ASTM D1048-24

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: D1048 − 22 D1048 − 24
Standard Specification for
Rubber Insulating Blankets
This standard is issued under the fixed designation D1048; 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.
This standard has been approved for use by agencies of the U.S. Department of Defense.
1. Scope
1.1 This specification covers acceptance testing of rubber insulating blankets for protection of workers from accidental contact
with live electrical conductors, apparatus, or circuits.
1.2 Two types of blankets are provided and are designated as Type I, not resistant to ozone, and Type II, resistant to ozone.and
Type III ozone resistant.
1.3 Five classes of blankets, differing in electrical characteristics, are provided and are designated as Class 0, Class 1, Class 2,
Class 3, and Class 4.
1.4 Two styles of blankets, differing in construction characteristics, are provided and are designated as Style A and Style B.
1.5 The values stated in SI units are to be regarded as standard. The values given in parentheses after SI units are provided for
information only and are not considered standard.
1.6 The following safety hazards caveat pertains only to the test method portion, Sections 16 – 19, of this specification: 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, health, and environmental practices and determine the applicability of regulatory
limitations prior to use.
1.7 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
D149 Test Method for Dielectric Breakdown Voltage and Dielectric Strength of Solid Electrical Insulating Materials at
Commercial Power Frequencies
D297 Test Methods for Rubber Products—Chemical Analysis
D412 Test Methods for Vulcanized Rubber and Thermoplastic Elastomers—Tension
This specification is under the jurisdiction of ASTM Committee F18 on Electrical Protective Equipment for Workers and is the direct responsibility of Subcommittee
F18.25 on Insulating Cover-Up Equipment. This standard replaces ANSI Standard J 6.4, which is no longer available.
Current edition approved July 1, 2022Feb. 1, 2024. Published August 2022February 2024. Originally approved in 1949 as D1048 – 49 T. Last previous edition approved
in 20202022 as D1048D1048 – 22.-20. DOI: 10.1520/D1048-22.10.1520/D1048-24.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D1048 − 24
D518 Test Method for Rubber Deterioration—Surface Cracking (Withdrawn 2007)
D570 Test Method for Water Absorption of Plastics
D573 Test Method for Rubber—Deterioration in an Air Oven
D624 Test Method for Tear Strength of Conventional Vulcanized Rubber and Thermoplastic Elastomers
D1388 Test Method for Stiffness of Fabrics
D2865 Practice for Calibration of Standards and Equipment for Electrical Insulating Materials Testing
F819 Terminology Relating to Electrical Protective Equipment for Workers
2.2 American National Standards:
ANSI/IEEE C 2C2 National Electrical Safety Code
C84.1 Electric Power Systems and Equipment—Voltage Ratings (60 Hz)
3. Terminology
3.1 Definitions:
3.1.1 beaded edge, n—a narrow border of thicker rubber which extends completely around the outer edges of the blanket.
3.1.2 breakdown, n—the electrical discharge or arc occurring between the electrodes and through the equipment being tested.
3.1.3 designated person, n—an individual who is qualified by experience or training to perform an assigned task.
3.1.4 electrical testing facility, n—a location with qualified personnel, testing equipment, and procedures for the inspection and
electrical testing of electrical insulating protective equipment.
3.1.5 electrode clearance—the shortest path from the energized electrode to the ground electrode.
3.1.6 flashover, n—the electrical discharge or arc occurring between electrodes and over or around, but not through, the equipment
being tested.
3.1.7 insulated, adj—separated from other conducting surfaces by a dielectric substance (including air space) offering a high
resistance to the passage of current.
3.1.7.1 Discussion—
When any object is said to be insulated, it is understood to be insulated in a suitable manner for the conditions to which it is
subjected. Otherwise, it is, within the purpose of this definition, uninsulated. Insulating covering of conductors is one means of
making this conductor insulated.
