ISO-187-1990.pdf

INTERNATIONAL STANDARD Second edition 1990-l 2-01 Paper, board and pulps - Standard atmosphere for conditioning and testing and procedure for monitoring the atmosphere and conditioning of samples Papier, carton et pstes - Atmosphere normale de conditionnement et d essai et mgfhode de surveillance de I atmosph 23 “C/50 % r.h. and 27 “C/65 Y!./o r.h. At the time of publication of this revision of IS0 187: 1977 the atmos- phere 23 V50 % r-h. is used almost exclusively in most countries and after 1 January 1993 is to be considered the IS0 standard test atmos- phere for testing of pulp, paper and board. However, the 23 “C/50 % r.h. atmosphere is difficult to attain in some of the countries located in tropical zones, and in such countries the 27 “C/65 O/o rh. atmosphere is permitted. Until 1 January 1993 the 20 “C/65 O/o r.h. atmosphere is ac- ceptable as a standard test atmosphere. . . . III -,-,- This page intentionally left blank -,-,- INTERNATIONAL STANDARD IS0 187:1990(E) Paper, board and pulps - Standard atmosphere for conditioning and testing and procedure for monitoring the atmosphere and conditioning of samples 1 Scope This International Standard specifies the standard atmosphere for conditioning, and for testing pulp, paper and board, and also the procedures for measuring the temperature and relative humidity. For the conditioning of laboratory prepared handsheets in accordance with IS0 5269-1, the standard atmosphere is that defined in this Inter- national Standard but the procedure is different? 2 Normative references The following standards contain provisions which, through reference in this text, constitute provisions of this International Standard. At the time of publi- cation, the editions indicated were valid. All stan- dards are subject to revision, and parties to agreements based on this International Standard are encouraged io investigate the possibility of ap- plying the most !*ecent editions of the standards in- dicated below. Members of IEC and IS0 maintain registers of currently valid International Standards. IS0 554:1976, Standard atmospheres for conditioning and/or testing - Specifications. IS0 4677-l :I 985, Atmospberes for conditioning and testing - Determination of relative humidity - Part I: Aspirated psychrometer method. IS0 526%1:1979, Pulps - Preparation of laboratory sheets for physical testing - Part 1: Conventional sheet-former method. IS0 526%211980, Pulps - Preparation of laboratory sheets for physical testing - Par? 2: Rapid-k oethen method. 3 Definitions For the purposes of this International Standard, the following definitions apply. 3.1 relative humidity (r.h.): The ratio, expressed as a percentage, of the actual water vapour content of the air to the water vapour content of air saturated with water vapour at the same temperature and pressure. 3.2 conditioning: A process of establishing a re- producible moisture content equilibrium between the sample and an atmosphere of specified temper- ature and relative humidity. This equilibrium is con- sidered to be attained when the results of two consecutive weighings of the sample, carried out at an interval of time of not less than I h, do not differ by more than a specified amount. NOTE 1 The interval between weighings is dependent on the grammage of the sample and the degree of agreement expected between successive weighings should take account of the known cycling characteristics of the particular test room. The establishment of moisture content equilibrium is accepted as ensuring that the paper is in a stable physical state, but in special circumstances, conditioning may have to be prolonged until the desired physical equilibrium is attained. Such circumstances are not within the scope of this International Standard. 4 Principle Exposure of the sample to a specific conditioning atmosphere in such a manner that a reproducible state of moisture content equilibrium is reached be- tween the sample and this atmosphere. 1) IS0 5269-l requires Pul p handsheets to be c followed by conditioning bY sorption of moisture. .ondi ti oned by desorption of moisture, whilst IS0 5269-2 requires drying -,-,- IS0 187:1990(E) 5 Standard atmosphere 6 Conditioning procedure The standard atmosphere for testing pulp, paper and paperboard shall be 23 “C + 1 “C and (50 + 2) % r.h. In tropical countries an atmosphere of 27 OC + .