In some compressed air systems, the only pressure control is on the compressor itself; this almost certainly results in too much air consumption. For example, most tools and many components have an optimum pressure for working and this is invariably less than the operating pressure of the compressor.
A pressure regulator reduces the input pressure to the desired output pressure of the system and will constantly maintain it despite any input variation. A device running at 7 bar will consume twice as much air as one running at 3 bar; using a pressure regulator reduces working pressure and saves energy and money.
How does a pressure regulator work?
The control knob is lifted and turned in a clockwise direction. This compresses a spring, placing the load on the diaphragm assembly. The diaphragm pushes down on a valve pin connected to the valve seat and the seat drops, this allows downstream air flow from the inlet port (P1) out of the outlet port (P2).
As air passes down P2 a breathe hole lets air into a chamber below the diaphragm; once pressure either side of the seat is equal, the seat closes with the aid of the spring. Downstream demand will cause a pressure drop in the chamber, opening the seat and allowing air to flow again until pressure is once more equalised and the seat closes. The process is continuous, maintaining P2 at a set value.
How do I select a pressure regulator?
There are several factors to consider when choosing the correct regulator for an application.
- Operating pressure - what is the operating pressure at the input port and the required controlled pressure at the output? What is the precision required in control of the output pressure?
- Flow requirement - a pressure regulator is not a flow controller, but clearly there is a relationship between the two. All manufacturers will provide a graph showing flow as a function of pressure and it is important to make sure the required flow range is in the linear part of the line.
- Operating fluid and environment - whilst we focus on compressed air as the medium, there are many applications with other gases; it is particularly important that the seals are resistant to any non-inert medium. The environment will impact choice, for example, in a hostile environment, it is likely that pilot operation will be required so adjustments can be made remotely.
- Operating temperature - materials chosen will be different for applications outside in the arctic circle, compared to a furnace!
- Size and weight - some applications, for example medical, may have restrictions on these physical parameters.
Typical applications of a pressure regulator
As can be imagined, there are numerous applications for pressure regulators, in most uses of air or a pressurised fluid. It is important to note that these are wide ranging and many, for example Medical and Gas Cutting, will require specialist regulators.
- Air compressors - As stated above, unregulated air, taken directly from the compressor will result in waste of energy and money. It is common for a pressure regulator to be fitted with the compressor to reduce the pressure to the maximum required in the system. Point of use pressure regulators, can then reduce this further to match the tool or component requirements.
- Aircraft - applications such as cabin pressurisation, portable water systems and canopy seal pressure control.
- Aerospace - propulsion pressure control for reaction control systems (RCS) and attitude control systems (ACS) are examples of applications. Here, vibration, temperature extremes and possible corrosive environments/fluids will need to be factored.
- Water pressure control - here the use of the pressure regulator is often to smooth out fluctuations in the supply pressure that could otherwise damage downstream equipment or components.
- Breathable air supply - clearly, the pressure in the supply tank will be much greater than that safe for the user. A pressure regulator reduces the pressure to a safe level and gives stability independent of the supply.
- Mining - mines often have complex water systems where the supply pressure will vary as a function of depth. Pressure regulators ensure the working pressure is matched to the safety levels of piping and operating equipment.
Other applications include:
- Medical
- Welding and cutting
- Oil and gas industry
- Propane/LP gas supply
- Gas powered and recreational vehicles
- Cooking
Do I need anything else to make a pressure regulator work?
Although most pressure regulators will have a relieving function, a pressure relief valve may also be fitted to ensure protection at point of use. As stated above, some applications will require air of a particular quality and the use of the correct filtration (for example, to 5 microns) is essential. Of course, the pressure regulator must be connected into the circuit, so the choice of correct fittings and tubing is critical.