• Adventures

    Fast Easy Way To Shutdown Plant

    We were having a new refrigerant monitor system installed in the plant and the service tech asked where the breakers were located for the two areas he was was installing the equipment. Locating the one for the main monitor was easy, everything was marked. The remote monitor wasn’t that clear cut. After locating a panel I saw a breaker marked flow meter. We used to have a city water pressure monitor installed where the new remote monitor was being mounted, so I switched it off. Bad idea. it shutdown the boilers! While I was trying to get the boilers back online, the service tech come by and said he didn’t need the breaker off, he installed while the circuit was live. A plant shutdown, switching a 20 amp breaker off, wasn’t required. I hate when these incidents are self induced. Oh, the breaker was for the steam flow indicators.

    Make sure your MCC breakers are clearly marked before experimenting to find the right one.

      

  • Study Material

    Cooling Tower Terminology

    Cooling Tower Terminology

    Approach – difference between cold water temperature and the measured wet-bulb temperature.

    Bleed Off – is the circulating water in the tower which is discharged to waste to help keep the dissolved solids concentration of the water below a maximum allowable limit. As a result of evaporation, dissolved solids concentration will continually increase unless reduced by bleed off.

    Blowdown – water intentionally discharged from the cooling system to control concentrations of salts and other impurities in the circulating water

    British Thermal Unit (BTU) – the heat energy required to raise the temperature of one pound of water one degree Fahrenheit in the range from 32° F to 212° F

    Cell – smallest tower subdivision which can function independently

    Cold water temperature – temperature of the circulating water leaving the cooling tower

    Counterflow tower – design in which air flows upward through the fill section and interfaces counter currently with the down coming hot water.

    Crossflow tower – design in which air flows horizontally across the fill section and interfaces perpendicularly with the falling hot water

    CTI – Cooling Tower Institute.  Organization for testing and certification of cooling towers

    Cycles of Concentration – compares dissolved solids in makeup with solids in the circulating water

    Drift – water lost from the tower as liquid droplets entrained in the exhaust air stream

    Drift eliminators – baffling to control the drift loss in towers

    Heat load – heat removed from the circulating water within the tower

    Makeup – water added to the circulating water to replace water lost from the system by evaporation, drift, blowdown and leakage

    Mechanical draft tower – tower in which a fan moves the air through the fill

    Natural draft tower – hyperbolic design in which air moves through the fill because of pressure difference between top and bottom of tower, creating a chimney effect

    pH – number between 0 and 14 indicating degree of acidity (below 7) and alkalinity (above 7)

    Pumping head – minimum pressure required to lift water from basin level to tower top and force it into the water distribution system

    Recirculation air – portion of the exhaust air which reenters the tower measured on the basis of the increase in entering wet-bulb temperature compared to the ambient

    TDS – total dissolved solids contained in solution in cooling system water

    Ton – an evaporative cooling ton is 15,000 Btu / hr

    Water loading – circulating water flow expressed in gal / min per square foot of effective horizontal wetted area of the tower

    Wet-bulb temperature – temperature indicated by a psychrometer

     

  • Study Material

    Boiler Heating Surface

    This is the formula used to calculate the heating surface of a power plant boiler:

    An HRT boiler is 5 ft in diameter and 16 ft long. It contains 60 tubes of 3 inch outside diameter and 2.732 inch inside diameter. Find the boiler-heating surface. Take the inner surface of tubes, half of the shell surface, and two-thirds of the tube plate area, less the area of the tube holes.

     

    Circumference of shell = 5 * 3.14 = 15.700 ft

    Half circumference of shell = 15,700 * ½  = 7.850 ft

    Area of half of shell = 7.850 * 16 = 125.60 sq. ft

     

    Inner circumference of fire tube = 2.732 * 3.14 = 8.578 in or         8.578 / 12 = 0.7148ft

    Surface of one tube = 0.7148 * 16 = 11.437 sq. ft

    Surface of 60 tubes = 60 * 11.437 = 686.2 sq. ft

     

    Total area of one tube sheet = 0.785 * 5 * 5 = 19.625

    Two-thirds area one tube sheet = 2/3 * 19.625 = 13.083 sq. ft

    Area of one tube hole = 0.785 * 3 * 3 = 7.065 sq. in

    Area of 60 tube holes = 60 * 7.065 = 423.9 sq. in or 423.9 / 144 = 2.94 sq. ft

    Net heating surface of one tube sheet = 13.08 – 2.94 = 10.14 sq. ft

    Net surface of two tube sheets = 10.14 * 2 = 20.28 sq. ft

    Total net area = 125.60 + 686.2 + 20.28 = 832.08 sq. ft

     

    832 sq. ft