- 1 T and (65 + 2) % r-h. may be used. - NOTE 2 The temperature and relative humidity condi- tions are those specified in IS0 554. The tolerances quoted are the reduced or close tolerances specified in IS0 554. A test atmosphere shall be deemed to be within the requirements of this International Standard if all the test results determined as described in annex A (see, in particular, A-4.2) are within the prescribed limits. Even short-term excursions of temperature or humidity beyond these limits, to the extent that the equilibrium moisture content of the sample will be affected, are not permitted. Whenever the test atmosphere is known to have been outside the limits and if there is any chance that the moisture content of samples has been changed by such excursions, all samples must be reconditioned (repeating clause 6) before any further testing is done. NOTES 3 If it is known or suspected that the relative humidity has exceeded the upper limit to the extent that the moisture content may have increased, all samples except those prepared in accordance with IS0 5269-1, must be subjected to the preliminary low humidity treatment dc- scribed in 6.1 before reconditioning. If it is known or suspected that the relative humidity has fallen below the limit to the extent that the moisture con- tent may have decreased, samples prepared in accord- ance with IS0 5269-l should be discarded and new samples prepared. If this is not possible and the samples are tested, the circumstance must be reported. 4 A recording hygrometer, either independent of or part of the control system, should be in continuous operation in the room, but such hygrometer must not be used to assess whether the atmosphere meets the requirements of this International Standard unless it also meets the re- quirements of annex A of this standard. The hygrometer should respond rapidly to changes in relative humidity, for example, less than 1 min +or a change in relative humidity of 10 O/o. 6.1 Pre-conditioning of the sample For tests in which the hysteresis of the equilibrium moisture content may lead to important errors, the sample shall be pre-conditioned before conditioning, for 24 h in air of relative humidity between IO % and 35 % and a temperature not above 40 “C. If it is known that conditioning (6.2) will result in an equi- librium moisture content equivalent to that achieved by sorption (see Introduction) this preliminary treat- ment may be omitted. NOTE 5 Since the effect of hysteresis may not be known until after the event, it is recommended that precondi- tioning be always carried out. 6.2 Conditioning The specimens of the sample shall be held such that the conditioning air has free access to all their sur- faces so that their moisture contents attain a state of equilibrium with the water vapour in the atmos- phere. This equilibrium is considered to be attained when the results of two consecutive weighings at least 1 h apart do not differ by more than 0,25 % of the total mass (3.2). The interval between weighings needs to be longer for higher grammage products and the degree of agreement expected between successive weighings should take account of the known cycling characteristics of the test room. NOTE 6 With good air circulation, a conditioning period of 4 h is usually sufficient for paper. A minimum time of 5 h to 8 h will be required for heavy papers. Boards of higher grammage and specially treated materials may require a conditioning period of 48 h or longer. 7 Test report The test report of any testing which is required to be done in this standard atmosphere shall include the following particulars: a) reference to this International Standard; b) the nominal conditioning atmosphere used; c) the time for which the sample was conditioned; whet her the paper or the board cond itioned b efore condit ionin cl- pre- -,-,- IS0 187:1990(E) Annex A (normative) Measurement of temperature and relative humidity A.1 Scope This annex is based on IS0 4677I:1985 and de- scribes the procedures for measurement of temper- ature and relative humidity to be used in determining compliance #with this International Standard. It aims to specify those features which are essential for accurate measurement without speci- fying a particular type of instrument. NOTE 7 Condensation type and impedance type hy- grometers may be used provided they can be shown to be at least as accurate as the aspirated psychrometer. A.2 Apparatws Aspirated wet and dry bulb psychrometer, compris- ing the following essential components: A.2.1 Thermometers These may be liquid-in-glass (either solid stem or enclosed scale type), thermocouples or electrical resistance thermometers with a working range of 10 “C or more. They shall be accurate to within + 0,l OC and the pair used in any instrument shall agree to within 0,05 C. Liquid-in-glass thermom- eters should be graduated in 0,l “C scale divisions so that reading s can be estimated to the nearest 0,05 C. Thermocouples and electrical resistance thermometers are usually connected to a digital display panel meter which rounds off to 0, l “C. However, a chart recorder with scale divisions of 0,05 OC may be connected to provide a permanent record of dry bulb readings and also either wet bulb temperature or preferably, relative humidity com- puted electronically within the instrument. The sensing section of the thermometers shall not be less than 1 mm or more than 4 mm in diameter for transverse ventilation, and 6 mm for axial