Mod­ern air com­pres­sors for pneu­matic sys­tems

DEMM Engineering & Manufacturing - - HYDRAULICS & PNEUMATICS -

Pneu­mat­ics is a sec­tion of science, en­gi­neer­ing and tech­nol­ogy that deals with the study and ap­pli­ca­tion of pres­surised air (or al­ter­na­tive pres­surised gas such as pres­surised ni­tro­gen) to pro­duce me­chan­i­cal mo­tion, con­trol ac­tion and ac­tu­a­tions. In other words, a pneu­matic ac­tu­a­tor or de­vice con­verts energy (in the form of com­pressed air) into me­chan­i­cal mo­tion. The mo­tion can be ro­tary or lin­ear, depend­ing on the type of ac­tu­a­tor (or de­vice). Ad­van­tages of pneu­matic sys­tems are: • Sim­plic­ity of de­sign and con­trol. • Re­li­a­bil­ity, pneu­matic sys­tems gen­er­ally have long op­er­at­ing lives

and re­quire lit­tle main­te­nance. • Op­er­a­tional ben­e­fits, for ex­am­ple, be­cause air is com­press­ible, ac­tu­a­tors or equip­ment is less sub­ject to shock dam­age. Air ab­sorbs ex­ces­sive force, whereas fluid in hy­draulics more di­rectly trans­fers force. Com­pressed gas can be stored, so ma­chines still run for a while if elec­tri­cal power is lost. • Safety – there is a very low chance of fire com­pared to hy­draulic oil or elec­tri­cal sys­tems. Newer and mod­ern ma­chines and de­vices are usu­ally over­load safe. The equip­ment, in­stru­ments, ac­tu­a­tors, con­trol sys­tems and tools which run on com­pressed air are ex­tremely crit­i­cal for mod­ern plants and units. The com­pressed air could be one of the most ex­pen­sive util­i­ties con­sid­er­ing the amount of valu­able energy con­sumed to com­press the air and com­plex dry­ing and fil­tra­tion sys­tems used. Some­times, be­cause of an in­ef­fi­cient air com­pres­sion sys­tem, poor air-sys­tem energy man­age­ment, im­proper ca­pac­ity con­trol and other rea­sons, more than 50 per­cent of the energy used in air com­pres­sion is wasted. Gen­er­ally, the is­sue of the energy ef­fi­ciency is over­looked in air com­pres­sor pack­ages.

Mod­ern air com­pres­sor tech­nolo­gies will be dis­cussed in this ar­ti­cle; there is a great mar­ket avail­able for turbo-com­pres­sors in air ser­vices. In­te­grally-geared cen­trifu­gal com­pres­sors and di­rect­driven cen­trifu­gal com­pres­sors (us­ing oil free bear­ings such as mag­netic bear­ings) for air com­pres­sion ap­pli­ca­tions are dis­cussed.

Plant op­er­a­tors strive to im­prove the clean­ness (par­tic­u­larly elim­i­na­tion of the oil car­ry­over) of the air in units and fac­to­ries since even a small amount of oil, liq­uid or dirt in many in­stru­ments or ac­tu­a­tors can lead to se­ri­ous prob­lems. Con­sid­er­ing this fact, it should be point out that all pos­i­tive dis­place­ment com­pres­sors are in­volved (in some ex­tent) mat­ing-part rub­bing, slid­ing, fric­tion or liq­uid seal­ing which could re­sult in oil, liq­uid or par­ti­cle car­ry­over by the com­pressed air. The se­lec­tion of the air com­pres­sor de­pends on fac­tors such as ca­pac­ity, dis­charge pres­sure, re­quired air qual­ity, and am­bi­ent con­di­tions. and in such cases turbo-com­pres­sors would be a bet­ter op­tion.

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