1. Function and Purpose

• Breather Valve: A breather valve is primarily used to maintain a balance of pressure within a tank or vessel by allowing air to enter or exit as needed. It is essential for preventing overpressure or vacuum conditions during inhalation or exhalation when the contents of the tank fluctuate due to filling or emptying. Its main purpose is to prevent atmospheric contaminants, moisture, or other particles from entering the tank while allowing the release of excess pressure or vacuum.

  • Common Use: It is most commonly used in storage tanks for liquids and gases, especially in oil, chemical, and food industries where there is a risk of contamination.

• Pressure Relief Valve: A pressure relief valve is specifically designed to protect the tank or system from exceeding a certain preset pressure limit. It opens automatically to release excess pressure, thereby protecting the system from overpressure, which could otherwise lead to damage, rupture, or failure of equipment. When the system pressure exceeds the set limit, the valve opens to release the pressure until it returns to a safe level.

  • Common Use: Used in pressure vessels, piping systems, and boilers to safeguard equipment from dangerous pressure levels.

2. Pressure Regulation

• Breather Valve: The breather valve is designed to maintain a controlled pressure range by regulating small fluctuations in pressure, usually within a specific range of a tank’s working pressure. It doesn’t function to protect from catastrophic overpressure, but rather to keep the tank pressure stable by allowing small volumes of air in and out.

  • Pressure Settings: It typically operates within a small range of positive or negative pressure, allowing for minimal changes to stabilize internal tank pressure.

• Pressure Relief Valve: This valve’s role is to protect against overpressure, meaning it is designed to handle larger, more dangerous pressure surges. It opens when the internal pressure reaches a set critical value and closes once the pressure returns to a safe level. It’s essentially a safety valve designed to prevent system damage or failure due to excessive pressure.

  • Pressure Settings: It is preset to open when pressure exceeds a specified limit and is typically used for high-pressure control in various systems.

3. Operation Type

• Breather Valve: A breather valve functions in two directions. It allows air or gas to enter the tank if a vacuum is created (e.g., as a tank is emptied), and it allows air or gas to exit when pressure rises above the desired level (e.g., during tank filling).

  • Operation: It opens and closes gently to release or allow air, thus preventing sudden surges in pressure.

• Pressure Relief Valve: A pressure relief valve only operates in one direction: when the pressure exceeds the preset limit, it opens to release excess pressure. It closes again once the system pressure drops back below the set level.

  • Operation: It typically opens abruptly when needed and closes quickly after pressure stabilizes, ensuring that the system pressure remains within a safe range.

4. Application and Use Cases

• Breather Valve:

  • Prevents vacuum conditions in storage tanks.
  • Protects from contamination by ensuring that no external debris or moisture enters the tank.
  • Used in liquid storage, oil storage, chemical containers, and tank farms.
  • Often employed in applications where the product inside the tank is volatile or sensitive to contamination.

• Pressure Relief Valve:

  • Protects tanks, piping systems, and pressure vessels from overpressurization.
  • Essential in systems that operate at high pressures, such as boilers, steam systems, and high-pressure gas pipelines.
  • Used in industries where pressure levels must be precisely controlled to avoid dangerous overpressure situations (e.g., natural gas, chemical processing, and oil refining).

5. Design and Construction

• Breather Valve:

  • Low-pressure settings and designed to be highly sensitive to minor changes in pressure.
  • Often has a dual function, managing both pressure relief and vacuum relief.
  • Typically features a simple construction with a spring mechanism and can be fitted with a vent to allow air exchange.

• Pressure Relief Valve:

  • Designed to withstand high-pressure conditions and features a sturdy spring or diaphragm to control opening and closing.
  • Often features high-precision settings to ensure exact pressure control and protect the system from overpressurization.