3.1.8 ozone, n—a very active form of oxygen that may be produced by corona, arcing, or ultra-violet rays.
3.1.9 ozone cutting and checking, n—cracks produced by ozone in a material under mechanical stress.
3.1.10 rubber, n—a generic term that includes elastomers and elastomer compounds regardless of origin.
3.1.11 user, n—the employer or entity purchasing the equipment to be utilized by workers for their protection; in the absence of
such an employer or entity, the individual purchasing or utilizing the protective equipment.
3.1.12 voltage, maximum retest, n—voltage, either ac rms or dc avg, that is equal to the proof-test voltage for new protective
equipment.
3.1.13 voltage, retest, n—voltage, either ac rms or dc avg, that used protective equipment must be capable of withstanding for a
specified test period without breakdown.
3.1.14 voltage, nominal design, n—a nominal value consistent with the latest revision of ANSI C84.1, assigned to the circuit or
system for the purpose of conveniently designating its voltage class.
The last approved version of this historical standard is referenced on www.astm.org.
Available from Institute of Electrical and Electronics Engineers, Inc. (IEEE), 445 Hoes Ln., P.O. Box 1331, Piscataway, NJ 08854-1331, http://www.ieee.org.
Available from National Electrical Manufacturers Association (NEMA), 1300 N. 17th St., Suite 900, Arlington, VA 22209, http://www.nema.org.
D1048 − 24
3.1.15 voltage, maximum use, n—the ac voltage, (rms), classification of the protective equipment that designates the maximum
nominal design voltage of the energized system that may be safely worked. The nominal design voltage is equal to phase-to-phase
voltage on multi-phase circuits.
3.1.15.1 Discussion—
If there is no multi-phase exposure in a system area, and the voltage exposure is limited to phase (polarity on dc systems) to ground
potential, the phase (polarity on dc systems) to ground potential shall be considered to be the nominal design voltage.
3.1.15.2 Discussion—
If electrical equipment and devices are insulated or isolated, or both, such that the multi-phase exposure on a grounded wye circuit
is removed, then the nominal design voltage may be considered as the phase-to-ground voltage on that circuit.
3.1.15.3 Discussion—
The work practices and methods associated with removing multi-phase exposures at any given work site are not addressed in this
specification. Users should refer to ANSI C2, National Electrical Safety Code, Section 44, for proper work practices.
3.2 For definitions of other terms, refer to Terminology F819.
4. Significance and Use
4.1 This specification covers the minimum electrical, chemical, and physical properties guaranteed by the manufacturer and the
detailed procedures by which such properties are to be determined. The purchaser may, at his option, perform or have performed
any of these tests in order to verify the guarantee. Claims for failure to meet the specification are subject to verification by the
manufacturer.
4.2 Blankets are used for personal protection; therefore, when authorizing their use, a margin of safety shall be provided between
the maximum voltage at which they are used and the proof-test voltage at which they are tested. The relationship between
proof-test voltage and the nominal maximum voltage at which blankets shall be used is shown in Table 1.
4.3 Work practices vary from user to user depending upon many factors. These factors may include, but are not limited to,
operating system voltages, construction design, work procedures and techniques, weather conditions, etc. Therefore, except for the
restrictions set forth in this specification because of design limitations, the use and maintenance of this equipment is beyond the
scope of this specification.
4.3.1 It is common practice and the responsibility of the user of this type of protective equipment to prepare complete instructions
and regulations to govern the correct and safe use of such equipment.
