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Category: Pneumatic Valve

The Many Uses of a Pneumatic Valve Actuator

Pneumatic valve actuators are found in countless industrial settings all over the world. There are various types of construction applications, oil and chemical plant, deep water and water management facilities that put these tools to use. These pneumatic valves are typically used for the delivery and control of liquids and compressed air through complex piping systems.

Made From a Variety of Materials

Depending on the particular application, pneumatic valves can be manufactured from plastics, aluminum or stainless steel. Stainless steel pneumatic valves for example, are typically found in oil or chemical plants where the flow of liquids and corrosive fluids are the primary product moving through their pipes.

Other Common Uses of Pneumatic Valves

Precise pneumatic valves such as turtorq actuators are used to regulate a required amount of compressed air. These types of systems are typically operated from remote locations for safety reasons. Usually away from the hazardous chemicals and liquids are flowing. With safety in mind in chemical plants, butterfly valves are sometimes used right inside the pneumatic valve or as a separate system altogether. It should be noted that if used separate, these systems would be placed along the same section of pipe when working in a hazardous liquid or chemical plant. Installing sensors in the pneumatic valve actuators can also monitor the flow of liquids.

Higher Benefits

Unlike hydraulic actuators, pneumatic valves have the capability to store energy so they can be used in emergency situations such as power interruptions. They can also work under larger energy payloads. Although these systems do not do very well in sub-zero temperatures, there are varieties of pneumatic valves that deliver compression using heated air. These systems will not compromise the performance of the valve. It’s always nice to know that fluid delivery system in cold weather locations use some sort of back up in order to minimize any unscheduled down time.

A Reliable System

It is very important that any liquid or fluid directional flow system, especially those that move potentially hazardous material, have some sort of fail-safe system. The ability to override and regain control of a system from a remote location in the event of an emergency is just what a pneumatic valve actuator is capable of.

 

The Safe Application of 3-Position Pneumatic Valves

Many pneumatic valves are fairly straightforward things — they’re open, or they’re shut, and it’s pretty clear when they should be in each position. But 3-position pneumatic valves with double-acting cylinders can be confusing.

3-position pneumatic valves are able to stop an attached pneumatic cylinder in mid-stroke, either ceasing motion or — their intended purpose — ‘jogging’ the cylinder for a heartbeat in mid stroke before continuing to extend or retract normally.

Often, such complexities are requested when they’re not needed, because the engineer designing the system believes that such a three-position valve is needed as an emergency response: if, for example, power cuts out in mid-job, they believe the third position is a useful way to prevent damage to the system.

In fact, that’s not the case; instead, two-position, detended pneumatic valves should be used on clamps and other devices to maintain cylinder position if power is unexpectedly removed. A spring-return, two-position valve will also work if no pinch point exists or the cylinder is moving in a guarded action and can return to its normal position safely.

The problem with using 3-position pneumatic valves as ’emergency response’ is that there is no position in which such a valve is actually safe during an extended power cut.

  • If the valve is in the all-closed position, the cylinder will be pressurized on both sides, which can lead to drift if the cylinder isn’t perfectly sealed.
  • If the valve is in the ‘let air in’ position, the cylinder will immediately move toward the extended position because of the higher surface area on the can end of the piston than the rod end.
  • If the valve is set to ‘let air out’ position, the cylinder will immediately move toward the retracted position because there will simply be no pressure present to maintain the extension.

There is a fourth scenario — if the 3-position valve is set to ‘let air out’ position and the circuit has a dual pressure system designed to provide ‘make-up’ pressure to overcome any leakage (which almost always comes with check valves in place to keep the cylinder pressurized against unexpected loads), the 3-position pneumatic circuit doesn’t suffer terribly in an emergency outage. However, this is an incidental byproduct of a system created for other purposes, and using a system like this as an emergency measure is expensive and less reliable than the aforementioned system of detended two-position valves and spring-return valves.

Pneumatic Air Regulators: The Basics

Pneumatic air regulators are a vital part of any pneumatic system, from a simple sandblaster to a jackhammer to some very delicate barostatic systems used for neurogastroenterology. It’s always important to get the right one for your needs, which means understanding what they are and how they work.

An air regulator is a pneumatic device that’s designed to reduce (or ‘regulate’) the pressure of the air that escapes the valve. They’re vital because, for many actuators (also known as “pneumatic cylinders“), the air supplied to the cylinder must be supplied at a constant pressure, or the cylinder will move jerkily or bounce. The pressure supplied by an air compressor varies dramatically as the compressor cycles, so an air regulator is critical to the smooth movement of the actuator.

The simplest kind of air regulator uses a spring to hold a poppet in place, preventing any air from flowing further down the line. As air pressure builds within the regulator, the pressure pushes against the strength of the spring, eventually moving the poppet and allowing airflow to continue past the poppet. A balance is struck between incoming air pressure and the strength of the spring, and the pressure that makes it past the poppet is constant until the flow is shut off.

Controls
There are three fundamental methods of controlling an air regulator — they can be static, pilot-operated, or electronically controlled. All three variations use the same basic concept of balancing the strength of one or more springs against air pressure. In static regulators, once the unit is assembled, it only ever does the precise job it was built to do — it’s input parameters and output parameters never change.

In pilot-operated regulators, there’s a manual screw on the unit that allows a user to adjust how strongly the spring pushes on the poppet, thus increasing (or decreasing) the amount of force the air has to use to open the valve and the pressure of the air that continues down the line.

Electronically-operated regulators use small electronic motors to turn the screws, and are themselves remotely operated either in real-time via switches, or they can be attached to a computer and preprogrammed to adjust the spring tension at certain times or under certain conditions without needing human attention to do so.