Tsurumi Submersible Aeration (1846 Kb) - Ferret

7. Operation System■ 7-1. Reduced Speed Operation by Variable Frequency Drive (VFD)There are two methods in the adjustment of “air flow rate” and the “oxygen transfer rate” of the result. One is to squeeze the valvethat is installed in the air-inlet piping, and the other is to reduce the speed of aerator by VFD. However, the aerator has thecharacteristics described below, and different effects are expected.· The motor load increases as the installation depth becomes deeper.· The motor load increases as we reduce the air flow rate squeezing the valve that is installed in the air-inlet piping.In most cases, the adoption of reduced speed operation by VFD will enable us to regulate the air flow rate in a more extensive range thanoperating the valve, without sacrificing the efficiency. A comparison in the methods of adjustment is made in the following table. Refer tothis table in your planning.The graph of 7-1-2. shows comparisons in adjustment range between the two methods and 7-1-3. shows characteristics of reducedspeed operation by VFD for an aerator (Model 50TRN43.7-62) at 2 meters’ depth which has the widest possible range in the adjustmentof air flow rate.▼ 7-1-1. Comparisons in the Method of AdjustmentMethods forFeaturesAdjustment(○: shows the merit, ☓: shows the demerit)○ Installation will be completed by simply connection the valve at the inlet port of the air-inlet pipe.Adjustment ☓ Low power efficiency (kgO 2 / kWh) ⇒ Disadvantage in the energy savingby squeezing ☓ It is difficult to make an accurate control as the air flow rate and the operating current cannot be stabilized.the valve ☓ Louder beat☓ Narrow adjustment range at a deeper installationAdjustmentby reducingthe speedwith a VFD☓ It is necessary to install a VFD (extra initial cost is necessary).○ The power efficiency (kgO 2 / kWh) shall be maintained virtually constant.⇒ Energy saving operation with reduced power consumption is possible.○ The air flow rate and the running current can be maintained constant.⇒ Possible to control the air flow rate and the oxygen transfer rate accurately.○ Reduction of the operating frequency (reduction in air flow rate) will decrease the sound level.▼ 7-1-2. Comparisons in Adjustment Range (for reference only)“1” shows the adjustment range served by a VFD, and “2” shows it served by a valve.Estimated Air Flow Rate at the Standard Condition (20 o C, 1atm)Test Result at Our Test Tank (5m x 5m) with Clean Water, Converted to 20 o CAir Flow Rate [m 3 /h]▼ 7-1-3. Characteristics of Reduced Speed Operation by VFD (for reference only)Estimated Air Flow Rate at the Standard Condition (20 o C, 1atm)Air Flow Rate [m 3 /h]9080706050403020908070605040301Installation Water Depth2mDecreasein LoadInstallationWater Depth2 mIncreasein Load35 40 45 50 55 60 65Operation Frequency [Hz]InstallationWater Depth4 mInstallationWater Depth3 m2The motor will be overloadedif the valve is squeezed morethan this point.Oxygen Transfer Rate [kgO2/h]Test Result at Our Test Tank (5m x 5m) with Clean Water, Converted to 20 o COxyge Transfer Rate [kgO2/h]32.521.510.535 40 45 50 55 60 6543.532.521.511Installation Water Depth2mThe changing trend of the motor load isthe※sameモータas負left荷 のgraph.変 化 傾 向 は 左 図 と 同 じOperation Frequency [Hz]InstallationWater Depth4 mInstallationWater Depth2 m2The motor will be overloadedif the valve is squeezed morethan this point.InstallationWater Depth3 m2035 40 45 50 55 60 65Operation Frequency [Hz]100.535 40 45 50 55 60 65Australian Operation Pump Frequency Industries [Hz] (02) 8865 3500