RU2382940C2 - Plate expansion joint of thermal stresses for horizontal-type system water heaters - Google Patents

Abstract

FIELD: heating systems.

SUBSTANCE: invention refers to heat engineering. In horizontal-type system water heaters, instead of lens expansion joint being used at the present moment, there offered is plate expansion joint of thermal stresses for horizontal-type system water heaters in the form of annular plate; at that, it is built in tube sheet; annular plate is of variable thickness; at that, the latter is obtained by means of annular slot turned in tube sheet or by thinning its edge.

EFFECT: increasing operational life of expansion joint, possible partial compensation of thermal elongations; simple design; decrease of stresses in tube sheet.

2 dwg

Description

The invention relates to a power system, to devices for compensating for temperature extensions in network heaters of a horizontal type. Currently, the design of network heaters accepts a lens compensator (Brodov Yu.M. et al. Heat exchangers for power plants. Yekaterinburg, Sokrat Publishing House. 2003, Fig. 4.11), which has the following disadvantages:

- in lens compensators, no more than 4 lenses are installed from recommendations on stability conditions (ibid., p. 640), therefore there are increased voltages and their service life is limited (about 10 years).

- With a lens compensator, the holding force N (Fig. 1) on the tube plate is small, which leads to an increase in its bending and stresses in the tubes.

- The lens compensator is difficult to manufacture, because for each case diameter a new stamp is required. In addition, the lenses are welded in a large diameter, and special control of the seams is necessary.

The closest analogue to the claimed technical solution is a compensator in the form of an annular plate of constant thickness embedded in the housing (see SU 1562652 A1, IPC F28D 7/00, publ. 07.05.1990 g). The disadvantage of this solution is the complex design of the housing with a stepwise change in diameter.

The objective of the claimed invention is to remedy these disadvantages. This goal is achieved by the fact that the plate compensator of temperature stresses for horizontal type network heaters in the form of an annular plate is built into the tube plate, the ring plate is made of variable thickness, the latter obtained by grooving the ring groove in the tube plate or by thinning its edge.

To compensate for temperature elongations, a plate compensator 1 is proposed in the form of an annular plate of variable thickness made by grooving an annular groove 2 in the tube plate 3 (Figure 1). Dimensions a, b, c, r are selected so that the stresses in the tubes 4, the housing 5, the tube plate and the plate compensator are less than the allowable ones. In this case, under operating conditions, the body experiences tensile forces N, which are transmitted to the tube plate, reducing its bending, elongation and stress in the tubes. Accordingly, it is possible to reduce the estimated thickness of the tube plate. If the supports are not installed under the tube plate, then instead of the groove, you can thin the edges of the tube plate (Figure 2).

To study the stress-strain state of the network heater, a finite element calculation program was used, which was approved by a specialized organization in accordance with the requirements of Gostekhnadzor. The results of calculating the stresses of the options for a network heater with lens and plate compensators for the heating mode are presented in table 1.

Table 1 The stress state of the elements of the network heater with various compensators Maximum stresses (deflection) Lens Lamellar % Bending stresses in the tube plate, MPa 109 80 27 Longitudinal stresses in the body, MPa 0 fifteen - Circumferential stresses in the case, MPa 45 45 - Equivalent stresses in the case, MPa 45 40 eleven Compression stresses in tubes, MPa 26 22 fifteen Tensile stresses in tubes, MPa 58 43 26 Deflection of the tube plate, mm 3.95 2.84 28

The last column indicates the voltage drop (deflection) of the heater with a plate compensator in relation to the heater with a lens compensator. Note that despite the presence of longitudinal tensile stresses in the housing with a plate compensator (15 MPa), the equivalent Mises stress is lower, which means that the margin of safety is 11% greater.

Of particular note is a 26% reduction in tensile forces in the tubes, as large tensile forces are one of the main factors of corrosion damage to tubes, which requires their complete replacement at some CHPPs in Moscow once every 5-7 years (see the article Trukhniy AD et al. "Study of the influence of operational factors on the resource of the pipe system network turbine heaters T-250 / 300-23.5 TMZ ", Power engineering, 2001, No. 3, p. 62-64).

The proposed plate compensator significantly reduces the above disadvantages of the lens compensator and has the following advantages.

- The voltage in the compensator decreases and its service life increases.

- The possibility of partial compensation of temperature extensions leads to a decrease in the maximum stresses in the tube plate and tubes.

- More simple to manufacture, as it is built into the tube plate and does not require additional welds. Improves steam supply to tubes of heat exchange surface. Allows more rational arrangement of supports, i.e. improves the layout of the heater.

- Reduces the bending of the tube plate and the thickness required from the strength conditions.

- Reduces maximum tensile forces in the tubes, which increases their resource.

Claims (1)

A plate compensator of temperature stresses for horizontal type network heaters in the form of an annular plate, characterized in that the compensator is built into the tube plate, the annular plate is made of variable thickness, the latter obtained by grooving an annular groove in the tube plate or by thinning its edge.

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