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1.6MPaDN300 ~ DN1000 British standard cast iron gate design knowledge
[Abstract] The structural features, design and calculation, design verification and type test of 1.6MPa DN300 ~ DN1000 British standard cast iron gate valve are expounded. [Key words] British Standard cast iron gate design and design verification 1 Overview BS5163, BS51501.6MPaDN300 ~ DNl000 British standard cast iron gate valve, in the United Kingdom, Singapore, Malaysia and the Middle East in some countries, water supply pipes and industrial pipelines are widely used, the structural features see : Open gear drive gate valve shown in Figure 1; closed gear drive gate valve shown in Figure 2. This article focuses on the 1.6MPaDN300 ~ 1000 British standard cast iron gate valve body wall thickness, valve cover wall thickness, gate thickness, stem diameter design calculations and design verification - type test. 2 Design 2.1 Body wall thickness design calculations BS5163, BS5150 standard push did not give the shell minimum wall thickness data, design, the body wall thickness must be calculated. Design, the valve body cavity cross-sectional shape designed to approximate the oval, see Figure 3, the design and calculation of the wall thickness S'B1, is calculated using the formula for calculating the elliptical wall thickness formula: Where K - Approximate wall thickness of the elliptical section valve body coefficient, of which DN300 ~ DN500, K take 1.13, DN600 ~ DNl000, K take 1.07; P - medium pressure, design, P take 1.6MPa; a - approximate oval cross-section length Shaft (mm); [σL] - Allowable tensile stress of cast iron (HT250), [σL] 35.28 MPa; C - Allowance for corrosion, C 5 (mm). DN300 ~ DN1000 valve wall thickness of the design calculations in Table 1. Design found that the body wall thickness design, in addition to considering the strength of the valve body, the valve body stiffness should also be considered, that is, the valve body cavity deformation (referring to the role of medium pressure 1.6MPa) controlled at 0.001DN Within the range, otherwise, the valve body can not be sealed due to the force deformation. To solve the stiffness of the valve body shown in Figure 1, in the valve body, the cavity design ribs, and the body of the external ribs and the valve body flange connected to increase the rigidity of the valve body, if necessary Designed to vary in wall thickness, ie to increase the approximate elliptical cross-section of the valve cavity in the wall thickness. 2.2 The design of the valve cover wall thickness, the valve cover wall thickness S'B2 usually no longer design calculations, the valve body wall thickness directly taken as 0.95 as the valve cover wall thickness. DN300 ~ DN1000 bonnet minimum wall thickness data in Table 2; bonnet stiffener design shown in Figure 1. 2.3 Gate thickness calculation design BS5163, BS5150 standard, also did not give the gate minimum wall thickness data, design, gate thickness S'B3 must be calculated, the formula is as follows: Where d - (Mm); P - medium pressure, designed to be 1.6 MPa; [σW] - allowable bending stress of cast iron (HT250), [σW] 56.84 MPa; C - corrosion allowance, C 3 (mm). DN300 ~ DN1000 gate wall thickness of the design calculations in Table 3. 2.4 stem diameter design calculations BS5163, BS5150 standard, the same did not give the smallest stem diameter data, design, the stem diameter must be calculated, the formula is as follows: Where K - stem design calculations Coefficient, DN300 ~ DN500, K take 0.70 ~ 0.75; DN600 ~ DNl00. K is 0.60 ~ 0.65; Q - axial force (N) when the valve stem is opened; [σL] - allowable tensile stress of cast iron (HT250), [σL] is 35.28MPa; Because QG (gate assembly weight) value is small, will not be calculated. Where QMF - the sealing surface to achieve the necessary pressure than the force (N); QMJ - sealing surface media hydrostatic pressure (N); d - diameter, d = DN (mm); bm - valve Body seal width (mm); qmf - Required seal pressure (MPa); P - Medium pressure, design, P take 1.6MPa. DN300 ~ DN1000 minimum diameter stem design calculations in Table 4. 3 Design verification - Type test DN300 ~ DN1000 British standard cast iron gate valve prototype, adopted by the Malaysian state quality authority SiRiM type test, the design was verified, type test in strict accordance with the British National Standard BS5163: 1986. Type testing of the pilot project are: appearance inspection, dimensional inspection, physical and chemical testing of materials, shell strength test, seal test, maximum torque test, the minimum strength torque test, cleanliness test, coating and mark inspection. Here to introduce the shell strength test, seal test, the maximum torque function test, the minimum strength torque test. 3.1 Shell strength test Shell strength test, test medium pressure 2.4MPa, to maintain the shortest duration of the test pressure 1h, no visible leakage. 