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	<title>Utilities - Articles</title>
	<link>http://www.cheresources.com/content/articles/utilities/</link>
	<pubDate>Fri, 24 Apr 2026 02:50:47 +0000</pubDate>
	<ttl>86400</ttl>
	<description></description>
	<item>
		<title>Water Chemistry and Treatment</title>
		<link>http://www.cheresources.com/content/articles/utilities/water-chemistry-and-treatment</link>
		<description><![CDATA[<p>Water is a natural solvent.  Rain water is acidic due to carbon dioxide picked up in the atmosphere.  Water and CO2 make carbonic acid (acid rain).  Water hardness is primarily calcium and magnesium.  Calcium is limestone - common throughout Midwest.  Acid water dissolves limestone, iron, and other minerals in soil.  All pure water has an affinity for metals.  Surface water supplies are generally low in dissolved minerals.  Well supplies vary in dissolved minerals with depth and location.  pH is the measure of acidity of a water supply based on the hydrogen ion.  Water with a pH below 7.0 is corrosive. Above is considered alkaline water which is not a problem except in industry.</p>

<p><p class="h1header">Ionization</p></p>

<p>Minerals dissolved in water are present as ions. Ions have an electrical charge; either positive or negative. Ion exchange resins take advantage of this charge.  Water Softeners are cation exchangers meaning they will exchange, or pick up all positive ions. Positive ions are calcium, magnesium, iron, copper, lead, sodium, zinc, manganese, mercury, and other metals.</p>{parse block="google_articles"}
<p>Negative ions are not exchanged, or removed, by a water softener and negative ions are called anions.  Negative ions are nitrate, sulfate, chloride, bicarbonate, and other similar minerals.</p>
<p>Minerals are measured by grains per gallon (gpg) or parts per million (ppm). The metric equivalent of ppm is milligrams per liter (mg/l).</p>
<p>A <em>grain</em> is a unit of weight (7,000 grains = one pound) parts per million is a finer measurement (17.1 ppm = one grain) one ppm = 8.33 pounds of mineral in one million gallons of water. More common minerals such as hardness are measured in gpg. Minerals such as iron are present in lesser quantities and are measured in ppm (or mg/l).</p>
<p>An analysis usually reports minerals as calcium carbonate equivalents to base results on a common denominator.  Calcium and magnesium reported separately are reported as individual ions and must be converted to calcium carbonate equivalents to arrive at total hardness.</p>

<p><p class="h1header">Total Dissolved Solids (TDS)</p></p>
<p>Total dissolved solids as reported on an analysis are the total of all minerals dissolved in the water. TDS levels below 900 ppm do not present a problem in residential or commercial applications. TDS levels above 900 ppm will affect the performance of water softeners in the form of hardness and iron "leakage". All waters contain some natural sodium, and the higher the TDS, usually the higher the sodium level.</p>

<p>Sodium is used to regenerate a water softener and high levels of natural occurring sodium, plus that used to remove the hardness, will combine to a level high enough to partially regenerate the softener. Thus, water with a TDS of 1500 ppm and 40 grains of hardness will cause hardness and iron leakage.</p>

<p>TDS is also a factor in performance of Reverse Osmosis Systems. The R.O. membrane has limitations on TDS due to its ability or inability to carry away solids which might plug the membrane.</p>

<p><p class="h1header">Alkalinity</p></p>
<p>Sometimes confused with pH, has nothing to do with pH level. Alkalinity is due to the presence of bicarbonate, carbonate, and hydrate ions. For our purposes alkalinity consists of calcium and magnesium bicarbonate.   This alkalinity will produce CO2 when water is heated; therefore, it can cause corrosion even though the pH is neutral. Usually alkalinity as high as 300 ppm is not a problem unless the hardness is below 10 gpg. An index called the saturation index is used to determine if a specific water will cause corrosion.</p>

<p><p class="h1header">Water Problems and Treatment</p></p>
<p>Frequently several minerals are involved in a given water problem.</p>
<p><p class="h2header">Hardness</p></p>
<p>Water hardness above 5 grains is considered for treatment. Hardness is calcium and magnesium which tends to revert back to the solid state when water is heated. This solid material will form scale and will also combine with chemicals added to water such as detergents. The higher the hardness, the faster scale will form or the "harder" it is to produce suds for good cleaning action.</p>

<p>High hardness (10 grains and above) will shorten the life of water heaters, electric heating elements, and water using appliances.</p>

<p>A water softener removes the hardness minerals from water and replaces it with sodium which is an inert mineral.  Sodium readily dissolves in water; it has a high solubility which means it will stay in solution unlike the hardness minerals. The source of sodium for regeneration of a softener is (sodium chloride). A softenerâ€™s capacity is based on how much sodium the resin will retain and what that represents in grains of hardness removed by ion exchange.</p>

<p>A water softener will also exchange (remove) other metallic ions in solution such as iron, manganese, copper, etc. These ions must be dissolved in the water for complete removal. Oxidized iron will pass directly through the softener.</p>