TABLE 1 Proof/Design-Test/Use Voltage Relationship
Nominal
Maximum
DC Design-
Class AC Proof-Test
Use
Test
of Insu- A Voltage,
Voltage
Voltage,
lating Blankets Phase-Phase, rms V
avg, V
ac,
rms, max
0 1 000 5 000 20 000
1 7 500 10 000 40 000
2 17 000 20 000 50 000
3 26 500 30 000 60 000
4 36 000 40 000 70 000
TABLE 1 Proof/Design-Test/Use Voltage Relationship
Maximum DC Design- Maximum
AC
Class
AC Use Test DC Use
Proof-Test
of
A
Voltage Voltage, Voltage
Voltage,
Blanket
rms, V
AC, rms, V avg, V avg, V
0 5 000 1 000 20 000 1 500
1 10 000 7 500 40 000 11 250
2 20 000 17 000 50 000 25 500
3 30 000 26 500 60 000 39 750
4 40 000 36 000 70 000 54 000
A
Except for Class O0 equipment, the maximum use voltage is based on the
following formula:
Maximum use voltage (maximum nominal design voltage) 0.95 ac proof-test
voltage − 2000
D1048 − 24
5. Classification
5.1 Blankets covered under this specification shall be designated as Type I I, Type II, or Type II;III; Class 0, Class 1, Class 2, Class
3, or Class 4; Style A or Style B.
5.1.1 Type I, non-resistant to ozone, made from a high-grade cis-1,4-polyisoprene rubber compound of natural or synthetic origin,
properly vulcanized.
5.1.2 Type II, ozone resistant, made of any elastomer or combination of elastomeric compounds.
5.1.3 Type III, made of any combination of an elastomer and thermoplastic polymers, elastic in nature.
5.1.4 The class designation shall be based on the electrical properties as shown in Table 1 and Table 2.
5.1.5 Style A, constructed of the elastomers indicated under Type I I, Type II, or Type II,III, shall be free of any reinforcement.
5.1.6 Style B, constructed of the elastomers indicated under Type I I, Type II, or Type II,III, shall incorporate a reinforcement; this
reinforcement shall not adversely affect the dielectric characteristics of the blankets.
6. Ordering Information
6.1 Orders for blankets under this specification should include the following information:
6.1.1 Type,
6.1.2 Class,
6.1.3 Style,
6.1.4 Size,
6.1.5 Eyelets, and
6.1.6 Color.
6.2 The listing of types, classes, styles, sizes, and eyelets is not intended to mean that all shall necessarily be available from
manufacturers; it signifies only that, if made, they shall conform to the details of this specification.
7. Manufacture and Marking
7.1 The blankets shall be produced by a seamless vulcanizing process.
7.2 Where eyelets are specified, each blanket shall be equipped with nonmetallic eyelets.
TABLE 2 Electrical AC Proof and DC Design Tests
AC DC
Nominal Electrode Nominal Electrode
Proof-Test Voltage,
Class
A Design-Test A
Clearances Clearances
rms,
B
Voltages, avg, V
V
mm in. mm in.
0 5 000 76 3 20 000 76 3
1 10 000 76 3 40 000 76 3
2 20 000 127 5 50 000 152 6
3 30 000 178 7 60 000 203 8
4 40 000 254 10 70 000 305 12
A
These nominal clearances are intended to avoid flashover and may be increased by no more than 51 mm (2 in.) when required by a change in atmospheric conditions
from the standard of 100 kPa (1 atm) barometric pressure and average humidity conditions. These clearances may be decreased if atmospheric conditions permit.
B
DC design-test voltages were determined using negative polarity.
D1048 − 24
7.3 Each blanket shall be marked clearly and permanently with the name of the manufacturer or supplier, ASTM D1048D1048,,
type, class, and style.
7.3.1 Blankets may be marked by either molding the information directly into the blanket or by use of a label; either method is
equally acceptable. The method shall be at the discretion of the manufacturer. If a label is used the color shall be that specified
for each voltage class; Class 0—red, Class 1—white, Class 2—yellow, Class 3—green, and Class 4—orange.
7.4 Blankets shall have a smooth, flat finish and beaded edges.
8. Chemical and Physical Requirements
8.1 The blanket material shall conform to the physical requirements in Table 3 and the accelerated aging in 19.2.7.
8.2 For Type I blankets, the rubber polymer may be determined in accordance with 19.1.1. This shall be the referee test if a dispute
exists between the manufacturer and purchaser regarding the elastomer content of Type I blankets.
