SH/T 0293-1992 Determination of Saturated Vapor Pressure of Vacuum Greases

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Card type: Test method

1. Method number / full title / English name / replacement relationship

• Standard number: SH/T 0293-92
• Chinese name: Determination of Saturated Vapor Pressure of Vacuum Greases
• English name: not provided in the available source
• Replacement relationship: replaces SY 2672-77
• Method composition: This standard includes two methods—A method (pendulum method), B method (evaporation method)
• Approval/implementation: approved by China Petrochemical Corporation 1992-05-20, implemented on 1992-05-20
• First issued: year 1966 (see additional notes)

2. Scope of application and non-applicability

• Scope of application: This standard specifies the method for determining the saturated vapor pressure of test samples; it is applicable to vacuum pump oils (greases), diffusion pump oils (greases), and silicone oils for diffusion pumps.
• Not applicable: not provided in the available source.

3. Method principle

• A method (pendulum method) method summary: under the specified test conditions, the saturated vapor pressure result measured by the pendulum method is expressed in millimeters of mercury at 20°C.
• B method (evaporation method) method summary: under the specified test conditions, the result measured with a vacuum grease saturated vapor pressure tester is expressed as the height in millimeters of mercury at 20°C.

4. Reagents and materials (purity / preparation)

• A method reagents:
  • 4.1 benzene: chemically pure.
  • 4.2 acetone: chemically pure.
• A method materials:
  • 3.2.1 aluminum sheet: circular, 0.3–0.5g, 0.5–1.0g.
  • 3.2.2 vacuum sealing grease.
• B method reagents:
  • 12.1 benzene: chemically pure.
  • 12.2 acetone: chemically pure.
• B method materials: vacuum sealing grease (11.32), semi-logarithmic paper (11.31), vacuum rubber tubing (11.30), etc.; see Section 5 Apparatus and Equipment for details.

5. Apparatus and equipment

A method (Chapter 3)

• 3.1.1 pendulum device (see Figure 1).
• 3.1.2 vacuum pump: pumping speed 30~150L/min, ultimate pressure 5×10⁻*mmHg (requires confirmation against the source standard (source-text extraction), exponent unclear).
• 3.1.3 diffusion pump: glass vertical three-stage oil diffusion pump.
• 3.1.4 ionization vacuum gauge: pressure measurement range 10⁻¹~10⁻'mmHg (requires confirmation against the source standard (source-text extraction), upper limit exponent unclear).
• 3.1.5 high-frequency spark tester: 220V.
• 3.1.6 constant-temperature oil bath: capable of maintaining constant at 160±0.5°C.
• 3.1.7 vacuum-coated small mirror: not smaller than 10mm×20mm.
• 3.1.8 level gauge.
• 3.1.9 graduated scale: 0~1000mm.
• 3.1.10 winding machine: modified.
• 3.1.11 𠃑-shaped long-arm funnel: inner diameter 10mm.

B method (Chapter 11)

• 11.1 vacuum pump: model 2HB150, ultimate vacuum 5×10⁻'mmHg (requires confirmation against the source standard (source-text extraction)), pumping speed 150L/min.
• 11.2 diffusion pump: ultimate vacuum 5×10⁻*mmHg (requires confirmation against the source standard (source-text extraction)), pumping speed 500L/s.
• 11.3 multi-purpose power supply: model EY591.
• 11.4 ionization gauge: model DZH-2.
• 11.5 AC voltage stabilizer: model WY2000, 2000VA.
• 11.6 electric fan.
• 11.7 potentiometer: model 303.
• 11.8 automatic acidity recorder: model 40.
• 11.9 transformer: 2kVA.
• 11.10 isolation transformer: output 127V, 0.6A.
• 11.11 high-temperature meter: 0~200°C.
• 11.12 ammeter: direct current 0~200mA.
• 11.13 ammeter: direct current 0~100μA, class 1.5.
• 11.14 ammeter: direct current 0~1000μA, class 1.
• 11.15 ammeter: alternating current 0~5A.
• 11.16 ammeter: 0~3A.
• 11.17 voltmeter: 0~300V.
• 11.18 voltmeter: 0~75V.
• 11.19 slide-wire rheostat: 2A, 48Ω (original text “480”, requires confirmation against the source standard (source-text extraction)).
• 11.20 double-pole double-throw switch: 250V, 3A; 125V, 6A.
• 11.21 indicator lamp cover.
• 11.22 small light bulb: 6.3V.
• 11.23 small light bulb: 12V, 10W.
• 11.24 square shed: 110/220V/6.3, 12V.
• 11.25 capacitor: 1F (requires confirmation against the source standard (source-text extraction), suspected to be 1μF).
• 11.26 photoelectric tube: CIIB-3.
• 11.27 thermocouple: copper-constantan (calibrated).
• 11.28 ionization gauge tube: JIM-2.
• 11.29 high-vacuum glass three-way stopcock.
• 11.30 vacuum rubber tubing.
• 11.31 semi-logarithmic paper.
• 11.32 vacuum sealing grease.
• Figure 2: oil vapor pressure measurement circuit diagram (the original text contains a circuit diagram, source-text extraction noise is high, specific component parameters require confirmation against the source standard (source-text extraction)).

