Two Stage Screw Air Compressor

Two stage air compressors work in a very similar manner with the primary difference being that they compress the air in 2 steps or stages. During the first step or stage, air is drawn in and compressed to an intermediate pressure. After being compressed in the first stage, the air is piped, usually through an intercooler where the air is allowed to cool, to be compressed in the final or second stage. Two stage compressors are normally good for pressures up to 200psi. Two stage pumps are more efficient at higher pressures because the air is cooled between the stages.

DCFM, SCFM and ACFM

            Displaced CFM (DCFM) is a mathematical formula that calculates the bore, stroke and rpm into a CFM figure(Bore x stroke x rpm/2200=DCFM). This figure will always be the highest CFM because this formula does not take into account variables like temperature, atmospheric pressure, humidity, friction and heat dissipation.

Another CFM term often used is Standard CFM (SCFM).  It defined as the measured flow of free air and converted to a standard set of reference conditions (14.5 PSIA, 68 Degrees F, and 0% relative humidity).

Yet another CFM term is Actual CFM (ACFM). AFCM can be determined in a number of different ways. The most common methods include measuring the volume of air that is moved through an orphic plate or measuring pump up times on large compressor tanks and running through a simple calculation. This CFM number takes in effect all the variables and will give the true output of the pump at the current working conditions (i.e. temperature, altitude, humidity, …).

Often times, CFM numbers are also shown at various pressures.  These numbers can be very useful to help determine if a compressor produces enough CFM for the desired application, but can be confusing when comparing differing pressures or volumes or different compressors.

The best way of comparing compressors is through SCFM. Since all the measurements are calculated back to a set of reference standard conditions, it levels the playing field among the multitude of different manufacturers.

Electric Motors and Horsepower

         Compressors are often rated by Horsepower(HP). As simple as this sounds, there are different variations of HP.  Some compressor manufacturers rate their air compressors by peak horsepower, also known as brake horsepower. Peak horsepower is the maximum output that a motor can produce while the motor has the start windings engaged. Peak HP can be as much as 5-7 times the rated or running HP. Under normal operating conditions, the start windings are only engaged for a small fraction of a second. Therefore, using peak horsepower as a comparison tool can be somewhat misleading since under normal operating conditions the motor only develops this horsepower during startup.  If  a motor drive system causes the start winding to remain engaged for a long period of time, the motor will either overheat if it has thermal protection or fail prematurely.

Most electric motor manufacturers rate their motors by the horsepower developed after the motor has come up to its designed operating rpm’s and disengaged the start windings. This is often referred to as running or rated horsepower and is a true indication of the HP a motor can sustain over a long period of time.

Some other factors to consider when looking at motors is Duty Cycle and Service Factor.  Duty cycle is normally rated as either intermittent or continuous and is defined as the time rating under full load.   In other words can the motor run at full load horsepower continuously or only intermittently. The other of the two noteworthy factors is the Service Factor (S.F.) rating of the motor. It is defined as the percentage of rated horsepower at which the motor can safely operate (i.e. 1.15 SF = 115% of rated HP).  Higher service factors allow motors to handle more varied conditions without causing motor overheating or premature motor failure.  Examples that could cause a motor to run within its Service Factor could be caused by low voltage, higher ambient temperatures, higher startup load …etc.

Shanghai Honest Compressor co.,Ltd 
www.osg-china.com/ 
TEL:+86-21-69177185 
FAX：+86-21-69177182 
Phone:+86 18916970085 
Mail/Skype:honestcompressor@126.com

www.screwtypeaircompressors.com

screw air compressor technical training: Shanghai Honest Compressor Co., Ltd PTC Exibition ...

screw air compressor technical training: Shanghai Honest Compressor Co., Ltd PTC Exibition ...: Shanghai Honest Compressor Co., Ltd., founded in early 2004, is a British-owned enterprise. The company, located in East industrial park of...

Shanghai Honest Compressor Co., Ltd PTC Exibition No.N1,E5-2 of 2015

Shanghai Honest Compressor Co., Ltd., founded in early 2004, is a British-owned enterprise. The company, located in East industrial park of Nanxiang Town, Jiading District, Shanghai, is a large-scale manufacturing enterprise specialized in the twin screw type air compressor and also important supplier of air system solutions.

OSG implements strict and full management in the whole process of production and strictly controls the product quality and environmental protection. The company has passed ISO9001: 2008 quality management system certification and national industrial product manufacture licensing certificate.

