A angle valve is a mechanical, pneumatically-powered valve with an adjustable piston actuator that provides linear directional control to lift an sealed stem off its seat. The stem is placed at a predetermined angle to give the best possible flow even when unseated. The valve's interior surface is usually made of brass or plastic and has a tapered, domed end. The tip of the dome may be rounded or pointed like a ball or cup.

It is widely believed that the angle valve was first patented by German scientists in the late nineteenth century. A valve whose opening is at a right angle to the flow direction creates a "wet" flow of liquid; the opposite is true for a "dry" flow of liquid. This basic principle is widely used in today's production of various kinds of household products including brake fluid and pharmaceuticals. When the angle of a valve is adjusted so that it can provide a controlled "dry" flow of liquid, this product behaves very much like a diaphragm. A diaphragm has the ability to expand to allow air flow into a space larger than its interior, while acting like a bladder to hold back the flow of liquid.

The angle valves of days gone by were not always reliable. They often caused serious problems in the event of a complete shutoff because they were so susceptible to mechanical failure. Although they are still used extensively in many manufacturing applications, new valve designs have been developed over the years that greatly reduce their incidence of stoppage due to mechanical failure. Many new valve designs combine the best features of open angle valves with the latest features such as seatbelts with silicone seals, and come in all manner of materials including, but not limited to, polycarbonate, stainless steel, and PTFE.

With the advent of plastics and their many applications, new types of angle valve parts have been developed for many types of industrial application. Some of the more common plastic parts include isolation valves, which isolate a closed end from a flowing stream of fluid or gas, or an expansion valve, which is used to control the amount of flow by controlling the opening of the valve. Some specialty parts include air-tight seals, which are used to prevent oil from flowing back into an oil tank. These valves may be used in a variety of applications.

In some circumstances it may be desirable to have a manual angle valve, or a "stop" or "use" valve. These are sometimes called "circuit breakers" or "turbine breakers", and are used to close the circuit before the pressure reaches a preset point. Stop valves sometimes are used to control the flow of an automatic pump. Sometimes called "drive breakers", these are typically used in the hydraulic systems of various types of machines. Their basic function is similar to that of a conventional safety valve.

When purchasing angle valves one of the most important factors is the quality of manufacture. There are a number of manufacturers in the United States that specialize in the manufacture of angle valves. One advantage of having your valves manufactured by a company that specializes in this industry is that you can usually be guaranteed that your valves will operate as described. However, it is also important to understand that not all suppliers are of the same quality, and it may sometimes be necessary to purchase your parts from a supplier that specializes in producing higher quality angle valves. These are valves that are manufactured with higher quality materials, and are designed to operate at higher efficiencies than traditional valves.