1.Summary of refrigerated container
As an essential means of transporting food, refrigerated container have unique materials requirements. Therefore, for the internal structure of the box, tasteless, non-toxic, anti-mildew, anti-corrosion, and other performance requirements are required, so there are strict requirements for the inner material of the refrigerated container. Due to the peculiarities and different use requirements of refrigerated containers, there are five refrigeration methods in the development history of refrigerated containers: water ice refrigeration, dry ice refrigeration, freezer plate refrigeration, liquid nitrogen refrigeration, and mechanical refrigeration.
In addition, refrigerated container manufactured and used abroad include:
- Jacketed refrigerated container.
- Air conditioning refrigerated container.
- Low-pressure refrigerated container.
- Liquid air refrigerated container.
- Liquid carbon dioxide refrigerated container.
There are two types of refrigerated container transport vessels in the development process, and there are two types of refrigerated containers corresponding to this.
The container itself has no refrigeration equipment but has a heat insulation structure and is centrally refrigerated by the container carrier. The cold air sent from the onboard refrigeration equipment enters the container through the air inlet, and the air return port opens at the end of the container. Another refrigerated container transport ship is equipped with a power socket on the cargo bulkhead. The container comes with its refrigeration unit and is equipped with a cable of more than 10 meters long. Insert the cable plug into the power socket on the ship’s bulkhead, and the refrigeration unit can be activated for refrigeration.
2.Introduce the unique material of refrigerated container
1)Refrigerated container cold-rolled stainless steel plate
Refrigerated container uses many stainless steel plate materials, mainly SUS304 (austenitic stainless steel referred to as HGSS) and SUS410L and SUS409L (both are ferritic stainless steel, referred to as MGSS for short). The higher the nickel content, the stronger the corrosion resistance. The lining board of the refrigerated container is in contact with the food, and all use this SUS304 material as the lining plate, and its thickness is 0.7mm. Mechanical performance index of SUS304, SUS410L, SUH409L
SUS304: yield strength ≥205MPa; tensile strength ≥520MPa; elongation ≥ 40%; surface hardness HV
SUS410L: yield strength ≥280MPa; tensile strength ≥350MPa; elongation ≥ 22%; surface hardness HV
R436LT: yield strength ≥250MPa; tensile strength ≥450MPa; elongation ≥ 30%; surface hardness HV
2)Refrigerated container hot-rolled steel plate
The outer frame of the refrigerated container is the primary stress point, and the frame is made of high-strength weather-resistant steel (CORTEN) and hot-rolled ferritic stainless steel (MGSS). These two plates have good bending and welding properties, and at the same time, have good mechanical properties, and can meet the strength requirements of refrigerated container. CORTEN is relatively cheap but has poor corrosion resistance. Still, hot spraying zinc can compensate its outer surface, while MGSS stainless steel is relatively expensive, but its corrosion resistance is more robust.
3)Refrigerated container aluminum alloy plate
Refrigerated container interior decoration, roof, box inner sealing plate, and some green refrigerated box outer plate and outer roof plate all use a grade of AA5052 aluminum-magnesium aluminum alloy, also known as anti-rust aluminum alloy, is a kind of aluminum alloy that can not be strengthened by heat treatment, high strength than pure aluminum and aluminum-manganese alloy, high corrosion resistance, fatigue strength, and good welding performance. The standard content of 5052 chemical composition%: Mg: 2.2 ~ 2.8; Si: However, due to the limitation of the pre-coating process, aluminum plates more than 2mm thick cannot be pre-coated and can only be solved by spraying the binder on the foaming surface of the aluminum plate at the production site.
4)Refrigerated container door sealing strip (EPDM)
Due to the refrigerated container’s high air tightness requirements, the air leakage rate is generally less than 3m3/hour. Usually, doors using O type of OC type have good airtightness and a low air leakage rate. But the opening and closing doors are tight. It is easier to open and close C-type doors, but the airtightness is poor. The door adhesive strips of refrigerated containers are made of EPDM synthetic rubber (EPDM).
Door sealing strips made of EPDM glue have good low-temperature performance and aging resistance and are suitable for internal and external door seals. The material requirements for door seals made of EPDM glue are as follows: The average service life of the door seal strip is 3-5 years, and the embedded door adhesive strip can be easily replaced.
5)Refrigerated container soft polyvinyl chloride (PVC)
Soft polyvinyl chloride (PVC) is mainly used for outer door sealing of wooden door panels, and it is characterized by beautiful molding and beautiful colors.
6)Refrigerated container polyethylene (PE) extrusion profile and low-pressure polyethylene (PE) tape
Polyethylene (PE) extruded profiles have both specific strength and heat insulation. Moreover, it can be sawed and planed, not moldy, and is suitable to replace wood. But the disadvantage is that it has a poor appearance, so it is mainly used for dividers in foam layers, floor mat strips, etc.
7)Refrigerated container sealant
The sealant of refrigerated container is used in large quantities. It is used for sealing anti-seepage water leakage between plates and plates, plates and profiles, profiles and profiles, and at the connection between the box and the refrigeration device. Joint refrigerated container sealants are as follows:
1) Refrigerated container modified silane sealant: the best all-around performance and good adhesion to various surfaces (metal, PVC). It is suitable for use both inside and outside the box, especially its odorless advantage, and is more ideal for use in refrigerated containers that need direct contact with food.
2) Refrigerated container silicone sealant: In addition to odor, the all-around performance of silicone sealant is about the same as the improved silane sealant and can be applied to all parts except the box.
3.Summary of refrigerated container
The refrigerated container is a unique means of transportation. Since refrigerated containers can meet sea transportation, it has a great demand for its strength. Refrigerated container is a modern transportation method that can realize “door-to-door,” the cold storage pre-cooling room in the middle of circulation. The “door” to the “door” of the retailer’s cold storage at the end of the refrigerated circulation container provides a broad development space for food cold chain operation.