Why the Hot Pressure Test Matters ? PVC is still the work-horse of low- and medium-voltage cable insulation. Yet every new solar farm, EV-charging loop and data-center bus-way pushes conductors to 90 °C, 105 °C, even 125 °C. If the PVC sheath softens, the copper migrates and the first knee-jerk failure is cracking. The hot pressure test defined in IEC 60811-3-1 / BS EN 60811-3-1 is the only accelerated method that reproduces 20 years of thermal creep in 240 minutes. Pass it once, and insurers approve your cable for 40-year life. Fail it, and you re-tool an entire extrusion line.
When purchasers Google “insulating and sheathing materials of electric cables Part 3: Methods specific to PVC compounds Section 3.1 Pressure test at high temperature-Tests for resistance to cracking”, they are not hunting for academic white papers—they need a fast, audit-ready protocol that keeps containers moving through Rotterdam, Jebel Ali and Long Beach without a $200 k customs re-inspection bill. The hot pressure test, hidden inside the twin standards IEC 60811-3-1 and BS EN 60811-3-1, is that silent gate-keeper. No certificate, no dock release; no dock release, no invoice paid.
| 8 Pressure test at high temperature for insulations and sheaths | Heat Pressure Test for PVC Compounds｜IEC 60811-3-1｜BS EN 60811-3-1 |
| NOTE: This test is not recommended for thicknesses of insulations and sheaths less than O.4 mm. | |
| 8.1 Test for insulations | |
| 8.1.1 Sampling | |
| For each core to be tested, three adjacent pieces shall be taken from a sample having a length of 250 mm to 500 mm. The length of each piece shall be 50 mm to 100 mm. | |
| The cores of flat cords without sheaths shall not be separated. | |
| 8.1.2 Preparation of test pieces | |
| From each core piece taken in accordance with Sub-clause 8.l.l, any covering including semi-conducting layer, if any, shall be removed mechanically. According to the type of cable, the test piece may have a circular or sector-shaped cross-section. | |
| 8.1.3 Position of each test piece in the test apparatus | |
| The indentation device is shown in Figure l, and consists of a rectangular blade with an edge O.70 ±0.01 mm wide,which can be pressed against the test piece. Each test piece shall be placed in the position shown in Figure l. Flat cords without sheaths shall be laid on their flat side. Test pieces having a small diameter shall be fixed on the support in such a manner that they do not curve under the pressure of the blade.Test pieces of sector-shaped cores shall be placed on a support provided with a fitting sector-shaped profile as shown in Figure 1. The force shall be applied in a direction perpendicular to the axis of the core; the blade shall also be perpendicular to the axis of the core. | |
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| 8.1.4 Calculation of the compressing force | |
| The force F, in newtons, which shall be exerted by the blade upon the test piece (of both round and sector-shaped cores) is given by the formula: F=k/2Dō-8², where | |
| k is a coefficient which shall be specified in the standard for the type of cable if a value is given,or,if a value is not specified in the cable standard, shall be: | |
| k= 0.6 for flexible cords and cores of flexible cables; | |
| k=0.6 for cores,with D<15 mm, for cables for fixed installations; | |
| k =0.7 for cores,with D> 15 mm,and for sector-shaped cores for cables for fixed installations; | |
| ō=mean value of the thickness of the insulation of the test piece; | |
| D= mean value of the outer diameter of’ the test piece. | |
| ō and D are both expressed in millimetres, to one decimal place, and measured on a thin slice cut from the end of the test piece, as specified in the test method in IEC Publication 81l-1-l: Common Test Methods for Insulating and Sheathing Materials of Electric Cables, Part 1: Methods for General Application. | |
| Section 1- Measurements of Thickness and Overall Dimensions. Tests for Determining the Mechanical Properties. | |