8.3 The Type II or Type III blanket material shall show no visible effects from ozone when tested in accordance with 18.6. Any
visible signs of ozone deterioration, such as checking, cracking, breaks, pitting, etc., shall be considered as evidence of failure to
meet the requirements of Type II or Type III blankets. In case of dispute, Method A of the ozone resistance test shall be the referee
test.
9. Electrical Requirements
9.1 Each blanket shall be given a proof test and shall withstand the 50-Hz or 60-Hz ac proof-test voltage (rms value). DC design
test to be performed on blankets and repeated if a change occurs to the manufacturing process or in the material. See Table 2. The
ac proof test and dc design test shall be performed in accordance with Section 18. The test voltage shall be applied continuously
for 3 minutes.
9.2 The blanket material shall show a 60-Hz dielectric strength of not less than 14.8 MV/m (375 V-rms/mil) of specimen thickness
for each individual test, when tested in accordance with 18.5.
TABLE 3 Physical Requirements
Type I Type II &
Type III
Style A Style B Style A
Blanket Blanket Blanket
Tensile strength, min, Die C, 17.2 (2500) 17.2 (2500) 10.3 (1500)
MPa (psi)
Elongation, min, % 500 500 500
Tension set, max, mm (in.) 6.4 (0.25) 6.4 (0.25) 6.4 (0.25)
Tear resistance, min, kN/m 21 (120) 26 (150) 16 (90)
(lbf/in.)
Puncture resistance, min, 18 (100) 26 (150) 18 (100)
kN/m (lbf/in.)
Drape stiffness, max at 89 (3.5) 89 (3.5) 89 (3.5)
25°C (77°F), mm (in.)
Drape stiffness, max at 89 (3.5) 89 (3.5) 89 (3.5)
25 °C (77 °F), mm (in.)
Drape stiffness, max at 110 (4.5) 110 (4.5) 110 (4.5)
−10°C (14°F), mm (in.)
Drape stiffness, max at 110 (4.5) 110 (4.5) 110 (4.5)
−10 °C (14 °F), mm (in.)
Flex stiffness, max at 25°C 0.028 (0.25) 0.028 (0.25) 0.028 (0.25)
(77°F), N·m (in.·lbf)
Flex stiffness, max at 25 °C 0.028 (0.25) 0.028 (0.25) 0.028 (0.25)
(77 °F), N·m (in.·lbf)
Flex stiffness, max at − 10°C 0.034 (0.30) 0.034 (0.30) 0.034 (0.30)
(14°F), N·m (in.·lbf)
Flex stiffness, max at − 10 °C 0.034 (0.30) 0.034 (0.30) 0.034 (0.30)
(14 °F), N·m (in.·lbf)
Moisture absorption, max, % 1.5 3.0 2.0
D1048 − 24
10. Dimensions and Permissible Variations
10.1 Length and Width—The length and width of the blankets shall be specified on the purchase order. Some standard sizes are
as shown in Table 4. Permissible variations from the specified length and width shall be 613 mm (60.5 in.) except for the 1160
mm by 1160 mm (45.5 in. by 45.5 in.) slotted size for which the permissible variation shall be 625 mm (61.0 in.).(61.0 in.).
10.2 Thickness—See Table 5.
10.2.1 Manufacturers must meet the minimum thickness requirements for each Class of blanket as specified in Table 5. The
manufacturer may label a blanket lower than actual Class value if so specified by the purchaser.
10.3 Bead on Edge—The bead shall be not less than 8 mm (0.31 in.) wide nor less than 1.5 mm (0.06 in.) high.
10.4 Eyelets—If other than manufacturer’s standard is desired; the number, size, and type of eyelet shall be given on the purchase
order. The eyelets shall not be less than 8 mm (0.31 in.) (0.31 in.) in diameter.
