Soft-Start valves are a very useful accessory to help prevent cylinder / actuator damage on your air-driven equipment.
While perhaps not critical on a small, one or two air-cylinder piece of equipment, more complex machine may have dozens or hundreds of air cylinders or other air actuators, all finely timed to ensure that they will not 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 completely dumped, and no compressed left in the air lines, air valves, or air cylinders. This is both for safety for the operator, and to enable a mechanic to easily move the air-driven tooling as they go about building, setting up, or fixing a piece of equipment.
That pressure level is commonly lowered to the minimum operating pressure required by the equipment the compressed air is running. Here is information on air regulators should you wish to have a look at regulator operation now.
This lowered pressure setting will help ensure that the pressure and volume to the machine air-driven equipment stays constant, as the compressor cycles on an off. As long as the pressure level to the machine is set below the compressor pressure switch cut in set point, the actuators on the machine should see a constant pressure.
Once the installation or maintenance work on that piece of equipment is complete, it is time to get the machine operational.
Some of the air cylinders and other air-driven 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 is no air in any of the lines. This means that even if the cylinders have flow controls, which work on controlling back pressure, there is no air in the cylinder to allow the flow control to moderate the speed of the cylinder piston.
By introducing air at full line volume and pressure, any wrongly-positioned air cylinder will respond at high speed with possibly catastrophic results. It is possible that pistons crash into end caps, various end-of-rod fixtures interfere with one another, as the pistons, rods and tooling all react to the incoming air stream.
A soft-start valve will, at first, open the air flow to the machine just slightly. It will 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 with no crashing, no banging, no damage.
Once all of the air-driven equipment on the machine 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.
In simple terms, a 3 ported, 2 position manual valve installed 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 is the air already in the machine, to bleed back upstream and out the exhaust port on that valve, to atmosphere.
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, pneumatically operated, or a combination of the above.
In either case, an integral pressure regulator senses the downstream pressure, and will not 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.
Whether it is a manual or an automatic soft-start valve you pick, installing one could save you a lot of time and money in the long run.