Document k90nj5XyRxJ3E9xQx0J08pQgq

WATIR GAGES .mm Two Other Deilgns of High-Pressure Woter-Level Goges ,Sp**d-0rocp com 8 Mica Intern In this gego for 2000 pst won't break, blow out A Loose-window door-gloss Qdge. v Cor working press, to 3000 p*l One-pleco high-pressure watery valve for 1500-2500 psi pretax Illumination. Tubular gage glasses ore often used on boilers with low or moderate height. Usually it is unnecessary to provide special Illuminelion. When required, one or two wellplaced bull's-eye illuminators suffice. For high-pressure boilers, clear and positive gage illumination is a must One recent type uses a 100-wstt mercuryvapor lamp in place of the usual Incan descent. Menlseus shows up os a bril liant starlike line over the entire range of insert risibility. This Is Important for direct viewing, but even more so where mirrors are needed. IntorleroncM. Where beams, columns and other structural ports interfere with gage observation, a system of mirrors. Fig. 5, may be necessary. By using a light shield at gage and enclosing re flecting system in ducts, level may be transmitted over distances exceeding I2S ft. Lower mirror, on floor stand,' may be soma distance from boiler front. It is swiveled, has vertical adjustment. While a simple mirror system costs least for transmitting gage reading to operator, mirrors may become dusty, break or require adjustment. Wired television, a recent development, over comes these troubles and has many other advantages. Televising Gage level. Typical instal lation, Fig. 4, shows how Industrial tele vision camera is placed with respect to water gage. Distance between camera and viewing screen may he as great as 500 (t, with screen located where it will be of maximum use. This is usually on tha operating or control panel. Camera is light and rugged. In sev eral installations, lube lias never been replaced after months uf service. Where distance between camera and screen is greater than 500 ft, auxiliary viewers may be used. With coaxial cable, maximum distance increases to 4000 ft. For greater distances, amplifiers or a microwave transmitter, or both, may be used. See "TV Sees Where You Can't Look," Power, April, pp 78-83. Oo0 Uses. Typical practices la ap plying modern gages are as follows: Perticd itibular glass finds use below 400 psi for low-height boilers. Viewing is direct; manufacturers are steadily improving glass life. Inclined round glass. Fig. 1, Is suit able for higher boilers at pressures to a maximum of 350 psi. Operator directly views an area of the meniscus. Top connection slopes toward column, pre vents glass erosion by causing conden sate to flow* back Into wator column. Fig. 7 shows goge valves used. Mice insert. Fig. 8, is held by a forged-steel body. Two windows of selected mica ore securely held under slotted cover plotes fastened by bolted clamps. For pressures to 2000 psi, mice Segments ore 0.035 in. thick. Mica is said to be a flexible material that bends but will not break or blow out when properly assembled. No glass Is used In this type gage. Loose-window dear-glass gage is suitable for pressures to 3000 psi, has patented construction. Insteod of clamp ing glass tightly between cover plotes and center section, glasses are bolted in place, remain loose. Steam joint is made by clamping gaskets and mica against center plate by means of lha projecting surfaces of cover piste stirrmimiiiifi the glove as shown in Fig. 9 above. Classes are inicu-piutected. Pressure-sealed insert, Fig. 10, hi o molded reinforced gasket fitted bis stainless-steel recess in body, provide a tight joint without excesiive tlgfa ening of cover. Wide-shouldered u screws and stainless steel spring coni limit sealing load on glass to pndj termined safe value. Cooes also tDr for slight variations in gaskets, glue cover and body. Mien, 0.015 In. thick, protect! glass. Tempered 'glut with a hlgli durance limit is used. Should this typ glass foil in service it will develop i interlocking-type fracture, reducing iS tendency to blow out. Oago Volvo*. Typical volve for 159 and 2500-psl service is shown In Fig. 1 Nozzle, with integral stellite test, welded to body, making valve a so piece unit. For 2500 psi, valve ditk stellited. Fig. 3 shows a complete gij assembly using these valves. Planning. Every gage