Keywords:
The sub-mother tank refers to an inner tank composed of multiple (more than three) sub-tanks in parallel, designed to meet the requirements for large capacity storage of low-temperature liquids. Multiple sub-tanks are assembled in a large outer tank (the mother tank). The sub-tanks are usually vertical cylindrical, while the outer tank is a vertical cylindrical shape with a flat bottom and dome top. Due to the large size and shape of the outer tank, it cannot withstand external pressure and cannot be vacuumed; thus, the outer tank is a normal pressure tank. The insulation method is powder (pearl sand) accumulation insulation.
Sub-tanks are usually transported to the site for installation after being completed at the pressure vessel manufacturing plant, while the outer tank is processed into components and assembled on-site.
The geometric volume of a single sub-tank is usually between 100 to 150 m3, and the volume of a single sub-tank should not be too large, as a larger size would lead to difficulties in transportation and installation. The number of sub-tanks is usually between 3 to 7, allowing for the construction of large storage tanks with capacities ranging from 300 to 1050 m3.
Sub-tanks can be designed as pressure vessels, with a maximum working pressure of up to 1.8 MPa, typically ranging from 0.2 to 1.0 MPa, depending on the user's pressure requirements.

1.1 Advantages of Sub-Mother Tanks
(1) Liquid can be discharged using the pressure of the container itself without the need for a liquid transfer pump, providing ease of operation and high reliability.
(2) Once the container meets pressure conditions, it can be stored under pressure, reducing emission losses during storage.
(3) The manufacturing and installation of sub-mother tanks are easier to achieve compared to spherical tanks, resulting in lower manufacturing and installation costs.

1.2 Disadvantages of Sub-Mother Tanks
(1) Due to the structure and size of the outer tank, the interlayer cannot be vacuumed, and the thickness of the interlayer is usually chosen to be over 800 mm, leading to poorer insulation performance compared to vacuum powder insulated spherical tanks.
(2) Due to the thick interlayer and the arrangement of sub-tanks, the external dimensions of the equipment are large.
(3) The interlayer volume of the sub-mother tank is too large, with pearl sand filling all interlayer spaces, resulting in excessive waste of insulation materials.
Sub-mother tanks are typically suitable for volumes ranging from 300 to 1000 m3, with working pressures between 0.2 to 1.0 MPa.

Nanyang Duer Gas Equipment Co., Ltd. is a joint-stock high-tech enterprise located in the picturesque area north of the Han River and south of the Funiu Mountains; the source of the South-to-North Water Diversion Project -- Nanyang, the place where the military strategist Zhuge Liang cultivated the land, and the famous battles of "Danyang" between the Qin and Chu states and the Three Kingdoms story of "Three Visits to the Thatched Cottage" took place.
Nanyang Duer Gas Equipment Co., Ltd. is mainly engaged in the research and development, design, manufacturing, and after-sales service of various industrial gas equipment and low-temperature equipment. The company has the following divisions:
1. Low-Temperature Equipment Division: Large normal pressure low-temperature storage tanks, powder vacuum low-temperature storage tanks, large air bath vaporizers, water bath vaporizers, low-temperature loading pumps and loading arm systems for large low-temperature storage tanks, metering skids, etc.
2. Gas Equipment Division: LNG refueling stations, L-CNG refueling stations, LNG vaporization stations, LNG vaporizers, LNG vaporization pressure regulation metering and odorization skids, LPG vaporizers.
3. Heat Exchanger Division: High-pressure coil heat exchangers, fixed tube sheet heat exchangers, U-tube heat exchangers, floating head heat exchangers.
The company always adheres to the concept of "building a reliable brand in the industry based on advanced DOER technology," actively exploring and developing new processes and technologies, and continuously introducing advanced technologies and research results from both domestic and international sources.
In recent years, the industrial gas equipment produced by the company has been widely used in various fields such as coal gas to LNG production, steel metallurgy, air separation, urban gas, heat treatment, coal and oil boiler renovation, as well as powder metallurgy, hot-dip galvanizing, petrochemicals, chemical fibers, float glass, food preservation, pharmaceuticals, electronics, automotive LNG refueling stations, ship LNG retrofitting, gas receiving station reserve peak-shaving stations, and laboratories of national defense, aerospace, and universities.