As to the technology research and development, the company pays more attention to market trend, is close to the user demand, actively absorbs the domestic and foreign brand performance structure advantages and integrates maintenance facilities which makes the air compressor more perfect structure, more excellent performance and obvious energy saving. Through the test of state compressor test center, energy consumption data is better than the national standard of energy saving and could supply multiple models and types of air-cooled, water-cooled screw air compressor ---5KW-400KW and 0.5m3/min–70m3/min flow of EU-EX series for the users to choose, supply inverter air compressor, oil-free compressor, mobile compressor and a full set of construction plans for the air compression station. The company has the capability of design and manufacture, user training, service support, overhaul and complete set of services. In order to contact the customers, we have opened service hotline for free---400-705-9168 and established branches and dealer sales and service teams in major cities to meet the various needs of users.

In the process of making the world first-class brand of the compressor, OSG takes the spirit of enterprise---technology, service and sincere to return customers as win-win goal.

PTC Exibition No.N1,E5-2 of 2015

screw air compressor technical training: screw air compressor technical training from shang...

screw air compressor technical training: screw air compressor technical training from shang...: Screw air compressor of the basic structure, working principle and composition Gong Yi write screw compressor is by the Swedish royal insti...

The working principle of the double screw air compressor

Screw refrigeration compressor screw refrigeration compressor is with spiral groove of one or two rotor (screw) in rotation in the air cylinder to gas compression refrigeration compressor. The work volume of the screw refrigeration compressor is rotary movement of the volume type compressor, according to the number of different screw rotor, the screw compressor with double screw and single screw two.

 一： screw compressor working process

一, working principle and working process 

1. The screw refrigeration compressor is mainly composed of rotor, chassis (including central suction, exhaust at the ends of the cylinder block and block, etc.), bearings, shaft seal, balance of piston and capacity adjusting device. Figure 3-1 is a typical open a pair of screw compressor rotor, on both ends of the cylinder and the end of the shape of the graph.

1 - suction side 2 - Yin rotor 3 - cylinder 4 - valve 5 - exhaust side 6 - Yang rotor

2. The working principle of the screw compressor's job is to rely on meshing movement with a male rotor with a female rotor, surrounded by and with the aid of the pair of the rotor of the casing wall around the space. 

3. The working process of the figure 3-2 for screw compressor working process diagram. Among them, the top view of a and b are a pair of rotor, c, d, e, f for a pair of rotor looked up from the bottom up.

 

Second, the characteristics in terms of the principle of the compressed gas, screw refrigeration compressor and reciprocating piston compressor, both belong to the volumetric compression machinery, in terms of its movement form, screw type compressor rotor with centrifugal compressor rotor, high-speed rotary motion. So has the characteristics of both screw refrigeration compressor. 1. The advantages

1) higher speed, and quality of light, small volume, cover an area of an area small, and a series of advantages. 

(2) dynamic balance performance is good, so the foundation can be very small. 

(3) simple and compact structure, less wearing parts, maintenance is simple, reliable use, to achieve automatic operation.

 (4) is not sensitive to liquid impact, single stage pressure ratio is high.

 (5) capacity is almost not affected by the influence of the exhaust pressure. In the wider range of conditions, can still keep high efficiency

2. The defects

 (1) large noise.

(2) requires special equipment and tools for processing of rotor. (3) large auxiliary equipment.      

The structure and basic parameters of the second quarter

  

A, the structure of the main components

The main screw refrigeration compressor parts, including casing, rotor, bearing, balance piston and shaft seal and capacity control device, etc.  

1. The chassis

The screw refrigeration compressor casing is usually split. It is composed of the body (cylinder block), suction side, exhaust side and end cover on both ends, as shown in figure 3-3.

 

 

1 - suction end cover

2 - suction side

3 - the body

4 - exhaust side

5 - exhaust end cove

2. The rotor

Is a major part of the screw refrigeration compressor rotor. As shown in figure 3-4, often adopts integral structure, make the screw on the shaft

1 - Yin screw 2, Yang screw (3) bearing and hydraulic balance piston screw refrigeration compressor is a high-speed overloading. In order to ensure accurate positioning of the rotor of the Yin and Yang and balance the axial force and radial force, must choose high precision, high speed and overloaded bearings and the corresponding balance mechanism, ensure the rotor reliable operation. Generally said, low load, small machine, using rolling bearing; High load, large and medium-sized machine, we adopt sliding bearing. In order to balance some or all of the axial force, usually with a balance piston to achieve this goal. As shown in figure 3-5 for a hydraulic balance piston structure. 4. Refrigeration system is very important for the seal of the shaft sealing, so in open overhung rotor shaft of the screw refrigeration compressor, usually adopt sealed performance is good contact type mechanical seal, it is mainly shown in figure 3-6 spring loaded and shown in figure 3 to 7 bellows type two kinds.

