Difference Between Relief Valve and Safety Valve

Edited by Diffzy | Updated on: September 13, 2022

       

Difference Between Relief Valve and Safety Valve Difference Between Relief Valve and Safety Valve

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Introduction

In the process sector, these names are interchangeable since safety devices are necessary for any pressurised system in order to safeguard people, property, and the environment. The two main safety devices used in process industries to prevent overpressure scenarios are relief valves and safety valves. Despite the fact that both devices serve essentially the same function, there are several key operational differences between them.

Although they both relate to valves that let pressure out of a pressurised system, the names' technical meanings differ slightly. Generally speaking, a relief valve is a valve used in pressurised systems to regulate pressure in order to maintain the system's best performance. Relief valves are intended to safeguard equipment from overpressurized circumstances and assist your business in preventing system breakdowns.

Contrarily, the phrase "safety valve" refers to pressure valves that are intended to safeguard people, property, and operations. To put it another way, a safety valve is a failsafe, last-resort valve that releases pressure to avert an emergency, often after all other relief valves have failed to appropriately manage pressure in a system.

Relief Valve vs Safety Valve

The main distinction between a Relief Valve and a Safety Valve is that a Relief Valve assists in keeping the proper pressure in a system so that it does not rise, whereas a Safety Valve assists in releasing extra pressure from the system when the pressure rises to a high level and is capable of causing overpressure. The methods used by each of these safety devices to handle overpressure situations vary.

A relief valve is a tool used in the process sector to safeguard equipment or systems against overpressure. A certain system pressure level is maintained by the device. The particular level is generally referred to as Setpoint. If the pressure climbs over the setpoint, overpressure and severe damages may result.

A Safety Valve, on the other hand, is a component intended to stop the buildup of excess pressure in a system. The safety valve releases the extra pressure from the system when the pressure exceeds the setpoint. As a result, overpressure circumstances are avoided.

Both safety valves and relief valves serve the same basic purpose. They are both pressure relief valves, and their purpose is to release pressure if a system gets overpressurized. Nevertheless, the ways in which relief valves and safety valves operate do differ slightly.

Relief Most frequently in fluid or compressed air systems, valves are used to manage pressure in a system. In proportion to the rise in system pressure, these valves open. As a result, even when the system is somewhat overpressurized, they don't fly completely open. They instead gradually open, enabling the system to regain the predetermined pressure level. The valve closes once more when that level is reached.

Safety is the only reason safety valves are utilised. They are made to instantly release pressure in the case of an emergency or system breakdown rather than managing the pressure in a system. Safety valves, as contrast to relief valves, open fully and instantly to prevent a catastrophe rather than to regulate a system's pressure.

Safety valves and relief valves both function to remove excess pressure, although they do so in slightly different ways. For further details on the variations between the two valves, see the table below provided by Difference Between:

Difference Between Relief Valve And Safety Valve in Tabular Form

Table: Relief Valve vs Safety Valve
Parameters of Comparison
Relief Valve
Safety Valve
Definition
A relief valve is a component that aids in maintaining a system's pressure at a particular level.
When pressure reaches the limit, a safety valve assists to relieve the excess.
Working
With an increase in pressure, it expands proportionately.
As the pressure builds, it instantly and completely opens up.
Operator
An operator assists in operating it.
While no operator is employed.
Setpoint
The working pressure limit is 10% lower than the setpoint.
While the working pressure limit is 3% lower than the setpoint.
Types
Pop-type, pilot-operated, direct-operated, and internal are the four types.
Depending on their intended uses, the categories are separated.
Purpose
It prevents the pressure from rising above a specific point.
While preventing overpressure and releasing excess pressure.

What is a Relief Valve?

Relief valves, sometimes referred to as pressure relief valves (PRVs), are a family of safety mechanisms created expressly to guard against the detrimental effects of overpressurized situations on pressure-sensitive equipment and systems. A relief valve device is periodically stripped down and is essentially resistant to the effects of a system's back pressure. One of the most important components of a pressure system that opens at a predetermined pressure level to prevent system failures are pressure relief valves. Every pressure system has a setpoint, which is a specified design limit at which the valve starts to open to prevent overpressure circumstances.

A relief valve, also known as a pressure relief valve (PRV), is a safety device that keeps the pressure in a system at a set level to prevent overpressure conditions. The device prevents the pressure from rising above the predetermined level.

With a rise in pressure, the relief valve tends to slowly open up. A relief valve's setpoint should be 10% higher than the working pressure limit. The valve opens to control the pressure and stop overpressure when it begins to rise above the setpoint. It reacts by returning any extra auxiliary channel flow to the tank in order to keep the system from failing.

The amount of pressure increase directly correlates to the relief valve's opening. Only until the pressure returns to the set limit does it open up. To finish this procedure, an operator is employed. The valve opens gradually throughout the procedure.

Conditions of overpressure affect a number of areas of an industry. So that the pressure is kept at the intended setpoint and no harm results, a relief valve is installed in the system.

What is a Safety Valve?