<p class="h2header">Iron (0.30 ppm will stain)</p>
<p>Stains fixtures and clothing red/brown. Unstable in water when water is exposed to oxygen. Yellow water indicates that part, or all of the iron, has oxidized and will precipitate out of the water.</p>

<p>Dissolved Iron is indicated when water drawn at tap is clear but turns yellow upon standing. A water softener will remove this "clear water" iron.</p>

<p>Oxidized Iron is indicated by yellow color as soon as water is drawn from tap. A sediment filter will remove this iron, but should be followed by a softener to remove iron still in solution. If iron removal only is desired, a manganese greensand (ML-FFE) filter will remove both oxidized and dissolved iron.</p>

<p>CAUTION: Greensand should not be used on waters where pH is below 6.8.</p>

<p>Iron Bacteria is indicated when water pressure diminishes and iron stains are present. Lift toilet tank cover to confirm; slimy, stringy, brown growth is iron bacteria. This is most difficult form of iron and is caused by harmless bacterial that live in the absence of oxygen and feed on iron in water. It will eventually plug plumbing lines to reduce flow. Chlorinating well periodically may control growth. Best treatment is continuous chlorination followed by activated carbon filtration (ML-ACF). Optional treatment for lesser cases is the installation of a large diameter manual sediment filter (18KF-AG) to provide a "home" for them to grow.</p>

<p class="h2header">Manganese (0.20 ppm will stain)</p>
<p>Similar to iron but difficult to oxidize; causes dark brown to black stains. Is frequently present with iron, but in lesser amounts. Best removal method is with water softener.</p>

<p class="h2header">Hydrogen Sulfide (rotten egg odor)</p>
<p>Caused by decayed vegetation; is most troublesome due to bad odor and will cause corrosion; hydrogen lowers pH.</p>

<p>Hydrogen sulfide is sometimes present with iron and/or manganese. It will then cause black sticky precipitate which stains everything. Removal can be accomplished with a manganese greensand filter (up to 2 ppm H2S) or chlorination using a chemical pump, retention tank, and followed by an activated carbon filter. The latter method is used when the H<sub>2</sub>S is above 2 ppm or is accompanied by iron and low pH. A combination of chlorine and acid neutralizer is fed to adjust pH, oxidize the sulphur and iron in one operation.</p>

<p>Hydrogen sulfide is a gas and must be tested for at the job site to determine total H2S level.</p>

<p class="h2header">Low pH</p>
<p>Acidic condition (6.8 down to 5.0 pH) will corrode plumbing, erode porcelain, and put copper or iron in water depending upon type of plumbing. Stains will be blue/green for copper and red/brown for iron. Adjustment of pH from 6.9 down to 6.5 can be done with an acid neutralizer filter (ML-ANF) which contains calcium carbonate (marble chips) media which slowly dissolves. Requires addition of more media about every two years depending upon pH level. Lower pH must be adjusted by feeding MAN-607 to the water with a chemical feed pump.</p>

<p class="h2header">Nitrates, Sulfates, Chlorides (Anions)</p>
<p>EPA or U.S. Public Health Service limits on the nitrate level permissible is 44 ppm as nitrate or 10 ppm as the nitrogen ion. Nitrate causes what is known as "blue babies" due to oxygen starvation (this can occur at 25 ppm nitrate). Nitrate presence is also an indicator of organic contamination.</p>

<p>Sulfates cause an astringent taste in the water. Concentrations of 30 gpg can have a laxative effect due to calcium sulfate.</p>

<p>Chlorides can combine with natural sodium or sodium produced by softening and result in salty tasting water.  Both sulfates and chlorides, as well as nitrates, are most economically removed by reverse osmosis.</p>

<p class="h2header">Reverse Osmosis</p>
<p>R.O. is a process of forcing water, by pressure, through a membrane (plastic) with microscopic pores which will separate the dissolved solids from the water. The water produced is equal in quality to distilled water.</p>

<p>R.O. removes up to 90-98 % of minerals, organics, bacteria, and viruses from water. dissolved gases such as chlorine or hydrogen sulfide are not removed. Many of todayâ€™s chemical contaminants are also removed.</p>

<p>R.O. requires water which does not exceed 8 grains of hardness and all iron must be removed prior to the R.O. unit.  A 5 micron cartridge filter is required ahead of the R.O. to eliminate sediment plugging of the membrane.</p>

<p>A water sample should be submitted to Marlo for analysis before installing an R.O. unit to ensure that the TDS does not exceed the limits. If nitrate removal is the purpose of the R.O. installation, we must have analysis to determine actual % of removal based on TDS.</p>

<p class="h1header">Sizing Conventional Water Softners</p>
<p>Assume 60 gallons of water per day per person (natural average) if iron is present: multiply ppm x 2 and add hardness to arrive at compensated hardness. Iron is more readily exchanged than hardness and this method compensates the softener capacity.</p>{parse block="google_articles"}