6. Recommended operating conditions

• A method:
  • After the vacuum system is connected to the pendulum device, it should be able to evacuate the system to below 5×10⁻⁸mmHg (5.1).
  • Constant-temperature oil bath: white oil oil bath, maximum oil temperature reaches 160°C, temperature variation not greater than ±0.5°C; glass constant-temperature cylinder diameter not less than 300mm, height not less than 300mm (5.3).
  • The height of the ground joint of the pendulum device is about 1.5m from the ground (5.2).
  • The scale is placed vertically at a height of 1m from the ground, the plane of the scale is parallel to the plane of the small mirror, and the distance from the small mirror is 1.5~2.0m (5.4).
  • During the test, approximately every increase of 5°C, one point is measured at constant temperature 3min; each test measures at least six points or more (6.5).
• B method:
  • Measurement is carried out when the system pressure is lower than 4×10⁻⁴mmHg (14.3, original text “4X10-‘mmHg”, requires confirmation against the source standard (source-text extraction)).
  • The distance between the aperture and the light-shielding plate is 2~3mm (13.6).
  • The distance between the balance pan and the cold box is 4~5mm (13.7).
  • At photoelectric balance, the meter current can be within 30~80μA (13.8, original text “30～80A”, requires confirmation against the source standard (source-text extraction)).
  • After continuing evacuation for 30min, measure the system pressure with an ionization vacuum gauge (14.2).

7. Sampling and sample preparation

• A method:
  • 5.5 Clean the pendulum device with benzene or acetone solvent, place in an oven at 110°C and dry.
  • 5.6 Using a 𠃑-shaped long-arm funnel, add test sample 5~10ml from the nozzle into the evaporation chamber of the pendulum device.
  • 5.7 Apply vacuum sealing grease to the top ground joint and the rotating ground joint, hang the aluminum sheet on the hook, and place it in the pendulum device.
  • 5.8 Fix the pendulum device on the universal clamp of the winding machine.
• B method:
  • 13.2 After venting the system, open the bell jar, immediately cover the photoelectric tube with a paper cover, remove the balance pan, carefully move the balance pointer out of the cold box, take out the evaporation pot, and pour out the sample.
  • 13.3 Wipe off oil traces in the system with a dry gauze; clean the evaporation pot, pot cover, and fixing plate twice each with benzene and acetone, then blow dry (the drying instruction is unclear in the source transcription; verify it before use).
  • 13.4 Load the sample into the evaporation pot to slightly above the two-thirds level, then place the evaporation pot on the heating furnace, put on the pot cover, fixing plate, limiting hole, evaporation hole, and align the opening of the cold box at one central position, and fix them.

8. Analysis procedure

A method (Chapter 6)

• 6.1 Start the vacuum pump, evacuate the system and inspect with a high-frequency vacuum tester; when the system appears light white, turn on the cooling water, heat the diffusion pump, and evacuate to below 1×10⁻'mmHg (requires confirmation against the source standard (source-text extraction)).
• 6.2 Adjust the measuring device at an offset angle of θ so that the scale reading can be seen from the level gauge. Use a steel tape to measure the distance from the scale to the small mirror, expressed in millimeters.
• 6.3 Determine the origin: when the aluminum sheet is vertical to the ground, rotate the pendulum device so that the disc just contacts the nozzle and completely covers the nozzle, record the scale reading and temperature. Repeat five times and take the average as the origin S₀.
• 6.4 Raise the oil bath until the evaporation chamber of the pendulum device is fully immersed in the oil surface, then determine the origin again by the same method as 6.3.
• 6.5 Heat the oil bath; after the aluminum sheet is blown by vapor, measure one point at constant temperature 3min approximately every increase of 5°C; each test measures at least six points or more, and the measurement method is the same as for the origin. The reading is S.
• 6.6 After the test, turn off all heaters; only after the diffusion pump oil has cooled, turn off the vacuum pump, connect the vacuum pump to the atmosphere, and keep the system under vacuum.
• 6.7 After the diffusion pump oil has cooled to room temperature, turn off the cooling water, let air into the system to atmospheric pressure, and only then may it be removed for cleaning.