In the process industry, there are boilers, power plants, and other such things. Here, a safety valve is a very important defence tool for people, property, and processes. The safety valve gets activated automatically to stop pressure from building up inside a vessel or system after a threshold limit. When that pressure is reached, the safety valve in the device automatically trips. It hardly lets the excess pressure gets released in order to safeguard the vessel from harm. It also ensures that the pressure does not exceed such limitations in the future. But the safety valve opens with the slight increase in pressure from the threshold limit and drops again as soon as the pressure drops to the permitted level.

A safety device known as a safety valve is created in such a way that it automatically activates when the pressure starts to build. The tool aids in releasing extra pressure from the system. As a result, overpressure situations are avoided.

As soon as the pressure exceeds the predetermined limit, the safety valve opens. A safety valve's setpoint is set at 3% more than the operational pressure limit. The valve opens up and begins releasing the extra pressure even if the pressure only slightly exceeds the set limit. When the pressure reaches the required limit, it returns to its initial state.

A safety valve does not employ an operator, in contrast to a relief valve. When the pressure level rises, it opens up immediately. When the extra pressure is released, it shuts. The valve opens and closes more quickly and abruptly.

The last line of defence against overpressure conditions is a safety valve. It is capable of running at any moment. When the valve is employed, the likelihood of losses and damages is reduced.

Difference Between Relief Valve and Safety Valve in Points

Relief vs. Safety Valve: Definition

The purpose of a relief valve, often referred to as a pressure relief valve (PRV) or safety relief valve, is to regulate or manage the pressure level in a system within a safe threshold limit in order to prevent an overpressure condition. A relief valve is, to put it simply, a tool used to regulate the pressure within a system or vessel to a certain level. On the other hand, a safety valve is a mechanism that releases extra pressure from a vessel or piece of equipment when the pressure exceeds a predefined limit. If the pressure rises, it only permits liquids or gases to escape without causing any harm.

Function

In hydraulic systems, pressure relief valves are typically used to limit system pressure to a predetermined level. When the system pressure exceeds the safety design limit, the relief valve reacts by releasing extra flow through an auxiliary passage from the system back to the tank to prevent equipment failure. A safety valve's primary function is to safeguard people, their belongings, and the environment from pressure failures in control systems. Simply simply, when the pressure rises above the predetermined pressure limit, a safety valve opens.

Safety valve versus relief valve operation

The opening of a safety relief valve increases in direct proportion to the rise in vessel pressure. This indicates that the valve opens more gradually than abruptly, opening only when the pressure reaches a predetermined level and releasing fluids until the pressure falls to the predetermined set pressure. On the other hand, a safety valve will open right away when the system pressure reaches the predetermined pressure threshold to prevent system failure. It is a safety feature that can always be in use and is the last line of defence against catastrophic system failure when there is excessive pressure present.

Setpoint

A pressure relief valve is made to open at a predetermined pressure level known as a "setpoint." The set pressure should not be confused with a setpoint. A relief valve's setpoint is actually lowered to its lowest maximum pressure rating, which means it is lower than the maximum system pressure permitted before an overpressure issue develops. When the pressure rises to a point over the setpoint, the valve starts to open. The setpoint must not be higher than the maximum permitted working pressure (MAWP), which is measured in pounds per square inch (PSIG) (MAWP). The setpoint is typically 3 percent higher than the working pressure level for safety valves while it is 10 percent higher for relief valves.

  • While the Safety Valve releases extra pressure, the Relief Valve keeps the pressure at a predetermined level.
  • The safety valve opens up instantly, but the relief valve opens up gradually.
  • The relief valve has an operator, whereas the safety valve does not.
  • Relief and safety valve setpoints are 10% and 3% higher than the limit, respectively.
  • While the relief valve has only three varieties, the safety valve has several.

Conclusion

The risk of harm to life and property exists in the industrial environment. It is important to take good care of any systems or equipment utilised for work in order to prevent any unavoidable problems. To aid in the procedure, many kinds of safety equipment are introduced.

The most widely utilised safety mechanisms for handling overpressure situations are the relief valve and safety valve. The safety valve releases any extra pressure while the relief valve keeps the systemic pressure within a predetermined range.

These two devices both guard against overpressure-related problems. Despite serving the same function, they operate in quite distinct ways. While the safety valve does not have an operator, the relief valve does. The safety valve operates more quickly and abruptly than other valves.

The two most utilised sorts of control valves are, in brief, safety valves and relief valves. The safety valve is a component of the pressure release mechanism, which can only be used to protect the system when the operating pressure is higher than the permitted range. The relief valve's operating procedure is continuous, and it can swiftly provide the high-pressure medium to satisfy the system's pressure needs.

References

  • Hellemans, Marc. The Safety Relief Valve Handbook. New York City: Elsevier, 2009. Print
  • Buel, Richard H. Safety-Valves. New York City: David Van Nostrand, 1875. Print
  • Matthews, Clifford. A Quick Guide to Pressure Relief Valves. New Jersey: John Wiley & Sons, 2005. Print

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"Difference Between Relief Valve and Safety Valve." Diffzy.com, 2022. Thu. 08 Dec. 2022. <https://www.diffzy.com/article/difference-between-relief-valve-and-safety-valve-672>.



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