<p><b>Example:</b> Number of Persons x 60 x Comp. Hardness = Grains Capacity Used Per Day.</p>

<p>Multiply: Grains per Day x 3 Days = Approximate Capacity of Softener Required. The number of days may be extended to arrive at a catalog unit which will not exhaust before regeneration.</p>

4 persons in household<br />










18 grains hardness<br />










1.5 ppm iron (clear water)<br />











<p>Compensated Hardness = 1.5 x 2 + 18 = 21 grains</p>

<p>4 x 60 x 21 = 5040 grains/day x 3 days = 15,120 grains capacity
ML-15S (15,000 grain capacity) is too small.
Timer can only be set for: Once/6 days, Twice/6 days, Three times/6days.     (Cannot be set for every 4th or 5th day.)</p>

<p>ML-22D (22,000 gr.) = 4.36 Days (too large)
ML-25S (25,000 gr.) = 4.96 Days (too large)
ML-30D (30,000 gr.) = 5.95 Days (too small)</p>

<p>Due to limitation of time clock there is not an efficient choice.
The closest time clock unit would be a ML-22D.
Consider metered (MP) unit: MP-25S (4.96 days average) or MP-36D (7.143 days average).</p>

<p class="h1header">Reduced Salt Setting Conventional Softners</p>
<p>Reduced salt dosage, 6 pounds per cubic foot of resin versus maximum salt dosage, 15 pounds per cubic foot of resin may be used to gain salt efficiency. Marlo softeners are set up to take advantage of this savings wherever it is possible to use it.</p>

<p>The reduced salt dosage, minimum salt setting, may not be used if iron is present in the water. With reduced salt the resin is not fully regenerated which means the resin bed retains some hardness and iron would also be retained. The iron will eventually oxidize within the resin bed and iron fouling will result in lost capacity.</p>

<p>Minimum salt setting can be used to obtain a more exact sizing of a unit based on 20,000 grains per cubic foot of resin versus 30,000 grains at maximum salting. This results in a smaller, less costly unit plus salt savings can be 30% or more.</p>

<p><b>Example:</b> 3 persons, 15 grains hardness, no iron</p>

3 x 60 x 15 - 3240 grains per day<br />










15,000 grain unit at minimum salt = 10,500 gr. cap./ 3240 = 3.24 days<br />










(25,000 grain unit at maximum salt = 25,000 gr. cap. / 3240 = 7.70 days)<br />










(25,000 grain unit at minimum salt = 16,500 gr. cap. / 3240 = 5.09 days)<br />











<p>ML-15S is best sizing.</p>

<p class="h1header">Common Symbols Used in Water Treament</p>

<table class="datatable" border="0" width="62%" align="center"><tbody>
      <tr>
        <td width="47%"><p align="left"><strong>CATIONS</strong></td>
        <td width="53%"><p align="left"><strong>ANIONS</strong></td>
      </tr>
      <tr>
        <td width="47%">Calcium, Ca<sup>++</sup></td>
        <td width="53%">Nitrate, NO<sub>3</sub><sup>-</sup></td>
      </tr>
      <tr>
        <td width="47%">Magnesium, Mg<sup>++</sup></td>
        <td width="53%">Chloride, Cl<sup>-</sup></td>
      </tr>
      <tr>
        <td width="47%">Iron, Fe<sup>++</sup></td>
        <td width="53%">Sulfate, SO<sub>4</sub><sup>-</sup></td>
      </tr>
      <tr>
        <td width="47%">Manganese, Mn<sup>++</sup></td>
        <td width="53%">Bicarbonate, HCO<sub>3</sub><sup>-</sup></td>
      </tr>
      <tr>
        <td width="47%">Sodium, Na<sup>+</sup></td>
        <td width="53%">Calcium Carbonate, CaCO<sub>3</sub><sup>-</sup></td>
      </tr>
      <tr>
        <td width="47%">Copper, Cu<sup>++</sup></td>
        <td width="53%">Hydroxide, OH<sup>-</sup></td>
      </tr>
      <tr>
        <td width="47%">Hydrogen Sulfide, H<sub>2</sub>S</td>
        <td width="53%"></td>
      </tr>
      <tr>
        <td width="47%">Carbon Dioxide, CO<sub>2</sub></td>
        <td width="53%"></td>
      </tr>
      <tr>
        <td width="47%">Oxygen, O<sub>2</sub></td>
        <td width="53%"></td>
      </tr></tbody>
    </table>
<br />



