Questions regarding the leakage levels of self-controlled valves

What standard is GB 2008? It seems to have nothing to do with the control valve.

GBT4213-2008 specifies that leakage levels are divided into six grades: I, II, III, IV, V, and VI. Even at the highest leakage level, grade VI, there is no scenario in which no leakage occurs at all

I’ve never heard of a valve that doesn’t leak at all; the amount of leakage is so small that it’s impossible to detect with the naked eye……

Share **The leakage level classification according to standard GB/T 4213-92: When using control valves, in some applications it is desired that the leakage at the seal surface between the valve core and the valve seat be as low as possible when the valve is closed； Some process conditions even require that control valves be leak-free; therefore, to achieve low leakage levels, a variety of structures and materials are used, such as soft seals, which employ flexible materials like rubber or polytetrafluoroethylene as the sealing surface. There are many factors that affect the leakage rate, such as the magnitude of the compression force, the material of the sealing surfaces, the wear condition of these surfaces, as well as the forces and deformations experienced by the valve components. According to **standard GB/T 4213-92, the following provisions apply to leakage amounts. a. The leakage rate of the control valve under specified test conditions shall meet the requirements in Table 2. b. Except for Class I, the leakage class of the control valve is determined by the manufacturer itself. However, the leakage class of control valves with a single-seat valve structure must not be lower than Class IV ； The leakage class of control valves with a two-seat valve structure shall not be lower than Class II. c. When the leakage rate is greater than 5×10-3 of the rated capacity, the structural design shall ensure that the product can be exempted from testing. d. The leakage amount shall be specified by the following code: X1 – leakage level as shown in Table 2 I. Ⅳ ； X2 — Test medium, G: air or nitrogen, L: water ； X3 — Test procedure 1 or 2. During Test Procedure 1, the pressure of the test medium should be 0.35 MPa; when the allowable pressure difference for the valve is less than 0.35 MPa, the allowable pressure difference specified in Design I shall be used ； In Test Procedure 2, it should be the maximum operating pressure difference for the valve. The medium used in both test procedures is a clean gas at 15–40°C (air and nitrogen) or water. Next, we will introduce the leakage grade classification of GB/T 4213-92. Table 2(A) Classification of leakage grades (GB/T4213——92)
Leakage grade | Test medium | Test procedure | Maximum seat leakage rate
Ⅰ | To be determined by the user and manufacturer using the formula | —— | ——
Ⅱ | L or G | 1 | 5×10-3×valve’s rated capacity, L/h
Ⅲ | L or G | 1 | 10-3×valve’s rated capacity, L/h
Ⅳ-S1 | L 1 or 2 | 10-4×valve’s rated capacity, L/h | G 1
Ⅳ-S2 | L 1 or 2 | 5×10-4×valve’s rated capacity, L/h | G 1
Ⅳ | G 1 | 2×10-4×ΔP×D, L/h
Ⅴ | L 2 | 1.8×10-3×ΔP×D, L/h
Ⅵ | G 1 | 3×10-3×ΔP×(leakage rate specified in Table 2(B))
Note: 1. ΔP is expressed in kPa. 2. D is the valve seat diameter, in mm. 3. The measured value for the volumetric flow rate of a compressible fluid under standard conditions of an absolute pressure of 101.325 kPa and an absolute temperature of 273 K.

This post was last edited by seiluobin on 2016-3-9 at 15:07. GB/T 13927 2008 – Hydrostatic testing: Maximum allowable leakage rate. Grade A indicates no visually visible leakage. Haha, it’s been a long time since I heard anyone mention this as a specification for valve leakage; it’s good to remember this again, haha

What is the difference between leakage grades IV-S2, IV-S1, and IV in 4213-2008?

What is the difference between leakage grades IV-S2, IV-S1, and IV in 4213-2008?

What is the difference between leakage grades IV-S2, IV-S1, and IV in 4213-2008?

I know there is a difference, but what does S1 mean? The leakage amounts of the two are 20 times different; are there any restrictions on the testing conditions?