Thermal expansion allowance

Figure 10.4 Diagram for the operation of barrel supports. The barrel slides on the supports during thermal expansion, allowing the barrel axis to maintain its elevation. If the barrel support does not allow the barrel to slide, then the discharge end of the barrel is forced down and possibly out of alignment...

Therefore, the remaining blanket thickness after compression is 6(1 — 0.84) = 0.96 mm. The thermal expansion allowance is 0.84 x 6 = 5.04 mm. The thermal expansion forces in the hning and shell are reduced to... 

Figure 5 Unstable division wall due to lack of adequate thermal expansion allowance.

The total running clearance is composed of a shaft allowance (tolerance) plus an installation allowance plus thermal expansion a allowance. The shaft allowance is about 0.005 in. on a 1.0 in.-diameter shaft and about 0.003 in. on a 10.0 in. shaft. The installation allowance is about 0.002 in. The thermal expansion allowance is calculated from the bearing temperature which has contributions from... 

The electronic configuration for an element s ground state (Table 4.1) is a shorthand representation giving the number of electrons (superscript) found in each of the allowed sublevels (s, p, d, f) above a noble gas core (indicated by brackets). In addition, values for the thermal conductivity, the electrical resistance, and the coefficient of linear thermal expansion are included. 

Positive-displacement meters are normally rated for a limited temperature range. Meters can be constmcted for high or low temperature use by adjusting the design clearance to allow for differences in the coefficient of thermal expansion of the parts. Owing to small operating clearances, filters are commonly installed before these meters to minimize seal wear and resulting loss of accuracy. 

Lithium carbonate is used to prepare Hthium aluminosiHcate glass ceramics which have low thermal coefficients of expansion, allowing use over a wide temperature range. It also finds uses in specialty glasses and enamels. 

Heat Recovery and Seed Recovery System. Although much technology developed for conventional steam plants is appHcable to heat recovery and seed recovery (HRSR) design, the HRSRhas several differences arising from MHD-specific requirements (135,136). First, the MHD diffuser, which has no counterpart ia a conventional steam plant, is iacluded as part of the steam generation system. The diffuser experiences high 30 50 W/cm heat transfer rates. Thus, it is necessary to allow for thermal expansion of the order of 10 cm (137) ia both the horizontal and vertical directions at the connection between the diffuser and the radiant furnace section of the HRSR. 

Storage and Handling. The acid should never be allowed to stand in a line completely sealed between two closed valves or check valves. Excessive pressure caused by thermal expansion of the Hquid can cause leaks or pipe mptures. AH lubricants and packing materials in contact with chlorosulfuric acid must be chemically resistant to the acid. Elanged connections are recommended over screwed fittings and flange guards should be used. 

Most coils are firmly clamped (but not welded) to supports. Supports should allow expansion but be rigid enough to prevent uncontrolled motion (see Fig. ll-29b). Nuts and bolts should be securely fastened. Reinforcement of the inlet and outlet connections through the tank wall is recommended, since bending stresses due to thermal expansion are usually high at such points. 

Interna] Insulation The practice of insulating within the vessel (as opposed to applying insulating materials on the equipment exterior) is accomplished by the use of fiber blankets and hghtweight aggregates in ceramic cements. Such construction frequently incorporates a thin, high-alloy shroud (with slip joints to allow for thermal expansion) to protect the ceramic from erosion. In many cases this design is more economical than externally insulated equipment because it allows use of less expensive lower-alloy structural materials. 

The allowable dimensional variation (the tolerance) of a polymer part can be larger than one made of metal - and specifying moulds with needlessly high tolerance raises costs greatly. This latitude is possible because of the low modulus the resilience of the components allows elastic deflections to accommodate misfitting parts. And the thermal expansion of polymers is almost ten times greater than metals there is no point in specifying dimensions to a tolerance which exceeds the thermal strains. 

In large gas turbines labyrinth seals are used in statie as well as dynamie applieations. The essentially statie funetion oeeurs where the easing parts must remain unjoined to allow for differenees in thermal expansion. At this junetion loeation, the labyrinth minimizes leakage. Dynamie labyrinth applieations for both turbines and eompressors are interstage seals, shroud seals, balanee pistons, and end seals. 

Provide flexibility to allow for thermal expansion, or contraction, of pipework and connected equipment. 

In this example it has been assumed that the service temperature is 20 °C. If this is not the case, then curves for the appropriate temperature should be used. If these are not available then a linear extrapolation between temperatures which are available is usually sufficiently accurate for most purposes. If the beam in the above example had been built-in at both ends at 20 °C, and subjected to service conditions at some other temperature, then allowance would need to be made for the thermal strains set up in the beam. These could be obtained from a knowledge of the coefficient of thermal expansion of the beam material. This type of situation is illustrated later. 

A rod of polypropylene, 10 mm in diameter, is clamped between two rigid fixed supports so that there is no stress in the rod at 20°C. If the assembly is then heated quickly to 60°C estimate the initial force on the supports and the force after 1 year. The tensile creep curves should be used and the effect of temperature may be allowed for by making a 56% shift in the creep curves at short times and a 40% shift at long times. The coefficient of thermal expansion for polypropylene is 1.35 x 10 °C in this temperature range. 

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