<p><span class="info">This article is shared with permission from Marlo Incorporated.  Original author: Tony Ramirez, ramirezt"at"marlo-inc.com</span></p>]]></description>
		<pubDate>Mon, 04 Jun 2012 18:26:45 +0000</pubDate>
		<guid isPermaLink="false">dbdc69ea6ccbdea0ca2d796e1af24ebf</guid>
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	<item>
		<title>Deaerators for Boilers</title>
		<link>http://www.cheresources.com/content/articles/utilities/deaerators-for-boilers</link>
		<description><![CDATA[Removing dissolved oxygen from boiler feed water is absolutely necessary to protect your boiler equipment from severe corrosion.   But the make-up water necessary in any boiler system inevitably contains dissolved oxygen.  Oxygen can sometimes enter condensate systems as well.  A good deaerator is essential to trouble-free boiler operation.<br /><a class='resized_img' rel='lightbox[5fe3f90ab99141af51f5c025d48f3209]' id='ipb-attach-url-5176-0-41061600-1776999047' href="https://www.cheresources.com/invision/uploads/monthly_05_2012/ccs-1-0-86757500-1337699580.gif" title="deaerator-1.gif - Size: 9.61KB, Downloads: 952"><img src="https://www.cheresources.com/invision/uploads/monthly_05_2012/ccs-1-0-86757500-1337699580_thumb.gif" id='ipb-attach-img-5176-0-41061600-1776999047' style='width:250;height:141' class='attach' width="250" height="141" alt="Attached Image: deaerator-1.gif" /></a>
<br />
<p align="left"><font face="Arial" size="2">{parse block="google_articles"}Above is a typical "older-style"
    boiler feed water deaerator.Â  You'll see why I call it "older" in a moment.
    Â  The theory here is relatively simple.Â  Treated water containing dissolved
    oxygen is fed onto a contacting device where the water can be heated and contacted with
    steam which is also fed to the vessel.Â  The steam heats the incoming treated water to
    around 250 Â°F (120 Â°C) and allows oxygen to escape (along with any small amount of
    uncondensed steam) to the atmosphere.Â  Notice that the returning condensate is NOT
    contacted with the steam in this system.Â  Some systems feed the treated water and
    condensate together to ensure a very low oxygen content.Â  Other systems do not bother
    as the returning condensate is expected to already have a low oxygen content.Â  You'll
    see that newer systems are designed to treat both sources in most cases.</font></p>
    <p align="left"><font face="Arial" size="2">A next generation deaerator system from <a
    href="http://www.hurstboiler.com" target="_blank">Hurst Boiler</a>, called the Oxy-Miser,
    utilizes a scrubbing section to contact oxygen-rich feedwater with steam rather than the
    more traditional tray arrangement.Â  </font></p>
    <p align="center"><a class='resized_img' rel='lightbox[5fe3f90ab99141af51f5c025d48f3209]' id='ipb-attach-url-5177-0-41065300-1776999047' href="https://www.cheresources.com/invision/uploads/monthly_05_2012/ccs-1-0-73949900-1337699587.gif" title="deaerator-2.gif - Size: 50.1KB, Downloads: 1154"><img src="https://www.cheresources.com/invision/uploads/monthly_05_2012/ccs-1-0-73949900-1337699587_thumb.gif" id='ipb-attach-img-5177-0-41065300-1776999047' style='width:250;height:161' class='attach' width="250" height="161" alt="Attached Image: deaerator-2.gif" /></a>
</p>
    <p align="left"><font face="Arial" size="2">Again, you can see that both the treated
    boiler feed water and the condensate return are sent through the scrubbing section of the
    deaerator.Â  The Oxy-Miser system is available in capacities ranging from 5,000 to
    200,000 lb/h (2300 to 91000 kg/h).Â  Below is an actual installation photo:</font></p>
    <p align="center"><a class='resized_img' rel='lightbox[5fe3f90ab99141af51f5c025d48f3209]' id='ipb-attach-url-5178-0-41068100-1776999047' href="https://www.cheresources.com/invision/uploads/monthly_05_2012/ccs-1-0-75320200-1337699595.gif" title="deaerator-3.gif - Size: 115.65KB, Downloads: 799"><img src="https://www.cheresources.com/invision/uploads/monthly_05_2012/ccs-1-0-75320200-1337699595_thumb.gif" id='ipb-attach-img-5178-0-41068100-1776999047' style='width:250;height:198' class='attach' width="250" height="198" alt="Attached Image: deaerator-3.gif" /></a>
</p>
    <p align="left"><font face="Arial" size="2">If you'd like to learn more about the
    Oxy-Miser Deaerator from Hurst Boiler, use this link: <a
    href="http://www.hurstboiler.com/oxymiser.htm" target="_blank">http://www.hurstboiler.com/oxymiser.htm</a><br>
    </font></p>]]></description>
		<pubDate>Tue, 22 May 2012 15:05:21 +0000</pubDate>
		<guid isPermaLink="false">628f16b29939d1b060af49f66ae0f7f8</guid>
	</item>
	<item>
		<title>Keeping Ejectors Online</title>
		<link>http://www.cheresources.com/content/articles/utilities/keeping-ejectors-online</link>
		<description><![CDATA[<p>Steam jet ejectors offer a simple, reliable means of producing vacuum, and have a low installed cost as well. They are commonly found in process plants having available steam. The vacuum produced is useful for many processes, including evaporation, cooling, hydration, crystallization, deaeration and filtration.</p> <p>Through the simplicity of its construction (Figure 1), the steam-jet ejector provides many years of troublefree operation. {parse block="google_articles"}When a problem <em>does </em>occur, many plant personnel do not have the experience to effectively troubleshoot an ejector system, and precious production time is lost.</p><p>For example, a loss of vacuum in a multistage ejector system might have many plant personnel disassembling the first-stage ejector booster, on the assumption that one must check a unit from inlet to outlet. In fact (as will be shown later in this article), this is the last place to look. Fortunately, downtime can be kept to a minimum when a logical sequence of steps -- a checklist -- is followed to locate the source of trouble.