Granular carbon dioxide (CO2) absorbent material for life support, diving, hyper- and hypobaric applications Requirements and tests

Transcription

1 CEN/TC 79 N 684 Date: pren CO2:2014 CEN/TC 79 Secretariat: DIN Granular carbon dioxide (CO2) absorbent material for life support, diving, hyper- and hypobaric applications Requirements and tests ICS: Descriptors: Document type: European Standard Document subtype: Document stage: Working Document Document language: E X:\TA1\TG1-2\NA027\Gremien\CEN\CEN-TC_79\zu verteilen\684_granular_carbon_dioxide_absorbent_material_(e).doc STD Version 2.5a

2 Contents Introduction Scope Normative references Terms and definitions Symbols and abbreviations Requirements Absorbent designations Carbon dioxide absorbent activity Volatile (water) content Carbon dioxide absorbent granule size and dust load Friability Flow resistance Indicators Testing Carbon dioxide absorbent activity General Volatile (water) content Volatile content method (a) Volatile content method (b) Carbon dioxide absorbent granule size and dust load Friability Flow resistance Indicators Marking Information supplied by the manufacturer Page 2

3 Foreword This document (pren CO2:2014) has been prepared by Technical Committee CEN/TC 79 Respiratory protective devices, the secretariat of which is held by DIN. This document is a working document. Introduction Carbon dioxide absorbents are used in a variety of life-support, diving and hyper- and hypobaric applications. The type and characteristics of absorbents typically vary dependent upon their intended field of use, differences in manufacturing techniques and chemical composition. This standard is intended to provide requirements and test methods for carbon dioxide absorbents, and to provide designations for such absorbents. This allows users to select appropriate materials when purchasing from manufacturers. However due to the wide range of applications for absorbent materials the grade framework is not exhaustive and is not intended to imply that material is fit or un-fit for purpose. 1 Scope This European Standard specifies requirements and test methods for granular carbon dioxide absorbent materials. This document is applicable to life-support, re-breathing apparatus on the surface and underwater, and hyperand hypobaric applications. It excludes applications in medical anaesthesiology, materials that also generate oxygen and monolithic pre-formed materials or those embedded within a polymer matrix. 2 Normative references The following documents, in whole or in part, are normatively referenced in this document and are indispensable for its application. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. ISO :2000, Test sieves Technical requirements and testing Part 1: Test sieves of metal wire cloth BS EN XYZ - For infrared volatiles 3 Terms and definitions For the purposes of this document, the following terms and definitions apply. 3.1 activity time time that a carbon dioxide absorbent material can maintain an effluent carbon dioxide level less than a given value 3.2 friability propensity to form dust 3

4 3.3 indicator material that changes colour as the absorbent is used 4 Symbols and abbreviations S-H S-L L-H L-L Li-S Li-L Small-granule, high-activity Small-granule, low-activity Large-granule, high-activity Large-granule, low-activity Lithium hydroxide, small-granule Lithium hydroxide, large-granule 5 Requirements 5.1 Absorbent designations This standard is to provide for the assessment of carbon dioxide absorbent, used for life-support applications, against a standard set of test procedures. The absorbent shall be either a granular or pelleted material. The absorbent shall be one of the following designations: Soda lime, S-H Soda lime, S-L Soda lime, L-H Soda lime, L-L Lithium hydroxide, Li-S Lithium hydroxide, Li-L 5.2 Carbon dioxide absorbent activity The absorbent material shall have an absorbent activity of: 90 min for soda lime S-H and L-H 60 min for soda lime S-L and L-L 125 min for Li-S and Li-L Testing shall be performed in accordance with Volatile (water) content The absorbent material shall have the following relevant volatile content: Soda lime materials, S-H, L-H, S-L and L-L, between 14 % and 22 %. Materials Li-S and Li-L, < 1.0 %. 4

