BS 848-9:2006 pdf download
BS 848-9:2006 pdf download.Part 9: Tolerances, methods of conversion and technical data presentation.
For nonadjustable tans operating away from the optimum efficiency point, there may still be a requirement, for example, where the system resistance can vary over a wide range, for a specified tolerance for a second operating point, In this case, a higher uncertainty is applicable and should be agreed using the above principles as a guideline.
For adjustable fans, operation away from the optimum efficiency is likely to be a requirement. Hence the tolerance grades are extended to cater for this condition using efficiency contours The base tolerance for the fan still relates to the operating point of the agreed or published performance envelope, but flow variation induced by blade angle, inlet vane angle or speed changes, is catered for by the variations shown (see above), In al cases, the design flow will be that applicable to the blade angle, flow control device setting or speed as appropriate (see Figure 2).
II the speed of the fan Is austable. for example, by inverter control, the tolerance grade may be based on a precise speed. However, as Is more usually the case. if the tolerance grade Is to be applied to a fan and motor combination, then the grade selected shall consider the possibility of the motor speed being slightly different from that quoted or published by the motor supplier and additional motor losses shall be considered. In all cases of speed control, the desagn flow shall be related to that applicable at the precise operating speed.
5.5.3 Performance acceptance testing
5.53.1 General
The full performance testing 01 a Ian can be extremely expensive and with small fans can even exceed the cost of the Ian itself. Suppliers and purchasers should always consider. In the first instance. whether this expense Is justified.
At the customer’s request, and by aeemenl with the supplier, the specified operational parameters shall be verified by the supplier The method and scope and price of testing shall be agreed between the customer and supplier. The scope of testing shall take into account aspects such as the tests required, the size of the fan, the facilibes available and the agreed tolerance grade.
5.5.3.2.2 Arrangements for performance venfication using standardized airways, subject to contractual agreement with the purchaser. may be made as follows.
a) The purchaser commissions the supplier to carry out the tests and supervises them himself or has them supervised by a qualified independent expert.
b) The purchaser commissions an accredited independent testing agency to carry out the tests. In this case. the supplier shall be informed and agree to the test set-up prior to the test.
C) The purchaser carries out the tests himself. In this case, the supplier shall be informed and agree to the test set-up prior to the teal
5.5.3.2.3 In all cases, standardized measuring methods shall use instrumentation that has been independently calibrated and shall have a vaid certification traceable back to national or International Standards.
5.5.3.2.4 If a model is used to verify the specified performance criteria, the conversion rules for relating the model test data to the full-scale fan performance data shall be previously agreed between the purchaser and supplier. As appropriate, these rules shall meet the requirements of. or be based on the information contawied in. ISO 5601 and ISO 13347-1.
5.5.3.2.5 On-site measurements on fans should be made as soon as possible after installation and preferably during the commissionang trials to ensure that all components of the system associated with the fan, including any controls, are operating correctly. This will assist in determining a proper judgemeni of the fan performance.
Before site tests are carried out, the supplier shall be given the opportunity to review scale drawings of the ducting arrangement. folowed by an inspection of the site installation. If site electrical supplies are available. preliminary mea5urements should be taken.
5.5.3.2.6 If on-site performance test results show that a specified operating point does not, allowing for the tolerance grade specified, lie on the actual system lines, it shall be agreed by what method the operating point can be temporarily changed for the perfomiance test (e.g. by short-circuiting or providing additional resistance). Alternatively, any permissible deviations from the specified operating points that result from a different system line shall be agreed. If this cannot be done, then tests should be carried out, by mutual arrangement between the purchaser and suppliers, in accordance with 5.5.3.2.1 b) or 5.5.3.21 c).
5.5.3.2.7 If certain installation conditions prevent testing to be undertaken in accordance with subclause.
