Why regulator

In contrast to a non-relieving regulator, a relieving also known as self-relieving regulator is designed to vent excess downstream pressure to atmosphere.

Typically there is a vent hole in the side of the regulator body for this purpose. In some special designs, the vent port can be threaded and any excess pressure can be vented from the regulator body through tubing and exhausted in a safe area.

If this type of design is selected the excess fluid should be vented appropriately and in accordance to all safety regulations. The materials selected for the pressure regulator not only need to be compatible with the fluid but also must be able to function properly at the expected operating temperature. The primary concern is whether or not the elastomer chosen will function properly throughout the expected temperature range. The inlet and outlet pressures are important factors to consider before choosing the best regulator.

Important questions to answer are: What is the range of fluctuation in the inlet pressure? What is the required outlet pressure? What is the allowable variation in outlet pressure? What is the maximum flow rate that the application requires?

How much does the flow rate vary? Porting requirements are also an important consideration. In many high technology applications space is limited and weight is a factor. Some manufactures specialize in miniature components and should be consulted.

Material selection, particularly the regulator body components, will impact weight. Also carefully consider the port thread sizes, adjustment styles, and mounting options as these will influence size and weight. In operation, the reference force generated by the spring opens the valve. The opening of the valve applies pressure to the sensing element which in turn closes the valve until it is open just enough to maintain the set pressure.

The poppet includes an elastomeric seal or, in some high pressure designs a thermoplastic seal, which is configured to make a seal on a valve seat. When the spring force moves the seal away from the valve seat, fluid is allowed to flow from the inlet of the regulator to the outlet. As the outlet pressure rises, the force generated by the sensing element resists the force of the spring and the valve is closed.

These two forces reach a balance point at the set point of the pressure regulator. When the downstream pressure drops below the set-point, the spring pushes the poppet away from the valve seat and additional fluid is allowed to flow from the inlet to the outlet until the force balance is restored. Piston style designs are often used when higher outlet pressures are required, when ruggedness is a concern or when the outlet pressure does not have to be held to a tight tolerance.

Piston designs tend to be sluggish, as compared to diaphragm designs, because of the friction between the piston seal and the regulator body. In low pressure applications, or when high accuracy is required, the diaphragm style is preferred.

Diaphragm regulators employ a thin disc shaped element which is used to sense pressure changes. They are usually made of an elastomer, however, thin convoluted metal is used in special applications. Diaphragms essentially eliminate the friction inherent with piston style designs. Additionally, for a particular regulator size, it is often possible to provide a greater sensing area with a diaphragm design than would be feasible if a piston style design was employed.

The reference force element is usually a mechanical spring. This spring exerts a force on the sensing element and acts to open the valve. Most regulators are designed with an adjustment which allows the user to adjust the outlet pressure set-point by changing the force exerted by the reference spring. The accuracy of a pressure regulator is determined by charting outlet pressure versus flow rate.

The resulting graph shows the drop in outlet pressure as the flow rate increases. This phenomenon is known as droop. Pressure regulator accuracy is defined as how much droop the device exhibits over a range of flows; less droop equals greater accuracy. When selecting a regulator, engineers should examine pressure versus flow curves to ensure the regulator can meet the performance requirements necessary for the proposed application.

Droop can also be caused by significant changes in the inlet pressure from the value when the regulator output was set. As the inlet pressure rises from the initial setting, the outlet pressure falls.

Conversely, as the inlet pressure falls, the outlet pressure rises. Increasing the valve orifice can increase the flow capacity of the regulator. This may be beneficial if your design can accommodate a bigger regulator however be careful not to over specify.

A regulator with an oversized valve, for the conditions of the intended application, will result in a greater sensitivity to fluctuating inlet pressures, and may cause excessive droop.

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Robert Longley. History and Government Expert. Robert Longley is a U. Facebook Facebook. Updated September 02, Key Takeaways: The Regulator Movement The Regulator Movement was a series of uprisings over excessive taxation and lack of law enforcement in the British colonies of North and South Carolina from to In South Carolina, the Regulator Movement protested the failure of British government officials to maintain law and order in the western frontier backcountry.

In the North Carolina Regulator Movement, settlers in the inland agricultural communities fought against unfair taxes and tax collection methods imposed by corrupt British officials. Some historians consider the Regulator Movement a catalyst to the American Revolution. Cite this Article Format. Longley, Robert. History and Significance. What Was the Regulator Movement? The Whiskey Rebellion: History and Significance. What Was the Sugar Act? Definition and History.

The Granger Laws and the Granger Movement. Continental Congress: History, Significance, and Purpose. History and Founding of Virginia Colony. American History Timeline: to The Founding of the Massachusetts Bay Colony. There is no single standard test for common performance characteristics recognized across industries, and thus there is wide variance in the thoroughness of equipment testing among different regulator manufacturers. When selecting and specifying pressure regulators for your industrial fluid systems, ask your supplier how they verify proof of performance.

Instead, a customized approach to testing across a range of performance attributes is needed to be confident that a regulator will perform as rated when conditions are most extreme. A sound method is to use predictive modeling to theoretically predict performance characteristics, then prove those theories using practical testing methodologies.

A few of the most important tests include the following:. Burst Testing. One of the first and most essential performance criteria of a pressure regulator is its ability to maintain its integrity when operating at pressure. Burst testing, which can be performed at pressures far exceeding expected regulator operational pressure, can help design engineers be certain their products will perform in accordance with their pressure rating.

The most reliable regulators are often designed to achieve steady performance under working pressures several times their rated pressure. Fluid Dynamic Testing. Consider a pressure-reducing regulator that is tasked with reducing pressure from psi at the inlet stream to psi at the outlet stream. In order to ensure steady, reliable outlet pressure, it is important for designers to identify any potential velocity traps or pressure buildup spots within the regulator.

Because the regulator itself measures its intended outlet pressure at the diaphragm, even small interior design inconsistencies can create pressure losses at the outlet stream and lead to underperformance. Computational fluid dynamics CFD and practical flow testing are some of the primary methods by which manufacturers investigate pressure zones within the regulator to ensure the device is accurately reading, and thereby controlling, outlet pressure per system specifications.

CFD uses numerical analysis and data structures to analyze and solve problems that involve fluid flows and pressures.

Supply Pressure Effect Testing. Supply pressure effect SPE , also referred to as inlet dependency, is a change in outlet pressure due to a change in inlet pressure. If the inlet pressure decreases, there will be a corresponding outlet pressure increase. Conversely, if the inlet pressure increases, the outlet pressure decreases.

Most suppliers will provide customers with a figure describing the change in outlet pressure per change in inlet pressure. In order to provide the smallest, most precise value possible, SPE testing is an essential part of regulator engineering and design.

Life Cycle Elements Testing. Once installed, operators should expect a regulator to provide years of performance across many actuation cycles.

To be confident a regulator will achieve that kind of performance longevity as designed, a battery of life cycle tests can be applied. Life cycle testing can be performed as a bench test where engineers run a range of different cycle loads, sometimes up to cycles per second.