Hot section wash

Find a way to overcome the constraint while still maintaining the areas. This is often possible by using indirect heat transfer between the two areas. The simplest option is via the existing utility system. For example, rather than have a direct match between two streams, one can perhaps generate steam to be fed into the steam mains and the other use steam from the same mains. The utility system then acts as a buffer between the two areas. Another possibility might be to use a heat transfer medium such as a hot oil which circulates between the two streams being matched. To maintain operational independence, a standby heater and cooler supplied by utilities is needed in the hot oil circuit such that if either area is not operational, utilities could substitute heat recovery for short periods.  [c.184]

Stir the mixture and reflux gently until praetieally all the permanganate colour has disappeared (about 2 hours). At this point add 37 5 g. more of potassium permanganate and reflux the mixture again until the permanganate eolour disappears (about 2 hours) the eolour of the solution can easily be seen by removing the flame and stopping the refluxing. Finally, add a seeond 37 -5 g. of potassium permanganate and eontinue refluxing until the permanganate colour has disappeared (about 2-4 hours) (1). Steam distil the mixture (Fig. II, 41,1) to remove unreacted o-chlorotoluene (about 12 g.). Filter the hot contents of the flask from the manganese dioxide with suction (2) and wash with two 125 ml. portions of hot water. Concentrate the filtrate to about 800 ml. (Fig. II, 37, 1) (3), and precipitate the o-chlorobenzoic acid by cautiously adding 75 ml. of concentrated hydrochloric acid with continual stirring. When cold, filter with suction, wash the acid with cold water, and dry at 100°. The yield of o-chlorobenzoic acid, m.p. 138-139°, is 42 g. Upon recrystallisation from hot water or from toluene (ca. 4 ml. per gram), the m.p. is raised to 139-140°.  [c.759]

More flexibility is obtained with apphed equipment (Fig. 6), which is normally used to condition a relatively large area of a plant. This is usually part of a "field erected" system. In apphed systems, outdoor air for ventilation or cooling (economizer cycle) is drawn through a preconditioning or preheat coil and mixed with air returned from the conditioned space. Dampers regulate the relative amounts of outdoor and recycled air for temperature control. The air is filtered before passing into the conditioning section which contains cooling and dehumidifying coils, air washers for humidity control, and heating cods. Bypass of return air may be included for temperature control. The refrigerating effect is provided in one of several ways. WeU water may be employed if avadable in sufficient quahty and quantity and at a suitable temperature. More commonly, refrigerating machines or "chillers" are used. In small systems, reciprocating compressors are employed and the refrigerant maybe directly admitted to the cooling cod. In larger apphcations, water is chilled and circulated through the central station unit. For apphcations in excess of 350 kW (1.2 x 10 Btu/h), reciprocating compressors may be replaced by centrifugal systems. Most systems are electrically powered however, steam or gas turbines are used occasionally. Absorption chillers are frequently used when a suitable supply of "waste" heat is avadable. Low pressure steam, hot water, and process streams may provide the motive force. Solar heated water is also finding apphcation (9) (see Solarenergy).  [c.361]

The project, code named Genesis, did not involve basic research into new solvents for cellulose so much as screening the known solvents against criteria felt to be important for the ceUulosic fiber process of the future. The solvent chosen had to be recyclable at a very high level of efficiency, and hence as near to totaUy containable in the process as possible. It had to be safe to work with and safe in the environment in the event of any losses. It had to be able to dissolve ceUulose completely without reacting with it or degrading it, and the resulting process had to be less energy intensive than the viscose route, which was already proven to be less energy intensive than the synthetics in an independent study (97). It was especiaUy important to choose a system which, like the melt-spun synthetics, would not require costiy gaseous or Uquid effluent treatment systems. FinaUy, the process would be capable of making good textile fibers to maintain, or even extend, the ceUulosics share of the global market against fierce competition from melt-spun synthetics based on cheap but nonrenewable oil reserves.  [c.352]

