Document p2e6QoxaQr3ew03edaQVqLMmX

ARGUMENTS Here's the place to unload you. gripes to editors, manufacturers '! and fellow engineers _.._______________ _______________________________ i Nibbles on Marmy's 'Knibbling Pin' JUST WHAT (j this "knibbling pin" that Marmaduke tell* about (Pouter, Jan* uary, p 142)? No one in our plant seems to know the answer. H W Holcombe Los Alamos, N. M. Editor's note: IVhen we checked this query with Marmy, he blasted: "Even a knucklehead can find out what a knib blinff pin ii--;us< look in the dictionary, and make damn jure Thor you're care ful to pronounce the K!" NOW aren't they known as nibbling ' pins? (For Arguments wo're striving!) 1 think perhaps "ka-nibble" wins: As in the word "conniving." C Ankers Yonkers, N. F. I'M WiUlNO to bet a bottle of Sand paper Cin that Marmy will be In the Novy a long time before he ever tells us-what s knibbling pin isl Ctoncs Burks Philadelphia, Pa. YOU EDITORS must really be noive to ask Marmaduke, "What is a knibbling pin" (Power, April, p 144). Be/ore becoming landlocked in Min nesota 1 carried a knibbling pin with me on the old 502's in round-the-world service end on 535's in the Pacific run. in foci. I've .seen knibbling pins in most any establishment from Sauciehall Street in Clasgow to the Tan Jon Pegsr in Singapore. But before you can really appreciate one you must have come the long way via Slivowiis, Tuborg, Aquavh, Pisco. S VI Krone Canfry, Minn. Readers Explain Meaning of 'Critical Pressure* 1ST MB EXPLAIN why steam cannot form above critical pressure of 3206 pai (Power, Apr, p 188): At the critical pressure, surface en ergy (energy per unit area) equals xero. Heat of vaporisation and surface tension also equal tero. Ordinarily, evaporation takes place when , a molecule of liquid has enough eneigy to escape through the liquid surface. If temperature is sufficiently high, kinetic energies of translation of the molecules exceed the maximum attraction between them. A liquid slate Is then impossible. Fotcea of attraction ond repulsion are equal at the critical temperature. Pres sure existing at this temperature Is the critical pressure. Above critical tem perature the liquid state is impossible for s single component, and Increasing pressure only compresses the vapor, which retains at] the properties char- cieristid of the gaseous state. H B Watnb Brooklyn, N. Y. HERE ARE several reasons why steam can't form above 3206 psl, in answer to Kuchinsky's request in April. (l) Highest vapor pressure that water can exert Is its critical pressure. (2) Bolling cannot occur above 3206 psi. (3) There is no change in enthalpy be tween liquid and vapor phases, hence no iaieni heal of vaporisation above 3206 psi. (4) Increasing pressure at saturation temperature decreases the dif ference in density between steom and water until the water level disappears. (5) Above the critical pressure, the substance is merely referred to os "fluid." There is no distinction between liquid and vapor phones. J L Cowan Sotvay, N. Y. IN ANSWER to the question about criti cal steam pressure, consider the usual procedure (or bringing up steam In a boiler. Water is heated with no gain in pressure until it reaches saturation tem perature. More heat Increases pressure and temperature along the saturation line, up to the critical temperoturc. Above this point, liquid phase oannot exist regardless of pressure; 3206 psi is corresponding pressure at the critical temperature. Instead of bringing up steam in the usual manner, you might fill the boiler, close the vents, and pump up pressure higher thon the critical point. Upon heating thia high-pressure water to criti cal temperature, you note an interest ing phenomenon. The water suddenly changes to steam, and no amount of compression can condense.the vapor. In passing, I would like to inquire whether this type of knowledge, or lack >f it, really has any effect on normal plant operating efficiency? II Holcombe Los Alamos, N. M. REGARDING Kuchinsky's question about why steam esn't form above 3206 psi, here are reasons I would give: Without a water or liquid stale in the boiler there is no free surface from which steam can be vaporised beoause there is no latent heat of vaporisation. Above 3206 psi, the only change that additional heat or firing can make is to increase pressure and temperature. A Belton Montreal, P. Q. ^ , ' * Thermometer Test Method T Trail suggests for eheeking thermometers (Power, Feb, p 129) is all very well if the water is relatively pure and elevation is not enough above sea level to affect boiling point. For example, on the upper floors of Empire Stale Building, in New York City, woter open to the atmosphere boils at approximately 210 F. Cook s piece of meat in it, and the temperature drops. Throw In a handful of salt, ond up it goes, above the 212 F mark. Art Cannon Laurence Harbor, N, J. i .' < 140 RUNT OPERATION AND MAINTENANCE SECTION POWEt PWIR JUir 19)3 WHEN THE compresses like a spring to make on effective seal when the bolting is applied and then robounds when the bolt load ia relaxed, that's a genuine Flexitallic Spiral-Wound Gasket Compression-gauge types prevent crushing of the gasket despite careless pull-up. The emaslng flexibility of the Flexitallic Gasket .mokes flanged joints leak-proof even after severe thermal shock, vibration and line strain ... Each Plexitellic Gasket is engineered to meet specific conditions of thermal and physical shock, corrosion, vibration, weaving and unpredictable joint stresses. Spirally wound V-crimped plies of required metal with alternating plies of proper Alter results in a resilient gasket having characteristics of a calibrated spring. Flexitallic Gaskets are at highest efficiency when bolted up cold at a predeter mined load. For all pressure/temperature ranges from vacuum to 4000 lbs., from extreme sub-aero to 2000 F, For all standard joint assemblies. In four thicknesses for special requirements: .125*, .175', .250*, .235*. With Teflon filler for ctrroaive chemical conditions. Write us your requirements... Flexitallic Gasket Company, 8th ft Bailey Streets, Camden 2, New Jersey. Representatives in principal dtles^onsult classified telephone directory. ITO/ANNIVERSART SPIRAL-WOUND GASKETS Lanqes, pressure vessels and process equipment Not nil tplr*|.wund pikiu ora FlnlitlUt. Look for th noma FLEXITALLIC Umpwt into lha motol tpiral of omry amain* Floxitalllr Qoibot. Look for Floxlfafffo Bin* ~ It'* our oactuffvo bTur-dyrd Canadian oibetloi Alltr- Ml