1、BRITISH STANDARD BS 3423:1986 Recommendations for Design of glass vacuum vessels (including desiccators) for laboratory use UDC 666.172.7:533.59:614.8:542.47 + 542.67BS3423:1986 This British Standard, having been prepared under the directionof the Laboratory Apparatus Standards Committee, was publis
2、hed underthe authorityof the Board ofBSI andcomes into effect on 30 September 1986 BSI 08-1999 First published February 1962 First revision September 1986 The following BSI references relate to the work on this standard: Committee reference LBC/25 Draft for comment 84/51100 DC ISBN 0 580 14150 0 Com
3、mittees responsible for this British Standard The preparation of this British Standard was entrusted by the Laboratory Apparatus Standards Committee (LBC/-) to Technical Committee LBC/25, upon which the following bodies were represented: British Laboratory Ware Association British Lampblown Scientif
4、ic Glassware Manufacturers Association Ltd. Chemical Industries Association Department of Health and Social Security Department of Trade and Industry (Laboratory of the Government Chemist) Glass Manufacturers Federation Institute of Medical Laboratory Sciences Institute of Science Technology Royal S
5、ociety of Chemistry Amendments issued since publication Amd. No. Date of issue CommentsBS3423:1986 BSI 08-1999 i Contents Page Committees responsible Inside front cover Foreword ii 1 Scope 1 2 Glass quality 1 3 Design features 1 4 Symbols 1 5 Base thickness (design features A and F) 2 6 Body thickne
6、ss and shape (design feature B) 3 7 Step thickness and radius of curvature (design feature C) 3 8 Flange thickness and shape (design feature D) 4 9 Lid thickness and curvature (design feature E) 6 10 Opening for vacuum (design feature F) 7 11 Grinding of flanges (design feature G) 8 12 Elastomeric j
7、oint seals (design feature H) 8 13 Tests 8 14 Size description of desiccators 8 Appendix A Equations for calculation of minimum thickness of lids based on stress considerations only 9 Appendix B Hydraulic external pressure tests 10 Appendix C Polarized light test 10 Appendix D Test for ground flat f
8、langes 12 Figure 1 Common design of vacuum desiccator with flat ground flange 1 Figure 2 Common design of vacuum desiccator with grooved flange 1 Figure 3 Base with radiused corners 3 Figure 4 Base with sharp corners 3 Figure 5 Methods of reinforcing radiused corners 3 Figure 6 Curved side-wall with
9、 subsidiary curve at corner 4 Figure 7 Form of step 4 Figure 8 Alternative flange designs 5 Figure 9 Part-spherical form lid 6 Figure 10 Hemispherical form lid 7 Figure 11 Semi-ellipsoidal form lid 7 Figure 12 Dished form lid 7 Figure 13 Part-spherical form lid 7 Figure 14 Factor k 4for hemispherica
10、l and semi-ellipsoidal lids 9 Figure 15 Hydraulic test rig 10 Figure 16 Tensometer for polarized light test 11 Figure 17 Apparatus for testing ground flat flanges 13 Table 1 Letter symbols 2 Table 2 Minimum side-wall thickness 3 Table 3 Minimum step thickness t e ; for = 55 calculated using equation
11、 3 4 Table 4 Examples of flange thickness t fcalculated using equation 4 6 Table 5 Examples of lid and flange thicknesses t fcalculated using equation 5 6 Table 6 Minimum safe-handling thicknesses (t eminimum) for lids 7 Publications referred to Inside back coverBS3423:1986 ii BSI 08-1999 Foreword T
12、his British Standard has been prepared under the direction of the Laboratory Apparatus Standards Committee and was first published in 1962 as “Recommendations for the design of glass vacuum desiccators”. This revision has been prepared to cover a wider range of glass vacuum vessels for laboratory us
13、e because the same basic principles are relevant to all such vessels. There has been a reduction in the number of different types of vacuum desiccators commercially available and, therefore, a number of the figures in the earlier edition have not been included in this revision; an O-ring type of sea
14、l for the lids of desiccators and similar vessels has been introduced. In this standard, glass vacuum vessels are considered as pressure vessels subject to an external pressure of 1 atm. Suitable structures and thicknesses of glass are recommended for each part of the vessel. The standard gives equa
15、tions which should be applied in calculating the thickness of glass vacuum vessels for laboratory use where the external pressure will not exceed 1 atm. The calculated glass thickness, however, is sometimes less than that considered adequate for ordinary handling hazards; in these cases, the recomme
16、nded minimum thicknesses given in this standard take these hazards into account and are greater than the calculated values. Appendix A gives equations for calculation of minimum thickness. Appendix B to Appendix D describe methods for the hydraulic testing of glass vacuum vessels, for examining them
17、 in polarized light under a strain-viewer and for testing the grinding of the flanges. It is not at present the purpose of this British Standard to specify a range of sizes of desiccators, and the sizes mentioned in the tables are given merely by way of example. The size of desiccators is designated
18、 by the internal diameter measured at the flange, which gives a better indication of the usable space compared with the practice in some countries of designating by the outside diameter of the flange. The use of a safety cage to contain the glass vacuum vessel is strongly recommended. At the time of
19、 publication of this British Standard, no corresponding International Standard exists. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of i
20、tself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, pages i and ii, pages1 to 14, an inside back cover and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will be
21、 indicated in the amendment table on the inside front cover.BS3423:1986 BSI 08-1999 1 1 Scope This British Standard recommends minimum thicknesses and safety considerations for the design and construction of glass vessels for use under vacuum in a laboratory, including desiccators and filter flasks.