RoU presses consist of the frame, the two roUs that do the pressing, and the associated bearings, reduction gear, and fixed or variable-speed drive (Fig. 9). Spacers between bearing housings prevent roU contact and aUow adjustment of roU spacing. The frame of the press is designed so that aU forces are absorbed internally. The roUs are forced together by a hydrauHc system which may incorporate a safety valve to prevent overpressure if foreign material intmdes between the roU faces. The roUs consist of a continuous roU shaft, the roU body, and attached mol ding equipment. The mol ding surface may be either soHd or divided into segments. Segmented roUs are preferred for hot briquetting, as the thermal expansion of the equipment can be controUed more easily. Segmented roUs can be made from harder materials more resistant to wear than can one-piece roUs.  [c.116]

In summation, the two-angle interval scattering method can provide CBC, RDW, PCT, and HDW. This two-angle interval method has been incorporated into the Technicon H 1 system which provides RBC, HCT, MCV, PLT, MPV, RDW, PDW, PCT, and HDW.  [c.403]

The flashed steam method is less efficient and its requirements for steam properties—cleanliness, high temperature, and high pressure— are usually unavailable in most geothermal fields. The situation is different with the binary cycle system, which is quite efficient and widely used. This wet system involves the transfer of heat from the hot well stream into a more manageable boiling fluid to generate power through a turboexpander.  [c.136]

The performance analysis of the new generation of gas turbines are complex and presents new problems, which have to be addressed. The new units operate at very high turbine firing temperatures. Thus, variation in this firing temperature significantly affects the performance and life of the components in the hot section of the turbine. The compressor pressure ratio is high which leads to a very narrow operation margin, thus making the turbine very susceptible to compressor fouling. The turbines are also very sensitive to backpressure exerted on them when used in combined cycle or cogeneration duty. The pressure drop through the air filter also results in major deterioration of the performance of the turbine.  [c.692]

Design of inorganic absorbers quite often involves a system whose major parameters are well defined such as system film control, mass transfer coefficient equations, etc. Ludwig gives design data for certain well-known systems sueh as NH3-Air-H20, CI2-H2O, COi in alkaline solutions, etc. Likewise, data for commercially available packings is well documented such as packing factors, HETP, HTU, etc.  [c.101]

In his 1878 abstract, Gibbs formulated two alternative but equivalent forms of the criterion for thermodynamic equilibrium For the equilibrium of any isolated system it is necessary and sufficient that in all possible variations of the state of the system which do not alter its energy (entropy), the variation of its entropy (energy) shall either vanish or be negative (positive) . Gibbs moved on immediately to apply this criterion to the issue of chemical equilibrium between phases. According to Klein, the result of this work was described by Wilhelm Ostwald as determining the form and content of chemistry for a century to come, and by Henri Le Chatelier as comparable in its importance for chemistry with that of Antoine Lavoisier (the co-discoverer of oxygen). From his criterion, Gibbs derived a corollary of general validity, the phase rule, formulated as 8 = n -1- 2 - r. This specifies the number of independent variations 8 (usually called degrees of freedom ) in a system of r coexistent phases containing n independent chemical components. The phase rule, when at last it became widely known, had a definitive effect on the understanding and determination of phase, or equilibrium, diagrams.  [c.76]

Quality improvement (innovation), is about raising standards and setting a new level. New standards are created through a process that starts at a feasibility stage and progresses through research and development to result in a new standard, proven for repeatable applications. Such standards result from innovations in technology, marketing, and management. A typical quality improvement might be to redesign a range of products to increase the achieved reliability from 1 failure every 5,000 hours to 1 failure every 100,000 hours. Another example might be to improve the efficiency of the service organization so as to reduce the guaranteed call-out time from the specified 36 hours to 12 hours. A further example might be to design and install a quality system which complies with ISO 9001 in a company that had no formal quality system.  [c.35]

The case study described here concerns a human factors audit of a computer controlled process system which was being introduced in a distillation imit of a chemical plant. The unit was in transition from replacing its pneumatic panel instrumentation with the new system. However, control had not yet been transferred and the staff were still using the panel instrumentation. The role of the project was to evaluate a preliminary design of the computer-based display system and provide recommendations for future development.  [c.330]

