Jacket type magnetic pump used in PA equipment
一. preface
PA, full name is phthalic anhydride, is an important organic chemical raw materials, widely used as one plasticizer, resin, medicine, dyes and pesticide raw materials and intermediates. Under normal temperature, PA crystallization is flake white solid, melting point 131.6 ℃. PA industrial production uses adjacent xylene of vapor-phase catalytic oxidation method, it is taken in inflammable, explosive, high temperature, toxic for conditions, oxidating temperatures as high as 440℃, liquid PA refining temperature is also as high as 180-250 ℃. In production process, if liquid PA splash into the skin, besides scalding, it also easy wicking and generate phthalic acid with strong corrosion, Gaseous PA, have strong excitability, after inhalation, cough, sore throat, mucosal hyperemia, eyes redness tears, etc great harm to human body, under the flame condition can also cause combustion explosion etc serious accidents. Therefore, PA equipment technology requirement is high, key equipments are imported. For instance PA pumps, domestic device generally choose German KSB Co.,ltd, USA durco company etc. product, are all the jacket type mechanical sealing centrifugal pump. But because PA physical and chemical characteristics, this type pump seal life is short, maintenance cost is high, and in equipment maintenance process, PA to human body and environmental damage are very large..
二 mechanical sealing centrifugal pump defects
According to the PA verdinglichung characteristics, and its harm to environment and human body, PA pump seal selects bellows mechanical seal, in order to ensure good sealing effect. But because PA is high melting point material, and in the open, stop process, mechanical seal temperature are often less than material melting temperature, can appear a few PA solidification or crystallization precipitation phenomenon, bellows will gradually lose flexibility because blockage reasons, friction pair failure , resulting in pump leaking. Secondly, in the PA pump operation process, bellows surface crystallization accumulation to cause axial bending, appeared bellows fracture or sealing compression value unevenly, auxiliary sealing ring high temperature ageing, compensatory reduced, causing seal failure and leakage. Third, due to PA oxidation reaction operates within the OX explosion limit scope, there is greater risk, the device occasional accident is more, PA pump mechanical seal service life is often shorter due to frequent open, stopping. Fourth, in maintaining pumps, pump body mechanical sealing chamber temperature has far below PA melting temperature, conveying medium has been all solidified in mechanical sealing chamber, so that full sets of seal components including bushings, etc will surely change entirely. Thus, even the localizatio same type bellows mechanical sealing price is 5 thousand / set, visible the equipment maintenance cost is higher, and materials have great harm to operators and environment, it is necessary to replace by no sealing pumps.
三 advantages
Choose static sealing pumps alternative dynamic seals centrifugal pump, first consider shielding electric pump, it is a kind of common no sealing pump, but exist high temperature media harmful to the shielding motor running and before first driving can not judge sliding bearing whether has melting solid media difficulties, so it is not suitable for conveying high melting point PA product requirements. Relative of the magnetic drive no sealing pump could satisfies the aboved conditions. First, consider conveying material will appear crystallization or solidification because of the pump chamber temperature drops, so increase heat jacket design to the gear shell body and isolation sleeve part, the gap between isolation and internal rotor is small, is very important technical requirements, jacket front and back must be insulation or heating consistency, fully guarantee heated, even in sliding bearing minute gap between place and isolation of the tail to ensure material complete molten state magnetic pump, in order to avoid damaging the key components. Insulation of HTM normally is steam. Attention, insulation jacket needs to ensure conveying medium and HTM absolute separation, avoid PA and water vapour combining to generate higher melting point phthalic acid jams pipeline. Magnetic pump hot jacket reasonable design, can achieve centrifugal pump body jacket heating effect. Secondly, conveying PA in completing internal circulation process, mobility will weaken due to the temperature drops, the tail vice impeller will make the little space to be high speed flow area, to avoid the possible jams fault. Meanwhile, when pump stops, magnetic area tail will not effusion, thoroughly empty, avoids due to material solidified to hard drive next time. This point is obviously better than the centrifugal pump stop caused effusion defects Furthermore, according to conveying high melting point material pump operation experience, after pump stop working, should empty all the medium. On one side to avoid damage due to material volume changes, another side increasing efficiency in preheated process before driving, maintain temperature uniformity. Before magnetic pump driving, can also check the rotor whether have jam phenomenon, after confirmation, feeding, warm pump, drive, effective guarantee the reliability of the pump start-up. To sum up, jacket magnetic pump can fully satisfy the PA produced technological conditions, after replacing dynamic seals centrifugal pumps, pump leakage repair rate is reduced greatly.
四 conclusion
As long as practical note jacket magnetic pump stopping empty and driving preheating process, ensure disc light, without damage the sliding bearing and isolation cover, this form pump superior to mechanical seal pump, it not only greatly reduced maintenance cost, and simple operation, is helpful for device continuous operation, and reduces the operators' injuries and pollution to the environment. It can be further to promote the type no sealing magnetic pump to the similar qualified production, such as DMT, tar, etc
