1、May 2005DEUTSCHE NORM English price group 10No part of this translation may be reproduced without prior permission ofDIN Deutsches Institut fr Normung e. V., Berlin. Beuth Verlag GmbH, 10772 Berlin, Germany,has the exclusive right of sale for German Standards (DIN-Normen).ICS 71.120.10!$H7“1379420ww
2、w.din.deDDIN 7080Circular borosilicate sight glasses with unlimited pressure resistance atlow temperaturesRunde Schauglasplatten aus Borosilicatglas fr Druckbeanspruchung ohne Begrenzungim TieftemperaturbereichSupersedesDIN 7080:1999-05www.beuth.deDocument comprises 14 pages Translation by DIN-Sprac
3、hendienst. In case of doubt, the German-language original should be consulted as the authoritative text. DIN 7080:2005-05 2 Foreword This standard has been prepared by Technical Committee FNCA AA 1 Anlagenteile of the Normenausschuss Chemischer Apparatebau (Process Engineering Standards Committee).
4、Annexes A and B are informative. Amendments This standard differs from DIN 7080:1999-05 as follows: a) Subclause 4.5.2 has been corrected in accordance with Corrigendum DIN 7080:1999-05. b) Subclause 4.5.4 has been corrected. c) “Permissible working pressure” has been replaced by “maximum permissibl
5、e pressure”. d) The standard has been editorially revised. Previous editions DIN 7080: 1943x-10, 1965-07, 1975-09, 1996-02, 1999-05 1 Scope This standard applies to thermally prestressed circular borosilicate sight glasses that can be continuously subjected on one side to liquid or gas pressures at
6、up to 280 C and, in exceptional circumstances, to 300 C (cf. subclause 4.3.2). The sight glasses can only be used at pressures and temperatures up to those specified if they are installed as described in clause 10. There is no limit on the use of sight glasses conforming to this standard at temperat
7、ures below ambient temperature. 2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) app
8、lies. DIN 28120, Circular sight glasses with case in main power connection DIN 28121, Circular sight glasses with case in metal to metal contact type flanged joint DIN ISO 695, Glass Resistance to attack by a boiling aqueous solution of mixed alkali Method of test and classification DIN ISO 718, Lab
9、oratory glassware Thermal shock and thermal shock endurance Test methods DIN ISO 719, Glass Hydrolytic resistance of glass grains at 98 C Method of test and classification DIN ISO 1776, Glass Resistance to attack by hydrochloric acid at 100 C Flame emission or flame atomic absorption spectrometric m
10、ethod DIN ISO 2859-1, Sampling procedures for inspection by attributes Part 1: Sampling schemes indexed by acceptance quality limit (AQL) for lot-by-lot inspection DIN ISO 7991, Glass Determination of coefficient of mean linear thermal expansion DIN 7080:2005-05 3 3 Dimensions and designation Dimens
11、ions in millimetres Key 1 Seal a Chamfered edge (cf. Table 1) Figure 1 Sight glass Designation of a circular sight glass having a diameter, d1, of 100 mm and a thickness, s, of 15 mm: Sight glass DIN 7080 100 15 The relationship between maximum permissible pressure and dimensions is shown in Table 1
12、. Table 1 Dimensions Maximum permissible pressure, in bar 8 10 16 25 40 50 Diameter d1Diameter d2Thickness s 45 32 10 12 (50) 35 10 12 (60) 45 10 12 15 63 48 10 12 15 80 65 12 15 20 100 80 15 20 25 125 100 15 20 25 150 125 20 25 30 175 150 20 25a30a 200 175 20a25 30 250 225 25a30 Only applicable to
13、containers made of enamelled steel 135 110 25 265 240 30 Diameters in brackets are not for use in new designs. aThe safety factor for these sizes is between 4,5 and 4,9. DIN 7080:2005-05 4 4 Material 4.1 General The material used shall be thermally prestressed borosilicate glass conforming to the re
14、quirements specified in subclauses 4.2 to 4.5. 4.2 Mechanical strength Unprestressed glass having a (tested) flexural tensile strength of about 40 N/mm2shall be thermally prestressed until the compressive prestress at the surface is not less than 100 N/mm2(see Annex A.1). 4.3 Thermal properties 4.3.