5 Testing shall be performed in accordance with Carbon dioxide absorbent granule size and dust load The absorbent material shall meet the criteria for small granules (S) or large granules (L) as specified in Table 1. Table 1 Granule size and dust load criteria for carbon dioxide absorbent grades Test S Limits L Granule Size (%) Retained on 5,60 mm sieve 1,0 max Retained on 4,75 mm sieve 1,0 max 7,0 max Retained on 2,80 mm sieve Retained on 2,00 mm sieve 30,0 max 76,0 min Retained on 1,40 mm sieve 48,0 min Retained on 600 µm sieve 20,0 max 15,0 max Dust Load 0,5 max 0,5 max Testing shall be performed in accordance with Friability The absorbent material shall meet the criteria for small granules (S) or large granules (L) as specified in Table 2. Table 2 Friability for carbon dioxide absorbent grades Test Limits S L Granule Size (%) Retained on 5,60 mm sieve 1,0 max Retained on 4,75 mm sieve 1,0 max 7,0 max Retained on 2,80 mm sieve Retained on 2,00 mm sieve 30,0 max 76,0 min Retained on 1,40 mm sieve 48,0 min Retained on 600 µm sieve 20,0 max 15,0 max Dust Load 3,0 max 3,0 max Testing shall be performed in accordance with Flow resistance The absorbent material shall have the following flow resistance: Materials, S-H, S-L and Li-S: 1.4 mbar. Materials L-H, L-L and Li-L, < 1.2 mbar. 5

6 Testing shall be performed in accordance with Indicators The absorbent material shall not contain any indicators. Testing shall be performed in accordance with Testing WARNING Carbon dioxide absorbents consisting of (or containing) lithium hydroxide are harmful by inhalation and corrosive to skin and eyes. It is essential that the tests described in these procedures are conducted in a suitable ventilated facility and that operators wear appropriate personal protective equipment. 6.1 Carbon dioxide absorbent activity General The tests to determine the activity at atmospheric pressure shall be conducted at 20 C ± 1 C and in accordance with the following procedure: Assemble a test rig as shown in Figure 1. Locate the activity tube, as shown in Figure 2, into the base of a snow storm filler as detailed in Figure 3 and Figure 4. Pour the absorbent at an even rate into the snow storm filler till the activity tube is filled to the 105 ml calibration mark. The mass (g) of absorbent added to the tube shall be recorded. Insert the activity tube into the test rig, the tube shall be vertical, with the test gas flowing top to bottom. Pass a flow of (3,0 ± 0,1) l/min of homogenous (5,0 ± 0,05) % carbon dioxide in nitrogen test gas mixture, maintained at (20 ± 1) C, through the humidifiers and activity tube. A sample of the effluent gas exiting the activity tube shall be drawn off and passed into a suitably ranged and calibrated closed loop carbon dioxide analyser, at a sufficient rate to provide accurate analysis. The sample gas shall pass through a drying agent that will not absorb carbon dioxide [e.g. MgClO 4 ] before passing into the gas analyser. The output signal from the inlet sample analyser and effluent sample analyser shall be recorded. Note the time taken for the effluent gas to reach a volume fraction of 0,50 % carbon dioxide. The test should be repeated a minimum of three times with the activity being the shortest recorded time. 6

7 Figure 1 Schematic carbon dioxide absorbent test rig 7

8 All dimensions in mm Figure 2 Absorbent activity tube 8

9 Figure 3 - Snow storm filler for activity tube 9

10 Figure 4 - Snow storm filler - throat detail 6.2 Volatile (water) content Volatile content method (a) Transfer approximately 10 g of absorbent onto an automatic volatile content infrared balance that conforms to BS XYZ and note the mass (M A1 ). Start the automatic drying cycle and note (if available) the percentage volatile reading when the absorbent is dry and/or the mass of the dried absorbent (M A2 ). The percentage volatile content can be calculated using Equation (1): ( ) M 1 M Volatile content, % = A A2 100 (1) M A1 10

