Pneumatic function fittings, as the name implies, do more than simply connect hose or tubing to a cylinder, valve, or other air-powered device — as is the case with conventional fittings. They perform additional control or safety operations, possibly eliminating valves and other devices from a circuit.

For pneumatic system designers, combining multiple capabilities into a single fitting offers compact size, greater design flexibility, elimination of potential leak paths, simplified installation, and potentially lower costs.

These fittings come in a variety of sizes, configurations, materials (such as brass, plastic, steel, and stainless steel), and with push-in connections or standard or metric threads. Here’s a look at some of the various types of function fittings available today.

Miniature ball valves
Mini ball valves come in 2/2 and 2/3 versions and let operators open and close a pneumatic circuit. Compact and light weight, they are suited to all types of installations, and a variety of mounting styles lets system designers select the best configuration for a particular application. A screwdriver slot allows closing and opening, even where access may be difficult. Full passage mini ball valves accommodate high flow with low pressure drop.

Operating specs include a maximum pressure of 10 bar, vacuum capability down to 755 mm Hg (99% of vacuum), and working temperature of – 20° to 80° C.

Blocking fittings
Designed to offer maximum flow capacity, blocking fittings lock a cylinder’s piston in place by simultaneously cutting off the supply and exhaust air. Functional locks are more precise and rapid when blocking fittings are mounted directly on the cylinder, the volume of air in the piping is no longer a factor.

They should be mounted in pairs, and some versions can fully swivel, providing flexibility in the design and installation of pneumatic circuits. Working pressure with compressed air ranges from 1 to 10 bar. Working temperature ranges from –20° to 70°C

Venting fittings
Fittings with venting capability come in several versions and configurations. Manually operated vent fittings can be used whenever a system must be frequently depressurized. They guarantee immediate isolation of the air line by venting to atmosphere when a simple manual lever is shifted.

Supply in the 3/2 version, for example, can be on the instant- connection side or on the threaded side — for instance, when mounted on a manifold. Maximum working pressure is 10 bar and temperature range is –10° to 80°C.

3/2 pneumatic sleeve valves may be used to bleed the air line by venting the system to atmosphere. Their in-line configuration permits compact mounting directly into the pipework. Moving the sleeve in one direction lets air freely pass through the valve. Moving it in the opposite direction shuts off the supply and exhausts downstream air. Temperature range is the same as for the manually operated vent fittings, but maximum working pressure is 16 bar, and flow direction is one way.

Pressure regulator
Pressure regulator fittings are used to stabilize the pressure applied to pneumatic actuators at a preset value, regardless of upstream pressure fluctuations. Outlet pressure is fully controlled by an adjustment screw. To aid pressure selection, the screw on fittings from some manufacturers is calibrated to show the pressure setting.

Pressure regulator fittings can be mounted downstream of the control valve to reduce pressure for one direction or mounted upstream of the control valve for reduced pressure in both directions. These fittings handle input pressure from 1 to 16 bar, and regulated pressure is 1 to 8 bar. Working temperature range is –10° to 70°C.