venti- lation. Thermocouples and electrical resistance thermometers shall have a response rate sufficient to track a temperature gradient of 1 “Urnin and a relative humidity gradient of I,5 %/min. A-2.2 Ventilation The instrument shall provide means of drawing air over the sensing sections of the thermometers which may be mounted for either transverse or axial ventilation. The thermometers shall be mounted so that the axes of the sensors are parallel and separ- ated by a distance of not less than three times the diameter of the wet bulb sensor. In the case of transverse ventilation both sensors may be located in the same air stream with the dry bulb off-set on the upstream side of the wet bulb. In the case of axial ventilation the direction of air flow shall be from the free end of the sensor to the sup- port end and a separate cylindrical radiation shield, of internal diameter I,75 to 3 times the wet bulb di- ameter, shall be provided for each sensor. The sensors shall be protected from all sources of heat radiation including that provided by the prox- imity of the operator. The air flow shall be provided by a fan located downstream from the sensors so that any heat generated by it will not affect the sen- sors, and exhaust air is directed away from the source of incoming air. The air speed over the sensors shall not be less than 3 m/s. However, the air speed shall not be suf- ficiently high as to allow the wick to become less than fully saturated or to allow droplets of water to form in the air stream. A.2.3 Wet wick The wet wick shall be a seamless fabric sleeve made from cotton or non-acetate rayon. It shall fit the sensor snugly but not tightly and shall cover the sensor completely for such distance that any de- crease in length covered does not change the tem- perature reading. This may be measured by operating both thermometers as wet bulbs and varying the distance covered on one of them. A.2.3.1 Cleaning and care of wicking material Cleanliness of wicks is essential for accurate re- sults, particularly in the case of thermocouples and electrical resistance thermometers, and they should be changed frequently in service. Even the slightest touch of the hand will affect wick performance. Wicks should be handled with tweezers or plastics gloves (or their equivalent) and it is important to ensure that any part of the tweezers or gloves to touch the wick has not been touched previously by the hand. -,-,- IS0 187:1990(E) A new wick or a particularly dirty wick is best cleaned by boiling for 30 min in distilled water con- taining 20 g of sodium hydroxide per litre. Wash the freshly boiled wick thoroughly in distilled water and then boil it three times, for 15 min each time, in successive 400 ml portions of distilled water. If organic contaminants are suspected of being present, wash with acetone and then successive portions of distilled water until free of odour. If the contamination is only loose particulate matter, a distilled water wash may be sufficient. After clean- ing, the wick must pass the absorption test (A.2.3.2). With experience the user will be able to select the appropriate cleaning procedure. A.2.3.2 Tests for wick cleanliness A properly clean wick will instantly absorb a drop of water placed on it. Any delay indicates that the wick needs to be cleaned. One quantitative test for cleanliness of longer wicks is the following: Mount about 120 mm of dry wick on a glass rod with about 20 mm hanging free from one end. Secure the rod in a vertical position with the covered end 15 mm above a dish of distilled water and the free end submerged in the water. After 6 min the water should have risen at least 85 mm up the wick. Any lower reading indicates that the wick is not suffi- ciently clean. Store clean wicks under distilled water or dry be- tween clean blotters and store in a clean and sterile glass container. A.24 Water supply The end of the wick away from the sensor may dip into a reservoir of distilled or deionized water lo- cated so that it is completely isolated from the in- coming air. Some instruments are not fitted with a water reservoir and, in using these instruments, it is necessary to thoroughly wet the wick before the test is started and to take particular care to repeat the wetting at frequent intervals to prevent the wick be- coming too dry. NOTE *8 The reservoir must be so located that water does not flow along the wick at a rate fast enough to result in water dripping or spraying from the wick. A.3 Procedure Locate .the instrument in or close to the working area but away from any heat producing equipment and personlnel. Turn on the fan and allow to run for a few minutes, monitoring the temperature reading, to achieve stable operation. During this period the wet bulb temperature should fall and then stabilize. Inspect the wick to ensure that it remains wet during testing. It should glisten when viewed in a beam of light and the a