Types, features, and applications of pressure vessels

Pressure vessels are broadly classified into Class 1 and Class 2 pressure vessels. Understanding their characteristics allows you to select the optimal pressure vessel for your specific application.

Differences between Class 1 and Class 2 pressure vessels

Since Class 1 and Class 2 pressure vessels have different design standards and regulations, appropriate selection is required based on the application and the pressure being handled. Class 1 pressure vessels often handle high-pressure gases, so more stringent safety standards are required for their design. For example, reactors and boilers in chemical plants are designed as Class 1 pressure vessels to withstand high temperatures and pressures while preventing the leakage of their contents.

On the other hand, Class 2 pressure vessels often handle lower pressures compared to Class 1, and therefore, safety standards allow for corresponding designs. Class 2 pressure vessels are used for applications where safety is relatively easy to ensure, such as household gas cylinders and compressed air tanks for small and medium-sized enterprises. As a result, cost and ease of installation are often prioritized.

Thus, when choosing a pressure vessel, it is important to carefully consider its intended use and the required pressure conditions. By selecting the appropriate type of pressure vessel, you can ensure safety while achieving efficient operation. Understanding the differences between Class 1 pressure vessels, which handle high pressure, and Class 2 pressure vessels, which can ensure safety at lower pressures, is essential for the proper selection and operation of equipment.

Applicable scope of Class 1 pressure vessels

Class 1 pressure vessels are large-scale pressure vessels that do not fall under either the (simple) vessels or small pressure vessels defined in Article 1, Item 5 of the Industrial Safety and Health Act Enforcement Order. They are subject to mandatory inspections by prefectural labor bureaus and other authorities at various stages, including manufacturing permits, manufacturing or importation, and installation. After they are put into use, a performance inspection by a registered performance inspection agency is required once a year.

The application categories are illustrated in the following diagram.

(1) Classification by maximum working pressure and internal volume


(2) Classification by shell inner diameter and length (maximum working pressure ≤ 0.1 MPa)

Applicable scope of Class 2 pressure vessels

Class 2 pressure vessels are pressure vessels defined in Article 1, Item 7 of the Industrial Safety and Health Act Enforcement Order, and are larger in scale than (simple) vessels. They are subject to mandatory requirements such as manufacturing based on the Class 2 Pressure Vessel Construction Standards, individual inspection at the time of manufacture or importation, and periodic self-inspections once a year.

The application categories are illustrated in the following diagram.

(1) Classification by maximum working pressure and internal volume

(2) Classification by shell inner diameter and length


For detailed information regarding the application categories of various pressure vessels, please refer to the link below.

・Application categories for Class 1 pressure vessels (small pressure vessels) (Japan Boiler Association) (https://www.jbanet.or.jp/examination/classification/vessel-1/)

・Classification of Class 2 Pressure Vessels (Japan Boiler Association) (https://www.jbanet.or.jp/examination/classification/vessel-2/)

Design standards and safety regulations for pressure vessels

Design standards and safety regulations for pressure vessels are extremely important for ensuring product safety and user trust. Complying with appropriate standards and regulations makes it possible to reduce risks and prevent accidents.

Domestic and international regulatory and safety standards

When installing and operating pressure vessels, it is necessary to follow domestic and international regulatory and safety standards. These regulatory and safety standards are established to prevent accidents and ensure user safety. By following them, risks can be minimized.

For example, in Japan, inspection and certification of pressure vessels are mandatory under the High Pressure Gas Safety Act. This law ensures that safety standards are met at each stage of manufacturing, installation, and use, and that thorough measures are taken to prevent potential accidents. Internationally, the ASME Boiler and Pressure Vessel Code is widely recognized and followed in many countries. This code is formulated by the American Society of Mechanical Engineers (ASME) and sets out detailed provisions for design, material selection, manufacturing, and testing.

Points to consider when choosing a pressure vessel

1. Operating pressure
2. Internal volume of the container
3. Temperature conditions
4. Purpose of use and environment

When selecting a pressure vessel, it is important to choose the appropriate size and material for its intended purpose. Using a pressure vessel that is not suited to its purpose can reduce safety and efficiency, and increase the risk of accidents. Therefore, choosing materials suitable for the application enables long-term, reliable operation.

For example, in chemical plants, where corrosive substances are often handled, it is recommended to choose pressure vessels made of highly corrosion-resistant stainless steel. On the other hand, for air compressors, lightweight and durable aluminum pressure vessels are suitable. By choosing the appropriate size and material, safety and efficiency can be ensured, allowing for long-term operation.

It is important to perform maintenance and management of pressure vessels regularly to detect problems early. By conducting periodic inspections and maintenance work, you can detect deterioration or damage to pressure vessels early and prevent accidents. In addition, preventing sudden breakdowns can also reduce operating costs.

Musashi Engineering's liquid feed tanks (pressure vessels)

Musashi Engineering's fluid feed tanks are designed to achieve continuous operation for high-flow dispensing.

To accommodate a wide range of liquid material viscosities, properties, and applications, we offer four types: Safety Lock Tanks, Straight One-Touch Tanks, One-Touch Tanks, and Gallon Tanks. There are two ways to load liquid materials: direct filling and using an inner container. With a wide variety of capacities ranging from 0.5L to 38.5L, please choose the most suitable tank according to your daily usage. They can also be used for filling syringes with liquid materials.

These fluid feed tanks are specified to handle the viscosity and fluidity of general liquid materials. Please feel free to contact us if you have special pressure conditions, require advanced control, or would like a custom specification.

Essential components of liquid transfer tanks

Key points for selecting tank components

*The following ①②④⑦⑩ correspond to the numbers of the "Essential Components of Liquid Feed Tanks" in the figure above.

The sizes indicated represent the effective volume inside the tank. When using material cans or inner containers, please be sure to check whether they will fit.

Please select an O-ring material that is resistant to swelling, according to the material being used.

The flow rate changes significantly depending on the diameter and length of the suction pipe and fluid feed tube.

(10) Piston for inner container (for 1kg can)
Essential for pressure-feeding high-viscosity materials.
In the case of grease or viscous adhesives, if a piston is not used, the material will be consumed in a mortar shape, making it impossible to feed properly.

The standard specification is for a general 1kg can.
It is sized to fit an inner diameter of Φ108.
Custom production to match the containers you use is also possible.
*We will need to borrow a container (used is acceptable) for measurement purposes.

Options to support easy and safe operation

At Musashi Engineering, we can propose solutions tailored to your needs regarding these pressure vessels and dispensing systems that incorporate pressure vessels. Depending on the usage conditions, they may be subject to legal regulations, so please consult us for details.

Please feel free to contact us here.