ASTM C537-87(2009)
(Test Method)Standard Test Method for Reliability of Glass Coatings on Glassed Steel Reaction Equipment by High Voltage
Standard Test Method for Reliability of Glass Coatings on Glassed Steel Reaction Equipment by High Voltage
SIGNIFICANCE AND USE
The widespread use of glassed-steel equipment in highly corrosive chemical processes has made it necessary to detect weak spots in the coating and repair them before catastrophic failure occurs in service. This test is intended to detect discontinuities and thin areas in a glass coating on metal to ensure that the coating is defect free and has sufficient thickness to withstand the prescribed service conditions. A test voltage may be selected at any desired value up to 20 000 V, thus making the test applicable to a wide range of thickness requirements. When, because of bubbles or defects, the thickness of glass at any spot is less than enough to withstand the applied voltage, a puncture results with an accompanying indication of a defect. Remedial action is then required to repair the defect before the equipment can be used for corrosive service. (When such defects are found before the equipment leaves the manufacturer's plant another application of glass can usually be applied and fired to become an integral part of the coating.)
SCOPE
1.1 This test method covers the determination of the reliability of glass coating on metal and is intended for use by manufacturers of equipment that is designed to withstand highly corrosive conditions where a failure of the coating in service would cause extreme damage to the exposed metal. Its use outside the manufacturer's plant is discouraged because improper or indiscriminate testing can cause punctures that are difficult to repair without returning the equipment to the manufacturer's plant. This test method detects not only existing discontinuities in the glass coating, but also areas where the glass may be thin enough to be likely to result in premature failure in service.
1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. For specific precautionary statements, see Section 7.
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NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
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Designation: C537 − 87 (Reapproved 2009)
Standard Test Method for
Reliability of Glass Coatings on Glassed Steel Reaction
Equipment by High Voltage
This standard is issued under the fixed designation C537; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope handle and cable. Wherever a discontinuity exists or the
coating is thin enough (by reason of a concealed bubble or
1.1 This test method covers the determination of the reli-
conducting inclusion, etc.) so that the dielectric strength of the
ability of glass coating on metal and is intended for use by
remaining glass is less than some preset desired amount, the
manufacturers of equipment that is designed to withstand
dielectric strength of air-plus-remaining-glass breaks down and
highly corrosive conditions where a failure of the coating in
a discharge occurs. Built-in current-limiting devices ensure
service would cause extreme damage to the exposed metal. Its
electrical safety to the operator. A variable voltage control
use outside the manufacturer’s plant is discouraged because
improper or indiscriminate testing can cause punctures that are
allows selection of a voltage which assures a predetermined
difficult to repair without returning the equipment to the
minimum thickness of glass.
manufacturer’s plant. This test method detects not only exist-
ingdiscontinuitiesintheglasscoating,butalsoareaswherethe
4. Significance and Use
glass may be thin enough to be likely to result in premature
4.1 Thewidespreaduseofglassed-steelequipmentinhighly
failure in service.
corrosive chemical processes has made it necessary to detect
1.2 The values stated in SI units are to be regarded as
weak spots in the coating and repair them before catastrophic
standard. No other units of measurement are included in this
failure occurs in service. This test is intended to detect
standard.
discontinuities and thin areas in a glass coating on metal to
1.3 This standard does not purport to address all of the
ensure that the coating is defect free and has sufficient
safety concerns, if any, associated with its use. It is the
thickness to withstand the prescribed service conditions.Atest
responsibility of the user of this standard to establish appro-
voltage may be selected at any desired value up to 20 000 V,
priate safety and health practices and determine the applica-
thus making the test applicable to a wide range of thickness
bility of regulatory limitations prior to use. For specific
requirements. When, because of bubbles or defects, the thick-
precautionary statements, see Section 7.
ness of glass at any spot is less than enough to withstand the
applied voltage, a puncture results with an accompanying
2. Terminology
indication of a defect. Remedial action is then required to
2.1 Definitions:
repair the defect before the equipment can be used for
2.1.1 glassed steel, glass-lined steel, or glass-coated steel—
corrosive service. (When such defects are found before the
designations generally applied to a class of porcelain enamels
equipment leaves the manufacturer’s plant another application
that have high resistance to chemical attack at elevated
of glass can usually be applied and fired to become an integral
temperatures and pressures.
part of the coating.)
3. Summary of Test Method
5. Interferences
3.1 This test method consists essentially of grounding the
metal structure of the equipment to the ground side of a
5.1 Sincethetestmethodiselectrical,itisnecessarytohave
direct-current high-voltage generator and sweeping the glass
a good ground connection between the instrument and the
surface with a high-potential probe on the end of an insulated
metal substrate of the equipment being tested. It is also
necessary that the surface of the glass be reasonably clean and
dry. A wet surface will conduct enough of the high voltage to
This test method is under the jurisdiction ofASTM Committee B08 on Metallic
and Inorganic Coatingsand is the direct responsibility of Subcommittee B08.12 on any exposed metal, including the edges of the glass coating, so
Materials for Porcelain Enamel and Ceramic-Metal Systems .
that an indication of a “contact” may be obtained over a large
Current edition approved April 15, 2009. Published June 2009. Originally
´1 area instead of at localized spots that can be marked and
approved in 1964. Last previous edition approved in 2004 as C537 – 87 (2004) .
DOI: 10.1520/C0537-87R09. identified for repair.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
C537 − 87 (Reapproved 2009)
FIG. 1 Circuit Diagram, 20 000-V D-C Tester
6. Apparatus 7.4 Unless the surface to be tested is clean and dry, there
may be sufficient conduction along the surface to cause a
6.1 Thetesteriscomposedofasourceofhigh-voltagedirect
capacitance discharge even if there is no direct path to ground.
current with a suitable device to limit the current. A constant-
Such a capacitance discharge is recognizable from a true
voltage transformer is used to supply a more uniform voltage
failure because the discharge spark is not confined to certain
source than the usual 115-V, 60-Hz line to which it is
spotsbutisageneraldischargetoalargeareaofthemoistglass
connected.The power supply unit consists of a suitable step-up
surface. Continuous application of the probe to such areas
transformer along with a voltage-control device, a current-
serves only to build up a capacitance charge on the surface of
limiting rheostat, a rectifier, and appropriate safety and remote
the vessel eventually resulting in a discharge through the
control relays,
...
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