Document kXeJJv5GyLG0rqK3pwOjNwkV

twin reducing station in the plant yard. Each of the two reducing valves can handle enough gas at 35 psi to carry top station load. An 18-in. header in the boiler room feedi individual units through 10-in. plug cocks, followed by two emergency shutoff cocks with an automatic vent between them ond a manual or automatic gas-control valve operated from the boiler board. This control valve reduces gas pressure to 1 to S psi, depending on burner load. On first starting up with gas, this User took the precaution of blowing the 23-ln. main feed line from the gas company's reducing station to the yard reducing station and atmosphere for 7 minutes. Then he purged the line from there to the individual burners, using nitrogen. Considerable foreign material was picked up from the new gas main -- enough in one case to cut out the internals of the yard-reducingstation valve. Oos-Systom Piping. It can be seen that the basie problem Is to install a correct gaa-piping system and to oper ate It properly. To help Industrial gas users in this connection, the American Oas Assn formed the Industrial Gas Practices Committee in April 1952. This committee Is to prepare a detailed statement of standard requirements for Industrial consumers' gas piping.. It Is hoped that the committee's work will serve as the basis for an American Standards Assn recommen dation for all gos-piping carrying pres sures above 0.5 psig. The committee's present thinking was summarised in a paper by E l Spanagel, Rochester Oas fii Electric Corp, at the 1953 Pall Meeting of ASMS. Much of the mate rial in this paper (Installation of Fue/Gas Piping) is presented on these pages, headed: "Recommended Prac tices for Industrial Gas Piping." Standby Provisions. Many Indus- trial-gas consumers take advantage of the lowest rates offered by the supplier, whieh often are for service of the inter ruptible type -- that Is, service may be cut off without notice and restored as the supplier's situation dictates. Plants using interruptible service usually make standby provisions of one kind or another. Often standby fuel is oil. In many plants, although gas Is not used as a boiler fuel, it is used in manufacturing operations, as in print ing machinery, heat treating, etc. Por such use any standby fuel should be gaseous ond should have nearly the same properties as the fuel usually burned so a minimum of adjustments are needed. Propane, bufane and combinations of them (usually referred to as LPG, for liquefied petroleum gases) are RECOMMENDATIONS FOR. INDUSTRIAL GAS PIPING, conld Take branch connections, when needed, off the top or tU ' of main horisontal pipes rather than off the bottom. This m? to ovoid pickup of condensate, scale, rust Equip braneh connections with suitable manual shutoff valves or plug cocks, placed in the closed position. Clou out lets with threaded cops, plugs or flanges until ready to tu/ Mein shutoff valves on lines to individual buildings be outside the building to permit cutting off in emergencies. Location should be plainly marked and posted, and provisions made to prevent operation except when authorised. Oat shutoffs should be gate valves or full-opening p)^. cocks. Lubricated plug cocks are usually recommended for pipe sixes over 1 in. Where gas pressure runs above 5 pd* tamperproof cocks ore a good safety measure. TESTING PROCEDURE. Subject the piping system to e test pressure at least i.S times maximum working pressure, hot never leas than 3 psig. System should hold bottled-up pressure for at least 10 min, without drop In pressure after test gas has had time to arrive at ambient temperature. Unusually long piping systems should be tested for longer periods--up to 34 hr. As test medium, use air or inert gas, such as carbon dioxide, nitrogen or combustion products. Never use oxygen, water or any other liquid. Purge piping after test and after gas meter has been set Do the purging at the most distant point from the meter, by hose or temporary pipeline leading outside the building. Simi larly purge each major branch Une. Make a final check after purging end filling up the gas lines. Test dial on gas meter can be used for over-all leak cheeks.' Observe for 5 min; U there's no movement, consider system tight If there is, shut gas off at meter and look for open fit tings, open ends, open shutoff valves, bad joints. SAFETY PRECAUTIONS. Never use gas piping for electrical grounding and never employ piping, control casings, panels or other metal parts in place of wiring. This doesn't apply to the got combustion system's own low-voltage control and ignition circuits, nor to electronic flame-detecticm circuits. Install a backpressure valve wherever air Is used for the combustion system at a pressure higher than normal gti pressure. It might possibly back up into the gas Una- Alio, put in an automatically operated gas valve with manual * reset In the gas-supply line to serve as an interlock between air supply and gas supply. This will prevent flow of gas with out accompanying flow of air necessary for combustion. A second manually reset, automatically operated gas valve should be put in the gas-supply line to close tight ot a preset low-pressure limit Where