BS ISO 2942-2018 pdf free download.Hydraulic fluid power — Filter elements — Verification of fabrication integrity and determination of the first bubble point
4 Apparatus and materials
4.1 Bubble-point testing apparatus, as shown in Figure 1, is comprised of the elements 4.1.1 to 4.1.5.
4.1.1 Compressed-air supply, with filter(s) and pressure regulator(s), adjustable up to 10 kPa.
4.1.2 Pressure-measuring device, with an accuracy of ±5 % of the reading.
4.1.3 Temperature-measuring device, with an accuracy of ±1,0 °C.
4.1.4 Test container, for containing the test liquid (see 4.2) in which to submerge the filter element under test.
4.1.5 Element retention and rotation fixture, for restraining the filter element during immersion to the required depth and allowing rotation about the element’s major axis either manually or with an automatic mechanism. The fixture shall include sealing bungs, of a material compatible with the test liquid (see 4.2) for sealing the compressed air supply line to the open end cap(s) of the filter element. One bung shall have an orifice which allows the transmission of the air pressure through an open end cap and if required a second sealing bung without an orifice to seal the opposite end cap of the filter element.
4.2 Test liquid The test liquid shall be clean 2-propanol (isopropyl alcohol) or an alternative liquid designated by the filter element manufacturer with a surface tension between 14 mN/m and 33 mN/m. Its cleanliness shall be consistent with subsequent test requirements. Its surface tension shall be regularly checked in accordance with the requirements of ISO 304. The liquid shall be replaced when its surface tension has changed by more than 15 % of its original value. If the test filter element has been exposed to other hydraulic fluids prior to being subjected to the fabrication integrity test, then it is permissible to use the same type of hydraulic fluid as the fabrication integrity test liquid, provided that the surface tension requirements of this subclause are met. If this is not possible, all residual previous liquid shall be removed by appropriate means before testing. This is to ensure correct and consistent wetting of the element’s media.
5 Test methods
WARNING — Exercise care when using solvents with low flash points, as there could be a risk of fire or explosion. Appropriate precautions shall be taken to avoid inhalation of fumes from
these solvents. Always use suitable protective equipment.
5.1 General procedure
5.1.1 Check that the manufacturer’s identification number or part number of the filter element to be tested complies with the manufacturer’s specification. Determine the minimum fabrication integrity of he filter element and the corresponding value for surface tension on which it is based from the filter manufacturer.
5.1.2 Remove any packaging or protective covering from the filter element. Visually examine the element for defects that might affect the validity of the test results. Install the clean filter element in the bubble-point testing apparatus (see 4.1) with the major axis of the filter element parallel to the surface of the test liquid (see 4.2).
5.1.3 Submerge the filter element in the test liquid, which shall be at a temperature of (22 ± 5 °C).
5.1.4 Allow the filter element to remain submerged in the test liquid for at least 5 min before proceeding, to ensure that the filter element media fibres are wetted. The filter element may be soaked in the test container (4.1.4) prior to its being secured in the element retention and rotation fixture (4.1.5).
If soaking is carried out while the filter element is secured in the element retention and rotation fixture,ensure that no pressure is applied to the filter during the soaking period.
5.1.5 Ensure that the lines connecting the pressure-measuring device (4.1.2) to the rest of the apparatus are void of liquid.
5.2 Verification of fabrication integrity (absence of air bubbles)
The preceding formula assumes that the designated P M uses 2-propanol with a surface tension of 21,15 mN/m as the reference fluid. If a different surface tension is used as the reference, then the value of P M should be corrected to correspond to the reference surface tension of 21,15 mN/m. NOTE In the formula, the constant 0,000 1 has units of measurement of mm (m/s 2 ) and the constant 21,15 has units of mN/m.
5.2.2 Apply an air pressure equal to about 10 % of P T to the inside of the filter element to clear any lines of test liquid and to pressurize the element. If necessary, readjust the depth of the test liquid covering the element to (12 ± 3 mm) above the top of the filter media.
5.2.3 After the pressure stabilizes, completely rotate the element around its major axis to ensure that no streams of bubbles are evident, and then gradually increase the pressure to P T in a minimum of four suitable increments [for example, 100 Pa]. Allow the element at least one rotation of 360° at each increment while checking for evidence of bubbles. Continue increasing the pressure until P This reached. Air bubbles might be trapped on or within the outer structure of the filter element, resulting in a few spurious bubbles. These bubbles shall be ignored. A steady stream of bubbles from the filter element at or below the manufacturer’s designated pressure is the only consideration. Adequate lighting is required for reliable observation.BS ISO 2942 pdf download.