| For sector-shaped cores, Dis the mean value of the diameter of the “back” or circular part of the sector, in millimetres, to one decimal place. This is determined from three measurements, by means of a tape measure, of the circumference of the core assembly (the measurements being made at three different places on the assembled cores). | |
| The force applied upon the piece of flat cord without sheath shall be twice the value given by the above formula, where D is the mean value of the minor dimension of the test piece described in Sub-clause 8.1.1 | |
| The calculated force may be rounded off down by not more than 3 %. | |
| 8.1.5 Heating of the loaded test pieces | |
| The test shall be carried out in an air oven in which the apparatus and test pieces are placed in a position free from vibration or in an air oven which is mounted on an anti-vibration support. No apparatus likely to cause vibration, such as an air stirring mechanism, should be directly attached to the oven. | |
| The temperature of the air shall be maintained continuously at the value specified in the relevant cable standard. | |
| The loaded, but not pre-heated, test piece shall be kept in the test position for the time specified in the relevant standard, or, if the time is not specified in the cable standard, for the following times: | |
| 4 h for test pieces having a value of D≤15 mm; | |
| 6 h for test pieces having a value of D> 15 mm. | |
| 8.1.6 Chilling of the loaded test pieces | |
| At the end of the specified durations (see Sub-clause 8.1.5), the test piece shall be rapidly cooled under load. In the heating cabinet, this operation may be caried out by spraying the test piece with cold water on the spot where the blade is pressing. | |
| The test piece shall be removed from the apparatus when it has cooled to a temperature where recovery of the insulation no longer occurs; the test piece shall then be cooled further by immersion in cold water. | |
| 8.1.7 Measurement of the indentation | |
| Immediately after cooling, the test piece shall be prepared for determining the depth of indentation. | |
| The conductor shall be withdrawn leaving the test piece in the form of a tube. | |
| A narrow strip shall be cut from the test piece in the direction of the axis of the core, perpendicular to the indentation as shown in Figure 2. | |
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| The strip shall be laid flat under a measuring microscope or a measuring projector and the cross-wire shall be adjusted to the bottom of the indentation and the outside of the test piece as shown in the same figure. | |
| Small test pieces, up to about 6 mm external diameter, shall be cut transversely at and adjacent to the indentation, as shown in Figure 3, and the depth of the indentation shall be determined as the difference between the microscope measurements on sectional views 1 and 2 as shown in the same figure. | |
| All measurements shall be made in millimetres to two decimal places. | |
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| 8.1.8 Evaluation of results | |
| The median of the indentation values, measured on the three test pieces taken from each core, shall be not more than 50 % of the mean value of the thickness of the insulation of the test piece (as measured in accordance with Sub-clause 8.1.4). | |
| Note: The value of 50 is inseparable from the underlying principle of the formula and is the same for all materials. The severity of the test can be changed by variation of the factor k only, without altering the value of 50 %. | |
| 8.2 Test for sheaths | |
| 8.2.1 Sampling | |
| For each sheath to be tested, three adjacent pieces shall be taken from a sample having a length of 250 mm to 500 mm from which the covering (if any) and all the internal parts (cores, fillers, inner covering, armour, etc., if any) have been removed. | |
| The length of each piece of sheathing shall be 50 mm to l00 mm (the higher values for the larger diameters). | |
| 8.2.2 Preparation of test pieces | |
| From each piece of sheathing (see Sub-clause 8.2.1), a strip, of width equal to about one-third of the circumference, shall be cut parallel to the direction of the axis of the cable if the sheath does not have ridges. | |
