1、| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | BRITISH STANDARD BS 7929:1999 ICS 23.080 N
2、O COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAW Guide for the verification of a pump casing design procedureThis British Standard, having been prepared under the direction of the Engineering Sector Committee, was published under the authority of the Standards Committee and come
3、s into effect on 15 April 1999 BSI 04-1999 The following BSI references relate to the work on this standard: Committee reference MCE/6 Draft for Public Comment: 98/704089 DC ISBN 0 580 28268 6 BS 7929:1999 Amendments issued since publication Amd. No. Date Text affected Committees responsible for thi
4、s British Standard The preparation of this British Standard was entrusted to Technical Committee MCE/6, Pumps and pump testing, upon which the following bodies were represented: Association of High Pressure Water Jetting Constructors British Chemical Engineering Contractors Association British Hydro
5、mechanics Research Group British Pump Manufacturers Association Electricity Association Energy Industries Council Engineering Equipment and Materials Users Association National Engineering LaboratoryBS 7929:1999 BSI 04-1999 i Contents Page Committees responsible Inside front cover Foreword ii Introd
6、uction 1 1 Scope 1 2 Normative references 1 3 Terms and definitions 1 4 Pump casing design procedure 1 5 Acceptance criterion for a pump casing design procedure 2ii BSI 04-1999 BS 7929:1999 Foreword This British Standard has been prepared by Technical Committee MCE/6, Pumps and pump testing. It is i
7、ntended to be used by those designing and manufacturing pumps subject to the exclusion clause in the Pressure Equipment Directive 97/23/EC. This British Standard recognizes that there may be more than one way to prove the adequacy of the design procedure for a pump casing and contains the principles
8、 with which all such methods should conform. This British Standard is based upon a draft prepared by the British Pump Manufacturers Association. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct app
9、lication. Compliance with a British Standard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, pages i and ii, pages 1 and 2, an inside back cover and a back cover. BSI 04-1999 1 BS 7929:1999 Introduction The Pre
10、ssure Equipment Directive excludes equipment where the design takes account of stresses arising from the loads resulting from the operation of the equipment (Art. 1, Clause 3.10). Pump casings are quoted as specific examples. This approach correctly assumes that the pressure casing is subjected to l
11、oads beyond that derived from pressure containment alone. Pump casings and associated pressure retaining parts are designed to provide adequate strength permitting safe operation over a working lifetime when operated within defined limits. The design procedures for these items take into account inte
12、rnally and externally imposed loads, characteristics of the pumped liquid, the temperature regime and the selected materials of construction. It is not possible in all cases to prove the adequacy of the item by physical test. This would be the situation, for example, where additional material is inc
13、luded because of corrosion risks, or where a unique item is designed for a particular application requiring only a small number of units. This British Standard sets out the features required of both physical and non-physical proving procedures. This British Standard is complementary to prEN 12162 wh
14、ich sets out the procedure for an in-process test used to prove the soundness and integrity of a production item. 1 Scope This British Standard gives guidance on the methods used to demonstrate that pump casings have been designed with sufficient strength and rigidity for the stability and dynamic o
15、perational effects of the pump working up to its defined limits, taking into account the materials selected and the temperatures to be experienced. 2 Normative references The following normative documents contain provisions which, through reference in this text, constitute provisions of this British
16、 Standard. For undated references the latest edition of the cited publication applies. BS EN 25199, Technical specifications for centrifugal pumps Class II. prEN 12162, Liquid pumps Hydrostatic testing. prEN 12723, Liquid Pumps General terms for pumps and installations Definitions, quantities, lette
17、r symbols and units. 3 Terms and definitions For the purposes of this British Standard the definitions given in prEN 12723 and the following apply. 3.1 margin of safety amount by which the value of a design parameter exceeds its maximum allowable working value NOTE This may be expressed as the diffe
18、rence in the values or as their ratio. 3.2 usable stress maximum value of stress a material may be allowed to develop at the design parameter 3.3 corrosion allowance additional material provided to allow for that lost to corrosion by the pumped product during use NOTE This additional material is ove
19、r and above that required to prevent the usable stress being exceeded. 4 Pump casing design procedure 4.1 Characteristics of a pump casing design procedure Pump casings, allied parts and their joints should be designed using methods which recognize stresses derived from internal and external loads,
20、the pump duties and the pumped liquid. An acceptable design procedure should: be defined and fully documented; use only those computer programmes for which full listings are available and which have been fully verified; require a clear statement of the intended conditions of service of the pump; inc
21、orporate checking procedures by a separate suitably qualified person; set out the methods to be used for verifying the adequacy of the items designed; require identification of the design conditions and margins of safety to be applied; require identification of the usable stresses for the materials
22、selected.2 BSI 04-1999 BS 7929:1999 4.2 Verification of the pump casing design procedure 4.2.1 Acceptable means of verification Confidence in the casing design procedure should be verified using one of the three means described below. These are based upon physically applying loads to the pump parts
23、and measuring the result, or by a non-physical means involving the use of load simulation and computerised responses resulting from calibrated relationships. a) Empirical verification. The design procedure is verified by demonstrating that it has been used to produce designs for casings, allied part
24、s and joints which have met defined conditions of service for a minimum operating period of five years without a failure arising from a design defect. b) Experimental verification. The design procedure is verified by tests carried out on a model or an example of the item being designed. The tests sh
25、ould be made by applying loads internally or externally as appropriate to simulate the loads which are expected to occur during normal usage, together with allowances for the margins of safety, and measuring or otherwise demonstrating that the model or example does not fracture nor give rise to irre
26、versible distortion beyond designed levels. c) Analytical verification. The design procedure using mathematical modelling by computer or otherwise, with or without finite element content, is verified by using data proven to be correct by direct physical experimental testing or by empirical proving.
27、4.2.2 Particular requirements for experimental verification Where a design method is verified using an experimental means, care should be taken to ensure that the test conditions accurately reflect the design conditions. Adjustments may have to be made for differences between the test arrangement an
28、d the intended operating arrangement and should be documented. Such differences may include bolting, orientation, mountings and finishes, as well as differences in operating temperature, material thickness and quality. Adjustments which obscure the effect being tested should be avoided. An experimen
29、tal means of verification is not suitable where the material thickness of the test item exceeds the design thickness by more than 10 %, whether by incorporation of a corrosion allowance or by variations in the manufacturing process. 4.2.3 Hydrostatic pressure testing Where internal hydrostatic press
30、ure testing is involved either in verifying a design procedure or as a quality control procedure, it should conform to prEN 12162. The test pressures should be derived from the maximum allowable design pressures for the parts under consideration, and incorporate adjustment for a difference in temper
31、ature. Adjustment for a small deviation in material thickness can be made to the test pressure, or to the acceptance criterion, or both. Where the test aims to simulate loads on branches, feet, bearing housing, crank case, etc., these should be applied in the directions shown in BS EN 25199 as well
32、as in any other specific direction necessary for the purpose of verifying the adequacy of the design. 5 Acceptance criterion for a pump casing design procedure The design procedure is considered to be acceptable when it has been shown that one or more pump casings designed by the correct application
33、 of the design procedure conforming to 4.1 and verified in accordance with 4.2.1 has satisfactorily achieved the requirements for safe operation under the stated conditions of service.blankBSI 389 Chiswick High Road London W4 4AL | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
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