22、 Other configurations of desiccating vessels which are not for use under vacuum are outside the scope of this standard. NOTEThe titles of the publications referred to in this standard are listed on the inside back cover. 2 Glass quality The vessels should be free from defects that will weaken the gl
23、ass, and substantially free from blisters, seed, striae, cord, etc. They should be well annealed. 3 Design features Figure 1 and Figure 2 indicate by the letters A to H the features included in this standard for vacuum vessels in common use. Recommendations for these features are given in the clause
24、s listed below. 4 Symbols The letter symbols used in this standard together with the quantities to which they refer are listed in Table 1. Feature Clause A Flat base with radiused or sharp lower corners 5 B Lower and upper parts of side-wall 6 C Step to carry perforated plate 7 D Flange of body or l
25、id 8 E Lid form 9 F Opening for vacuum 10 G Flange, ground finish 8 H Flange, grooved with elastomeric insert 8 Figure 1 Common design of vacuum desiccator with flat ground flange Figure 2 Common design of vacuum desiccator with grooved flangeBS3423:1986 2 BSI 08-1999 Table 1 Letter symbols 5 Base t
26、hickness (design features A and F) 5.1 Flat base with radiused or sharp lower corners 5.1.1 Recommendations. The minimum thickness t eof a flat base should be not less than the larger of the two values given by the following equations. where In the construction shown in Figure 3, where the internal
27、corner radius r is greater than 3t e , k 1is derived from the following equation. In the construction shown in Figure 4, where the internal corner radius r is less than 3t e , k 1is given the value 5.25. It is recommended that, for desiccator bases, r should be not less than t e . NOTEEquation 1, wi
28、th k 1= 5.25, is applicable in the calculation of the minimum thickness of flat plates. 5.1.2 Calculations of minimum values of t e . Using equation 1, with an example of a 150 mm diameter base, of different corner radii, where t e= 0.05d i , the following values are obtained. a) Base with radiused
29、corners r = 32 mm, k 1= 8.0, t e= 6.5 mm r = 25 mm, k 1= 6.6, t e= 7.4 mm Symbol Unit Quantity p kPa Maximum pressure differential (i.e. excess of external pressure over internal pressure) to which the vessel is subjected when in use f N/mm 2 Design tensile stress f c N/mm 2 Maximum compressive stre
30、ss E N/mm 2 Modulus of elasticity of glass k 1 , k 2 , etc. Factors for various forms of construction as defined in clauses 5 to 10 d i mm Internal diameter d o mm External diameter t e mm Lid, base or step thickness t w mm Wall thickness t f mm Flange thickness r mm Internal corner radius r 1 mm In
31、ternal radius of vessel or lid r 2 mm External radius of vessel or lid h o mm External height of lid h i mm Internal height of lid l mm Cantilever length, i.e. the width of the flange face external to body or lid degree Angle between the sloping side and the vertical axis degree Angle between the ax
32、is and the tangent to the curve of a part-spherical lid where it meets the flange degree Half-angle of a conical lid or section t e= 0.05 d i 1(a) 1(b) d i is the internal diameter measured at the base (in mm); k 1 is a factor derived from equation 2; p and f are defined in Table 1. (2)BS3423:1986 B
33、SI 08-1999 3 b) Base with sharp corners r = 13 mm, k 1= 5.25, t e= 8.0 mm NOTE 1Desiccators having well-radiused corners (see Figure 3) are generally in accordance with the recommendations of 5.1.1, the base thickness being not less than0.05d i ; those of smaller corner radius require a base thickne
34、ss greater than 0.5d i . NOTE 2Extra glass may be provided externally, as shown in Figure 5(a), to form a protective rim or to increase the stability of the vessel, or internally in the form of lugs to support a perforated plate, for example, as shown in Figure 5(b). NOTE 3When the side-wall makes a
35、n obtuse angle with the base, as shown in Figure 3 and Figure 4, the angle between the side-wall and the vertical axis of the vessel being , an extra compressive stress is exerted about the corner, proportional to sec ; this can generally be ignored. 5.2 Semi-ellipsoidal base A base of semi-ellipsoi