gas compressors or other devices are installed to, raise consumer's gas pressure above that nor mally supplied, install a similar low-pressure gas cutoff vttve with manual reset finding increasingly wide use for stand by service as well as regular fuel in areas where natural gas isn't available. In the typical standby setup, storage tanks of horisontal cylindrical design are used, with relief valves and extra heavy pipe and Rtringi. An external mixer proportions gas and air to match the physical proper ties and burning characteristics of the riotural-gos supply. Most mixers p mlt wide turndown rate, os much os IS to I, so lood swings should e*us* no trouble. A vaporiser unit ln*urt* that the liquefied gas la property con ditioned for mixing. With such a setup, no changes in settings ond burner * justments are needed. Nor does gas raise any problems of sludge & gas deposits in the oriAees or bura***1 91 FUCl HANOIINO ANO ITQIAOI POWfl HEID-TESTED DESI0N5, fully outomeik operation, moke pockoged wolertube boilers ideal if they get good water treatment Packaged Watertube Boiler Treatment jv Compact, faclory-ojiombled, packaged watertubo boiler, feature con centrated water-circulation path., economy of metal, doe tolerance*. So .team and water pauage. mu.t be kept free of Kale and corro.ion Weds acceptance of the packaged firetube boiler set off a strong iolereit is developing its counterpart -- the & packaged watertube boiler. Current doligns reflect this interest quite marked- $ly. You'll find these new units s sharp f `departure from tho long-established tow-head watertube boilers. Bui because of these design differences they require special considerations for proper water {$ treatment, much at do the packaged i-6ietube designs, covered in Power, g June, p 76. Design. For years, boiler manufactur ers bare been making their single- and 2-drum, bent-tube designs more and bore compact. Today, they have reached ?!.(ha ultimate. These boilers now leave // ike manufacturer completely shop-as- fetnbled and nearly reedy for operation ' delivery, photo obovje. At this early age of packaged watertube boiler de. totopment, units are available for steam capacities ranging from 4000 to 33,000 Jb per br and for operating pressures as * high as 400 psi. . The watertube package wholly'en cases the boiler proper within in inbiltied sectional-steel jacket, suitable -for either indoor or outdoor installs- don. It requires no special or costly foundation and occupies comparatively ., foil* floor spaee, with low headroom, .^xe or two burners may be employed, Bring oil or gas, either atone or in com- By PAUl BRINDISI, Chemicof tnglnoar, Ce/ce Labantwiii Mnaiion. In the single-drum boiler the burner goes in just beneath the steam drum, while in the 24rum unit you'll And it to the aide of the drums, draw ings, top of p 101. The integral furnace is entirety watercoolcd with bare waitlubes. However, the single-drum unit has longitudinal sidewall header* on either side of the burner, while the 2drum unit has none. Waterwall tubes of the 2-drum design connect directly from the steam drum to the mud drum. In some designs both drums have Identical diameters, while in others the lower drum runs slightly smaller than the upper. These two drums extend the full length of the boiler, but are not always on the same vertical centers.. The steam drum of either design generally carries steampurifying baffle plates or internal sepa rators. In addition, there's usually one blowdown connection from the bottom of the mud drum,- about a quarter of the way in from the cooler end. The single-drum design, incidentally, makes blowdown connections lo the rear of each of its sidewall headers. Either forced or induced draft may be provided, although the last named la the more common. Superheat it avail- able, and an external economiser or air preheater ean be attached to these units when desired. Installation on the user's premises requires only a simple founda tion and the tying of fuel, gas duel, eleotrical, steam and water connections to ready these boilers (or operation. Oas Travel. The single-drum design has a single, but split, gsa pas* in which the comboetion products return lo (he front dual-exits by way of side corridors through the wsterwaUs, righthand drawing, p 101. Tubes, comprising the cooling bank in front of the rear target wall, are quite widely aeparated ond are staggered with respect to each other. Those forming the aide waterwalls are also four or five rows deep, but more closely spaced. The 2-drum design may have one, two or three gas passes, left-hand draw ing. P 101, depending on the unit's site. Designers take advantage of the extra length of larger boilers and use only one large gas pass, with no convection baffling whatever. The combustion prod ucts leave by way of the from, top eorner, away from the burner. Except for the few eomewhat widely staggered tubes ot the gas entrance, the drum connecting tubes go In on fairly close and equal centers. Medium-slxe 2-drum boilers have a 2-paaa, U-shaped travel with the gases escaping through the rear, top comer, ` OfCCMIH 1953 ENQlNfEftlNO AND MANAOEMCNT SECTION 99 :tr 9; / , F- A* I ; i T? w Ti! >>> :a -in1 ?.'i :rl li M. ft #! n-