Are most oil‑gas separators in screw air compressors classified as simple pressure vessels?

Definition and Characteristics of Simple Pressure Vessels

Before discussing the classification of oil–gas separators for screw air compressors, it is first necessary to clarify…Simple pressure vesselThe concept of a simple pressure vessel refers to a pressure vessel that is structurally straightforward, poses relatively low risks, and has a volume and working pressure within specified limits. Such vessels are subject to stringent design constraints: their design pressure, volume, and the product of the two must all remain below certain established standards.

Due to their simple structure and controllable risks, the relevant safety technical specifications for special equipment impose relatively streamlined regulatory requirements on simple pressure vessels during manufacturing, installation, and operation. For example, such vessels are typically exempt from periodic inspections within their design service life; however, enterprises are still required to carry out routine safety management.

Classification and Definition of Oil–Gas Separation Cylinders for Screw Air Compressors

The oil–gas separator tank of a screw air compressor is primarily used to separate lubricating oil from compressed air and to store high-pressure gas. Whether it qualifies as a simple pressure vessel cannot be determined across the board; it depends mainly on the equipment’s…Design pressureandVolume.

• Small and medium-sized low-voltage equipment:Common small- and medium-sized screw air compressors on the market typically operate at conventional low-pressure levels, with oil‑gas tank capacities generally not exceeding a few hundred liters. The product of pressure and volume for such equipment usually falls below the upper limit defining a simple pressure vessel; accordingly, the associated oil‑gas tanks or air receivers largely meet the criteria for simple pressure vessels.
• Large or high-pressure equipment:For large screw air compressors with high discharge pressures or substantial displacements, the parameters of their oil–gas separators often exceed the scope of simple pressure vessels. Such oil–gas separators are classified as conventional…Fixed Pressure Vessel, must be registered, inspected, and managed in strict accordance with the relevant standards for conventional pressure vessels.

How to accurately determine the equipment category of an oil and gas cylinder

When using screw air compressors, enterprises should never rely on guesswork to classify oil‑gas separators; instead, they should determine the classification accurately through the following methods:

• View the equipment nameplate:Oil and gas cylinders manufactured by reputable producers are all equipped with a product nameplate. The nameplate clearly indicates whether the vessel is classified as a “Simple Pressure Vessel” or a “Fixed‑Type Pressure Vessel,” and it also specifies key parameters such as design pressure, volume, material, and the designed service life.
• Verify factory documentation:Refer to the product quality certification documents provided with the equipment. If the documentation specifies that the equipment was manufactured in accordance with the relevant standards for simple pressure vessels, it falls under this category; if it states that the equipment was manufactured according to the standard requirements for conventional stationary pressure vessels, it shall be managed as conventional equipment.
• Confirm the special equipment code:In the special equipment registration system, pressure vessels of different categories are assigned distinct equipment type codes, which can be used to verify their statutory classification.

Daily Use and Safety Maintenance Recommendations

Whether or not an oil and gas cylinder is classified as a simple pressure vessel, it still experiences internal pressure, and routine safety maintenance must never be overlooked.

• Regularly inspect safety accessories:Ensure that safety valves, pressure gauges, and other safety accessories are sensitive and reliable, and conduct regular verification as required to prevent operation under overpressure.
• Pay attention to corrosion protection and drainage:Regularly drain the condensate from the bottom of the oil‑gas drum to prevent water accumulation, which can cause corrosion and reduce the vessel wall thickness and pressure‑bearing capacity.
• Pay attention to the service life:Although simple pressure vessels are exempt from inspection during their design service life, they must be promptly scrapped or subjected to a safety assessment upon reaching their service life limit; continued operation beyond this period is strictly prohibited.