Design allowables

Wetox uses a single-reactor vessel that is baffled to simulate multiple stages. The design allows for higher destmction efficiency at lower power input and reduced temperature. Its commercial use has been limited to one faciHty in Canada for treatment of a complex industrial waste stream. Kenox Corp. (North York, Ontario, Canada) has developed a wet oxidation reactor design (28). The system operates at 4.1—4.7 MPa (600 to 680 psi) with air, using a static mixer to achieve good dispersion of Hquid and air bubbles. 

Filtrate is collected in the underdrain system, which may be as simple as a network of perforated pipes covered by graded gravel or a complex structure with slotted nozzles or conduits that will retain the finest sand media while maintaining high flow rates. This latter design allows the use of both air and liquid for the backwashing and cleaning operations. 

The design is viable only if it can be produced economically. The choice of production and fabrication method is largely determined by the choice of material. But the production route will also be influenced by the size of the production run, and how the component will be finished and joined to other components each class of material has its own special problems here they were discussed in Chapters 14, 19, 24 and 25. The choice of material and production route will, ultimately, determine the price of the product, so a second major iteration may be required if the costing shows the price to be too high. Then a new choice of material or component design, allowing an alternative production path, may have to be considered. 

A seeond type of design allows the regenerator to operate at a pressure high enough so that the expander has a horsepower reeovery potential exeeeding the requirements of the air blower. Most new FCC units are likely designed for higher pressure. 

Since it not cost-effective to test all foreseeable bond configurations, occasionally actual parts, or specimens containing features that are very similar to specific parts, are tested to generate point-design allowables . 

This device is similar to a plate-and-frame filter press but the whole plate assembly is also housed in a tank or pressure vessel. This design allows higher pressures to... 

Natural ventilation design allows one to size the inlets, and outlets, / p based on their pressure loss characteristics, Cp, and on the airflow rate, G , required to maintain the occupied zone within desired limits. The reverse design procedure is commonly used to evaluate the airflow rate through the building given the sizes, characteristics, and locations of inlets and outlets and the heat load and characteristics of heat sources. 

The collector configuration can be single compartment or multicompart-ment. Multicompartment designs are used where it is important to maintain a relatively constant pressure drop during collector operations. Multicompartment design allows compartments to be taken off-line for cleaning or maintenance with the collector system still in operation. 

Ran Y. Kim, personal communication, 8 April 1981. For additional information, see Ran Y. Kim, On the Off-Axis and Angle-Ply Strength of Composites, in Test Methods and Design Allowables for Fibrous Composites, C. C. Chamis (Editor), Dearborn, Michigan, 2-3 October 1979, ASTM STP 734, American Society for Testing and Materials, 1981, pp. 91-108 (reprinted with permission). 

Some flame arrester designs allow in-place inspection (via a removable honsing cover plate) however, others have to be removed from the vent nozzle or in-line piping to inspect the flame arrester element. 

Internal pressure P (absolute) at failure. (A typical BLEVE is caused by a fire whose heat raises vessel pressure and reduces its wall strength. Safety-valve design allows actual pressure to rise to a value 1.21 times the safety valveopening pressure.)... 

The adjustable weir feature of many tray designs allows a standard tray to be utilized in different services by readjusting the weir height as needed. The fixed portion of the weir should never be lower than the top of the slots of the bubble caps. Depending upon service, the adjustable weir... 

Removable tube bundle permits easy internal cleaning. Design allows free expansion of tubes in high-temperature service. Needs no expansion joint if shell is used. 

The clearance pockets may be of many different shapes and arrangements (see Figures 12-6B, 12-30A, and 12-30B). Fixed volume pockets allow for fixed or set volume changes while the variable volume designs allow for changes to suit a particular operating condition or balance and are of value when the cylinder must be used in several different alternating applications. 

The dump valve is a very important feature of the positive displacement motor. The positive displacement motor does not permit fluid to flow through the motor unless the motor is rotating. Therefore, a dump valve at the top of the motor allows drilling fluid to be circulated to the annulus even if the motor is not rotating. Most dump valve designs allow the fluid to circulate to the annulus when the pressure is below a certain threshold, say below 50 psi or so. Only when the surface pump is operated does the valve close to force all fluid through the motor. 

A problem which seems to occur frequently is that contractors do not give sufficient thought to allowance for maintenance in the future. To install plant without means of maintaining it is bad practice and should be avoided. The plant engineer should make sure that the design allows for adequate maintenance. This item comes under the scope of the clerk of works to interpret the design. 

Some of the recently developed high-performance EP soluble oils have a cutting performance that almost matches that of additive-type neat oils, and they are particularly suitable for demanding operations in machine tools whose design allows the use of water-based fluids. 

In many assemblies the clearances around fasteners, the degrees of failure or yield in adhesives, and warpage or creep will tend to relieve the thermal stress. As with metal-to-metal attachments having different CLTEs, proper design allows for such temperature changes, especially with large parts that might be subject to wide temperature variations. 

With the application of plastics in combination with other materials, the coefficient of expansion plays an important role in making design allowances for expansions (also contractions) of various materials at different temperatures so that satisfactory functions of products are ensured. 

Design allowable Statistically defined material property allowable strengths, usually referring to stress and/or strain. 

A technological variation that permits a continuous process is the polymer extrusion through a spinneret of the desired design allowing crystallization inside the spinneret26. In this way, the cold extrusion stage used in Porter s method can be avoided. The degree... 

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