A rise in conductivity indicates a rise in the “contamination” of the boiler water. It is necessary to measure the conductivity of the boiler water inside the boiler or in the blowdown line. Boiler is operating near to its design pressure. Automatic blowdown control is achieved by constantly monitoring the conductivity value of the boiler water, adjusting the blowdown rate, and the duration based on a specific conductivity set point. Digital or SMART sensors maintain specific measurement and calibration data on an integrated chip along that is an integral part of the sensor. In its simplest form, this is a needle valve. The probable reasons and the corrective action that can be taken are listed. This lowers energy efficiency of the steam and can result in salt crystal deposits on the boiler equipment. Toroidal Conductivity Sensors consist of two small electromagnetic coils (driver and receiver) encased in a plastic coating that isolates them from the process. Also, water containing ammonia, particularly in the presence of oxygen, attacks copper and copper bearing alloys. The conductivity of wastewater is due to the presence of dissolved ions in the wastewater. They’re designed for use in thick, sticky, gooey, or sludgy applications with conductivities above 200μS. Start with these. Since acidity and alkalinity have a large effect on the electrical conductivity, it is necessary to neutralise the sample of boiler water before measuring its conductivity. Boiler problems are avoided by periodically discharging or “blowing down” water from the boiler to reduce the concentrations of suspended and total dissolved solids. A probe measures the conductivity and provides feedback to the controller driving a modulating blowdown valve. This increases both the size and flow characteristic (coefficient of discharge) of the orifice, resulting in a progressively increasing blowdown rate. Various installation options including retractable, flow thru, immersion, and direct insertion. If the steaming rate were to: The water being drained from the boiler is at saturation temperature, and there is a drop in pressure over the orifice almost equal to the whole boiler pressure. ), Another alternative would be Toroidal or Inductive Conductivity Sensor:  Copyright © 2020 Bright Hub PM. A steam layer forms between the boiler water and the tube wall, causing an inefficient heat transfer. A very sensitive hydrometer is required which needs careful handling and use if a satisfactory measurement of TDS is to be obtained. The increasing concentration of dissolved solids leads to carryover of boiler water into the steam, damaging piping, steam traps, and other process equipment. Where the present method is solely manual blowdown from the bottom of the boiler, it may be possible by looking at past water treatment records, to obtain some idea of how much the boiler TDS varies over a period of weeks. To determine the extent of scaling, making a conductivity measurement with a continuous online conductivity monitor is recommended. 0 0. rajasekar. or . The orifice size can be determined based on: However, pipeline friction and backpressure is inevitable, so for the purposes of this Module, a ssume the pressure on the downstream side of the orifice is 0.5 bar g. There is a problem: an orifice is not adjustable and therefore can only be correct for one specific set of circumstances. The problem of flashing increases with boiler pressure. To avoid obtaining false readings it should be regularly checked against distilled water. Water treatment specialists, in order to understand the process better, use grab sample testing methods or online pH, conductivity, TDS (total dissolved solids) and dissolved oxygen instrumentation. Calibration of your conductivity probe is critical to maintaining the proper cycles of concentration in your boiler. However, you do want some ions in the feedwater, just the right ones. For boiler water, however, a hydrometer can be used to obtain an approximate measurement of the dissolved solids, since for boiler water each increase of 0.000 1 relative density at 15.5°C is approximately equal to 110 ppm. A reliable conductivity motoring and control system consists of a sensor(s), mounting hardware or flowcell, conductivity transmitter, interconnect cable and, sometimes high temperature junction box(es). In addition to generating power, the steam may also be used directly in plant processes or indirectly via heat exchangers or steam jacketed vessels. In the case of the hot well, if the conductivity reading is below 2 μS/cm, then it is an indication of LP dosing failure. Scaling buildup on metal surfaces reduces heat transfer within the boiler itself, making it more costly to power. Minimized energy loss from boiler blowdown can save about 2% of a facility’s total energy use with an average simple payback of less than one year. Knowing this, they can design a program for external or internal boiler water treatment. and . However, the steam and water do not have the opportunity to separate properly, which results in water droplets travelling at a very high velocity with the steam into the pipework. 0 0. redbeardthegiant. why need to maintain conductivity in boiler water. If the measured value is greater than the set point, the blowdown control valve is opened until the set point is achieved. %%EOF Here’s a brief summary of the where conductivity measurement is used to help determine potential challenges to boiler water treatment. Without proper mechanical and chemical deaeration, oxygen in the feedwater will enter the boiler. What is the conductivity of the boiler water at 10 bar g?ses at the rate of approximately 2% (of the value at 25°C) for every 1°C increase in temperature. When the above information is available the required blowdown rate can be determined using Equation 3.12.5: There are a number of different ways that the blowdown rate can be controlled. endstream endobj startxref To defray energy costs, many industrial plants have their own boilers to generate steam in order to produce a portion of their energy needs. The raw water used to feed the boilers contains varying levels of impurities that must be removed to protect the boiler and associated equipment. In plan view, there is an annulus with the: If an increase in flowrate is required, the needle is adjusted out of the seat and the clearance between the needle and seat is increased.