 

1, 2 - drive pin

3 - transmission set

The spring seat 4 -

5 - spring

6 - ring auxiliary seal ring

7 - ring

8 - card ring

9 - static ring

10 - static ring auxiliary seal ring

11 - stop pin

5. Capacity regulating valve Capacity regulating valve is used to adjust the screw refrigeration compressor capacity of a structure element, although there are many types of screw refrigeration compressor capacity adjustment method, but the slide valve adjusting method obtained widespread application. As shown in figure 3-8 a.

 

1 - lock nut

2, sealing gasket

3 - screw

4, drive set

5 - bellows

6 - ring

7 - static ring auxiliary seal ring

8 - static ring

9 - stop pin

A) valve working schematic diagram b) valve structure diagram 1, Yang rotor

2 - Yin rotor

3 - slide valve

4, hydraulic piston

6. Injection structure of screw refrigeration compressor are mostly adopt injection structure. As shown in figure 3-8 b.

7. Coupling

Open the screw refrigeration compressor by coupling and motor. 2, 1. The basic parameters of rotor tooth profile: driving rotor and driven the tooth surface of the rotor are profile, is the space curved surface.

Open the screw refrigeration compressor by coupling and motor.  

2, 1. The basic parameters of rotor tooth

Profile: active driven rotor and rotor tooth surfaces are profile, is the space curved surface.  

A) symmetric circular arc tooth profile b) asymmetric arc tooth profile

Tooth: type surface on the perpendicular to the axis of the rotor plane (face) projection is called the rotor tooth shape, is a plane curve.  

Meshing line: Yin and Yang rotor tooth meshing movement of mesh point on the surface of the platforms, trajectory, called tooth meshing line, as shown in figure

3-9, general by a circular arc tooth profile, cycloid, elliptic, parabolic and radial line, etc.  

Lines: the tooth profile curve of rotor is called lines.  

(1) the basic requirement of tooth shape

 

1) good air tightness Leaking ways as shown in figure 3-10. The direction of the contact wire leakage as shown in figure 3 to 11. As shown in figure 3-12, called leakage triangle.

 

2) the contact line length of short 3) as far as possible the larger area of utilization coefficient. (2) typical tooth In the screw compressor, for the same on both sides of the center line of the tooth shape contour line according to symmetrical line (FIG. 3-9 a), according to different asymmetric lines (FIG. 3-9 b), tooth profile are pitch outside or inside of the pitch circle type according to the single line (FIG. 3-9), otherwise known as bilateral lines. 1) X X tooth shape of tooth profile as shown in figure 3-13, it is composed of Atlas copco company of Sweden in arc cycloid unilateral asymmetric tooth shape on the basis of improvement. 2) the Sigma Sigma tooth shape of tooth profile as shown in figure 3 to 14, it is composed of German Kaeser compressor company in arc cycloid unilateral asymmetric tooth shape on the basis of successful development.

 

3) CF tooth profile CF tooth shape as shown in figure 3 to 15, which is designed by German GHH company.

Should see, in order to evaluate or comparing different tooth profile of a number of factors are mutually restricted. Such as: in order to reduce leakage triangle, ensure the screw's axial air tightness using point meshing cycloid, will inevitably increase the contact line length; In order to protect the occurrence of cycloidal point, use small circular arc or straight line type line addendum, then increase the leak triangles, and so on. So should be used according to different occasions to choose different tooth profile. Now all kinds of new tooth profile emerge in endlessly, such as Japan's Hitachi a tooth shape, of kobe b tooth shape (FIG. 3-16 a), Sweden, darfur (Stals) tooth shape (FIG. 3-16 b), greatly improve the performance of the screw compressor.

 

screw air compressor technical training from shanghai honest com[pressor co.,ltd

Screw air compressor of the basic structure, working principle and composition Gong Yi write screw compressor is by the Swedish royal institute of technology professor Lysholm invented in 1934. Because of the limitation of design and manufacture level 60 s slow growth in screw compressor; Early sixties injection technology was introduced into the screw compressor, reduce the machining accuracy of the screw rotor profile requirements, as well as the unit of noise, such as structure, rotation speed has a favorable effect. At present, the injection screw compressor has become main model of aerodynamic, refrigeration and air conditioning industry, in the medium volume flow air power unit and the refrigerating capacity of the secondary cooling device, screw compressor has accounted for in the market leading position. 

1 the basic structure of screw compressor

which we usually said double screw compressor, its basic structure as shown in the above.

 In compressor host configuration in parallel with a pair of mutually meshing of spiral rotor, usually outside the pitch with a convex tooth rotor (from cross section), known as the male rotor or Yang screw; The pitch has a concave tooth rotor (from cross section), called Yin or vaginal screw rotor. A BanYang rotor as the active rotor, driven by Yang rotor Yin rotor rotation. The ball bearing rotor on the rotor to realize axial positioning, and axial force of the compressor. At the ends of the rotor tapered roller thrust bearing make rotor radial orientation,

And the radial force and compressor and axial force. On both ends of the compressor host with a certain shape and size of orifice, a call for suction suction mouth; Another call for exhaust vent. 

