1、BRITISH STANDARD BS 7793-1: 1995 Vitreous enamel coatings for use on bolted steel panels Part 1: Specification for coatings on bolted steel panels for use in agricultural slurry tanks UDC 631.248:669.14.693BS7793-1:1995 This British Standard, having been prepared under the directionof the Materials
2、and Chemicals Sector Board, was published under the authority ofthe Standards Board and comesinto effect on 15August1995 BSI 10-1999 The following BSI references relate to the work on this standard: Committee reference STI/36 Draft for comment 93/507615 DC ISBN 0 580 23733 8 Committees responsible f
3、or this British Standard The preparation of this British Standard was entrusted to Technical Committee STI/36, Vitreous enamel coatings, upon which the following bodies were represented: Agricultural Engineers Association Association of Manufacturers of Domestic Electrical Appliances British Steel p
4、lc Institute of Vitreous Enamellers Metal Sink Manufacturers Association Vitreous Enamel Development Council Amendments issued since publication Amd. No. Date CommentsBS7793-1:1995 BSI 10-1999 i Contents Page Committees responsible Inside front cover Foreword ii 1 Scope 1 2 References 1 3 Definition
5、s 1 4 Information and requirements to be agreed and documented 2 5 Chemical resistance 2 6 Steel sheet base 2 7 Requirements for the vitreous enamel on test samples 2 8 Requirements for finished panels 2 Annex A (informative) Guidance on vitreous enamelling processing 4 Annex B (informative) Guidanc
6、e on handling and packing 4 List of references Inside back coverBS7793-1:1995 ii BSI 10-1999 Foreword This British Standard has been prepared by Technical Committee STI/36. It specifies the requirements to be met by vitreous enamel coatings for use in agricultural slurry tanks. The quality of the vi
7、treous enamel coating is one of the most significant aspects of the manufacture of this type of tank for storage of animal slurry because of the important environmental considerations that exist. This standard has been prepared in recognition of the need for a specification equivalent, although not
8、necessarily technically identical, to standards in existence in other European countries, which specify a minimum quality for the vitreous enamel. Assessed capability. Users of this British Standard are advised to consider the desirability of quality system assessment and registration against the ap
9、propriate standard in the BSENISO9000 series by a third party certification body. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself
10、 confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, pages i and ii, pages1to4, an inside back cover and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicat
11、ed in the amendment table on the inside front cover.BS7793-1:1995 BSI 10-1999 1 1 Scope This British Standard specifies requirements for vitreous enamel coatings applied to bolted steel panels for use in the construction of agricultural tanks for storing animal slurry above ground on farms. This Bri
12、tish Standard applies to the vitreous enamelling elements of the manufacturing process. In addition to the definitive requirements, this standard also requires the item detailed in clause4 to be documented. For compliance with this standard, both the definitive requirements and the documented item h
13、ave to be satisfied. 2 References 2.1 Normative references This British Standard incorporates, by reference, provisions from specific editions of other publications. These normative references are cited at the appropriate points in the text and the publications are listed on the inside back cover. S
14、ubsequent amendments to, or revisions of, any of these publications apply to this British Standard only when incorporated in it by updating or revision. 2.2 Informative references This British Standard refers to other publications that provide information or guidance. Editions of these publications
15、current at the time of issue of this standard are listed on the inside back cover, but reference should be made to the latest editions. 3 Definitions For the purposes of this British Standard, the following definitions apply. 3.1 slurry a mixture consisting wholly or mainly of excreta produced by li
16、vestock whilst in a building or yard, bedding, rainwater and washings from a building or yard used by livestock, of a consistency that allows it to be pumped or discharged by gravity at any stage in the handling process NOTEAttention is drawn to the following statutory regulations. Statutory Instrum
17、ent No. 324. 1991. Water, England and Wales. The control of pollution (silage, slurry and agricultural fuel oil) regulations1991 1. Statutory Instrument No. 356. 1991. Water, Scotland. The control of pollution (silage, slurry and agricultural fuel oil) regulations1991 2. 3.2 vitreous enamel a glazed