The third region is one for which the Q values are of the order of chemical bond energies the r values become quite large, indicating that desorption may be slow, and F as computed by Eq. XVII-3 becomes preposterously large. Such values are evidently meaningless, and the difficulty lies in the assumption embodied in Eq. XVII-3 that the collision frequency gives the number of molecules hitting and sticking to the surface. As monolayer coverage is approached, it is to be expected that more and more impinging molecules will hit occupied areas and rebound without experiencing the full Q value. One way of correcting for this effect is taken up in the next section, which deals with the Langmuir adsorption equation.  [c.603]

After returning to the CrossFirc Commander the eoinbincd search can be started. First the fact retrieval is performed. Then the given generic formula is searched. Hereby the specified query options, which can be recognised as check boxes in Figure 5-19 in the right-hand column besides the display of the retrieved structure, neglect multicomponent systems, isotopic and charged species, radicals, and ring annelations. Finally, both intermediate results are automatically combined by means of the Boolean AND operator and the final result is offered for display. In the present update 28 substances result after about 30 seconds. Because, in general, the entries can be veiy extensive, it is recommended to use the display format Hit only , which displays only the identification data together with that information which fulfills the given logical requirement. How to select display formats is described at the end of Example 2 (Section 5,7.2).  [c.252]

Place 20 -4 g. (20 ml.) of aniline in a 250 ml. conical or round-bottomed flask and cautiously add 74 g. (40 ml.) of concentrated sulphuric acid in small portions swirl the mixture gently during the addition and keep it cool by occasionally immersing the flask in cold water. Support the flask in an oil bath, and heat the mixture at 180-190° (fume cupboard) for about 5 hours (1). The sulphonation is complete when a test portion (2 drops) is completely dissolved by 3-4 ml. of ca. 2N sodium hydroxide solution without leaving the solution cloudy. Allow the product to cool to about 50° and pour it carefully with stirring into 400 g. of cold water or of crushed ice. Allow to stand for 10 minutes, and collect the precipitated sulphanilic acid on a Buchner funnel, wash it well with water, and drain. Dissolve the crude sulphanilic acid in the minimum volume of boiling water (450-500 ml.) if the resulting solution is coloured, add about 4 g. of decolourising carbon and boil for 10-15 minutes. Filter through a hot water funnel (Fig. 77, 7, 6) or through a Buchner funnel and flask which have been preheated by the filtration of boiling distilled water. Upon cooling, the sulphanilic acid dihydrate separates in colourless crystals. When the filtrate is quite cold, filter the crystals with suction, wash with about 10 ml. of cold water, and press thoroughly with a wide glass stopper. Dry between sheets of special absorbent paper or in a desiccator containing anhydrous calcium chloride in the latter case, the water of crystallisation (and hence the crystalline form) is lost. The yield of sulphanilic acid is 20-22 g. The substance does not melt sharply and no attempt should be made to determine the melting point the crystals are efflorescent.  [c.586]

Surround the reducing solution in the 1-Utre beaker (which is equipped with a mechanical stirrer) with a bath of crushed ice so that the temperature of the solution is about 10°. Attach, by means of a short length of rubber pressure tubing, to the stem of a dropping funnel a glass tube which dips well below the surface of the solution and is bent upwards at the end and constricted so that the opening is about 2 mm. (this arrangement ensures that the diazonium solution reacts with the ammoniacal solution in the beaker and prevents the latter rising in the stem of the funnel). Place about 45 ml. of the cold diazonium solution in the funnel and add it at the rate of about 10 ml. per minute whilst the mixture is stirred. Add the remainder of the diazonium solution at the same rate continue the stirring for 5 minutes after the addition is complete. Heat the solution rapidly to boiling and carefully acidify with 125 ml. of concentrated hydrochloric acid the diphenic acid precipitates as pale brown crystals. Allow to stand overnight and filter with suction wash the crude diphenic acid with about 25 ml. of cold water. Suspend the crude acid in 100 ml. of water and add 20 g. of sofid sodium bicarbonate. Filter the resulting solution by gravity, and then boil with about 0 5 g. of decolourising carbon filter and acidify the filtrate while stiU hot with excess of dilute hydrochloric acid (1 1). Collect the precipitated diphenic acid on a Buchner funnel, wash it with 20 ml. of cold water, and dry at 100°, The yield of diphenic acid is 18 g. it melts at 227-228° and usually possesses a fight cream colour.  [c.617]