</p><p>Â <span class="h1header">Ejector Basics</span></p><div class="imagecaption" style="display: inline-block; float: left; margin: 5px; width: 250px; background-color: #ffffff; padding: 5px;"><a class='resized_img' rel='lightbox[2]' title="In total, this illustration represents a four-stage ejector system with two surface-contact intercondensers. A simple single-stage system would comprise only the section in the outlined box. In either case, motive force is provided by steam jets, which draw vapor from a vessel and through the system. The condensers act to reduce the load on the next ejector." href="&#46;&#46;/&#46;&#46;/&#46;&#46;/&#46;&#46;/invision/uploads/images/articles/ejector1.gif" target="_blank"><img style="float: left;" src="&#46;&#46;/&#46;&#46;/&#46;&#46;/&#46;&#46;/invision/uploads/images/articles/thumbnails/thumb_ejector1.gif" alt="ejectors" width="250" height="130" /><br style="CLEAR: none" /></a><div class="imagecaption" text-align: center; padding: 5px;">Figure 1: Typical Ejector Arrangement</div></div><p>Ejectors can be classified as <em>single-stage </em>or <em>multistage</em>. Multistage ejectors may be further divided into condensing or noncondensing types. The single-stage ejector, the simplest and most common type, is generally recommended for pressures ranging from atmospheric pressure (30 in. Hg absolute) to 3 in. Hg abs. Discharge is typically at or near atmospheric pressure. The boxed section of Figure 1 shows a single-stage system. The effects of injected steam on process vapors is shown in figure 4. Multistage noncondensing ejectors (MNEs) are used to produce suction pressures lower than 3 or 4 in. Hg abs. Steam consumption in an MNE is relatively high. Each successive stage is required to handle the load plus the motive steam from the previous stage. MNEs are frequently used when low first cost is more important than long-range economy. They are also used for intermittent service or when condensing water is not available. MNEs are usually two-stage, although six-stage units have been used successfully.</p><p>Multistage condensing ejectors (MCEs) are available in two through six stages. Intercondensers (surface or direct-contact) between stages condense steam from the preceding stage, reducing the load to be compressed in the succeeding stage. A multistage system is shown in Figure 1.</p><p>Four-, five- and six-stage ejectors are used to achieve suction pressures as low as 5 Âµm Hg abs. Under such vacuum conditions, pressure between the preliminary stages is too low to permit condensation of ejector steam, and only the final two stages are fitted with condensers. MCEs remove condensable vapor ahead of a given ejector stage. They also permit use of a smaller ejector, and a reduction in the amount of steam required. Condenser nomenclature is determined by the corresponding operating conditions and functions.</p><p><em>Precondensers </em>are used when the absolute pressure of the process is sufficiently high to allow condensation at the temperature of the available water supply. Noncondensables are removed from the precondenser by one or more ejector stages. Condensers or <em>inter-condensers </em>liquefy process vapor and motive steam from one or more preceding booster ejectors. <em>Aftercondensers </em>condense steam discharging from the last-stage ejector, generally at atmospheric pressures.</p><p>There are two basic types of condensers -- direct-contact and surface-contact. In direct-contact (countercurrent, barometric design) condensers, cooling water is mixed directly with the vapor to be condensed, then discharged to atmosphere through a barometric leg or tailpipe of sufficient length to overcome the atmospheric pressure. A means of cleaning up or otherwise disposing the water that has become contaminated by process material is often required. The surface-contact condenser permits main-condenser cooling water to be used as cooling water through inter- and aftercondensers, for energy and process-water conservation.</p><p class="h1header">Where to Start</p><p>When a vacuum problem arises there are several preliminary checks that should be made on an ejector system before components are disassembled. First, is the system design data readily available? Most ejector systems are custom-designed to operate at a specified vacuum, given process loads, minimum available steam pressure, maximum steam temperature, maximum discharge pressure and maximum water temperature. It is impossible to evaluate the complete system unless the manufacturer's design parameters are known.</p><p>{parse block="google_articles"}A data sheet can be obtained from the manufacturer of the ejector system and should list the design vacuum, capacity, interstage ejector vacuums, motive steam pressure and temperature, condenser water-inlet and -outlet temperatures, and discharge pressure. Critical dimensions such as the diameters of the ejector nozzle orifice and the diffuser bore should also be know.</p><p>Once the design data are located, there is an ordered series of steps to take in isolating ejector problems. One should check:</p><ul><li>Gauges </li><li>Steam </li><li>Water </li><li>Process loads </li><li>Field report and process logs </li></ul><p class="h1header">Pay Attention to Instruments</p><p>When troubleshooting the ejector system, accurate pressure and temperature measurements are needed to quickly locate the source of the problem. Therefore, a check of the system's instrumentation is a necessity. All vacuum, pressure, and temperature gages should be calibrated or replaced. A malfunctioning vacuum gage may be found to be the entire vacuum "problem."