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Check List for Selecting Packaged Watertube Boilers 32 Jon mounting on twin-burner design,- obvf. lets you service fan from floor level, while reducing node ond drofl lots a Motcrlols of proper fype, adequate auxiliaries DIVB . working boiler of high ovollability, long . senile* |jf,S I about the tame width* and height*. With euch A rigid limitation on furnace width your burner selection ought to be one in which the flame shape does not impinge on boiler side walls. You coo get burners that give'a nar row (email included angle) fleme ;cone, but combustion efficiency suffers I from poor, ineffective air mixing. Theoreti cally a 180-degree flame cone is perfect since air supplied behind this (lat'tangle comes in instant contact with the atom ized fuel to give complete mixing.' The narrower the flame angle, the greater chance for stratification and low COf. With this understanding o( oil-burner flame propagation we feel two burners, with relatively short, wide-angle flames rather than a single burner of any de sign, will give improved combustion efficiency, broader flexibility ana less danger of florae impingement for larger-iteamJng-capacity units (prefer ably above 20,000 lb per hr). i We know operating engineers who've suffered problems from a loss of steam production when they've changed tips for higher firing rates or replaced- dirty atomizers. A fouled burner inevitably hows up at high steam loads. Along this same lino, loss of a burneron a single-burner unit because of unfore seen accidents means shutdown. * A 2burner selection, Fig. 2, avoids this. Manholos. While we're on the sub ject of servicing, let's look at the selec tion points for manholes. In all in stances, packaged steam generators are longitudinal designs ranging in length from 8 to 23 ft, depending on;boi(er capacity. Boilers with two manholes per drum permit ventilating by fans, allow a speed-up in cleaning, inspection or neclcd motor load as well as servklngl servicing not possible with a tingle needs are much less and, what's more^r manhole. The smell additional coat pays no gas pockets can form. - for itself during the equipment life. Soot blowers, to our way of thinking Access Poors, ftogltfers. Engineer* should be vafve-fn-head with a chaia-* generally prefer that burner registers operated valve for control from the' be hinged to you can get at register operating floor in addition to auxiliary- flights and buraer-diflusers without ro- steam stop-valves on all connecting1 moviag the windbox mounting. Operat piping. Drain valves ought to be sup ing engineers, though, do not like using plied so all condensate can be removed?, burner openings as access doors. Field before using the soot blowers. If you* reports show servicing costs' run high run into a packaged boiler requiring for units of this type. We suggest hinged soot blowers over 18 ft, we suggest use registers and refractory-lined doors. of shorter blowers from both ends. Construction Details. Packaged steam Valve bypasses, also, are special generators are highly competitive. items that engineers .believe should be You'll find, as o rule, recognized manu made a part of every bid. In order of facturers pretty much provide units that importance they rate these points u give satisfactory operation under nor most in need of bypass protection: (l) mal conditions. We fool, however, that feedwater-regulator control valve (2) good design requires consideration of (ucl-contfol valve, gas or oil, or com** conditions beyond normal. Industry bjnation (3) atomising-ageat control shares this feeling and expects a high valve. What's more, they prefer that availability from these packaged boilers. valves be plant osaembled, piped sad As such we recommend first-quality mounted to eliminate field labor. I" fire-clay tile as waterwall backing to tome instoncca, os in large-sized valves give safe operation in a tube failure. and piping used for gas or feedwater Bureau of Yards and Docks, U.S. control, or both, for high-pressure onlti. Navy, covers the above point in its rec they may be plant assembled and re ommendations for military purchases of moved as an assembled unit for rsil- packaged weletiube ateam generators road cloarancea. jj in this way: "Refractory behind water- Operation. All too often both con? walla shall be of a quality and construc sultsnts and operating engineers find 'j, tion that, in event of watertube failure, form of operation badly confused with no damage will result to refractory, in form of combustion control. But they \ sulation or casing." ure distinct and separate. Operation ^ . Baffles are another ilem that may may be manual, semi-automatic or fully J cause confusion when you are selecting automatic. Combustion control, on lb* packaged boiler. All engineers agree other hand, can be the automatic regu- ) they prefer a unit that produces equnl lotion of the combustion component* efficiencies without any ballling. Here with any of' the choices of operation, why. Draft loss, fan sire and con- For industrial installations a qualified ENGINEEttNO AND MANAOEMCMT SECTION fowl* gtim;etlc v* Semiautomatic veij&A on cheesing opcrolina typo: 'trThtrs fl hearing feed needing open.gmsnrs ol IS prig or lower tn west Mfff'Juk a ngMsr In ottendeoco? ' fully oufenwfie. SiWtot It load type? Will wide Optra?. ?fong#1 (about * f* I) prove best? `Tn.' .Ulo unleotomotie. engine** in attendance? 'iv'Um temloutomatic. mW.:il-l peek koilti load teach or go ,'#000 Op pet hi? fn.:`Uta MAletftemofic. r|:i'.JJwWe uld it per ovoid boiler shutdown tkioeflhi burner occidiat nr fovltd tlpt by ator* than one humor? AfjjYk I/m ttmltxtemtic. O a.