What is the typical pressure rating required for the housing of a screw air compressor?

I. The Difference Between Working Pressure and Design Pressure

When examining the pressure‑resistance requirements of screw air compressor housings, it is first necessary to clarify…Work stressandDesign pressureThe concept of working pressure refers to the maximum pressure that may be reached at the top of the vessel under normal operating conditions. In contrast, the design pressure is the specified maximum pressure at the top of the vessel, typically defined in conjunction with the corresponding design temperature as part of the design load conditions.

To ensure safety, the design pressure of a vessel is typically higher than its maximum operating pressure. In engineering design, the design pressure is usually taken as 1.1 to 1.25 times the operating pressure, or rounded up to the nearest standard pressure class.

II. Pressure-Resistance Range of the Casing for Conventional Screw Air Compressors

The pressure‑resistance requirement for the housing of a screw air compressor is not a fixed, single value; rather, it is determined by the equipment’s discharge‑pressure rating. For typical industrial screw air compressors, the discharge pressure generally ranges from 0.7 MPa to 1.3 MPa.

• Low-pressure and conventional medium-pressure modelsFor standard models with discharge pressures ranging from approximately 0.8 MPa to 1.0 MPa, the oil–gas separator tank or housing is classified as a simple pressure vessel or a conventional pressure vessel, and its design pressure is typically set at around 1.0 MPa to 1.3 MPa.
• Medium- and high-pressure modelsFor medium- and high-pressure screw air compressors with discharge pressures reaching 1.3 MPa or higher, the design pressure of the compressor casing is correspondingly increased, typically ranging from 1.5 MPa to 1.6 MPa or even higher; this must be strictly matched to the unit’s rated operating pressure.

It should be noted that the oil–gas separator vessel is the primary pressure‑bearing shell component in a screw air compressor, and its pressure rating must strictly comply with the relevant national or industry standards for pressure vessels.

III. Key Factors Affecting the Pressure-Resistant Design of the Shell

In addition to the basic working pressure, the actual pressure‑resistance design of the shell must also take into account the following factors:

• Material Selection: The shell is typically fabricated from carbon steel or stainless steel. The material’s yield strength, tensile strength, and weld quality directly determine the shell’s ultimate pressure‑bearing capacity.
• Safety factor: When performing design calculations, a safety factor must be incorporated. According to the relevant pressure vessel design codes, the ratio of the material’s allowable stress at the design temperature to the safety factor serves as the fundamental basis for determining the shell thickness.
• Work environment: If the equipment is exposed to high temperature, high humidity, or corrosive gases, the enclosure’s pressure‑resistance may degrade due to material corrosion or high‑temperature creep; therefore, a corrosion allowance should be incorporated into the design.

IV. Safety Accessories and Routine Maintenance

The pressure‑resistant design of the casing is fundamental; however, during actual operation, it is essential to rely on well‑designed safety accessories to prevent overpressure. A calibrated device must be installed on the casing of a screw air compressor.Safety valveandPressure sensor.

The set pressure of a safety valve is typically adjusted to approximately 1.1 times the equipment’s rated working pressure. When the system pressure rises abnormally and reaches the safety valve’s set point, the valve automatically opens to relieve pressure, thereby preventing the vessel from deforming or rupturing due to overpressure. In addition, enterprises should conduct regular visual inspections, thickness measurements, and safety‑valve verification to ensure that the vessel’s pressure‑resistance remains safe and under control at all times.