10.5 No eyelets, holes, or slots are permitted in a blanket which will reduce the test electrode clearance to less than the values
listed in Table 2.
11. Workmanship and Finish
11.1 The blankets shall be free of harmful physical irregularities, which can be detected by thorough test or inspection.
11.1.1 Harmful physical irregularities may be defined as any feature that disrupts the uniform, smooth surface and represents a
potential hazard to the user, such as pinholes, cracks, blisters, cuts, conductive imbedded foreign matter creases, pinch marks, voids
(entrapped air), prominent ripples, and prominent mold marks.
11.2 Non-harmful Irregularities —Irregularities—Surface irregularities may be present on all rubber goods due to imperfections
on forms or molds and inherent difficulties in the manufacturing process. These irregularities may appear as indentations,
protuberances, or imbedded foreign material that are acceptable provided that:
11.2.1 The indentation or protuberance tends to blend into a smooth slope upon stretching of the material.
11.2.2 The rubber thickness at any irregularity conforms to the thickness requirements.
11.2.3 Foreign material remains in place when the blanket is rolled and stretches with the material surrounding it.
12. Guarantee
12.1 The manufacturer or supplier shall replace, without charge to the purchaser, unused blankets which, at any time within a
period of nine (9) months from the date of initial delivery of shipment to the purchaser or his designee, fail to pass the tests in
this specification. This guarantee will be binding on the manufacturer or supplier only if the blankets have been properly stored
and have not been subjected to more than an original acceptance test and one retest.
TABLE 4 Standard Blanket Sizes—Length and Width
Without Slot mm (in.)
457 by 910 (18 by 36)
560 by 560 (22 by 22)
690 by 910 (27 by 36)
910 by 910 (36 by 36)
910 by 2128 (36 by 84)
1160 by 1160 (45.5 by 45.5)
With Slot mm (in.)
560 by 560 (22 by 22)
910 by 910 (36 by 36)
1160 by 1160 (45.5 by 45.5)
D1048 − 24
TABLE 5 Thickness Measurements
Thickness
Class
mm in.
0 1.6 to 2.2 0.06 to 0.09
1 2.6 to 3.6 0.10 to 0.14
2 2.8 to 3.8 0.11 to 0.15
3 3.0 to 4.0 0.12 to 0.16
4 3.2 to 4.3 0.13 to 0.17
12.2 Any acceptance test made by the purchaser, or the purchaser’s designee, shall be performed within the first two (2) months
of the guarantee period unless otherwise specified.
NOTE 1—Proper storage means that the blankets are stored flat, not folded nor stored directly above or in proximity to steam pipes, radiators, or other
sources of artificial heat, or exposed to direct sunlight or other sources of ozone. It is desirable that the ambient storage temperature shall not exceed 35°C
(95°F).35 °C (95 °F).
13. Sampling
13.1 Each blanket in a lot or shipment shall be subject to inspection and test to meet the requirements of Sections 7, 11, 15, and
9.1.
13.2 An original sample of 1 % of the lot or shipment or not less than one blanket, whichever is greater, shall be selected at random
from the lot or shipment for the test requirements of 9.2 and Section 10. If a failure occurs in the first sample, a second sample
of the same quantity shall be selected and tested.
13.3 An original sample of 0.1 % of the lot or shipment or not less than one blanket, whichever is greater, shall be selected at
random from the lot or shipment for the test requirements of 8.1 and 8.3.
14. Rejection
14.1 Individual blankets shall be rejected if they fail to meet manufacturing and marking requirements of Section 7, the electrical
requirements of 9.1, the minimum thickness requirements of 10.2, or the workmanship requirements of Section 11.
14.2 Individual blankets may be rejected at the option of the purchaser if they fail to meet the requirements stipulated in 10.1, 10.2,
10.3, 10.4, and Section 15.
14.3 The entire lot or shipment of blankets shall be re
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