2, the work principle of screw compressor

A(Breath process) B(close process)                           

 working cycle can be divided into the suction process (including inspiratory and closed process), the compression process and exhaust process. As the rotor rotate each pair of gears tooth have done the same work cycle, for the sake of simplicity we only study of a pair of teeth. 

 the suction process (a) (b) closed suction process With the movement of the rotor, without meshing formed gradually at the end of the tooth between volume, the expansion of volume between the teeth in its internal form a vacuum, while the volume only between the tooth and inspiratory mouth connected, therefore, the gas under the effect of differential pressure flow into it. In the later in the process of rotor spinning, the rotor teeth constantly from the female rotor tooth, tooth at this time between volume is constantly expanding, and keep connected with inspiratory mouth. As the rotation of the rotor teeth volume has reached the maximum value, and the position of tooth between volume and inspiratory mouth off, suction process is over. Suction process at the same time, the rotor teeth, Yin and Yang and the end of the casing seal, tooth groove gas surrounded by a rotor tooth and casing in a closed space, i.e. a closed process. 

2, the compression process

With the rotation of the rotor, due to the rotor tooth meshing teeth volume shrinking, sealed between the teeth there is less volume of the volume occupied by the gas, result in higher gas pressure, so as to realize the compression of gas process. The compression process can be continued until volume is between tooth and vent connected before.

3 3, the exhaust process 

Volume between tooth and vent connected after start exhaust process, with the shrinking volume between your teeth has the end of the compression pressure in the gas is expelled through the vent port gradually, this process continues until the end of the tooth type wire mesh in full, the volume of the gas between the tooth is completely discharge through the vent port, the volume of a closed volume between tooth will become zero. Can be seen from the above principle, the screw compressor is through a pair of rotor inside the casing as rotary motion to change the working volume, volume was reduced, the density increases, thus improve the pressure of the gas. Three, the constitution of the screw air compressor, a fuel injection screw air compressor unit is mainly composed of main and auxiliary machinery of two parts, the host, including screw air compressor host and main motor, auxiliary engine including inlet and exhaust system, fuel injection and oil and gas separation system, cooling system, control system and electrical system, etc. In the inlet and exhaust system, free after air inlet filter to dust, impurities, into the air compressor suction mouth, and in the process of compression and injection of lubricating oil blending. After compression of the mixture of oil and gas into the separation of barrels of oil and gas, through the primary and secondary oil and gas separation, after the minimum pressure valve, the back of the cooler gas and water separator was taken to use the system. In the oil and oil and gas separation system, the compressor during normal operation, the oil and gas separation of barrels of oil, relying on air compressor exhaust pressure and differential pressure, nozzle to maintain flow in the circuit. Lubricating oil here under the action of pressure difference, temperature control valve into the oil cooler, again after the oil filter to remove impurity particles, most of the lubricating oil is sprayed into the air compressor compression chamber, have the effect of lubrication, sealing, cooling and noise reduction. The rest of the lubricating oil is sprayed into the bearing chamber and growth gearbox respectively. That part of the spray into the compression chamber together with the compressed air into the oil and gas separation of barrels of oil, after centrifugal separation, the vast majority of lubricating oil is separated out, and a small amount of lubricating oil filter for secondary separation, are two separate lubricating oil after return pipe to return to the compressor suction mouth of low pressure side. (1) the role of lubricating oil, cooling effect As a cooling agent, it can effectively control compression heat caused by temperature rise; lubrication As a lubricant, it can be formed between the rotor oil film; Sealing function As a sealant,

It can fill between rotor and shell, rotor and rotor

4 the leakage clearance. The noise reduction effect Oil is A viscous fluid, injection on acoustic energy and acoustic absorption and damping effect, general noise injection can reduce 10 ~ 20 db (A). (2) the role of the minimum pressure valve To ensure that the minimum oil circulation pressure; For valves, in order to avoid the air compressor shut down or no load case, the gas pipeline in the compressed air back into the unit; Ensure that oil and gas separator filter has a certain pressure difference before and after, in order to avoid too much just boot when the filter pressure difference before and after bumping phenomenon. (3) the role of temperature control valve Maintain lubricating oil temperature is higher than the pressure above dew point temperature, so as to avoid precipitation of moisture in the air. (4) barrels of oil and gas separation effect As a primary oil and gas separation device, it can be greater than 1 mu m diameter droplets effectively separated by using the mechanical collision method. As the air compressor lubricant oil reservoir; As the support body of the oil and gas separator filter, the filter can be under 1 microns diameter droplets first knot diameter larger droplets, and then separated.

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