18、 surface finish produced by fusing an inorganic glass on to a steel sheet base 3.3 vitreous enameller the company undertaking and controlling the process of vitreous enamelling the steel sheet base 3.4 supplier any company supplying the vitreous enameller with any materials for use in the vitreous e
19、namelling process 3.5 defect any break in the surface; burn off, crawling or tearing, fish scaling or lamination NOTEExamples of these defects can be found in the IVE Atlas of enamel defects 3. 3.6 burn off rough bareness of enamel coatings 3.7 crawling agglomerates or irregular-shaped islands of vi
20、treous enamel surrounded, or partially surrounded, by exposed substrate which is either a mild form of roll back (see3.12) where the enamel has only partially rolled back or a severe form of tearing where the cracks in the biscuit have failed to heal during fusion 3.8 fish scaling half moon shaped c
21、racks or shales resembling the scales of a fish in both ground or cover coats, which may vary in size and distribution, may occur some time after the pieces are fired and only occur on pieces coated on both sides 3.9 lamination a linear defect comprising a line or lumps or single elongated ridge 3.1
22、0 discontinuity any defect which allows an electric current to pass through the vitreous enamel coating when tested using the specified testing instrument operated in accordance with8.4 3.11 inspection area that area inside a boundary25mm from any panel edge or hole, and outside a boundary25mm from
23、any opening or hole within the body of the panelBS7793-1:1995 2 BSI 10-1999 3.12 roll back bare areas of substrate from which the vitreous enamel has rolled back during processing leaving a build-up of enamel around the edges of the exposed areas 4 Information and requirements to be agreed and docum
24、ented The following item to be agreed between the contracting parties, which is specified in the clause referred to, shall be fully documented. Both the definitive requirements specified throughout the standard and the following documented item shall be satisfied before a claim of compliance with th
25、e standard can be made and verified. a) Use of materials to cover discontinuities (see8.4). 5 Chemical resistance The vitreous enamel used shall be chemically resistant to slurry. NOTEIf the vitreous enamel finish meets the requirements given in clause7 it will be chemically resistant to slurry. Any
26、 materials used on the surface of the finished panels, as a part of the manufacturing or vitreous enamelling process, which may come into contact with the slurry, shall be chemically resistant to slurry. 6 Steel sheet base A grade of steel deemed suitable by the enameller to produce enamel suitable
27、for the purpose shall be used. NOTEA.1 gives information on procedures for inspection of the steel sheet base. 7 Requirements for the vitreous enamel on test samples NOTESince the slurry tanks, or panels from which they are made, are large the tests on the coatings of the slurry tanks as built may b
28、e represented by tests on test samples. 7.1 Production of test samples The vitreous enamelled test samples shall be produced in accordance with BS1344-12:1975. NOTEThe test samples produced as above may be used at regular intervals as a check on the consistency of the processing (seeA.2). The tests
29、in7.2 to 7.8 shall be carried out. 7.2 Resistance to citric acid at room temperature When tested in accordance with BS1344-2:1975, the minimum resistance to citric acid at room temperature shall be class A. 7.3 Resistance to boiling citric acid When tested in accordance with BS1344-8:1984, the maxim
30、um loss in mass shall be10g/m 2after simmering in the citric acid solution for2; h. 7.4 Resistance to boiling distilled water When tested in accordance with BS1344-9:1987, the maximum loss in mass shall be3.5g/m 2after a24h test period. 7.5 Resistance to sodium hydroxide solution at80 C When tested
31、in accordance with BS1344-17:1975, the maximum loss in mass shall be3.5g/m 2after exposure to the sodium hydroxide solution at80 C for5h. 7.6 Impact resistance When tested in accordance with BS1344-21:1993, using a force of20N, the maximum cracking shall be2mm after24h. 7.7 Adhesion When tested as f
32、ollows, the adhesion of the vitreous enamel to the steel shall be at least “very good” as defined in the IVE Atlas of enamel defects 3. Place a flat test sample, measuring at least30cm 30cm, on a rigid surface and hit it with a ball-pane hammer with sufficient force to shatter the vitreous enamel. R
33、emove loose flakes and crushed vitreous enamel to leave the area clear. Compare the fractured area with the IVE visual classification of adhesion given in 3. Repeat the test at least three times over the area of the test sample. 7.8 Scratch hardness When tested in accordance with BS6431-13:1986, the
34、 vitreous enamelled surface shall give a hardness of at least5on the Mohs scale. 8 Requirements for finished panels 8.1 General Finished panels shall be inspected following the enamelling process, prior to packing and despatch from the enamellers premises. The inspections given in8.2 to8.6 shall be
