Power Plant Guruji

  Function of volute casing in centrifugal pump? Functions of a pump volute: To convert kinetic energy impaired by the impeller into  pressure energy To minimize losses during this energy conversion process The pump casing does not take any part in dynamic head generation The best volutes are of constant velocity design Kinetic energy is converted into pressure energy only in the  diffusion nozzle immediately after the volute throat Various types of volute Single volute Double volute Vertical pump with diffuser Volute with diffuser vanes Circular volute Double Volute A double volute casing has two single volutes 180° apart Total throat area of two volute is same as the throat area of a comparable  single volute Double volute significantly reduces the radial load problem of the  single volute pump Hydraulic performance of a double volute pump is nearly the same as  that of a single volute Double volute pump is around 1-1.5 point less efficient at   B.E.P but about two points more effici

 Why Use Mechanical Seals ? 1. Lower Mechanical Losses Mechanical seals cause lesser mechanical losses compared to packed glands and thus makes the pump more efficient. Mechanical losses due to frictional drag of the shaft sleeve running against packing account for the largest of the mechanical losses generally incurred in a centrifugal pump. 2. Lesser Sleeve Wear For mechanical seal fitted pumps handling clean, non-corrosive liquids, shaft protecting sleeve can be eliminated. Even where shaft sleeves are used, they are not subject to wear for mechanical seal fitted pumps. In case of packed gland pumps the sleeve under the packing is subjected to wear especially when the pump liquid contains abrasive particles or when the packing sit fixed very tightly on the sleeve. Sleeve damage is costly not only because of the cost of sleeve but also due to the time involved in replacing the worn sleeve with a new one. 3. Seals high pressure as well as low pressure Increased pressure puts a limit o

  Voltage Transformer or Potential Transformer Voltage Transformers (VTS) - Importance Voltage transformers are the next  important component of Protection. Voltage Transformers: are used for measuring and protection may be single phase or three phase provide isolation from high voltages must operate in the linear region to prevent accuracy problems must be capable of driving the burden, specified by relay manufacturer Types of Voltage Transformers (VTS)  There are two basic types of VTs-Electromechanical VTs and Capacitor VTS. Electromechanical VTs Are similar to a power transformer May not be economical above 132kV Robust and more reliable Capacitor VTs Used at high voltages (132 Kv or above) Main difference is that CVT has a capacitor divider on the front end Require maintenance as capacitor is used

Gland Seal vs. Mechanical Seal – What’s the Difference? Gland Packing  Advantages Lower initial cost Easily installed & dismantled when lantern rings and glands are split Good reliability to medium pressure  & shaft speed Can handle a large axial  movements (Thermal expansion of stuffing box Vs shaft) Leakage tends to increase gradually, giving warning of impending breakdown Gland Packing Disadvantages Relatively high leakage Requires regular maintenance Wear of shaft & shaft sleeve can be relatively high Power loss may be high Relatively high product loss Mechanical seals Advantages Negligible or no leakage Requires no maintenance Eliminates sleeve wear/shaft wear Very high reliability Can handle higher pressure & speed Application range far wider-Easily applied to carcinogenic, toxic,flammable or radio-active fluids Low power loss Mechanical seals Disadvantages Higher initial cost May require some disassembly of pump parts. Example - Coupling, Bearing Bracket etc. Rea