instsllslb should provide easy, aeeurote reading; boiler-water level for longest potsftj service period. It should be designed * if failure occurs, it is not n hazard operating personnel. See that gage valves reqatre < periodic lubrication, stay tight, aode be quickly and dependably opertt when necessary. Cage repairs should | easy to moke, with a minimum of tool For best results it should be pott"t to make repairs on only one face oi insert at a lime, without disturbing 4 posite side. Oage Caro. Follow manufactur instructions carefully. Post where are readily available whenever ten mice personnel want to use (Coniinuctl on page 192) 04 ENGINEERING AND MANAGEMENT SECTION rotf . 1I ^Bottom eorafiress^cfl I'.*4* flrvtsoehronous governor control! speed droop by an oil eon- Fft | neciloh between the power piston ond pilot-valve piston 2- Speed-droop lover acting orf the speeder spflng provides permanent spoed droop, which can be adjusted by operator Diesel Governor Modification and Use i To bo sure engines In different types of service hove suitable speed characteristics, a correct governing unit must be chosen. Here ore several good examples of choices for many usual jobs By EOOAtt J KATES Comv/tJflg fngfottr, New'Tori, N. V. > J0un Atmci.z in the June issue "Fuowed bow an Isochronous governor T.eould be made stable by using aetueting fiad receiving pistons end a floating ^ever to apply temporary speed droop .'^(compensation). Siability ean also be 'obtained by making the power piston v .directly on the pilot valve by means V''?f a hydraulic connection. v'TypIcol Unit. Fig. 1 shows such a goventor. Pilot valve controls flow of pres.furlzed oil to move power piston and change the position of engine throttle . in usual way. However, pilot valve is j,.. fecebtered by on oil connection to power I- . Pi*|n instead of by mechanical levers. Governor ecu like this: When engine load decreases, speed of engine and gov- entor increase. Flyweights move out ond pull pilot valve down, uncovering the Prts to admit pressurized oil to under . f power piston. Piston moves up ' decrease fuel flow. y,. , - pow-e*r piston imt.wov.wes wup, buuailiance PMon displaces compensation oil up- ward to the place of least resistance, which Is the proportionor piston. It moves up against its top spring, com pressing spring to a force equal to tha downward force existing on the pilot valve. Further movement of balance pis ton pushes pilot valve back to center,stopping the movement of the power piston at a decreased fuel position. Proportionor piston, being still above center, is pushed back to center by its top spring at a gradual rate, determined by rate at which oil bleeds through needlo valve. Opening of this valve Is adjusted so pilot valve Is kept centered by pressure of compensation oil until engine responds to decreased fuel rate end returns to its original speed. When compensation period ends, engine and governor are running at the originol speed, and both pilot valvo and proper* tioner piston are recentered. Power pis ton, however, is in a new position, supplying the amount of oil needed for 'prevailing load. Governor Modifications. The basic governors described In earlier issues are often modified or fitted with auxiliary devices to meet speoiol requirements. Let's look at some of them. Many electrle power plants contain several units generating alternating cur rent. Each unit must take a share o! the load while a constant frequency Is held in the power system. This requires use of isochronous governors fitted with a mechanism to provide adjustable per manent speed droop. Units like this employ both temporary and pertnsnent speed-droop mechanisms. Temporary speed droop Is always effective, to pre vent hunting. Permanent speed-droop mechanism can be adjusted, as required, from no droop (isochronous) to about 5% droop in steady speed. Fig. 2 shows how adjustable per manent speed droop is added to the iso chronous governor described In June Power, p 82. Speeddroop lever Intro duces permanent droop by changing the force of the speeder spring. To odjutt droop, speed-droop lever is shifted endwise to change Its leverage. With lever shifted to right, a given movement of fuel rod causes a greater (Continued on page 86) fcy.*U0U5t 1MJ ENOINEERINQ and management section