1. PURPOSE
1.1 This global specification defines Air Products’ requirements for perlite insulation used in fully evacuated enclosures containing equipment in the temperature range -254 to +316C (-425 to +600F).
2. SCOPE
2.1 Air Products – Global.
3. RELATED DOCUMENTS
3.1 American Society for Testing and Materials (ASTM) C 177 Test Method for Steady-State Heat Flux Measurements and Thermal Transmission Properties by Means of the Guarded-Hot-Plate Apparatus C 518 Standard Test Method for Steady-State Thermal Transmission Properties by Means of the Heat Flow Meter Apparatus
4. PHYSICAL, CHEMICAL, AND MECHANICAL PROPERTIES
4.1 Composition
4.1.1 Perlite insulation shall consist of expanded perlite ore, produced by the application of heat to the ore and graded to meet the service requirements.
4.1.2 The chemical composition shall be approximately 76% silica, 14% alumina, and minor amounts of bivalent and trivalent oxides.
4.1.3 The addition of any organic material or other substances other than those above shall be made only with the approval of Air Products.
4.2 Moisture Content
4.2.1 The moisture content shall not exceed 0.15% by weight at the point of delivery. Measurement shall be obtained by heating a representative sample of the perlite to 104°C (220°F) and weighing the sample before and after this heating process. The size of sample selected shall be matched to the measuring equipment used such that the measured result is accurate within 0.005%.
4.2.2 The perlite is intended for high vacuum applications, and it is therefore essential that every effort be made to minimize any increase in the moisture level. Ideally, the perlite batch shall be shipped on the day of manufacture. It shall be stored and shipped in sealed bags or sealed dry containers that prevent exposure of the perlite to damp air or free water.
4.2.3 All tankers used to transport bulk (unpackaged) perlite shall be inspected by the vendor prior to filling to ensure that they are dry internally. They shall not be filled if there is evidence of condensation or other free water on the walls.
4.3 Combustibility
4.3.1 The fusion point of perlite insulation must be above 1200°C (2200°F) and it shall not spark when in contact with glowing platinum wire in an oxygen atmosphere.
4.4 Density
4.4.1 The packaged density (uncompacted ‘As Poured’ density) shall be within the range of
70–100 kg/m3 (4.4–6.3 lbs/ft3) for every sample taken. Not less than three samples shall be taken for each batch produced, the timing providing representative batch sampling (e.g., one at the start, one in the middle, and one at the end of the batch process).
4.4.2 Compacted density shall be within the range 90–120 kg/m3 (5.6–7.5 lbs/ft3). It is not necessary to measure this value for every batch, but the vendor shall demonstrate by periodic testing and records that this compacted density range is valid for perlite falling within the ‘Packaged’ density range specified above.
4.4.3 To measure the compacted density, pour a weighted amount of perlite into a standard 2000 ml (0.5 gal) glass or plastic graduated cylinder. Drop the graduate from a height of 76 mm (3 in) onto a large rubber stopper five hundred times. If compaction or settlement ceases before 500 drops, no further dropping is required. Determine the compacted volume and calculate the compacted density.
4.5 Thermal Resistance
4.5.1 The thermal resistance at atmospheric pressure of the compacted perlite insulation when tested in accordance with ASTM C 177 or C 518 shall not be lower than the values listed in Table 1.
Table 1 Thermal Resistance for 2.54 m (1 in) Thickness
| Mean Temperature °C (°F) | Thermal Resistance m2°K/W (hft2°F/Btu) |
| 4 (40) | 0.56-0.53 (3.2-3.0) |
| 24 (75) | 0.53-0.51 (3.0-2.9) |
4.6 Sieve Analysis
4.6.1 The perlite shall be separated through a series of sieves of progressively smaller openings. Perlite particle size distribution on a weight basis shall comply with those given in Table 2 and the sieve analysis shall be performed on a representative sample at least once per production run.
Table 2 Percentages Retained on each Sieve
| Sieve Size (microns) | Weight Retained (%) |
| 1160 | 3% max |
| 600 | 10-40 |
| 300 | 15-50 |
| 150 | 10-30 |
5. TESTING
5.1 The manufacturer shall perform the following tests and record the values obtained: Specific testing for moisture content per delivery of bulk perlite when this perlite has been stored at the vendors’ premises for more than 48 hours. Samples shall be selected such that they are fully representative of the perlite to be shipped. By means of a dispensation, testing for moisture is not required providing that the vendor can demonstrate that the method of storage consistently maintains the moisture content at not more than 0.15% up to the time of delivery. Specific ‘In Process’ testing of the packaged density. Specific testing for the sieve analysis.
5.2 Refer to Section 4 for the acceptance standards. The manufacturer shall retain the test records for not less than six months after shipment.
5.3 With each ‘bulk’ delivery, documented test data shall be supplied indicating the density values and also the moisture content when applicable.
5.4 Test documentation is not required for perlite supplied in bags.
5.5 Perlite not conforming to this specification shall not be shipped without a written dispensation from Air Products.
6. PACKAGING AND MARKING
6.1 The preferred method of supply is in bulk (i.e., by tanker). For such deliveries in addition to the test data requested in Section 5 above, bulk perlite shipments shall include documentation that clearly states the name and grade of the insulation, shipped weight, and the Air Products purchase order number.
6.2 Where bulk supply is not possible supply in bags can be accepted. However the bags shall be marked, as a minimum, with the name and grade of the insulation, weight, and the name of the manufacturer. The bags shall be moisture, puncture, and tear resistant, and of a size and weight that can be readily handled by one person.