</p><p>If the vacuum gage is several feet or more from the ejector system, check the line running from the system to the gage for air leakage. It would take a very small amount of air leakage in an instrument vacuum line to throw off the measurement. If leakage is suspected, connect the test gage directly to the ejector and compare vacuum measurements. If there is a valve in the vacuum line, close it and observe the vacuum line, close it and observe the vacuum gage. If it slowly loses vacuum, air leakage is occurring.</p><p><div class="imagecaption" style="display: inline-block; float: left; margin: 5px; width: 200px; background-color: #ffffff; padding: 5px;"><img src="&#46;&#46;/&#46;&#46;/&#46;&#46;/&#46;&#46;/invision/uploads/images/articles/ejector2.gif" alt="ejector" width="200" height="93" /><div class="imagecaption" style="text-align: center; padding: 5px;">Figure 2. Steam-jet Ejectors Often Provide a Compact Means of Delivering Vacuum.</div></div>For troubleshooting purposes, overall, an absolute pressure gage is preferred over a common vacuum gage. A common vacuum gage that reads in units of inches of mercury vacuum is food for rough measurements by operators, but this gage does not five the accuracy needed for a system analysis. Besides relative inaccuracy, vacuum gages require a barometric pressure measurement to determine an ejector's vacuum in units of inches of mercury absolute. There are a variety of suppliers of such absolute-pressure gages.</p><p>Typically, an absolute mercury manometer is used for measuring the vacuum in the Y and Z stages (Figure 2). It can be flooded with water and still give a relatively accurate reading.</p><p>Replacement mercury U-tubes are also inexpensive, and are available from various suppliers. Mercury-free units are also available, and are typically used for the higher-vacuum ejectors such as W or X stages. There are also many manufacturers of electronic vacuum gages that offer very accurate and portable instruments. The gages are well worth the investment and should be kept in stock only to be used when troubleshooting ejector systems.</p><p>Steam-pressure gages should be located on the steam chest of the ejectors or as close to the unit as possible. It is important to know the actual operating steam pressure since an ejector of critical-flow design (suction pressure less than half discharge pressure) will not operate properly when even a few psi below its design motive pressure. Compound steam pressure gages are recommended since they will not be damaged when exposed to vacuum.</p><p class="h1header">Steam</p><p>Motive steam plays probably the most important role in the operation of a steam jet ejector. Since internal dimensions are fixed, the ejector is designed for only one steam condition. When the steam condition changes there will be a change in the operation and efficiency of the ejector.</p><p>{parse block="google_articles"}In a critical-flow ejector a decrease in steam pressure of just a few psi will result in a broken or unstable vacuum. An increase in steam pressure above design will not have a noticeable effect in the operation of an ejector unless the increase is significant (>25%).</p><p>Besides wasting steam, excess motive pressure tends to choke the venturi with steam, thereby decreasing the suction capacity of the ejector. Note too that the performance of ejectors designed for saturated steam will be adversely affected if operated with super-heated steam.</p><p>The specific volume of steam increases with increasing temperature, which may require an increase in pressure to maintain required steam flow. Otherwise, as in the case of low steam pressure, the manufacturer must be consulted for a redesign of the ejectors.</p><p>Excess moisture in steam is one of the most common problems found in ejectors. Wet steam causes poor performance and, depending on the degree of wetness, can permanently damage an ejector in a very short period of time. A steam quality of less than 2% moisture is tolerable with most moderate vacuum systems. However, ejectors designed for a vacuum of 5 mm Hg abs or less should have steam that is completely dry or with a few degrees of superheat.</p><p>A telltale sign of wet steam is a fluttering needle on a steam pressure gage during operation. But the only sure way to determine quality of steam is to test it with a throttling calorimeter. This is a constant-enthalpy device that measures steam pressure and temperature. When used in combination with a Mollier chart, a reading of steam quality is obtained.</p><p>If steam is found to be wet, a steam separator should be installed in the steam line as close to the ejector as possible. Keeping all steam piping, and the steam separator, completely insulated will also help prevent the formation of wet steam.</p><p class="h1header">Water</p><p>Multiple-stage ejector systems will normally include condensers between some or all stages. Condenser designs are based on maximum water temperature and available flow. When inlet water temperature increases above design maximum, loads to the following stage increase, resulting in a poorer vacuum at that stage. If the affected stage is the last (Z) stage, then the vacuums of all the preceding stages could also be affected.