Reduction with stannous chloride. a-Amino-P-naphthol hydrochloride. Into a 350 or 500 ml. round-bottomed flask, provided with a reflux condenser and containing 100 ml. of methylated spirit, place the crude phenyl-azo-p-naplithol reserved above and boU gently until most of the azo compound has dissolved. Meanwhile dissolve 20 g. of a good grade of stannous chloride in 60 ml. of concentrated hydrochloric acid (warming is necessary to produce a clear solution), add this to the contents of the flask and boU under reflux for a further 30 minutes. All the azo compound dissolves rapidly and is reduced by the stannous chloride the solution acquires a very pale brown colour. Decant the solution to a beaker and cool in ice the a-amino- -naphthol hydrochloride separates as fine greyish-white crystals. Filter with suction, and wash with dilute hydrochloric acid (1 4). Recrystalhse from the minimum volume of hot water which contains a few drops of staimous chloride solution in an equal weight of hydrochloric acid (this reduces atmospheric oxidation), cool the clear solution in an ice bath, and collect the recrystalfised product as before. Dry the colourless crystals in a desiccator. The yield is 3-4 g. The compound will remain colourless, or nearly so, if protected from light during storage.  [c.623]

Method 1. In a 500 ml. round-bottomed flask, place a solution of 35 g, of potassium hydroxide in 70 ml. of water, then add 70 g. (87 ml.) of rectified spirit and 35 g. of recrystaUised benzil (preceding Section). A deep bluish-black solution is produced. Fit a reflux condenser to the flask and boil the mixture on a water bath for 10-15 minutes. Pour the contents of the flask into a porcelain dish and allow to cool, preferably overnight. The potassium salt of benzilic acid crystallises out. Filter off the crystals at the pump and wash with a little ice-cold alcohol. Dissolve the potassium salt in about 350 ml. of water, and add 1 ml. of concentrated hydrochloric acid from a burette slowly and with stirring. The precipitate thus produced is coloured red-brown and is somewhat sticky. Filter this off the filtrate should be nearly colourless. Continue the addition of hydrochloric acid with stirring until the solution is acid to Congo red paper. Filter off the benzilic acid with suction, wash it thoroughly with cold water until free from chlorides, and allow to dry. The yield of crude benzilic acid, which is usually light pink or yellow in colour, is 30 g. Purify the product either by recrystallisation from hot benzene (about 6 ml. per gram) or from hot water with the use of a little decolourising carbon. The coloured and sticky material obtained by the first precipitation may be recrystallised from hot water with the addition of a little decolourising carbon, and a further 1-2 g. obtained. Pure benzilic acid has m.p. 150°,  [c.715]

Method 2. Dissolve 10 g. of finely powdered, pure anthracene in 110-120 ml. of boihng glacial acetic acid contained in a 500 ml. round-bottomed flask provided with a reflux condenser. Prepare a solution of 20 g. of chromium trioxide in 15 ml. of water and then add 50-75 ml. of glacial acetic acid. Add the chromium trioxide solution slowly (during 1 hour) to the boiling anthracene solution by means of a separatory funnel fitted into the top of the condenser with a grooved cork boil for a further 15 minutes. Allow the deep green solution to cool and pour it into 500 ml, of cold water. Filter the crude anthraquinone by gentle suction, wash with a little hot water, then with a hot dilute solution of sodium hydroxide and finally with cold water until the washings are colourless, and drain well. RecrystaUise from glacial acetic acid as in Method 1. The yield is 11 g., m.p. 286°, Alternatively, dry the crude product in the steam oven, and sublime it from a smaU evaporating dish (compare Fig. II, 45, ) beautiful yeUow needles are obtained.  [c.740]

