BS EN ISO 4490:2018 pdf download – Metallic powders – Determination of flow rate by means of a calibrated funnel (Hall flowmeter) (ISO 4490:2018)
This document specifies a method for determining the flow rate of metallic powders, including powders for hard metals, by means of a calibrated funnel (Hall flowmeter).
The method is applicable only to powders which flow freely through the specified test orifice.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
No terms and definitions are listed in this document.
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4 Principle
Measurement of the time required for 50 g of a metallic powder to flow through the orifice of a calibratedfunnel of standardized dimensions.
5 Apparatus
5.1 Calibrated funnel, the dimensions of which are shown in Figure 1. The funnel shall be made of a non-magnetic, corrosion-resistant metallic material with sufficient wall thickness and hardness towithstand distortion and excessive wear.
5.2 Stand and horizontal vibration-free base, which shall support the funnel rigidly. An example isshown in Figure 2.
5.3 Balance of sufficient capacity, capable of weighing the test portion to an accuracy of ±0,05 g.
5.4 Timing device, capable of measuring the elapsed time to an accuracy of ±0,1 s.
5.5 Reference grit, a reference powder 1) used for calibration of the funnel, shall be used.
6 Calibration of the funnel
6.1 Calibration by the manufacturer of the funnel
The manufacturer shall supply the flowmeter calibrated as follows.
a) Dry the reference grit (5.5) in an open and clean glass jar at 110 °C for 60 min in air.
b) Cool the reference grit to room temperature in a desiccator.
c) Weigh out 50 g ± 0,1 g of the reference grit.
d) Follow the procedure outlined in Clause 8.
e) Repeat the procedure with the same 50 g mass of reference grit, until there are five determinations within 0,4 s.
f) The average of these five determinations is stamped on the bottom of the funnel and the durationof flow shall be within 40,0 s ± 0,5 s.
6.2 Calibration by the user of the funnel
It is recommended that the users periodically verify whether a correction is needed or not.
The flow rate of the reference sample shall be determined by the above method. If the flow rate has changed to be outside 40,0 s ± 0,5 s/50 g, a correction factor shall be used when measuring different powders. This correction factor is obtained by dividing 40,0 by the value obtained above. It is recommended that, before a correction factor is adopted, the cause of the change be investigated. If the flow rate has decreased, it is probable that repeated use has burnished the orifice and a (new) correction factor is justified. An increase in flow rate may indicate a coating of soft powder on the orifice. This coating should be carefully removed and the calibration test repeated. It is recommended that the use of a funnel be discontinued after the duration of flow of the reference sample has decreased to less than 37 s.
7 Sampling
7.1 General In general, the powder shall be tested in the as-received condition. In certain cases, and after agreement between the supplier and user, the powder may be dried. However, if the powder is susceptible to oxidation, the drying shall take place in a vacuum or in inert gas. If the powder contains volatile substances, it shall not be dried.
7.2 Test sample weight
The mass of the test sample shall be at least 200 g.
7.3 Test portion weight
Immediately before the test, weigh out a 50 g ± 0,1 g test portion.
7.4 Number of test portions
The determination shall be carried out on three test portions.
8 Procedure
a) Transfer the test portion to the funnel, keeping the discharge orifice properly closed, for example with a dry finger or a mechanical shutter. Take care that the stem of the funnel is filled with powder.
b) Start the timing device (5.4) when the orifice is opened and stop it at the instant when the last ofthe powder leaves the orifice.
c) Record the elapsed time measured to the nearest 0,1 s.BS EN ISO 4490 pdf download.