</p><p><div class="imagecaption" style="display: inline-block; float: left; margin: 5px; width: 250px; background-color: #ffffff; padding: 5px;"><a class='resized_img' rel='lightbox[2]' title="The three basic parts of an ejector are the nozzle, mixing chamber and diffuser. High-pressure motive fluid passes through the nozzle, expands in the mixing chamber (where pressure is converted to fluid velocity), and passes through the venturi throat of the diffuser. Process fluid enters the suction port and is drawn into the mixing chamber. The curves show the changes in velocity (top) and pressure (bottom) of the motive fluid and Process fluid." href="&#46;&#46;/&#46;&#46;/&#46;&#46;/&#46;&#46;/invision/uploads/images/articles/ejector3.gif" target="_blank"><img src="&#46;&#46;/&#46;&#46;/&#46;&#46;/&#46;&#46;/invision/uploads/images/articles/thumbnails/thumb_ejector3.gif" alt="ejector" width="250" height="243" /></a><div class="imagecaption" style="text-align: center; padding: 5px;">Figure 3: Ejector Profiles (expand for more info)</div></div>The water temperature rise across a surface-contact condenser should be compared with design. A temperature rise larger or smaller than design could be an indication of a flow problem or fouling.</p><p>In direct-contact condensers, high or low water flowrates can cause problems in the vacuum system. High water flow could flood the condenser, increasing pressure drop, and therefore, the back pressure on the stage discharging into it. Low water flow may not be distributed properly, allowing condensable load to bypass into the following ejector and resulting in a poor vacuum.</p><p class="h1header">Process Loads</p><p>A change in process load will have a direct effect on the ejector system. Ejectors operate over a unique capacity curve, and any increase in load will result in a higher absolute pressure. An increase in noncondensables will travel through the system, affecting the following ejector stages. Discharge pressures of each stage will increase to the point of a breakdown in operation. As in the case of a changed steam condition, a change in process load will require redesign by the manufacturer, if design vacuum is to be maintained.</p><p class="h1header">Check the Logs</p><p>Manufacturers' field service reports or process logs may offer clues to present operational problems. the symptoms of a vacuum problem may be similar to a past problem outlined, with solutions, in a service report. Process logs may also indicate problems with steam pressure or changes in process conditions that will have a direct effect on the vacuum system.</p><p class="h1header">Now Look at the Process</p><p>If the preliminary checklist is completed with no obvious problems found, the next step is to determine whether the problem lies in the ejector system or the process. The steps remaining to be considered are: no-load vacuum test (single- or multistage) and an internal inspection.</p><p>The best way to determine if the vacuum problem lies in the ejector system or the process is to isolate and test the ejector separate from the process. The standard method of testing an ejector is to attach a blank, or blind flange, on the suction flange of the ejector and measure the vacuum at no-load conditions. A stable no-load vacuum is more difficult for an ejector to reach than a point under load conditions, simply because there is a greater suction-to-discharge pressure differential.</p><table class="imagecaption" border="0" align="left"><tbody><tr><td><img src="&#46;&#46;/&#46;&#46;/&#46;&#46;/&#46;&#46;/invision/uploads/images/articles/ejector6.gif" alt="piccolo" width="175" height="116" /></td></tr><tr><td>Figure 4: A Piccolo Gauge is Used to Check Vacuum Quality</td></tr></tbody></table><p>If the no-load vacuum measures the same as the manufacturer's test, then it is reasonably safe to assume that the ejector is working at its design load point. The problem may lie upstream from the suction of the ejector- possibly an increase in air leakage or process load. It should be noted that unless specified, an ejector may not have a stable vacuum at no-load even though it works at its design load.</p><p>To test an ejector at its design load point involves metering the design load into the suction of the ejector. Use a calibrated orifice or a series of orifices (such as can be found on an instrument known as a piccolo -- Figure 5), and then compare the measured vacuum to the design vacuum. A curve can be plotted and compared with the manufacturer's. This procedure should be considered only after all other tests are exhausted. (The manufacturer should be consulted for the proper field testing procedure if a test under design load conditions is desired.)</p><p>If the ejector does <em>not </em>obtain the manufacturer's tested no-load vacuum, the ejector should then be disassembled and internally inspected. No-load testing is easily accomplished on a single-stage ejector system, but a multistage ejector system must be evaluated by checking the <em>last </em>stage <em>first</em>.</p><p class="h1header">Multistage, No Load Vacuum</p><p>Typically, a multistage ejector system is started up backwards from the last (Z) stage to the first. The Y stage cannot operate properly until the Z stage is working, the X stage will not work unless the Y and Z are operating, and so on.</p><p>{parse block="google_articles"}Troubleshooting a multistage ejector system should also proceed in this back-to-front order. Check the vacuum of each stage during process load conditions, and compare it to its design value. When the measured vacuum of a stage is worse than its design, the cause of the problem at that stage must be found and corrected before proceeding any further.</p><p>The next step is to performance-test the stage in question by checking its no-load vacuum. For example, if the stage being checked is the Y stage of a three-stage ejector system, a blank should be installed on the Y suction flange. Since the Y stage is designed to discharge to a vacuum created by the Z stage, the Z stage, and intercondenser if present, must operate simultaneously during this test.