3.2 Seal Test Seal test, the test medium pressure 1.76MPa, to maintain the shortest duration of the test pressure 15min, no visible leakage, that is, the sealing surface of the valve body, 15min can not have any visible leakage, including hanging Sealing surface of the small drops of water. Again, it is important to note that the design of the valve body must have sufficient strength and rigidity. The deformation of the housing must be controlled within the 0.001DN range of the seal test, otherwise it will be very difficult to pass the seal test. 3.3 The maximum torque test function The maximum torque test refers to the valve in the absence of medium pressure and medium pressure in the case of the opening and closing of the whole process, any moment of its maximum torque can not exceed the torque specified in Table 5. 3.4 Minimum strength torque test Minimum strength torque test is PN1.6MPaDN300 ~ DNlO00 British standard cast iron gate valve design verification, the test steps: 3.4.1 fully open, fully closed test with the maximum torque of the test valve fully open, all Close operation test, and make full open, all off the mark of the location, at the same time record the full open, full close the valve stem rotation. 3.4.2 Minimum strength of the valve in the fully closed position After the torque test valve is in the fully closed position, the torque of the maximum functional test torque of 3X shall be gradually applied to the square head of the valve stem in the direction of tightness (clockwise) , That is, the minimum strength test torque, see Table 6; to verify the body, bonnet, gate, stem, stem nut, stuffing box and other major components and flange bolts in the strength of BS5163: 1986 standards. 3.4.3 Minimum strength of the valve in the fully open position After the torque test valve is fully open, apply a torque three times the maximum functional test torque in the opening direction (counterclockwise) over the square head of the valve stem , That is, the minimum strength test torque, see Table 6; to verify the body, bonnet, gate, stem, stem nut, stuffing box and other major components and flange bolts in the strength of BS5163: 1986 standards. 3.4.4 Sealing Test Re-use the maximum functional test torque to make the valve in the fully-closed position and perform the sealing test again. The test medium pressure is 1.76MPa. Keep the test pressure for a minimum duration of 15min. No visible leakage should be confirmed to confirm whether the valve is generated Deformation; design meets the requirements of the BS5163: 1986 standard. 3.4.5 fully open, fully closed test Again with the maximum torque test valve fully open, full close operation test, and check the full open, close the full position of the test with 3.4.1 is fully open, the position is fully closed Coincide; once again record the full open, full close the valve stem rotation laps, check with the 3.4.1 test the number of rotation of the valve stem is the same, to confirm the stem, the stem nut strength, stiffness meets the BS5163 : 1986 standard requirements. 3.5 Parts Inspection Disassemble the parts, check valve body, bonnet, gate, stem, stem nut, stuffing box and other parts and flange bolts, nuts are intact to confirm the body, bonnet, gate , Stem, stem nut, stuffing box and other major parts and flange bolts in the design to meet the BS5163: 1986 standard requirements. 4 Conclusion Design verification - type test to confirm BS5163, BS51501.6MPaDN300 ~ DNl000 British standard cast iron gate valve design to meet the BS5163: 1986 standard requirements, put into mass production, and bulk exports to Malaysia, Singapore. Through the design, deeply felt that BS5163 standard type test method - the minimum strength torque test is very scientific and should be popularized in the valve industry, which is a good way to verify the design of new products for valves; deeply feel that the valve industry should regulate all types The maximum torque test valve, that is, regulate the opening and closing torque of all types of valves, which is the development of the times, the social progress of the human valve design put forward new requirements. References [1] Yang Yuanquan, valve design manual [M] Beijing: Mechanical Industry Press, 1992 [2] Hong Miancheng, Lu Peiwen, high accordion, valve design calculation manual [M]. Beijing: China Standard Press, 1994 [ 3] BS5163-1986 Gate valve for water supply system technical conditions [4] BS5150-1974 General purpose cast iron wedge single gate double gate valve [5] BS2080-1989 Valve structure length [6] BS4504-1989 Part 3.2 cast iron flange Technical conditions More Keyword search: Cast iron gate