Empirical rules for the allowable leakage rate of mechanical seals and the leakage rate in the event of failure

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Empirical rules for the allowable leakage amount of mechanical seals and the leakage amount in case of failure – China: 1. Classification and basic properties of mechanical seals for pumps: light-duty mechanical seals, with the sealed medium being a liquid. . . . . . Reference standard: JB/T 4127.1-1985/1999 \"Mechanical Seals – Technical Requirements\". Scope: This standard specifies the technical requirements related to the quality of lightweight mechanical seal products, including their performance, testing, acceptance, marking, and packaging. This standard applies to mechanical seals for centrifugal pumps and other similar rotary machinery. Its typical operating parameters are as follows: the operating pressure ranges from 0 to 1.6 MPa (referring to the actual pressure within the sealing chamber), and the operating temperature ranges from –20 to 80°C℃ ； (Average temperature inside the sealed chamber) Shaft ； (The outer diameter of the shaft sleeve is 10~120mm) ； The rotational speed shall not exceed 3000 r/min; the medium can be clean water, oils, and generally corrosive liquids. Mechanical seal performance requirements: Leakage rate. When the medium to be sealed is a liquid, the average leakage rate is specified as follows: when the outer diameter of the shaft (or shaft sleeve) is greater than 50 mm, it shall not exceed 5 mL/h ； When the outer diameter of the shaft (or bushing) is not more than 50 mm, the flow rate shall be no more than 3 mL/h. This limit does not apply under special conditions or when the medium to be sealed is gas. 2. Test conditions on the test bench: normal temperature and clean water, rotation speed not exceeding 3000 r/min, chamber pressure of 2. 0MPa。 II. Japan (JIS B2405-1977/2003): When the medium is a liquid, the leakage rate must not exceed 3 mL/h; this restriction does not apply under special conditions or when the sealed medium is a gas. Third, the former Soviet Union (rOCT5-2018-73) specified in \"End-face Seals for Centrifugal Oil Pumps – Quality Requirements for Product Inspection\" that the leakage rate on the kerosene test bench should not exceed 20 mL/h (with the shaft seal box pressure at 2). 5 MPa, speed 3000 r/min). Fourth, from these three different standards, anyone who is not particularly unintelligent can realize that any so-called standard or regulatory data is based on specific conditions; its scope of application is limited and subject to constraints. 5. What level of seal leakage during use is considered excessive? ------In our country: As a rule of thumb, if the leakage rate of a standard contact mechanical seal exceeds 250 times the theoretical value (calculated using the Mayer leakage formula), it can be considered that the mechanical seal is not functioning properly. However, for special media that are toxic, explosive, or flammable, even a small amount of leakage should be considered a failure. ===Kalite Ebara Company: The pump manual states the following: \"When setting the alarms and interlocks for mechanical seals, the allowable leakage volume for each mechanical seal is 600 cc/hour.\" 6. Note: (1) Fluids with an open flash point of ≤45 are considered flammable; the flash point of diesel ranges between 50 and 55. (2) 1 mL of gasoline ≈ 30 drops ； 1 mL of engine oil ≈ 10 drops ； 1 mL of water ≈ 23–25 drops ； 1 mL of saline used in medical treatments ≈ 20 drops ； (3) When the outer diameter of the shaft (or sleeve) in question is greater than 50 mm, it shall not exceed 5 mL/h ； When the outer diameter of the shaft (or bushing) is not greater than 50 mm, it shall be no more than 3 mL/h. It can be fully understood as the average value calculated using Mayer’s leakage formula within a certain diameter range.