36、dal form should be designed as described in 9.2 for a semi-ellipsoidal lid. 6 Body thickness and shape (design feature B) 6.1 Straight and stepped side-walls The side-wall of the vessel should be either stepped or straight and the design principles are the same in each case. The body should be cylin
37、drical or conical with a cone half-angle of less than 15 . 6.2 Part-spherical body The form of body shown in Figure 6, having a curved sidewall terminating at an angle to the axis of the vessel, should be designed as recommended in 9.3 for a part-spherical lid with an extra thickness allowance adjac
38、ent to the flange as given by equation 8 in Appendix A, or with the appropriate safe-handling minimum thickness given in Table 2. Table 2 Minimum side-wall thickness 7 Step thickness and radius of curvature (design feature C) 7.1 Recommendations The internal corners of each step should be radiused a
39、s shown in Figure 7. The radii r 1and r 2should each be not less than t eas shown in Figure 7. NOTETo obtain a significant increase in strength, r 1and r 2need to be not less than 3 t e . If the angle in Figure 7 is less than 60 the step should be treated as a short conical section or swage and the
40、thickness needed at any point should be not less than the value of t e(in mm) given by the following equation. where Figure 3 Base with radiused corners Figure 4 Base with sharp corners Figure 5 Methods of reinforcing radiusedcorners Internal diameter Recommended thickness mm mm 150 4 200 5 250 6 30
41、0 7 (3) d c is the diameter of the cone at the point under consideration (in mm); is the half-angle of the conical section (indegrees); f and p are as defined in Table 1.BS3423:1986 4 BSI 08-1999 7.2 Examples Table 3 gives values of t efor various values of d c , with = 55 . Table 3 Minimum step thi
42、ckness t efor =55 calculated using equation 3 8 Flange thickness and shape (design feature D) 8.1 Recommendations 8.1.1 For a flange of the form shown in Figure 8(a), Figure 8(b) and Figure 8(c), the flange thickness t f(in mm) should be not less than the value given by equation 4(a) if d o d ior no
43、t less than the value given by equation 4(b) if d o d i . where NOTE 1For the construction shown in Figure 8(a) and Figure 8(b) the width of flange face is equal to the cantilever length l plus the wall thickness t w . NOTE 2Equation 4 indicates that it is an advantage to make the flange as narrow a
44、s is compatible with obtaining a good joint. If the tangent at the flange to the curve described by the inside of the lid meets the flange at an angle to the vertical axis as shown in Figure 8(b), the thickness t fcalculated in equation 4 should be increased by the amount given in equation 8 to coun
45、ter the radial stress introduced. For the construction in which the flange terminates outside the line of the wall, the angle shown in Figure 8(d) should not exceed 130 . Figure 6 Curved side-wall with subsidiarycurve at corner Figure 7 Form of step (for example, for supporting a perforated plate in
46、 a desiccator) d c t eminimum mm mm 150 3.5 200 4.5 250 5.5 300 6.8 4(a) 4(b) k 2 is the factor, equal to 2.25, for the flanges shown in Figure 8(a), Figure 8(b) and Figure 8(c); d o is the external diameter of the lid or body at the flange (in mm); d i is the internal diameter measured at the flang
47、e where the joint faces meet (in mm); l is the cantilever length (in mm); f and p are as defined in Table 1.BS3423:1986 BSI 08-1999 5 8.1.2 For a vessel in which the flange and lid take the form shown in Figure 8(e) and Figure 9, the lid being part-spherical and the flange and lid being of substanti
48、ally the same thickness, the thickness t f(in mm) of the flange and of the lid should be not less than the value given by the following equation. where If the ground face of the lid extends inwards from the point at which the two faces meet as shown in Figure 8(e), it should not do so by more than 0
49、.5t e , and r 1should be not greater than d and the corner radius r not less than 2t e . NOTEFor flanges with a recess to accommodate an elastomeric sealing ring the calculated flange thickness t fis that shown in Figure 8(f) measured from the bottom of the recess. Figure 8 Alternative flange designs (5) d is the internal diameter (in mm) measured at the flange where the joint faces meet.BS3423:1986 6 BSI 08-1999 8.2 Examples 8.2.1 Table 4 gives examples of flange th