15、1 Mean coefficient of linear thermal expansion The mean coefficient of linear thermal expansion, (20 C, 300 C), determined as specified in DIN ISO 7991 shall not exceed 5,0 106K1. 4.3.2 Permissible working temperature The continuous working temperature of the sight glass shall normally not exceed 28
16、0 C. It should be borne in mind that, at temperatures above 280 C, a permanent decrease in the prestress is likely to occur (see Annex B 1). For example, at a working temperature of 300 C, the prestress will probably be only 90 % of the initial value after the sight glass has been in service for 300
17、 hours. However, use at temperatures between 280 C and 300 C is permissible provided suitable precautions are taken, such as protecting the sight glass with mica and restricting the cumulative working time above 280 C to a maximum of 300 hours. 4.3.3 Thermal shock resistance The thermal shock resist
18、ance of the sight glass determined as specified in DIN ISO 718 and subclause 7.4 shall be 230 C. 4.4 Chemical resistance The chemical resistance of borosilicate glass shall comply with the following: hydrolytic resistance class HBG 1 as in DIN ISO 719; acid resistance class as in DIN ISO 1776 not ex
19、ceeding 100 g Na2O/100 cm2; alkali resistance class A2 as in DIN ISO 695 (see also Annex A.2). DIN 7080:2005-05 5 4.5 Material defects 4.5.1 General Bubbles, striations, bands of striations, viscous knots and crystalline inclusions shall not exceed the values given below and shall not affect the mec
20、hanical strength or have a technically significant effect on transparency (see Annex B, 2). 4.5.2 Bubbles The diameter of spherical bubbles in the glass and the average of the length and width of oval ones shall not exceed 2 mm. Tapered bubbles are not permitted. The number of bubbles in a given siz
21、e range shall be within the limits specified in Table 2. Table 2 Permissible number of bubbles Bubble diameter, d3Permissible number of bubbles d3200 10 s 20 s 20 0,5 0,8 1 5,025,0+8,04,0+6.2 Shape tolerances and positional tolerances The maximum allowable deviations of the faces from flatness and p
22、arallelism are shown in Table 4. Table 4 Flatness and parallelism Dimensions in millimetres Diameter d1d1 100 100 200 Flatness e 0,05 0,08 0,12 0,15 Parallelism p 0,2 0,25 0,3 DIN 7080:2005-05 7 6.3 Edge tolerances The edge finishes resulting from the chamfer are shown in Table 5. Table 5 Edge toler
23、ances Dimensions in millimetres Diameter d1Edge dimensions 100 0,13,0 100 5,13,07 Testing 7.1 General The manufacturer shall test the sight glass for conformity with the specifications given in clauses 3, 4, 5 and 6 and shall confirm that the requirements have been fulfilled by marking the sight gla
24、ss as specified in clause 8. 7.2 Qualitative prestress assessment by photoelastic analysis Every sight glass shall be tested by viewing it perpendicularly to the flat glass surface. Several clearly distinguishable circular lines closed upon themselves (isochromatics) shall be visible at the rim (see
25、 Figure 3). The line pattern described indicates the presence of compressive prestress. Figure 3 Sight glass viewed in polarized light 7.3 Quantitative prestress assessment by random burst pressure tests Depending on batch size, random sample tests shall be performed on every (prestressed) batch pro
26、duced in accordance with the following scheme. DIN 7080:2005-05 8 Number of samples Batches of less than 20: 1 sample Batches of 20 to 50: 2 samples Batches of more than 50: 3 samples Procedure Samples shall be taken from every prestressed batch of finished sight glasses in accordance with the above
27、 scheme. Key 1 Plastic ring a Ground b Pressure side Figure 4 Testing device Before testing, one of the two flat sides of the sight glass shall be spoilt beforehand by grinding a central circular area having a diameter of 0,5 d1in all directions with a circular movement using wet grade 220 emery pap
28、er. In doing this, it is important to avoid anomalous individual scratches by drawing off the wet emery paper over a metal edge. To prevent a wide variation in the burst test measurements, it is advisable to work with emery paper from a single batch. After being spoilt, the sight glasses shall be bu
29、rst-tested with cold water in the device shown in Figure 4, with the side spoilt by grinding facing away from the water. The latter should have film glued to it beforehand to prevent injury due to splintering. The bursting pressure, pBG (the pressure at which the sight glass shatters), in bar, shall
30、 be measured and used to determine the bursting stress, BG, in N/mm2, for every thermally stressed sight glass using equation (1): 210 =smBGBGdCp (1) Every sample shall fulfil equation (2): BG BU = DV 100 N/mm2(2) DIN 7080:2005-05 9 where in equations (1) and (2) BUis the bursting stress of sight gl
31、asses that have not been thermally prestressed (i.e. are stress-relieved), in N/mm2; DV is the compressive prestress determined by a bursting test, in N/mm2; pBU is the pressure at which the sight glass shatters that have not been thermally prestressed (i.e. are stress-relieved), in bar; C is a calc
32、ulation coefficient (here, 0,55); dmis the mean seal diameter, in mm, calculated using equation (3): 221mddd+= ; s is the thickness as in Table 1, in mm. dmand s are to be substituted in equation (1). The value of BUin equation (2) shall be determined in the same way by burst-testing sight glasses t
