money in the long run.







Here's more info on compressors in general soft start.

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