Braking power, calculation

Because power is the rate of doing work, the fan shaft power - frequently called brake power - is calculated from Equation 5.7. 

Pump characteristics curves are developed in accordance with the setup of Figure 4.7. The pressure at the outlet of the pump is found to be 196 kN/m gage. The outlet diameter of the discharge pipe is 375 nun. If the rate of discharge is 0.15 mVs, calculate the input brake power to the pump. 

If the accelerometer only shows accelerations which result from movements in the direction of the brake power, it is possible to calculate these movements by a double integration of the accelerations over the measurement time. 

Pump brake power was calculated using three methods with hand calculation the brake power is 1.57 hp, Hysys value is 1.58 hp, PRO/II result is 1.1859 kW (1.589 hp), and Aspen Plus result is 1.585 hp. Al results were almost the same. 

Power. There are two main ways to measure the power deUvered by the driver to the pump. The first method is to install a torque meter between the pump and the driver. A torque meter is a rotating bat having a strain gauge to measure shear deformation of a torqued shaft. Discussion of the principle of torque meter operation is available (16). The benefit of this method is direct and accurate measurements. The power deUveted to the pump from the driver is calculated from torque, T, and speed (tpm) in units of brake horsepower, ie, BHP (eq. 4a) when Tis in lbs-ft, and kW (eq. 4b) when T is N-m. 

Drive motors should be of the high-starting-torque type and selected for 1.33 times maximum rotational speed. For two- or three-diameter Idlns, the brake horsepower for the several diameters should be calculated separately and summed. Auxiliaiy drives should be provided to maintain shell rotation in the event of power failure. These are usually gasohne or diesel engines. 

Use Eq. (24) in Chap. 14 of this text to calculate the theoretical compressor power. The brake horsepower efficiency of the electric motor... 

After calculating the head, then calculate the power supplied to punp by the shaft of the pun driver, i.e., the brake horsepower, which is given by... 

The actual strip tension in pounds force, which may be u.seful in determining an uncoiler brake pressure setting, is calculated by multiplying the adjusted web stress by the cross-sectional area. Thus, the above example strip in a 24-in. width calculates to a tension of 2162 pounds force, which at 150 fpm equates to an additional 10 HP. Therefore, for this pull-through application, the recoiler would have to be powered by a 763-HP motor in order to overcome the uncoiler tension and the slitting load. 

To calculate the power of a fan where the pressure difference is of the order of a few hundred mm of water, a linear average density of the gas between the inlet and outlet of the fan is used to calculate and brake kW or horsepower. 

Determine the useful power input needed to overcome the friction losses in a pipeline. Calculate brake kW for pumps and compressors. 

---