</p><p>With the Y stage steam valved off, first check and record the Z stage no-load vacuum to be sure it is meeting the manufacturer's tested value. Then, with the vacuum gage still connected to the Z stage, turn the Y stage steam on. If the Z stage vacuum steadily falls off, the intercondenser is most likely the cause of trouble and should be inspected.</p><p>As mentioned in the preliminary checklist, a condenser temperature rise much greater or less than design may be an indication of a water-flow problem. A water-flow problem can result in a higher condenser temperature and an overloading of the following stage with uncondensed vapor. In this case, as the Z stage falls off, the Y stage vacuum would follow.</p><p>Examples of direct-contact condenser problems include: a blocked tailpipe, air leakage into tailpipe, damaged water distributor, or a plugged water nozzle. Surface condenser problems include: a blocked drain, air leakage into tailpipe, or split or fouled tubes.</p><p>If the Z stage vacuum is within specifications, move the vacuum gage to the Y stage. If the Y stage vacuum measures exactly the same as that of the Z stage, a blocked Y stage nozzle may be the cause. However, at this point, if the Y stage vacuum does not measure reasonably close to the manufacturer's tested no-load value, the stage should be disassembled for internal inspection.</p><p>Finding the Y and Z stage vacuums within specifications, remove the blind flange from the Y stage suction and repeat the procedure at the X stage. It is important to remember that each stage must meet its design vacuum before continuing the testing.</p><p>At times it may be impractical to make and install a blind flange on the suction connection of an ejector due to the size of the unit. In most cases, however, these larger stages will be the W or X. If the no-load testing has ruled out the Y and Z stages and the condensers ass possible causes of the vacuum problem, and internal inspection of these larger stages may be the more practical step to follow.</p><p class="h1header">Internal Inspection</p><p>There are several things to look for when performing internal inspection of an ejector. Usually any kind of corrosion or erosion that is obvious to the eye and touch will affect the performance of an ejector. An indication of wet steam will show as lines ("wiredrawing") etched up and down the inside of the steam nozzle. The point along the diameter where the steam contacts the venturi is another location that may be gouged due to wet steam.<p>Steam leaking around the nozzle puts an artificial load on that stage, resulting in poor vacuum. Leakage of this sort should be noticeable as a discoloration where the nozzle seats on the steam chest, or as erosion of the nozzle threads. A process that causes corrosion or buildup of material on the internals of an ejector will also effect the performance of that unit.</p><p>Critical dimensions such as the nozzle orifice or venturi bore diameter, obtained from the manufacturer, will enable a measurement of dimensions to determine extent of wear. Part numbers of the various ejector components should be checked to ensure they are in the right unit. Many ejector parts, and complete stages, are physically interchangeable and care must be taken not to mix them.</p><p class="h1header">Keep Spares on Hand</p></p><p>At a minimum, keep at least the following components in stock:</p><ul><li>One steam nozzle for every single nozzle ejector stage </li><li>One diffuser for every stage, at least in sizes through 6 in. -- higher, if continuity of service is critical </li></ul><p>If continuity of service is important to a process, keep a spare steam nozzle in stock for every size ejector in the system. Spare diffusers are also worthwhile to keep in stock, especially for smaller systems. While it is theoretically possible for the plant engineer to recondition these parts, the practice is not recommended because critical dimensions may be altered.</p><p>Since most nozzles are relatively inexpensive they should be considered sacrificial; if wear is evident they may be discarded and easily replaced. A complete Z stage should be kept in stock for important systems in critical operations.</p><p>If these simple tips fail, don't despair. Check the nameplate and call the manufacturer. A condition may be new to you, but chances are the manufacturer has seen it, and corrected it, many times before. Since troubleshooting an ejector system is quite straightforward, suppliers can usually work with you over the phone to get the problem corrected. Experienced service people estimate that at least 50% or more of the troubles referred to them can be solved over the phone.</p><p>Of all vacuum-producing devices, the steam-jet ejector is the most forgiving. Occasional inspection, replacement of parts, and adherence to design conditions will keep it operating reliable for many years. Knowledge of these simple procedures for avoiding trouble, and locating it if it does occur, will save time and product in you plant.</p><table class="datatable_inset" border="0" align="center"><tbody><tr><td><p align="left">This article first appeared in <em>Chemical Engineering</em> magazine in May 1992.Â  Special thanks to Mr. Norman Diegnan for permitting the reproduction of this article at <em>The Chemical Engineers' Resource Page.</em></p></td></tr></tbody></table>Â Â ]]></description>
		<pubDate>Mon, 08 Nov 2010 18:50:19 +0000</pubDate>
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