Caster cooling water system features and water quality requirements. The characteristics of the butterfly valve and the ball valve are mainly explained, and the role of the valve in the cooling water system of the caster is analyzed, and the selection method is given.
The purpose of the valve is extensive and very effective. In the continuous casting machine cooling water system (hereinafter referred to as the water system), the valve regulates the flow, starts, closes, overhauls, etc. It can ensure the normal operation of the continuous casting machine, prolong the service life of the equipment and ensure that the continuous casting machine can produce qualified Slabs.
However, the valve is often overlooked compared to other devices in the caster. If the valve is improperly sized, the entire cooling system will not be able to adjust its capacity, resulting in low productivity or other accidents. Therefore, the water system valve should be selected rationally according to the special requirements of the caster.
2. Caster cooling water systemThe cooling water system is divided into four systems: (1) Crystallizer cooling water system, the water quality is soft water, the inlet water pressure is about 1.0 MPa, and the temperature is 35-55°C. (2) Equipment Indirect cooling water system, the water quality is net circulating water, the inlet pressure is 0.6-0.8 MPa, and the temperature is 40-55°C. (3) In the secondary cooling water system, the water quality is turbid water, the constant pressure of the water inlet pressure is 1.0 MPa, and the temperature is about 40°C. (4) Equipment direct cooling water system, water quality is turbidity circulating water, inlet water pressure is not less than 0.4MPa, temperature is about 40°C. Table 1 shows the water quality requirements for each system.
3, the selection of water system valvesAccording to the requirements of the caster cooling water system, the system should use low pressure PN ≤ 1.6MPa, room temperature -40 °C ≤ t ≤ 120 °C, non-extra large diameter DN ≤ 1400mm metal valve. Water system valves must meet the general performance requirements, but also to meet the special performance requirements of the caster, the following on the water system commonly used butterfly valve, ball valve selection analysis.
3.1. Selection of butterfly valves
A butterfly valve is a type of valve that opens, closes, and regulates a fluid passage using a disc-type opening/closing member that reciprocates from 0° to 90°.
(1) commonly used in the water line butterfly valve and double eccentric sealing butterfly valve
When the valve plate of double eccentric butterfly valve is opened from 0° to 90°, the valve plate can be completely separated from the sealing surface of the valve seat when passing from 0° to 8° to 12°, so that relative mechanical wear occurs between the sealing surfaces of the valve plate and the valve seat. Shorter extrusion angles improve valve life. Figure 1 shows the principle of opening and closing double eccentric butterfly valves. Because the filter of the water system piping (pipe above DN100) often needs inspection and cleaning, the double-eccentric butterfly valve is especially suitable for the inlet, outlet and bypass of the filter. The rest of the selection of the midline butterfly valve can meet the water system life requirements.
(2) has a good seal
Valve sealing materials include synthetic rubber seats and composite valve seats made of PTFE and synthetic rubber. Because synthetic rubber is susceptible to aging, wear, and falling off, it may clog mold copper seams, fan segment nozzles, fan segment bearing housings, etc. Therefore, composite valve seats made of PTFE and synthetic rubber are more suitable for continuous casting equipment. Figure 2 shows the composite valve seat midline butterfly valve consisting of PTFE and synthetic rubber.
(3) Has good flow adjustment characteristics
When the butterfly valve is opened between 15° and 70°, it can perform sensitive flow control. It is especially suitable for the cooling circuit of crystallizer copper plate. The pneumatic control valve and electromagnetic flowmeter on the circuit can effectively compensate the adjusting range of the pneumatic regulating valve. Figure 3 shows the application of the butterfly valve in the cooling circuit of the mold copper plate.
(4) The pressure loss of the butterfly valve in the pipeline is relatively large, about three times that of the gate valve. Therefore, the influence of pressure loss in the pipeline system should be fully considered when selecting the butterfly valve.
Fig. 3 Application of butterfly valve in crystallizer copper plate cooling circuit
The pressure loss caused by the valve in the pipeline can be expressed as:
In the formula
ΔP is the pressure loss caused by the valve in the pipeline, MPa; K is the pressure loss coefficient of the valve; K1 is the pressure loss factor caused when the valve is partially opened; when the valve is fully opened, K1=1; v is the average speed of the water flow, m/ s; Ï is the density of water, kg/m3.
The pressure loss coefficient K of the butterfly valve is approximately 0.2 to 1.5 depending on the thickness of the valve plate. Figure 4 shows the approximate result of butterfly valve K1.
3.2, ball valve selection
The ball valve is evolved from the plug valve. Its opening and closing part is a ball. The ball is rotated 90° about the axis of the valve stem to open and close.
(1) Floating ball valves and V-shaped ball valves are often used in the water system and are used in pipelines with a diameter of not more than DN125. Floating ball valve mainly acts as opening and closing; V-shaped ball valve is used for flow regulation. Figure 5 is a floating ball valve and Figure 6 is a flanged V-shaped opening adjustment ball valve.
(2) has a good seal. The commonly used sealing material for water systems is PTFE, which has a low friction coefficient, stable performance, and is not susceptible to aging.
(3) Compared with the butterfly valve, the V-shaped open ball valve has better flow regulation characteristics. Turbine-driven V-shaped opening ball valve has the function of precise adjustment and reliable positioning. The flow characteristic is approximately equal percentage, the adjustable range is large, and the maximum adjustable ratio is 100:1. Figure 7 shows the adjustment characteristic curve of V-shaped open ball valve. This type of ball valve is suitable for the branch of the secondary cooling system. It can be used to match the adjustment range of the pneumatic control valve with the pneumatic control valve and the electromagnetic flowmeter on the circuit. It is suitable for the indirect cooling and return branch of the equipment and can be displayed in the local area. The flow meter can accurately adjust the amount of water distributed to each sector.
(4) With the lowest flow resistance, the flow resistance can be considered zero for a fully-meshed ball valve in the fully open state.
4 Conclusion(1) The butterfly valve is applicable to pipelines above the DN125 of the water system; dual-eccentric sealing butterfly valves are used for the inlet and outlet of the more frequent filter inlet and outlet and its bypass; in the crystallizer return pipeline, the midline butterfly valve is used for flow regulation; Composite valve seat composed of tetrafluoroethylene and synthetic rubber; pressure loss should be taken into consideration when selecting the butterfly valve.
(2) The ball valve is suitable for the pipeline below DN125; in the secondary cooling branch and the indirect cooling and water return branch of the equipment, the turbine transmission V-shaped open ball valve is used for accurate flow regulation; the PTFE valve seat is used for sealing; The ball valve, in the fully open state, does not consider the pressure loss caused by the ball valve on the pipeline.
(3) For the caster cooling water system requirements, the choice of butterfly valve and ball valve can fully meet the opening and closing of the pipeline and the precise adjustment of flow, can replace the valve, valve and other valves.
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