Dissolve 100 g. (104 -5 ml.) of purified p-picohne (Section 11,47,2S) in 1 litre of water and oxidise it with 450 g. of potassium permanganate follow the experimental details given under Picolinic Acid (preceding Section). Wash the manganese dioxide cake with four 500 ml. portions of water evaporate the combined filtrate and washings to about 1250 ml. Adjust the pH to 3-4 (the isoelectric point) with the aid of B.D.H. narrow-range indicator paper 120-130 ml. of concentrated hydrochloric acid are required. Allow to cool overnight, collect the voluminous precipitate of nicotinic acid by suction filtration, wash with three 50 ml. portions of cold water, and dry at 90-100°. Concentrate the filtrate to about 650 ml. and cool slowly to 5° and so obtain a second crop of nicotinic acid the purpose of the slow coohng is to reduce the contamination by potassium chloride. The first crop of acid weighs 90 g. and has a purity of about 90 per cent. (1) the second crop weighs 10 g. and the purity is about 80 per cent. Recrystalhse from hot water (2) and dry at 100° the yield of pure nicotinic acid, m.p. 235°, from 90 g. of the crude acid is 67 g. A further quantity may be obtained by concentrating the mother liquor.  [c.848]

Uramil. In a 3-litre flask place 38 g. of anhydrous nitrobarbituric acid and 300 ml. of concentrated hydrochloric acid heat the mixture on a boiling water bath. Add 125 g. of granulated tin and 200 ml. of concentrated hydrochloric acid over a period of about 30 minutes continue the heating until the yellow colour, due to the nitro compound, in the hquid is no longer visible. Introduce 1500 ml. more of concentrated hydrochloric acid and heat until all the white. solid dissolves add a httle decolourising charcoal, and filter the hot mixture through a sintered glass funnel. Keep the filtrate at 0° overnight, collect the uramil by filtration with suction, wash well with dilute hydrochloric acid and finally with water. Concentrate the filtrate under reduced pressure (water pump) to about 500 ml. and cool overnight. Collect the second crop of uramil, wash it as before, and combine it with the first product. Dry in a vacuum desiccator over concentrated sulphuric acid. The resulting uramil (23 g.) is a fine white powder it does not melt below 400°, and becomes pink to red on standing, particularly if ammonia is present in the air.  [c.851]

Azlactone of a-benzoylaminocinnamic acid. Place a mi.xture of 27 g. (26 ml.) of redistilled benzaldehyde, 45 g. of Mppuric acid (Section IV,54), 77 g. (71-5) ml. of acetic anhydride and 20-5 g. of anhydrous sodium acetate in a 500 ml. conical flask and heat on an electric hot plate with constant shaking. As soon as the mixture has liquefied completely, transfer the flask to a water bath and heat for 2 hours. Then add 100 ml. of alcohol slowly to the contents of the flask, allow the mixture to stand overnight, filter the crystalline product with suction, wash with two 25 ml. portions of ice-cold alcohol and then wash with two 25 ml. portions of boiling water dry at 100°. The yield of almost pure azlactone, m.p. 165-166°, is 40 g. Recrystallisation from benzene raises the m.p. to 167-168°.  [c.910]

The purified commercial di-n-butyl d-tartrate, m.p. 22°, may be used. It may be prepared by using the procedure described under i o-propyl lactate (Section 111,102). Place a mixture of 75 g. of d-tartaric acid, 10 g. of Zeo-Karb 225/H, 110 g. (136 ml.) of redistilled n-butyl alcohol and 150 ml. of sodium-dried benzene in a 1-litre three-necked flask equipped with a mercury-sealed stirrer, a double surface condenser and an automatic water separator (see Fig. Ill, 126,1). Reflux the mixture with stirring for 10 hours about 21 ml. of water collect in the water separator. FUter off the ion-exchange resin at the pump and wash it with two 30-40 ml. portions of hot benzene. Wash the combined filtrate and washings with two 75 ml. portions of saturated sodium bicarbonate solution, followed by lOu ml. of water, and dry over anhydrous magnesium sulphate. Remove the benzene by distillation under reduced pressure (water pump) and finally distil the residue. Collect the di-n-butyl d-tartrate at 150°/1 5 mm. The yield is 90 g.  [c.952]