35、carried out.BS7793-1:1995 BSI 10-1999 3 8.2 Visual inspection of the outside surface The entire outside surface of all panels shall be inspected visually, using normal or corrected vision at a distance of not less than1.5m under good daylight or equivalent artificial lighting having an intensity of
36、at least1500lx, for defects in the enamel coating. Any panel having visible defects larger than1mm (see3) shall be rejected. Any panel having more than a total of three visible defects, smaller than1mm, per square metre of panel area, shall be rejected. 8.3 Visual inspection of the inside surface Th
37、e inside surface of all panels shall be inspected visually, using normal or corrected vision under good daylight or equivalent artificial lighting having an intensity of at least1500lx, for defects in the enamel coating. Any visible defect which also shows as a discontinuity when inspected using a l
38、ow voltage wet swab tester approved by the enameller for this purpose and used in accordance with8.4.3 and8.4.4 shall be reason to reject the panel. Any panel having more than a total of three discontinuities per square metre of panel area, or more than five discontinuities in any area 1m 1m square,
39、 shall be rejected. 8.4 Low voltage inspection of the inside surface 8.4.1 The inspections shall be confined to the defined inspection area (see3.11). 8.4.2 As a means of monitoring the visual inspection, panels shall be selected using a sampling procedure in accordance with BS6001-1:1991 and shall
40、be checked on the inside surface only, using a low voltage wet swab tester approved by the enameller for this purpose and used in accordance with8.4.3 and8.4.4. Any panel having more than a total of three discontinuities per square metre of panel area, or more than five discontinuities in any area1m
41、 1m square shall be rejected. If this inspection reveals more than the specified number of discontinuities, the inspection shall continue until such time as the enamelling process is rectified and the inspection again indicates numbers of discontinuities within the specified limits. When agreed betw
42、een the vitreous enameller and the purchaser (see clause4), it shall be permissible to cover discontinuities on the inside surface revealed by the low voltage inspection. The material used shall conform to clause7 of BS5502-50:1993, and shall be applied in accordance with the manufacturers instructi
43、ons. 8.4.3 The conducting solution used to wet the swab shall consist of tap water containing an industrial, low sudsing wetting agent at the rate of 8ml per litre of water (see4). 8.4.4 The tester shall have an excitation voltage of9V% and be set such that the alarm sounds or indicates when the ele
44、ctrical resistance of the vitreous enamel surface drops below900007 10%. The tester shall have a valid calibration record. 8.5 Inspection of vitreous enamel thickness The thickness of the vitreous enamel on panels selected using a sampling procedure in accordance with BS6001-1:1991 shall be measured
45、 using an instrument approved by the vitreous enameller for this purpose and suitable for a measurement range of04m to5004m which is regularly checked against a calibration standard. At no point within the inspection area shall the thickness of the vitreous enamel be less than1804m or more than5004m
46、. Panels having vitreous enamel thicknesses outside these limits shall be rejected. If this inspection reveals a vitreous enamel thickness outside the specified limits, the inspection shall continue on all panels until such time as the vitreous enamelling process is rectified and the inspection agai
47、n indicates vitreous enamel thicknesses within the specified limits consistently for a batch length of20panels. 8.6 Inspection of vitreous enamel colour Both surfaces of panels, selected using a sampling procedure in accordance with BS6001-1:1991, shall be inspected using a colour comparator approve
48、d by the vitreous enameller for this purpose, in order to check the colour against specified limits set by the vitreous enameller. Panels of a colour outside these limits shall be rejected. If this inspection reveals a colour outside the specified limits, then this inspection shall continue on all p
49、anels until such time as the vitreous enamelling process is rectified and this inspection again indicates vitreous enamel colour within the specified limits. NOTEColour in vitreous enamel is subject to process controls and it is recommended that acceptability of colour should be agreed between the purchaser and vitreous enameller prior to vitreous enamelling. +10 5BS7793-1:1995 4 BSI 10-1999 Annex A (informative) Guidance on vitreous enamelling processing A.1 Raw materials All raw materials used in the production of the vitreous enamelled panels need
