BS 7929:1999 pdf free.Guide for the verification of a pump casing design procedure.
Confidence in the casing (lesign prcweltin should be verified using one of the three means described below. These are based upon physically applying loads to the pump l.rl5 and measuring the result, or by a non-physical means involving the use of load simulation and coniputerised responses resulting from calibrated relationships.
a) Empirical vcrfication. The design procedure is verified by demonstrating that it has been used to I)r(xIllce designs for casings, allied paris and joints which have met defined con(litions of service for a minimum operating period of five yeam without a failure arising from a design (lefeet.
b) E.rperimenlal eerification. The design procedure is verified by tests carried out on a model or an example of the item being designed. The tests should be made by applying loads internally or externally as appropriate to simulate the loads which are expected to occur (luring 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 irreversible distortion beyond designed levels.
c) Analytical ..‘erfication. The design procedure using mathematical modelling by computer or otherwise, with or without fmite element content, is verified by using data proven to be correct by (hrecL physical experimental testing or by empirical proving.
4.2.2 Particular requirements for experimental t’erjJication
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 and the intende(l 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 expernuental means of verification is not suitable where the material thickness of the test item exceeds the design thickness by more than lO% whether 1w Incofl)oration of a corrosion allowance or by variations in the manufacturing process.
4.2.3 Hydrostatic pressure testing Where internal hydrostatic pressure testing is
involved either in verifying a design procedure or as a quality contn)l procedure. it should conform to prEN 12162. The test pressures should be derived from the maximum allowable design pressures for tie parts under consideration, and incorporate adjustment for a difference in temperature. Adjustment for a small deviation in material thickness can be ma(le to the test pressure, or to the a(ceplafl(e crltenon, or both.
Where the test aims to simulate loads on branches, feel, bearing housing, crank case, etc., these should be applied in the directions shown in 13S EN 25199 as well 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 designe(l by 1.1w coflect aI)l)liration of the design procedure conforming to 4.1 and verified in accordance with 4.2.1 has satisfactorily achieved the rcquireliwnb for safe operation under the slated conditions of service.BS 7929 pdf download.