Design and development of marine tongue valve

The technical parameters and working principle of a marine tongue valve are introduced, and the selection of valve parts materials, structural design, key manufacturing technologies and tests are described.

Overview

The tongue valve is a key locking device of the control system on board, and if it leaks or fails to open and close, it will lead to fluid leakage from the system and cause serious accidents. The tongue valve is subject to the double corrosive effect of high-temperature flue gas and seawater when working, and the working conditions are complex and harsh. Compared with other structures of marine valves, tongue valves are complex in structure, difficult in design and manufacture, and strict in test and evaluation.

Technical parameters

Nominal diameter DN250 applicable medium seawater and high temperature flue gas nominal pressure PN4 (internal pressure), PN30 (external pressure) environmental conditions to meet the requirements of the marine environment

Working principle

Tongue valve (Figure 1) is a rotary valve, which mainly consists of valve body, valve cover, vent pipe, pipe bend, spindle, connecting rod, valve plate, spool and guide shaft and other components. The spindle is installed in the shaft seat of the valve body, and the spindle and the valve plate are driven by a transition linkage. When the spindle rotates, it drives the linkage to turn the valve plate to open and close the tongue valve, and the valve plate has two sealing positions, horizontal and vertical. Considering the use of tongue valve working conditions and external pipe system material matching requirements, the parts connected with external equipment or pipeline are made of carbon steel, and the internal parts are made of stainless steel (Table 1).

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Figure.1 Structure diagram of tongue valve

Structure design

Valve body

The valve body (Figure 2) is made of cast steel, with seawater pipeline flange on the left and pressure-resistant flue gas flange on the right, and the middle flange is connected to the valve cover. The flue gas flange is equipped with a water jacket outside, which is used to reduce the temperature of the sealing surface of the valve body and protect the rubber seal of the valve plate. The sealing surface is welded with stainless steel. In order to ensure the stability of the valve installation, the valve body is designed with supports on the front and rear sides of the bottom, and the supports are fastened to the hull support by bolts.

Table.1 Material selection of parts

Parts Design material selection
Housing Cast steel
End cap, cooling water jacket Carbon steel
Pipe parts Carbon steel
Threaded joint Carbon steel
Bushing type Copper alloy
Valve plate, shaft parts Stainless steel

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Fig. 2 valve body

Valve cover

The valve cover (Figure.3) consists of vent pipe, cover plate, flange, connecting block, bottom plate, side ring, joint and other components welded together to form the cooling water chamber. The valve cover is bolted to the flange in the valve body. The cooling water cavity is connected to the valve body cooling water sleeve through an elbow to reduce the temperature of the sealing surface of the valve cover to protect the valve plate seal.

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Fig. 3 valve cover

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Fig. 4 double link transmission mechanism

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Fig. 5 main shaft and connecting rod are connected by involute spline

Transmission mechanism

The transmission mechanism is a double-link mechanism consisting of the spindle, connecting rod, valve plate, spool and guide shaft parts (Figure 4), and the spindle and connecting rod are connected by involute splines (Figure 5). The connection of the drive mechanism is conducive to improving the load-bearing capacity and rigidity of the spindle and having good auto-centering capability. The connecting rod is connected to the arbor through a quadratic hole. The valve plate is set on the spindle, and the valve plate is limited by retaining rings and set screws in the left and right directions. The guide shaft is fixed to the valve body through the guide groove at the end of the valve plate, and a reasonable clearance is designed between the guide shaft and the guide groove to achieve 90° rotational movement of the valve plate smoothly.

Anti-loosening

In order to ensure the usability and safety of the product, the threaded connection parts are protected against loosening by metal winding wire and stop washers (Figure 6).

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(a) spiral wound wire locking. (b) lock washer locking.

Fig. 6 locking of threaded connector

Process analysis

Welding deformation control

In order to ensure the sealing performance of the tongue valve, the angle of the valve plate in the horizontal or vertical two positions after assembly needs to ensure 90 ° (Figure 7). To ensure the angle requirements, the distance from the centerline of the valve body spindle hole to the centerline of the guide shaft hole L1, the distance from the centerline of the valve body spindle hole to the sealing surface of the valve body overlay layer L2, the distance between the centerline of the valve body spindle hole to the sealing surface of the middle flange L3, etc. need to be strictly controlled. At the same time, the pressure-resistant flange side of the valve body needs to be welded seawater cooling water jacket and joint, the sealing surface needs to be overlay welded stainless steel, because the overlay layer area is large is very easy to occur welding deformation. In order to solve the problem of welding deformation, the valve body manufacturing process, the finishing process as the last process, while increasing the overlay welding process evaluation, welding before and after the size inspection, welding should be eliminated and other measures to better solve the valve body welding deformation problem.

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Fig. 7 main machining dimensions of valve body

Mechanical processing

The sealing performance of the tongue valve mainly depends on the control of welding deformation and improve the accuracy of machining to ensure. Valve body processing, the flange sealing surface as a benchmark for both sides of the flange finishing, while the right side of the pressure-resistant flange centerline and the centerline of the flange to ensure good perpendicularity, the valve body spindle hole, the coaxiality between the mounting holes on both sides of the spindle and the spindle hole centerline to the space between the two sealing surfaces of the valve body are strictly guaranteed by mechanical processing. After the completion of machining, the spatial position dimension inspection is carried out by CMM.

High temperature anti-corrosion

Tongue valve machine performance test qualified, by sandblasting clean up the casting surface oxidation, oil and other residues, and then spraying anti-rust primer and epoxy modified silicone heat-resistant paint (composed of modified silicone resin, special temperature-resistant pigments, fillers and organic solvents, etc.), heat-resistant paint can be cured at room temperature, self-drying fast, strong adhesion, coating film has excellent heat resistance and good rust resistance, can withstand long-term 400 ℃ high temperature, resist high temperature flue gas and seawater corrosion, can improve the high temperature corrosion resistance of the tongue valve.

Test

The main inspection items of the tongue valve are general physical characteristics test, material performance test, functional test, strength test (internal pressure + external pressure), tight type test (internal pressure + external pressure), life test, etc. In accordance with the technical requirements of the project, the inspection and test item by item, the test results meet the requirements of the indicators.

Conclusion

After the actual use, the newly developed tongue valve with reasonable material selection, reliable design, key manufacturing links strictly controllable, etc., in the factory test and type test assessment, to meet the technical requirements specified, good performance.

Authors: Dai Le, Ding Qiangwei, Liu Xingyu, Niu Long, Zhang Xinqi

Source: China Valves Manufacturer – Yaang Pipe Industry Co., Limited (www.sfutube.com)

(Yaang Pipe Industry is a leading manufacturer and supplier of nickel alloy and stainless steel products, including Stainless Steel Valves, Stainless Steel Flanges, Stainless Steel Pipe Fittings, Stainless Steel Pipe. Yaang products are widely used in Shipbuilding, Nuclear power, Marine engineering, Petroleum, Chemical, Mining, Sewage treatment, Natural gas and Pressure vessels and other industries.)

If you want to have more information about the article or you want to share your opinion with us, contact us at sales@sfutube.com

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