21-01-2013, 04:50 PM
DESIGN OF 65m3 LIQUID NITROGEN (N2) STORAGE TANK
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ABSTRACT
Cryogenics is a part of science, which deals with low temperature study. Cold convertor is one kind of pressure vessel which is meant for storage of liquid Oxygen or Nitrogen or Argon under certain required pressure. The materials used for this equipment are discussed in this report. The project report follows the same procedure for the designing of cold convertor as the industry does.
The procedure conforms to ASME SECTION VIII, division- 1. The procedure for designing nitrogen cold convertor to required specifications has been shown. The design calculations and results have been shown.
INTRODUCTION TO BHPV:
BHARAT HEAVY PLATE AND VESSELS LIMITED is established in 1966 by the government of India in Andhra Pradesh, Visakhapatnam.
It is the largest fabrication industry of process equipment in India for the fertilizers, petroleum, chemical, petro-chemical and alled industries, it is fully owned by the government of India and managed by the autonomous board of directors.
BHPV Ltd means Bharat Heavy Plate & Vessels Ltd is a fabrication industry. BHPV is located at Vishakhapatnam which is 20km away from the city on the highway towards Anakapalli. BHPV is constructed in 378 acres of land with man power of 1500 employees out of which 300 are executives and 150 are supervisors, balance are technical and non- technical. The turnover of this company is 350 crores per annum. At the moment the government is thinking of merging with BHEL which produces industrial and power boilers.
Thus BHPV is equipped to manufacture a wide variety of fabricated product lines for the process of industries either to its own design or to the specification of the customer’s consultant. In any industry or company, a department is always made to handle some external projects. These kinds of projects which cannot be fabricated in the shop floor of any industry are handled in this section. Research & development comprises of many branches of engineering in BHPV, these are mechanical, computers, metallurgy and chemical engineering working together to assist each other.
Quality certificates of BHPV:
1. “Lloyds” register of industrial services class- 1 for fusion welded pressure vessels.
2. ASME (American society of mechanical engineering)
• U & U2stamps on pressure vessels.
• S- stamp for industrial boiler.
3. National board of boilers and pressure vessels inspectors (USA) R- stamp for repair of coated vessels.
4. Semi carbon urea reactor.
5. Haldor tops for ammonia reactors & high pressure heat exchangers.
6. Arabian American Oil Company: process plants.
INTRODUCTION TO CRYGENICS:
The word cryogenics was derived from Greek, which means generation of the temperature.
Cryogenic engineering is concerned with developing and improving low temperature process and equipment. It determines the physical properties of structural and applications of low temp techniques and process.
Cryogenics has no more remained a more pleasure of a research scientist but finds ever increasing applications in various industrial sectors such as in steel production, fertilizers, factories, petro chemical-complexes, in meal working industries, in food and fish preservations, in space research, in education etc..
A vide technology gap exists in the design engineering and fabrication of cryogenic components, material and plant equally vide gap exists in respect of its various applications, areas. Today we are almost entirely dependent on imports for cryogenic materials and even materials and plans.
As a first step to the establishment of cryogenic corporation a tie up between R&D laboratory and D&E organization together should start on collecting information undertaking studies for the design and fabrication of a small cryogenic plant that will also be providing for testing indigenously developed components and materials.
LOW TEMPERATURE SIGNIFICANCE:
Metals and alloys become softer on heating resulting in tensile strength. On the other hand at temperature below the atmospheric these is an increase in tensile strength and hardness and decrease in plastically.
All metals and alloys in the solid state posses lower coefficient of expansion at sub ambient temperature than at elevated temperature while increase in strength and thermal conductivity cause no anxiety. Loss of ductility can be important due to fact stresses encountered are not likely to be static or constant.
Generally it is found that carbon and low alloy steels that are low at ambient and elevated temperatures behave in increasingly brittle manner as the temperature is lowered. This temperature can be called as the ductile brittle transition temperature. Finally at some specific low temperature the silky ductile appearance of fracture disappears and is wholly replaced by a crystalline appearance.
REQUIREMENT OF CRYOGENIC MATERIALS:
While plain carbon and alloy steels show marked change from ductile to brittle state as temperatures are lowering and no marked change occurs in the case of nickel steel, stainless steel, copper, aluminum etc. A metallurgical generalization is possible by saying that metals other than iron which posses a body centered cubic metals such as aluminum, copper and nickel show only a slightly increase in yield strength and retain the room temperature ductility as low as -196°C and in addition, face centered lattice structure can distort to a greater extent than a body centered lattice structure.