As the core component of the system, the correct installation of the cryogenic air separation cold box is crucial to ensure the operation efficiency of the equipment, product purity and operational safety. This article will discuss you around the installation specifications of cold box and provide relevant data support, hoping that it can help you.
Preparation and design considerations
Before starting the installation, the cold box needs to be designed and planned in detail. According to the requirements of the national standard GB/T 16954-2018 "Safety Rules for the Use of Low-Temperature Liquid Storage Equipment", the design of the cold box should take into account the impact of ambient temperature changes on its internal pressure. Typically, the internal working temperature of the cold box can be as low as -196°C (liquid nitrogen boiling point), which means that the material selection must consider its performance under extremely low temperature conditions.
In addition, sufficient expansion space should be reserved during design to cope with the thermal expansion and contraction effect caused by temperature changes. Generally, a shrinkage rate of about 0.5% to 1% is considered when a pipe or structural member of each meter is reduced from room temperature to operating temperature.
Foundation construction requirements
The foundation construction quality of the cold box directly affects the stability of the entire system. According to the ASME B31.3 standard, the flatness error of the foundation surface must not exceed ±3mm/m to ensure that the equipment will not be deformed or damaged due to uneven settlement after installation of the cold box. At the same time, the strength grade of the foundation concrete should not be lower than C30, and it will take at least 28 days of maintenance before the equipment installation can be carried out.
Pipeline layout and connection
The pipeline layout follows the principle of "short, straight and few bends" to minimize energy losses. For pipes with a diameter of DN50, the flow rate is recommended to be controlled between 5-10m/s; for pipes with larger diameters, the flow rate is appropriately reduced to reduce pressure drop. All pipe joints are connected by welding and non-destructive testing is carried out in accordance with EN 13480-2 to ensure that the weld quality meets the requirements. It is particularly noteworthy that the treatment process before and after welding cannot be ignored. Measures such as preheating and slow cooling can effectively prevent the occurrence of welding cracks.
Insulation layer construction
Good thermal insulation effect is an important guarantee for maintaining the low temperature environment in the cold box. Common thermal insulation materials include pearlescent sand, glass wool, etc. Taking pearlescent sand as an example, its thermal conductivity is about 0.03W/(m·K), which can effectively reduce heat transfer. During the construction process, it is necessary to ensure that the thickness of the insulation layer is uniform and the cold bridge phenomenon caused by local excessive thinness is avoided. Generally, the thickness of the thermal insulation layer is not less than 150mm.
Safety protection measures
Security management during installation is equally important. The construction site should be equipped with obvious warning signs and necessary fire-fighting equipment. According to NFPA 50A standards, the safety passage width of at least 1.5 meters is maintained around the cold box to facilitate evacuation and rescue operations in emergencies.
The installation of cryogenic air separation box is a complex but orderly process involving knowledge in multiple fields such as materials science and mechanical engineering. Strictly implementing in accordance with relevant national standards and industry specifications can not only improve the overall performance of the equipment, but also ensure the safety of the lives and property of the operators. It is hoped that the above content can provide valuable reference information for professionals working in this field.
