Industries that deal with compressed liquids or gasses use pressure regulators to control the input and output pressure of the respective fluid media. By regulating the pressure levels, these devices ensure consistent fluid flow at the system’s outlet for optimal performance and safety.
Figure 1: https://tameson.com/pressure-regulator.html
Pressure regulators are designed to reduce a high input pressure to low and controlled output pressure. They also help avoid fluctuations in the output by keeping the pressure levels fairly constant. These devices are available in various designs and are used in industrial and domestic applications. For instance, they can be used at home to regulate propane gas used in gas cookers, hospitals to regulate oxygen, and automotive engines to regulate fuel consumption.
Pressure Regulators Working Principle
Now that you know the basic function of a pressure regulator, let’s look at the working principle or how these devices reduce and regulate fluid pressure. To understand this better, we’ll need first to highlight the three elements of a pressure regulator and their role in regulating fluid pressure. These elements are:
- Pressure reducing element – One commonly used pressure reducing element is the spring-loaded popper valve. The latter comes with elastomeric sealing for low-pressure applications and thermoplastic sealing for high-pressure applications. This valve uses the spring force and the output pressure to control the closing and opening mechanism.
- Sensing element – common sensing elements used in pressure regulators are pistons and diaphragms. A piston is used for high-pressure and rugged applications where wider pressure tolerances are acceptable. They also tend to have more friction between the regulator body and the pinion sealing; hence they are less effective for high-precision applications. On the other hand, diaphragms suffer less friction and offer more accuracy. They are made from thin elastomer material that is very sensitive to pressure changes.
- Loading element – this element forces the sensing element to open the valve. The spring force can easily be adjusted to vary the outlet pressure obtained.
Types of Pressure Regulators
Pressure regulators fall into either of the two categories, i.e., directed-operated or pilot operated. Each of these pressure regulators has its ways of regulating input pressures. Let’s take a look at these two.
Direct Operated Regulators
They are also called self-operated regulators due to their self-contained design. It’s one of the most common pressure regulators used to control fluids at lower pressures, typically below 0.07 bar and up to 35 bar. The regulator doesn’t need an external sensing line to operate since it uses the diaphragm to control a spring-actuated valve.
The diaphragm is activated by the pressure from the fluid medium, where an increasing downstream pressure closes the valve by compressing the spring. When the downstream flow reduces, the spring force becomes greater than the force exerted by the fluid media, opening the valve and allowing the fluid to flow.
Pilot Operated Regulators
These pressure regulators are generally designed for applications with large flow rates or high-pressure fluctuations at the inlet. They are available in two types: single-stage regulators and double-stage regulators. Single-stage regulators are common with the less-demanding applications, which require relatively smaller pressure reductions.
On the other hand, double-stage regulators are the most common since they provide precise pressure control even with large pressure fluctuations and high flow rates. When the pressure of the fluid medium is low, there’s no downstream flow.
But as soon as the fluid pressure on the spring-actuated pilot increases, the spring compresses, opening up the pilot valve and creating some pressure differential between the inlet and output valves. This pressure difference forces the main operating valve to open, and hence the fluid flows at a reduced pressure via the outlet valve.
Pilot-operated regulators can effectively handle fluids of varying pressures and capacities but only work with clean liquid and gases. This is because it has small ports and passages that can easily get clogged.
Selection Criteria and Applications
When choosing a pressure regulator, there are several factors that you’ll need to consider. These include the operating pressure range, the flow capacity required, and the nature of the fluid medium to be transmitted/controlled. Similarly, you want to pay attention to the operating temperature range, the material requirements and compatibility, and the accuracy required.
Some of the many applications of pressure regulators are in households, industrial settings, and business premises, e.g., for inflating tires, welding & metal cutting operations, etc. The environment where you’ll be using your pressure regulator will also influence your selection criteria. For instance, safety will be a key concern when dealing with flammable or hazardous gases and liquid.