33、hat have been stress-relieved by heating and slowly cooling. It can be taken as the mean of current operating tests, but no test value shall be more than six months old. The value of BUsubstituted in equation (2) shall not be less than 35 N/mm2. 7.4 Thermal shock test Random samples shall be taken f
34、rom every prestressed batch in accordance with the sampling scheme in subclause 7.3, heated to 250 C and completely immersed in flowing water at 20 C for at least one minute. The failure criterion shall be complete shattering. 7.5 Tolerance checking Tolerance checks shall be performed on random samp
35、les taken from every prestressed batch. The single sampling plans for normal inspection in accordance with DIN ISO 2859-1 test level I apply to each attribute (diameter, thickness, flatness, parallelism and edge tolerances), the acceptance quality limit (AQL) being 10. All the attributes may be test
36、ed on a single test piece. 7.6 Test report For every prestressed batch, the manufacturer shall document the results of the tests specified in subclauses 7.2 to 7.5 and, if requested to do so by the client, make them available for inspection. The test report shall include the following details: a) pr
37、estressed batch marking; b) the values of BU, BGand BG BU; c) confirmation that a photoelastic test has been performed on every sight glass in the batch; d) thermal shock test result; e) confirmation that every sight glass has passed the visual test for material defects; f) dimensional test results.
38、 DIN 7080:2005-05 10 8 Marking The following permanent markings shall appear in the area shown in Figure 5 on the smaller face, i.e. the one remote from the pressure, of every sight glass with the dimensions shown in Table 6: DIN 7080; the numerical value of the permissible pressure as specified in
39、Table 1, in bar. The following shall be marked on the cylindrical glass rim: the manufacturers logo or trademark; the prestressed batch mark in such a way as to permit clear traceability of the documented test results. The manufacturers logo or trademark (e.g. XYZ) can appear in the area shown in Fi
40、gure 5 with the dimensions shown in Table 6. Figure 5 Marking areas 9 Packaging The packaging design may be freely chosen by the manufacturer provided that every sight glass is protected against impact and scratches during transportation, including interdepartmental transportation, and storage at th
41、e clients premises. 10 Installation and safety requirements The maximum permissible pressures shown in Table 1 will only be attained if the sight glasses are installed in such a way that internal plant pressure is applied to the larger face and the sight glasses are uniformly clamped using sight gla
42、ss fittings with the dimensions, seals and numbers and sizes of screws specified in DIN 28120 or DIN 28121 if sealing takes place on the flat glass faces. Other fittings may be used if their suitability is demonstrated. Sight glasses shall be fitted only by personnel who have been given detailed ins
43、tructions on the following: how to handle sight glasses with care; DIN 7080:2005-05 11 how to clean the fittings, sight glasses, seals and shims, i.e. remove foreign bodies, such as splinters, from them, before installation; how to tighten up the fixing screws uniformly. Sight glasses removed after
44、being in service shall not be reused. Table 6 Marking dimensions Dimensions in millimetres Diameter d1a b h 45 9 (50) (60) 63 80 10 6,5 2,5 100 12 125 135 150 175 200 250 265 15 12 5 DIN 7080:2005-05 12 Annex A (informative) Explanatory notes A.1 Mechanical strength The simultaneous exposure of circ
45、ular sight glasses to severe thermal, mechanical and chemical conditions necessitates the use of heat-resistant borosilicate glasses having high mechanical strength and also the highest possible resistance to chemical attack. Such glasses can withstand the liquid or gas pressure acting on one side,
46、the clamping forces and the thermal stresses resulting from temperature differences only if their normal tensile strength is increased by thermal prestressing. The crucial quality criterion is that the compressive surface stress produced by prestressing is not less than 100 N/mm2, thereby increasing
47、 the normal flexural tensile strength of about 40 N/mm2by a factor of at least 2,5. It is essential that no tensile stresses occur after installation. The level of the surface stress resulting from the liquid or gas pressure acting on one side will then remain below the value of the compressive pres
48、tresses. Assuming a minimum value of the compressive prestress, DVzul, of 100 N/mm2and a safety factor, S, of 5, the thicknesses were calculated so as to fulfil the following inequality: zulDVm10 SpdCs (A.1) where p is the maximum permissible pressure, in bar. As the flexural tensile strength increa
49、ses, the prestressing also results in an increase in the thermal shock resistance, the value of the latter being primarily determined, for a given temperature gradient, not only by the elastic properties, but also by the heat conduction and the coefficient of expansion. The safety of sight glasses when under pressure is crucially dependent on the de