Commercial o-clilorobenzoic acid may be purified in the following niannor. Dissolve 60 g. of the technical acid in 200 ml. of hot water containing 20 g. of sodium carbonate, d 10 g. of decolourising carbon, boil for 15 minutes, and filter at the pump. Add the filtrate with stirring to 31 ml. of concentrated hydrochloric acid diluted with an equal volume of water. Collect the purified acid with suction, wash it with a little cold water, and dry at 100°.  [c.991]

Derwent World Patents Index (WPI) and WPI Markush. Derwent s in-depth documentation services began in 1963 with the FARMDOC service for pharmaceuticals, followed by AGDOC for agricultural chemicals. PLASDOC covering polymers began in 1966. FARMDOC and AGDOC featured a chemical fragmentation code searched on IBM punch cards or corresponding computer tapes. A fragmentation code developed by the U.S. PTO was adopted by Derwent to handle steroid molecules. PLASDOC had its own punch card code. The code systems were severely limited because of the restrictions placed by the 960 positions on the punch card there was considerable grouping of concepts that might better have been separated, as well as overcoding of alternatives on the same card rather than on separate cards. These limitations produced false retrieval, but such false retrieval was not a severe problem in the early days of the system, which contained modest numbers of references in the databases. Besides the punch code system, these early databases featured a manual code system for the manual searching of classified sets of documentation abstracts on search cards.  [c.61]

The discovery that histamine receptors, just like adrenergic and cholinergic receptors, may be divided into subtypes H and H2, combined with the recognition that the bronchial receptors were of the type, set the stage for a newer generation of antihistamines. Clinical investigation in the late 1970s of the H -antihistarnines clemastine (21) (129) and chlorpheniramine (22) (130,131), shown in Table 4, revealed that these agents had a bronchodilating effect and provided some protection against exercise-induced asthma. But the side effects, induced at H -receptors in the central nervous system which produced sedation and at cholinergic receptors, limited the maximal doses that could be given. These dmgs were not useful as antiasthmatic agents.  [c.444]

Atactic polypropylene (APP) is a by-product of the crystalline or high density polypropylene manufacturing process (see Olefin POLYMERS). Its use as a modifier for asphalt was developed in Italy. The addition of APP to asphalt gives a uniform matrix that increases the flexibiUty of the asphalt at both high and low temperature and improves water penetration resistance as well as ultraviolet resistance. The addition of between 20 and 35% APP increases the softening point of the asphalt mixture to about 149°C, which is high enough to prevent sHppage on the rooftop. This higher temperature does not allow fusion between the APP coating and the mopping asphalt to take place or a bond to develop between the mopping asphalt and the membrane. Eor this reason, APP membranes are generally installed using a gas-fired torch to melt the thick back coating of APP-modifted asphalt thus it is used as the mopping or interply asphalt. This apphcation technique is valuable when it is difficult to get hot asphalt to the rooftop. Even though the ultraviolet resistance is improved over nonpolymer modified asphalt, most manufacturers recommend that APP membranes have a coating or other protective surface apphed to protect the bitumen from ultraviolet radiation damage. Most APP membranes use a nonwoven polyester mat as the reinforcement in the membrane. This increases the flexibihty of the sheet. Also, APP membrane systems generally include a basesheet or other undedayment sheet, making them a minimum of a two-ply system, which provides a second layer of protection against leaks.  [c.321]

