Document yr0YJy4a5oxNja5kzM4X50mVd

PLANT PROBLEMS. .. put your know-how to How Can We Detect Not Machine Bearings? I run an Industrial power plan! and am in charge of all equipment for both power generation and process work. Recently we're run Into tome serious trouble with bear* Inga on heavy roll* overheating and burning out. Thli always oecara before we dUeorer whet it happening. I'm convinced this wouldn't happen If we knew the bear* Ing temperature, or had an alarm that Indicated tempera* ture waa rlalng. If we know how a bearing behaves, we gel to It soon enough to prevent burning out. Have Power renders ever built simple devices that work well for this Jobf How are they best buittT What materials and parts are needed?---JFC, Way Power Here Are the Answers. IfpelMl# 500-w immersion heater "'n Thermometer ifa-hp motor Oibboffte 0.025`in. copper took, to"* to" r o" deep \Bypass SEEINO WC't QUESTION brought back many memories. I've wrestled with this problem any number of times and have come to the conclusion that slsndard temperature relays, photo, as mantifac* tured by a number of firms, are best. This might not seem like the brightest answer of the month, but, brother, I know these units work, and work well. These reloys can be arranged to stop the machine when bearings overheat. They act at a temperature of 100 C, volatile liquid in'metal bulb expanding to actuate relay. Expansion takes place instantaneously when liquid reaches crit ics! temperature. Bulb is Installed in a horizontal hole drilled in bearing's lower half, os close in bearing surface as possible. Tubing is run to reloy. Joe Nordquist, writing In Operating Engineer in August 1949, gave some fine hints for a thermal relay tester. I'm borrowing Joe's illustration because hla tester is realty tops. Aa you ace in the sketch, it consists of an oil-filled copper HIRE'S AN OLDIf. I picked this up -fits tlte Dec 20, 1884 issue of Scientific^ American. It shows that as far back siJ 69 years ago engineers were concemed|j over bearing temperatures. ;i5f| This device has a fusible head smJI Inched to the end of a wire eonneetedm with a lever, fulcrumed on a post fai\ff tened to the box. Outer end of lever isH bent downward to form nn arm to whlckjq o bell is connected. End of arm carrfcitT a foot piece, which is struck by s atudw on the ahaft when bearing becomes hl3 enough to melt fusible head. Bell weight^, carries lever arm down to shaft, * bell rings ot every shaft revolution. ,9 Illustration, right, shows similar ds-J vice for crankpin bearing of an engin^.-R It ridca in fusible plugs fitted ind|ll& into end bores in the wristpin. ' CiiAnLRs Wkllky Penacook, S. If- 130 PUNT OPERATION AND MAINTENANCE SECTION more double-wire leads that enter it. Temperature indicator may be used for a tingle monitor. Or a portable one may be used when plant lias more than one monitor. It indicates bearing tem perature directly. H B Wavhk Brooklyn, N. Y. USE SNAP-ACTION bimetallic thermo* stats mounted in bearing lube-oil reter* voir, as top sketch shows. High ail tem perature cause* thermostat to snap closed, energising an alarm and warning light. Adjusting screw permits chang ing temperature at which thermostat closes. Mount alorm and warning light near bearing or on a central panel, whichever is most convenient. Though sketch shows only two bear ings, any number may be served with this type of hookup. Installation cost Is low. Bottom sketch shows a typical hookup available from severol manufacturers. Temperature probes may be located in reservoirs containing hoi oil leaving bearings. Two wires lead from hot jimetion to monitor. This may have 25 or HOOK UP thermoswilches as shown In sketches. Clip to bearing housing or install in lapped holes in bearing shell. Bearing-temperature rise causes switch to close, lighting a warning bulb or sounding an alarm. Lower sketch shows how relays can be used to sound an alarm, in addition to lighting a warning bulb. Each relay has two.normaily open contacts; one for the signal-light circuit, the other for the common alarm. M E Hrath Cincinnati. Ohio. SEVERAL WAYS to determine bearing temperature are: (I) by feel during periodic rounds, if bearings are acces sible (2) with a thermometer taped or clamped to bearing housing (3) with thermometer inserted in hole drilled in bearing (4) with an electronic device. Though homemade devices have been used, a unit built specifically for this purpose is better. Before buying special equipment, check overheated bearings to see they ore suitable for the Job and are not loaded beyond manufacturer's specifica tions. L E PoLiicorp Brooklyn, N. Y. (Continued on page 132) RIANT OPERATION AND MAINTENANCE SECTION 111