Compare oil and oil-free compressor

The com­pres­sor is an impor­tant device when it comes to mov­ing and com­press­ing gas­es. Pis­ton com­pres­sors have no equal in this mat­ter. Man­u­fac­tur­ers offer a wide vari­ety of mod­els of such units. Until recent­ly, the mar­ket lead­ers were tra­di­tion­al oil, but a new com­peti­tor has appeared — units that do not require cylin­der lubri­ca­tion. Which option is bet­ter and what is the dif­fer­ence between them? Our experts fig­ured it out.

Features and principle of operation of the unit

The first pro­to­types of a com­pres­sor based on a pis­ton were cre­at­ed a cou­ple of cen­turies ago and until the begin­ning of the 20th cen­tu­ry, such devices were the only ones used in met­al­lur­gy to sup­ply air com­pressed under pres­sure. The work­ing part of a rec­i­p­ro­cat­ing com­pres­sor is a cylin­der with two valves in its walls — dis­charge and suc­tion.

When pres­sure drops between the com­pres­sor cylin­der and its cham­bers, the valves auto­mat­i­cal­ly open. The move­ment of the pis­ton begins, entrain­ing air, which is pumped until the desired gas pres­sure is reached, enter­ing the receiv­er (stor­age tank).

The design of the device pro­vides for the pres­ence of a pipeline with fil­ters. If we are talk­ing about a unit of sig­nif­i­cant per­for­mance, its cylin­ders are equipped with water cool­ing. For low pow­er devices, air cool­ing is suf­fi­cient.

Regard­less of the per­for­mance and dri­ve of a rec­i­p­ro­cat­ing com­pres­sor, the main prin­ci­ple of its oper­a­tion is the com­pres­sion of gas in a cylin­der. To achieve the desired effect, a sig­nif­i­cant por­tion of the pow­er is used to reduce fric­tion from the pis­ton and cylin­der. To reduce the neg­a­tive effect, the pis­ton moves in such a way that there is no con­tact with the cylin­der walls, and the gap is filled with seal­ing rings.

Advantages and disadvantages of compressor units

Oil compressors

Oil com­pres­sors are a reli­able and time-test­ed device that allows you to car­ry out long and com­plex work of var­i­ous direc­tions.

Oil-free compressors

Main differences

Depend­ing on the char­ac­ter­is­tics of the seals, com­pres­sors are lubri­cat­ed (oil) and with­out it (oil-free). Con­sid­er their main fea­tures and dif­fer­ences.

In design

The design of the oil-type com­pres­sor uses an oil sup­ply sys­tem (pipes, lubri­ca­tor, pump). Addi­tion­al­ly, it is also com­pli­cat­ed by the pres­ence of sev­er­al holes on the walls of the cylin­der and its cov­er. Due to the pres­ence of lubri­ca­tion, fric­tion between the oil sys­tem rings and the cylin­der walls is reduced to a min­i­mum. The pis­ton is addi­tion­al­ly mount­ed with split oil scraper rings with grooves for remov­ing grease.

Oil-free com­pres­sors have 2 types of rings on the pis­ton. Seal­ings pre­vent gas leak­age, guides do not allow the pis­ton to come into con­tact with the walls of the cylin­der. Rings are made of poly­mer com­po­si­tions, graphite com­pounds, pho­toro­plas­tic.

ON A NOTE. The rings of oil-free com­pres­sors are non-con­tact, so wear occurs very quick­ly. Due to the reduced resource of such rings, the oper­at­ing cycle of the prod­uct at high pres­sure is no more than 200 hours.

In appointment

Con­ven­tion­al­ly, com­pres­sors can be divid­ed into three large groups: indus­tri­al (the most pow­er­ful, respec­tive­ly), semi-indus­tri­al (up to 1000 l / min) and house­hold. The lat­ter are self-con­tained devices for air sup­ply to refrig­er­a­tors, small instal­la­tions, pneu­mat­ic tools, etc. The choice of a suit­able mod­el in this case depends sole­ly on per­son­al pref­er­ences, the type and scope of work. Oil-free — the best option for short-term work, oil — for long-term.

There are a cou­ple of sup­port­ing cri­te­ria to con­sid­er when choos­ing the right indus­tri­al com­pres­sor:

1. Type of gas — oil-type com­pres­sors should be cho­sen very care­ful­ly, since with some types of gas the lubri­cant can enter into an uncon­trolled reac­tion and an explo­sion will occur;

2. Fre­quen­cy of ser­vice — it is bet­ter to choose units with a sig­nif­i­cant oper­a­tional resource.

In operation

In the process of using the com­pres­sor with lubri­ca­tion, its lev­el must be con­stant­ly mon­i­tored with peri­od­ic addi­tion of the required amount and oil change. More­over, spe­cial brands are rec­om­mend­ed for use. If we are talk­ing about portable (mobile) mod­els of com­pres­sors, they must be kept strict­ly in a hor­i­zon­tal posi­tion (oth­er­wise it is fraught with spilling oil from the tank).

Oil-free com­pres­sors do not have the same prob­lems as units with an oil sys­tem, but at the same time, such devices require reg­u­lar replace­ment of pis­ton rings. As for the oth­er actions relat­ed to the main­te­nance of com­pres­sors (clean­ing fil­ters, check­ing equip­ment, etc.), every­thing here is iden­ti­cal, regard­less of the type of unit.

How to choose the right compressor?

In order for the pur­chased prod­uct to please not only with its appear­ance, but also to per­form the nec­es­sary task as effi­cient­ly as pos­si­ble, you should choose the unit very care­ful­ly. We rec­om­mend using use­ful tips and the pur­chase will cer­tain­ly be suc­cess­ful:

1. An oil-free com­pres­sor is bet­ter suit­ed for short-term, low-pres­sure pneu­mat­ic work;

2. To per­form work in the phar­ma­ceu­ti­cal, food indus­try, the oil-free option is opti­mal, again;

3. For con­struc­tion work, as well as in indus­tri­al con­di­tions, there is no bet­ter option than an oil com­pres­sor. Despite the rather high cost, it will ful­ly jus­ti­fy it in this case.