| If the sheath has ridges caused by more than five cores, the strip shall be cut in the same manner and these ridges shall be removed by grinding. | |
| If the sheath shows ridges caused by five or less cores, the strip shall be cut in the direction of the ridges so that it contains at least one groove which lies approximately in the middle of the strip throughout its length. | |
| If the sheath is directly applied on a concentric conductor, an armour or a metallic screen, and therefore has ridges which cannot be ground or cut away (unless the diameter is large), the sheath shall not be removed and the whole cable piece shall be used as a test piece. | |
| 8.2.3 Position of the test piece in the test apparatus | |
| The indentation device shall be the same as specified in Sub-clause 8.1.3 and shown in Figure 1. | |
| The strips shall be supported by a metal pin or tube, which may be halved in the direction of its axis to make a more stable support. | |
| The radius of the pin or tube shall be approximately equal to half the inner diameter of the test piece. | |
| The apparatus, the strip and the supporting pin (tube) shall be arranged so that the pin supports the strip and the blade is pressed against the outer surface of the test piece. | |
| The force shall be applied in a direction perpendicular to the axis of the pin (or of the cable when a whole cable piece is used) and the blade shall also be perpendicular to the axis of the pin or tube (or of the cable when a whole cable is used). | |
| 8.2.4 Calculation of the compressing force | |
| Unless otherwise specified, the force F, in newtons, which shall be exerted by the blade upon each test piece of sheath, shall be as given by the formula: F=k/2D6-8² | |
| 8.2.5 Heating of the loaded test pieces | |
| The test pieces shall be heated as described in Sub-clause 8.l.5, for the time specified in the standard for the type of cable, or, if the time is not specified in the cable standard, for the following times: | |
| 4 h for test pieces having an outer diameter not exceeding l5 mm | |
| 6 h for test pieces with an outer diameter exceeding 15 mm | |
| 8.2.6 Chilling of the load test pieces | |
| The test pieces shall be chilled by the method described in Sub-clause 8.1.6. | |
| 8.2.7 Measurement of the indentation | |
| The indentation shall be measured on a narrow strip cut from the test piece, as described in Sub-clause 8.1.7 and shown in Figure 2. | |
| 8.2.8 Evaluation of results | |
| The median of the indentation values measured on the three test pieces taken from the sheath under test shall be not more than 50 of the mean value of the thickness of the sample when measured in accordance with Sub-clause 8.2.4. | |
| Note: The value of 50 is inseparable from the underlying principle of the formula and is the same for all materials. The severity of the test can be changed by variation of the factor k only,without altering the value of 50 %. | |
| 8.3 Test method using a dial micrometer | |
| Under consideration. |
| Equipment Model | WEW-150-SW | WEW-270-SW | WEW-480-SW | WEW-1000-SW |
| Volume Size | 150 Liters | 270 Liters | 480 Liter | 1000 Liters |
| Interior Size (W*D*H)mm | 500*500*600 | 600*500*900 | 800*600*1000 | 1000*1000*1000 |
| Exterior Size (W*D*H)mm | 800*690*1320 | 920*690*1690 | 1120*790*1790 | 1320*1190*1790 |
| Max Shelf Load | 25 Kgs | 25 Kgs | 40 Kgs | 40 Kgs |
| Power Voltage | AC220V±10% | 50Hz/60Hz | AC 380V±10% | 50Hz/60Hz |
| Temperature Range | +10 ºC~ +220 ºC | +15 ºC~ +320 ºC | +10 ºC~ +220 ºC | +15 ºC~ +320 ºC |
| Temp. Constancy | ±0.2 ºC~0.3 ºC | ±0.3 ºC~0.3 ºC | ±0.2 ºC~0.3 ºC | ±0.3 ºC~0.3 ºC |
| Temperature Uniformity | ±2.0 ºC / 15 ºC~ 200ºC | ±2.5 ºC / 15 ºC~330C | ±2.0 ºC / 20 ºC~ 200ºC | ±2.5 ºC / 20 ºC~330C |
| Heating Up Time | 6 min / 50 ºC to 200 C | 10 min / 52 ºC to 300 ºC | 6 min / 50 C to 200 C | 10 min / 55 C to 300 ºC |
| Power Watts (kW) | 3.0 kW | 6.5 kW | 8.5 kW | 10.0 kW |
| Gross Weight (Kgs) | 65.0 Kgs | 90.0 Kgs | 120.0 Kgs | 185.0 Kgs |
