BS EN 421:1994 download free.Protective gloves against ionizing radiation and radioactive contamination.
1 Scope
BS EN 421 specifies requirements and test methods for gloves to protect against ionizing radiation and radioactive contamination. The standard is applicable to gloves offering protection to the hand and various parts of the arm and shoulder. It also applies to gloves to be mounted in permanent containment enclosures.
2 Normative references
BS EN 421 incorporates by dated and undated references, provisions for other publications. These normative references are cited at the appropriate places in the text and the publications are listed hereafter. For dated references, subsequent amendments to or revisions of any of these publications apply to BS EN 421 only when incorporated in it by amendment or revision. For undated references the latest edition of the publication referred to applies. EN 374-1, Protective gloves against chemicals and micro organisms — Part 1: Terminology and performance requirements.
EN 374-2, Protective gloves against chemicals and micro organisms — Part 2: Determination of resistance to penetration.
EN 374-3, Protective gloves against chemicals and micro organisms — Part 3: Determination of resistance to permeation by chemicals.
EN 388. Protective gloves against mechanical risks.
EN 420, General requirements for gloves.
Iso 1431-1:1989, Rubber, vulcanized or
thermoplastic — Resistance to ozone cracking — Part 1: Static strain test.
ISO 4648. Rubber, vulcanized or thermoplastic — Determination of dimensions of test pieces and products for test purposes.
3 Definitions
For the purposes of BS EN 421, the following definitions apply:
3.1
irradiation
exposure of a living being or matter to ionizing radiation by external sources X, Alpha. Beta, Gamma or Neutron radiations)
3.2
radioactive contamination
presence of radioactive substances in or on a material or in a place where they are undesirable or could be harmful
5 General requirements
5.1 Attenuation efficiency and uniformity of distribution of protective material
The efficiency of the glove material to absorb radiation is normally quoted as equivalent lead thickness. For gloves covered by this standard, the following range of lead equivalences (in millimetres) is specified: 0, 0,05, 0,1, 0,15, 0,2, 0,25, 0,3,0,35, 0,4, 0,45, 0,5. The equivalent lead thickness shall be measured by one of the methods described in 6.1. Other equivalent lead thicknesses may be manufactured by special agreement between the manufacturer and user.
Unless otherwise agreed (see 4.3) the uniformity shall be such that no single measurement shall be below the specified value of the stated equivalent lead thickness. A minimum of three measurements shall be taken (see 6.1 and 6.2).
5.2 Glove integrity
The purpose of the glove to protect against ionizing radiation or radioactive contamination is to isolate the user from the potential hazard. This is only possible if the integrity of the glove is proven. The integrity shall be tested by the method given in EN 374-2 or by either of the test methods described in 6.2. These methods shall be assumed to be interchangeable.
5.3 Water vapour permeability Gloves used in containment enclosures are often required to offer an impermeable barrier to water and water vapour when the enclosures are required to work under anhydrous conditions. Measurement of water vapour permeability can therefore be an important factor in glove selection. The performance level for water vapour permeability shall be determined by the method described in 6.3, and reported as the performance level, as shown in Table 1.
The method given in 6.3 is applicable to impermeable materials offering a degree of resistance to the passage of water vapour, and should not be confused with the method given in EN 420 which is designed to measure the permeability of leather.
6 Test methods
6.1 Determination of equivalent lead thickness and uniformity of distribution
BS EN 421 specifies two methods by which equivalent lead thickness may be measured. Either method may be used for determination as agreed by the manufacturer and user, The determination of equivalent lead thickness does not lead to an absolute answer but will depend upon the source and energy spectrum of the radiation and hence should always be used as a relative measure. If the glove is loaded with another heavy metallic element, the principle of the test method is the same except for the calibrated wedge which is fabricated with the considered heavy metallic element.
6.1.1 Method 1: X-ray tube source Principle
Millimetres lead equivalence shall be determined by a standard X-ray tube source. The gloves shall be compared with a calibrated lead step wedge.
The method consists of placing an X-ray film inside the glove and placing another film with a calibrated lead step wedge beside the glove for reference. The whole system is then exposed to a standard X-ray tube source.
Procedure
The glove may be tested as a whole or in part. The section of material is placed such that it is between a standard X-ray film and the X-ray source. Beside the glove is placed another film protected by a calibrated lead step wedge; care should be taken that both glove and calibrated lead step wedge are exposed to the same intensity of radiation. The system is then exposed to the radiation from a standard X-ray source, the films are developed and the images are evaluated on a densometer. Exposure times will be dependent on both the intensity of the X-ray source and the attenuation efficiency of the glove. Exposure conditions are energy 50 kV to 70 kV with current, time, and distance such that a readable density is obtained. A measurement of lead equivalence shall be taken at a minimum of three points on the centre line of the palm side of the glove, at the centre of the palm at a distance of 10 cm from the cuff, and at the midpoint between these two readings. The minimum value taken as the lead equivalence. For gloves that are to he used in containment enclosures it is usual that the lead equivalence will not be measured in the last 10 cm of the cuff.
Expression of results
The results should be expressed in equivalent lead thickness in millimetres. This shall be the minimum value obtained from the point results taken. The test report shall also state the X-ray tube energy and any other special test conditions.
6.1.2 Method 2: gamma source Principle
The method consists of placing a gamma source inside the glove and a detector on the outside. Millimetres lead equivalence shall be determined by comparison with a calibrated lead step wedge.
Procedure
A collimated gamma source (e.g. Am241) is placed inside the glove and a detector is placed outside the glove. The detector and the source may be moved in unison over any position on the glove. The millimetre lead equivalent shall be determined by the use of a calibrated lead step wedge and the detector and source as used on the glove. A minimum of three readings shall be taken over the area of the glove and the lowest value taken as the lead equivalent, see 6.1.1.
Expression of results
Equivalent lead thickness shall be stated in millimetres; the report shall also state the source and detector type together with any special test conditions.
NOTE Ideally the detector should be as small as possible and of the fluorolithium type.
6.2 Determination of glove integrity
Selection of test method will be dependent upon the production procedure and the glove material. Any of the three stated procedures may be used to prove the integrity of the glove as agreed between the manufacturer and user.
6.2.1 Air leak test — method A
The method used shall be that defined in EN 376-2. 6.2.2 Air leak test — method B
Principle
The method allows for verification of glove tightness of containment enclosure gloves in conditions similar to their use. The gloves are mounted on a vertical glove port and inflated with air at ambient temperature. Due to internal pressure the glove rises to the horizontal position and may be checked for leaks.
Acceptance criteria
Any leak brought about by a hole or porosity of glove or bad fitting of a glove on a glove port induces a decreasing internal pressure and a deflation of the glove. Gloves showing deflation in under 1 h should be regarded as faulty.