11 6.2.2 Volatile content method (b) Transfer approximately 100 g of absorbent to a previously weighed (M M1 ) clean dry squat-form weighing dish and accurately weigh (M M2 ). (Note: The dish shall be a minimum of 100 mm diameter and minimum depth of 20 mm. The dish shall be able to withstand temperatures in excess of 150 C). Remove the lid and place the dish, with the lid alongside, in a well-ventilated oven maintained at (150 ± 5) C. After 120 minutes replace the lid and transfer the dish to a desiccator, containing freshly activated silica gel. Allow to cool for 30 minutes. Release the lid on the dish momentarily and re-weigh (M M3 ). The percentage volatile content can be calculated using Equation (2): ( MM 2 MM 3 ) ( ) Volatile content, % = 100 (2) MM 2 MM1 6.3 Carbon dioxide absorbent granule size and dust load Perform a visual inspection of the sieves shown in Table 3, in accordance with ISO :2000, 5.2, Test 1. Table 3 Sieve stack components Sieve Aperture Size mm 5,60 4,75 2,80 2,00 1,40 0,60 Receiver pan Assemble the nest of clean dry sieves indicated in Table 3 in order of aperture size with the receiver pan at the base. Distribute (100 ± 0,1) g of absorbent on the top sieve. Record the amount of absorbent used. Attach the lid and shake the assembled sieves for 5 minutes on a mechanical shaker. The mechanical shaker shall be set to a frequency of X Hz and amplitude of Y mm. Remove the nest of sieves from the shaker and weigh the amount of material retained on each sieve, and the dust passing into the receiver at the base of the nest. Any granules lodged in the meshes of a sieve shall be included as the material retained on the sieve. Report the mass of material on each sieve, and the dust in the receiver, as a percentage of the absorbent mass used. 6.4 Friability Perform a visual inspection of the sieves shown in Table 3, in accordance with ISO :2000, 5.2, Test 1. 11

12 Assemble the nest of clean dry sieves indicated in Table 3 in order of aperture size with the receiver pan at the base. Distribute (100 ± 0,1) g of absorbent on the top sieve. Record the amount of absorbent used. Attach the lid and shake the assembled sieves for 60 minutes on a mechanical shaker. The mechanical shaker shall be set to a frequency of X Hz and amplitude of Y mm. Remove the nest of sieves from the shaker and weigh the amount of material retained on each sieve, and the dust passing into the receiver at the base of the nest. Any granules lodged in the meshes of a sieve shall be included as the material retained on the sieve. Report the mass of material on each sieve, and the dust in the receiver, as a percentage of the absorbent mass used. 6.5 Flow resistance The test should be conducted during the absorbent activity test (6.1). A differential pressure monitor with a minimum accuracy of ± 0.01 mbar shall be connected to the top and the bottom of the activity tube. During the full duration of the activity test the differential pressure across the activity tube shall be measured and the maximum differential pressure recorded. 6.6 Indicators The presence of an indicator may be identified by observing the absorbent during the absorbent activity test (6.1) and noting any colour change that occurs. 7 Marking The external packaging of the absorbent material shall: a) identify the manufacturer by name, trade name or other means of identification; b) state the number and date of this European Standard; c) state the designation of material; d) state the batch or lot number, date of manufacture and expiry date; e) include any relevant health and safety warnings such as corrosive; f) storage conditions. 8 Information supplied by the manufacturer The manufacturer shall supply all necessary information for trained and qualified persons to safely use the absorbent material. This information supplied by the manufacturer shall include the application and anticipated field of use of the absorbent material alongside a suitable warning regarding the inappropriate use of material. Warning shall be given against any problem normally expected e.g. Canister channelling. The information supplied by the manufacturer shall be precise and comprehensible. If helpful, illustrations shall be added. 12

13 The information supplied by the manufacturer shall be in the official language(s) of the country of application. The manufacturer may supply the results of individual tests as a guide to users. This information supplied by the manufacturer shall include (but is not limited to): a) limitations on use of the material e.g. the poor performance of absorbents when wet; b) an assessment of risks; c) the effect of temperature conditions; d) the effect of work rates; e) checks to be performed prior to use; f) storage and shelf life of absorbent material. 13