Temperature and Mechanical Action. Absorption of external thermal or mechanical energy by a detersive system influences the rate and extent of soil removal. Raisiag the temperature generally iacreases the cleaning rate and, therefore, the amount of soil removed duiing any fixed-time laundeiing cycle. The effect is only strong at two critical temperatures one is the temperature where the fatty soil ia the system Hquefies. As temperature iacreases through this region, the detergency iacreases markedly. Typical curves of detergeacy versus temperature are showa ia Figure 2 (48). The secoad critical temperature is the boiling poiat. Boiling greatly iacreases detergeacy because of the localized mechanical action of steam bubbles forming, expanding, and breaking away at the sofld— Hquid interfaces. However, in the United States, boiling effects are never encountered in home washing machines. U.S. laundry wash temperatures have declined to an average wash temperature of about 35°C, and the average hot water wash temp is only 54°C. From 1970 to 1988 hot water wash declined from 48 to 20% of washes (49). Temperature effects are also important with certain detergent additives. Thus the efficacy of certain bleaches and enzymes is markedly reduced at the low wash temperatures now popular. These effects emphasize the problems inherent in the current trend to lower wash temperatures.  [c.531]

Upon completion of the list of causes, the team addresses the potential consequences from cadi of the listed causes to any node in the system. I hat is, the evaluation considers con.sequences arising anywhere in the system, which can effect the subject deviation in the subject node. These consequences include potential operating problems and safety concerns.  [c.90]

From the standpoint of inspection to see if the stiffener is properly made, it is relatively easy to inspect the sandwich-blade stiffener, but the hat-shaped stiffener is difficult to inspect on the inside. We must get some kind of device to peer inside. If we were going to try to inspect from the outside, about all we can tell from ultrasonics is how well the flanges are bonded to the base of the panel. Typically, we must have some kind of a mold around the stiffener, and we must remove that mold. A mold is necessary so that during the cure process when the stiffener is under pressure it does not collapse. As a matter of fact, there might be instances in which, for the sake of simplified manufacturing process, we might want to leave a core or mold of some kind inside the stiffener simply because it is too difficult to get out. That situation is especially true for intersecting stiffeners at 90° or some other angle to one another where there is an intersection region where webs of one stiffener pass through and intersect webs of another stiffener. We do not have the freedom to cut the stiffener sides and remove whatever core exists inside to prevent the stiffener from collapsing during curing. If we do leave the core inside, we cannot inspect the stiffener from the inside. Thus, inspection is a much more involved operation for the hat-section stiffener than for the sandwich-blade stiffener.  [c.406]

From the standpoint of inspection to see if the stiffener is properly made, it is relatively easy to inspect the sandwich-blade stiffener, but the hat-shaped stiffener is difficult to inspect on the inside. We must get some kind of device to peer inside. If we were going to try to inspect from the outside, about all we can tell from ultrasonics is how well the flanges are bonded to the base of the panel. Typically, we must have some kind of a mold around the stiffener, and we must remove that mold. A mold is necessary so that during the cure process when the stiffener is under pressure it does not collapse. As a matter of fact, there might be instances in which, for the sake of simplified manufacturing process, we might want to leave a core or mold of some kind inside the stiffener simply because it is too difficult to get out. That situation is especially true for intersecting stiffeners at 90° or some other angle to one another where there is an intersection region where webs of one stiffener pass through and intersect webs of another stiffener. We do not have the freedom to cut the stiffener sides and remove whatever core exists inside to prevent the stiffener from collapsing during curing. If we do leave the core inside, we cannot inspect the stiffener from the inside. Thus, inspection is a much more involved operation for the hat-section stiffener than for the sandwich-blade stiffener.  [c.406]

Air conditioning systems are categorized by the method used to control cooling or heating in a conditioned space. They are further described based on their terminal cooling or heating media. The most common type for cnnliiig is the refrigerant based all-air system which uses a refrigeration cycle to transfer heat from indoor air to outdoor air with heat exchangers commonly called coils. Most heating systems in residences and small buildings are all-air-using fossil-fueled furnaces. Hydronic (hot water) or steam heating systems also are common, particularly in large buildings. Many systems employ unitary equipment—that is, they consist of  [c.23]

See pages that mention the term Hot section wash : [c.454]    [c.400]    [c.569]    [c.760]    [c.776]    [c.824]    [c.150]    [c.24]    [c.439]    [c.304]    [c.781]    [c.15]    [c.742]    [c.150]    [c.16]    [c.126]    [c.261]   
Gas turbine engineering handbook (2002) -- [ c.0 ]