- Ii food o roprasenfotire Industrie! on* --that Is, abors 15 psig? Ai Y*. Uto uwloatomotit, O 71 Is toed intermittent, with periods of little or no steam reqvlromtnh, maximum capacity below 20,000 lb par hr with bailor room hit unattended for considerable periods? A? Yes. Use fully automatic. Auxiliaries and Construction Betroctary, Insolation should be fop grads. Ask supplier fer detailed list of materials far each specific vail. . Foreed-droft loos should hors reosoaoblo sofoty lectors sad overload copocitiei. Look for typo designation of fan, motor rating, volume and static pressure doto to guard against largo contacted motor toads, excostive draft tosses. Yatvss, tltftlogs, trim cannot all be the some material. See that the baiter manufac ture* nates sica, type, catalog dumber and manufacturer when listing volves. Thus you ovoid broat* or cast-iron selections whore' their service may be questionable, as in the. feedwoter line. Soof blovfers. Check closely so you knew whether you're getting vetve-ln-haad or re volving designs. See, toe, thot loet-blover head materiel, cost iron or stool, is definitely specified. Instruments, panels can stand o word ol caution. Be sure yo get tho basic instru ments of draft gage, stoam flowmetsr, flue gas temperature indicator, steam pressure, inlot fuel pressure end temperature gages. Study all antral fairly close as to whether their advantage outweighs their maintenance. Wr . . . ,, (pefsting engineer is practically manifklpry: Controls cannot take the place V^s competent engineer. They are M.eant to produce efficient operation at min/mum cost under various load con ditions. . Even though package units caFry automatic devices to start, purge, :|pcfele with automatic restart, and so enj'you still need a good operator. ;Witb possibly one exception wateribVsnd firetube packaged-boiler man- lecturers employ rotary-cup burners, `pproved by the Underwriters* Labora tories,. Factory Mutual, and similar regencies. Boiler onlJ*, nor including Approved firing equipment, when de signed for automatic slop and start havo tojie examined and approved at the inTullstlon point. Control systems that db not bear type approval must employ ^component parts passed by the Under'jiAiitiei rs' Lobs or Factory Mutual, $3iSilteam generators, with capacities up ito!20,000 lb per hr, working pressures Wp to a 300-psig maximum, and with fs^single rotary-cup burner approved jfJftby/Underwrkers' Laboratories, usually w^pwate fully.automatic with full com- week-end heating loads. Many stales, employing semi-automatic units there in fact,'with this form of equipment is a choice of ignition method*--a torch permit lower pressure, healing service of saturated waste, a gas torch, a man (below 15 psig) without an attending ually operated gas-electric ignition tied operating engineer. But you can't use a burner where ateam at SO psi serves as the atomicing medium for pressure duty below 50 psl Semi-automatic combustion controls into a flame-failure circuit. The inexpensive saturated waste torches, in use for years, work well enough, except they do dirty up the fir ing aisle. A gas torch does a similar work well on fully-automolie-operated, ' job in a much cleaner way. packaged steam" generators with these The manually operated gas-electric characteristics: (1) all capacities with ignition system, with its electrical in in listed limits of packaged designs (2) terlocking to a flame-failure safety cir pressures limited only by the unit de sign (3) initial start-up by manual means. For best results you wont the burners, single or multiple, to have wide* rsngo controls (about 8 to 1) so ihe boiler con run continuously without fre quent stops and starts, and accompany ing heating and cooling losses. Further, you gel best results with a fully modu lating eontrol with an inertia stabilizer. cuit, has become increasingly popular. During starting cycles an automatic time or foot-treadle switch holds the flame-failure circuit open while the transformer and^gas solenoid valve of the gas-electric system stays energized. The combustion controls on these semi automatic designs may be actuated by electric, pneumatic or hydraulic means. They may be modoiating-poai- ' This form of modulating control has s responsiveness and sensitivity that can't .be matched by less.expensive high-low, on-off controls, occasionally designated improperly .as modulating equipment. tionlng or modulating-metering. Prop erly arranged, all forms give equivalent performance. Somesystems offer a com bination of electric-pneumatic or elec tric-hydraulic, and employ the electric ^burtlon control. `^`STTiU fuel combustion control, usually V^electrically run, snpplies these func- Jrffitiwu: ignition, purge, preignition trial' low fire start, flame-failure protec- `^FjJtion, ohutdown on override pressure, .ijirecycle and start, operation at any presInsure at or below design pressure. ^iv'Thii last operating fncton at reduced is tn important one. Small $&pUnu working at high pressures for v/ejjlV normal 5-day run find a fully auto matic-controlled unit capable of lower- ISr .pressure service highly desirable for The semt-automstic unit just de scribed provides all similar features of an automatically operaled-and-controlled steam generator except automatic ignition and recycling (restarting). But you Ho get the advantages of greater over-all efficiencies, lower maintenance ond higher availability. Ignition. The fully automatically con- Irolled-and-operaled boiler (up to about 20,000-lb-per-hr capacity) has to have an automatic ignition as part of the basic purging and low fire start. For the industrial installation, though, ity for the safety-protection phase. The pneumatic or hydraulic energy Is said to prevent shutdown during power failure. Tn this event the operating en gineer lakes over the safety phose. We feel electric power failures con stitute so minor a risk thot we would prefer to have our electric-protection circuit function as It i meant to, that is, to complete boiler shutdown. A portable, standby gasoline-driven singfo-phase 60-cycle generator provides enough low-cost energy to serve combus tion controls in rare power failures. Vjv-'l.; 79 ^TOMIMIES 1953 ENOINEItlNO ANO MANAGEMENT SECT1QN