BS 6256:2021 pdf download

BS 6256:2021 pdf download.Packaging for terminally-sterilized medical devices — Method for determination of methylene blue particulate penetration
4 Principle
COMMENTARY ON CLAUSE4 The layout of the apparatus is ilustrated in Figure 1 and Figure 2. The atomizer, working under a constant pressure and flow of compressed air; disperses a solution of methylene blue into a mist at a uniform rate. The mist passes into the evaporation tube (E) where it is diluted to a total volume of 30 dm3/min by dry air entering at (B). The droplets of solution evaporate before reaching the control cock (C), leaving a residue of solid particles of methylene blue. When the control cock [C) is in the test position, the test cloud passes to the test circuit which contains the sample under test and the filter paper. When the control cock is turned to the central or air position, the cloud is diverted to the by-pass . circuit and at the same time air is drawn through the test circuit. In the off position of the control cock, the cloud remains diverted to the by-pass circuit, but there is no flow through the test circuit. The rates of flow in the circuits are adjusted to 30 dm3/min by means of the air valves V2 and V:. To test a sample, the control cock is first turned to the off position and the sample and filter paper are inserted into their respective holders. The test cloud is then passed to the sample for a predetermined time, following which air is passed for a further period of 2 s in order to sweep out the residual cloud from the test circuit. The control cock is then turned to off and the filter paper removed. Finally, the test stain is developed with steam and the penetration assessed by comparing the stain with the standard stains.
6.1 Preliminary
6.1.1 Fill the atomizer with a 1% methylene blue solution up to a level 6 mm below that of the spray orifice:approximately 500 ml of solution are required.
6.1.2 After a maximum of 8 h operation, discard the methylene blue solution and replace with a fresh 1% solution of methylene blue.
NOTE The methylene blue solution in the atomizer with the standard nozzle is consumed at a rate of approximately 10 ml per hour. This loss is due in part to the atomization of the solution and in part to the evaporation of water from the main bulk of the liquid. The concentration of the solution in the reservoir therefore increases steadily during the operation of the apparatus. The volume of the reservoir is chosen so that the change in concentration, and loss of volume, of the solution during a period of 8 h operation or less, will not cause an appreciable change in the concentration of the test cloud.
6.2 Start-up instructions
6.2.1 Start up the apparatus as follows.
a) Turn the control cock (C) to OFF.
b) Switch on the suction pump.
c) Close and clamp the unloaded test piece holder (T).
d) Clamp the unloaded test paper holder (F) firmly closed.
e) Turn the control cock (C) to TEST
f) Adjust the air valve (V) to give a flow of 30 dm3/min through the bypass circuit.
3) Turn the control cock (C) to 0FF.
h) Adjust control valve V3) to give a flow of 30 dm/min through the test circuit.
i) Turn on the compressed air to the atomizer and adjust the needle valve (V) until the pressure gauge (D) registers 205 kPa. The ball in the compressed air flowmeter (M) should now rise to the calibration mark. If the air flow is insufficient, turn off the compressed air and clear the atomizer jets.