[ Petrochemical ]
[ Petrochemical ]
Steel welding fittings
these grades can withstand working temperatures in the range of 975- 1175 ° C . Heavy work is carried out down to 1050 ° C by standard methods and equipment .
2 . Machining – the machinability of grades 310 and 310S is similar to that of grades 304 and 316 . Work hardening can be a problem , and it is customary to remove the workhardened layer using slow speeds and heavy cuts with sharp tools and good lubrication . Powerful machines and heavy , rigid tools are used .
3 . Weldability – Grade 310 / 310S products in any shape are a great way to connect two pieces of metal and have many advantages over other welding methods . Grade 310 is corrosion and heat-resistant , does not require a heat treatment step , and can be welded using various welding equipment . It is also ideal for projects that involve environmental protection and safety aspects . Stainless 310 / 310S grade is welded with matching electrodes and filler metals . Products are readily welded by standard welding manuals using techniques such as GMAW ( MIG ), GTAW ( TIG ) and SAW . Preheat and post-heat are not required , but postweld solution annealing is essential for corrosion service in liquids . Pickling and passivation of the surface to remove high-temperature oxides are necessary to restore complete aqueous corrosion resistance after welding . This treatment is not required for hightemperature service , but welding slag should be thoroughly removed . Grades 310 / 310S are solution annealed by heating to 1040-1065 ° C , holding at temperature until thoroughly soaked , then water quenching .
Design and fabrication The primary function of heat exchangers in the petrochemical industry is solvent condensation undergoing chemical cooling and heating reactors . The design of the equipment is based on temperature ranges , product mix , pressure drops across the exchanger , fluid flow capacity , cleanability , repair and maintenance . Seamless or welded tubes of suitable materials are used without compromising quality during manufacture .
Fouling problems – cause & remedy Fouling is a membrane separation phenomenon resulting from several mechanisms : precipitation of sparingly soluble salts , adsorption , cake or gel formation , and pore blockage because of the composition of the water in the system , causing a decrease in the heat transfer coefficient with time . Klarex ’ s ( Netherlands ) self-cleaning heat exchanger consists of a design that reduces the surface area by approximately 20 %. Scaling occurs because the water flowing through the heat exchanger contains impurities such as calcium
Nozzle inlet
Impingement plate
Tube bank
Figure 1 . Sectional view of a heat exchanger
carbonate , magnesium , chloride or iron . Fouling represents the theoretical resistance to heat flow due to a buildup of a layer of dirt or other fouling substance on the tube surfaces of the heat exchanger . A method for reducing the formation of deposits on the inner walls of a tubular heat exchanger through which a petroleum-based liquid is flowing comprises applying fluid pressure pulsations to the liquid flowing through the tubes of the exchanger and vibration to the heat exchanger to effect a reduction of the viscous boundary layer adjacent to the inner walls of the tubular heat exchange surfaces . Reduction of the viscous boundary layer at the tube walls not only reduces the incidence of fouling with a resulting beneficial effect on equipment life , but it also has the desirable effect of promoting heat transfer from the tube wall to the liquid in the tubes . Using a coating on the inner wall surfaces of the exchanger tubes may further reduce fouling and corrosion .
Conclusion The high nickel content of austenite 310 grade is superior to grades 304 , 316 , 321 and 309 . It combines high corrosion resistance and high-temperature properties with good ductility and fabrication characteristics . Due to the chemical composition of this grade , with chromium up to 25 % and nickel up to 20 %, products manufactured in grade 310 provide solid corrosion resistance , excellent resistance to oxidation , and superior strength at high temperatures up to 1150 ° C . High nickel ( 25 +%) alloys are most commonly used to construct process equipment , including heat exchangers , when superior corrosion resistance and high-temperature mechanical properties are required .
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