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Advantages of Rotodel Pumps

Advantages of 'ROTODEL' Rotary Twin-Gear Pump type RDNXJ over Conventional Gear Pump of AIRAUTO, TUSHAKO & HYDROPOWER

Conventional gear pumps

A) GEAR IMPELLER:
1. More nos. of teeth on impeller (12 to 15) increases size of the pump, moment of inertia of the impeller resulting into more frictional losses.
2. Gears cut to standard profile & pressure angle resulting into under cutting of the teeth thus reducing the tooth life.
3. All the 4 gears are fixed keyed to the shaft resulting into unequal load distribution & fast wear & tear of the gears.
4. Gears are EN-8 & generally soft.
5. Smaller diameter shaft due to use of ball bearings is more susceptible to bending. Material is EN-9 hardened & ground.
6. LID ratio is low which give high peripheral velocity, high noise level & frictional losses.
B) BEARINGS:
1. Pumps are provided with single raw ball bearing having lesser static & dynamic load carrying capacity.
2. Bearing are mounted on 4 nos. separate wearing plates fitted inside the pump body, hence bearings are subjected to vibration.
3. Bearings are self lubricated & its life depend on lubricating property of the pumping liquid.
C) RELIEF VALVE:
1. Pump is provided with build in relief valve hence change R.V. entire pump is required to open out.
2. R.V. design is stem type which tends to till in the operating condition.
D) PERFORMANCE:
1. Efficiency is generally low in the range of 30% to 45% for transfer application upto 10 Kg/Cm2.
2. Volumetric Efficiency is low because of large leakage path.
3. Life of the pump is less for continuous operation duty.
E) NOISE LEVEL:
1. Noise level is generally higher than 95 dB.                                                                                        

Rotodel Rotary Twin gear pump

A) GEAR IMPELLER:
1. Less nos. of teeth (8 to 10) the impeller reduce the size of the pump, moment of inertia of the impeller resulting into less frictional losses.
2. Gears are cut to modified profile hence there is no under cutting & the life of the gear is enhanced considerably.
3. Out of 4 gears 1 gear is keyless or is floating giving uniform load distribution & silent running.
4. Gears are EN-24, gas nitrided hardened & lapped.
5. Larder diameter shaft due to use of needle bearing is less susceptible to blending. Material is SAE-8620 case carburised hardened & ground.
6. L/D ratio is high which gives low peripheral velocity, less noise level & less frictional loss.
B) BEARINGS:
1. Pumps are provided with needle roller bearing having higher static & dynamic load carrying capacity.
2. Bearing are firmly mounted on two bearing cover & hence there is no vibration.     
3. Bearing are independently lubricated & life of the bearing does not depend on the lubricating property of liquid.
C) RELIEF VALVE:
1. Pump is provided with add on type pressure relief valve hence R.V. can be changed without disturbing the pump.
2. R.V. assembly is piston type hence relief valve seating is always perfect.
D) PERFORMANCE:
1. Efficiency is high in the range of 45% to 70% for transfer application upto 10 Kg/cm2.
2. Volumetric Efficiency is high due to low leakage path.
3. Life of the pump is more for continuous operation duty.
E) NOISE LEVEL:
1. Noise is less than 75 dB upto the size of 3" less that 85 dB upto the size of 6" & less than 95 dB upto size of 8".

Advantages of 'ROTODEL' Rotary Twin Gear Pump over Twin Screw Pump of TUSHACO, BORNEMANN, ROTC & IMO MAKE

Rotary Twin Gear Pump

1. Capacity of the pump is determined by each tooth gap hence the capacity transferred per unit size of rotor is much higher.
                                                                        
2. Due to above advantage the gear size is small thereby peripheral velocity & frictional losses are less resulting in increased efficiency & less noise level of the pump.
3. High pressure can be developed in the same configuration simply by tightening the internal clearance of the pump thereby maintaining the same size & shape of pump.
4. The meshing impellers are self driven hence no timing gear is required thereby reducing the size, cost & maintenance effort.
5. Because of lesser number of modified profile teeth with sharp tip there is no break up of the flow & resulting into pulsation free flow.
6. The liquid directly enters into pump chamber & perpendicular to the shaft axies, hence NPSH required is much less.
            
7. Efficiency upto 65% is committed for transfer application upto 10 Bar pressure.    
8. Because of modified profile teeth there is no undercutting as in the conventional gear pump. Further the gears are made out of alloy steel with gas nitriding hence the life of the pump is as good as screw pump.
9. Pumps upto 8"size can be run at 1500 RPM maintaining the same efficiency standard for all the pumps.
10. The gear technology is under-stood well at all level of technical people & hence the pump can be repaired / maintained without special assistance. Hence less time is consumed & the cost is also less.
11. Offers advantage of triple screw pump at the price of conventional gear pumps with considerable saving on initial cost as well as long run expenditure.

Twin Screw Pump

1. Capacity of pump is determined by only one pitch length per screw element ( i.e. 4 pitch length per pump) Hence the liquid transferred per unit size of the rotor is less.
2. Because of the above constrain the peripheral velocity is more, the frictional losses are high & multiplies with increase in viscosity. The noise level is also high due to this.
3. For developing higher pressure nos, of threads in each screw is required to be increased resulting into increase in size & shape of the Pump.                                                     
4. Timing gear is required to drive the screw, this increases size, cost & maintenance of the pump.
5. In screw construction the flow breaks at each pitch length due to meshing of screw.
6. The incoming liquid has to take the entry from he side of the screw, while the inlet flange is oriented perpendicular to screw axis, The sharp turning of the incoming liquid resulting in pressures drop & thus require more NPSH.
7. Efficiency of the pump is committed upto 50% for transfer application upto 10 Bar pressure.
8. Because of the timing gear there is no metal to metal contact of the screw. Hence the life of pump is claimed much higher.                                                                                             
9. Pumps upto 8" size can be run directly at 1500 RPM. However in the large size the power consumption increases thereby reducing the efficiency.
10. The screw manufacturing is complicated & not generally understood by ordinary maintenancestaff. Hence maintenance any becomes costly tricky & time consuming.
11. Under the name of new technology the customers are royally screwed by charging abnormal prices.
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