B method (Chapter 14)

• 14.1 Rotate the vacuum stopcock to connect it with the system, and start the vacuum pump.
• 14.2 Connect the thermocouple gauge or use an electron gun to test the system pressure; when the system pressure reaches below 10⁻'mmHg (high-temperature meter higher than 60°C), connect the diffusion pump cooling water, heat the diffusion pump, continue evacuation for 30min, then measure the system pressure with an ionization vacuum gauge.
• 14.3 When the system pressure is lower than 4×10⁻⁴mmHg, perform the measurement. Adjust the electrical balance, and record the balance current, check whether the temperature of the thermocouple cold point is at degrees (original text "whether at degrees", requires confirmation against the source standard (source-text extraction)). Adjust the zero point of the 303 type potentiometer. Turn on the heater to heat the oil bath, slowly raise the temperature to the desired test temperature (depending on the evaporation situation), and keep the temperature constant.
• 14.4 When the balance current of the balance reaches an integer division, start the stopwatch. When it reaches another integer division, stop the stopwatch. Record the time, temperature, and current value.
• 14.5 Take different evaporation temperatures and repeat the above operations to determine the evaporation rate at different temperatures.
• 14.6 After the measurement is completed, the mechanical pump continues to operate, and turn off other power supplies.
• 14.7 When the oil temperature of the diffusion pump drops to near room temperature, turn off the cooling water of the diffusion pump, turn the valve so that the atmosphere is connected to the mechanical pump and isolated from the system, and stop the mechanical pump.
• 14.8 Normally, the vacuum system is evacuated to maintain cleanliness.

9. Qualitative and Quantitative and Calculation Formulas

A Method (Chapter 7)

• 7.1 The vapor pressure P (mmHg) at each temperature is calculated according to formula (1):
  • P = 0.00136 × (m·S·d)/A (original formula source-text extraction is incomplete, requires confirmation against the source standard (source-text extraction))
  • In the formula: m— mass of the aluminum plate, g; A— area of the nozzle of the suspension pendulum device, cm²; S— the reading S at a certain temperature minus the value of the origin S₀, mm; d— distance from the small mirror to the scale, mm; 0.00136— coefficient for converting the pressure unit "bar" to micrometers of mercury.
• 7.2 According to the formula logP = A − B/T (in the formula, A and B are constants; T is absolute temperature), it is necessary to convert each temperature to the reciprocal of the absolute temperature, and plot the obtained vapor pressure on semi-logarithmic paper (abscissa 1/T, ordinate P).
• 7.3 Connect the points into a straight line, on the straight line subtract the 1/T values corresponding to any two points whose vapor pressures differ by one order of magnitude, and the reciprocal of the difference gives the B value. Substitute the P of any point on the straight line and the corresponding T obtained B value into the formula logP = A − B/T to obtain the A value.
• 7.4 Substitute A, B, and 20°C at T into the formula logP = A − B/T to obtain the saturated vapor pressure P₂₀ at 20°C (expressed in millimeters of mercury).

B Method

• 13.1 Determination of the K value of the balance and the instrument constant K' value: adjust the meter balance, successively add unequal amounts of weights ΔW on the balance pan, determine the corresponding meter current ΔI, according to K = ΔW/ΔI the K value can be obtained, then according to formula (2) calculate the K' value:
  • K' = √2E × ... × 7.5×10⁻... (original formula (2) source-text extraction is incomplete, requires confirmation against the source standard (source-text extraction))
• B Method vapor pressure calculation: no explicit calculation formula is provided in the available source (only 14.5 states "determine the evaporation rate at different temperatures", the method of extrapolating to 20°C is not provided in the available source).

10. Precision

A Method (Chapter 8)

• 8.1 The difference between two results of repeated determination (extrapolated to the saturated vapor pressure at 20°C) should not be greater than one order of magnitude.
• 8.2 If the difference between two results of repeated determination is greater than one order of magnitude, a third determination is required. The arithmetic mean of the two results not greater than one order of magnitude is used, and one significant figure is given as the determination result.

B Method (Chapter 15)

• 15.1 The difference between two results of repeated determination (extrapolated to the saturated vapor pressure at 20°C) should not be greater than one order of magnitude.
• 15.2 If the difference between two results of repeated determination is greater than one order of magnitude, a third determination is required, and the arithmetic mean of the two results not greater than one order of magnitude is used, and one significant figure is given as the determination result.

11. Report

• A Method (Chapter 9): take the arithmetic mean of two results of repeated determination as the determination result of the sample.
• B Method (Chapter 16): take the arithmetic mean of two results of repeated determination as the determination result of the sample.

12. Reference Documents

• No independent "Reference Documents" chapter is provided in the available source; the text cites Figure 1 (suspension pendulum device), Figure 2 (oil vapor pressure determination circuit diagram).

13. Source and verification

This page is an AI translation of the available Chinese method card. Human verification is pending. It is not an official translation of the standard. Check the source standard and product certificate before use.

14. Quick Reference Q&A