【Technical Report 】 How to choose, How to use and Trouble Case Study for Thermoplastic Valves Enhancement of Longevity of Piping by Using Thermoplastic Valves ASAHI YUKIZAI CORPORATION Valve & Piping Systems Administration

Introduction ASAHI YUKIZAI CORPORATION has dealt with the manufacturing and marketing of thermoplastic valves for more than 60 years. Since the manufacturing of thermoplastic valves in the 1950s, we have accumulated abundant achievements and knowledge. Capitalizing on the properties of corrosion resistance, chemical resistance, and light weight, thermoplastic valves have been widely used in various types of factories including electrolysis, ironworks , and semiconductor factories, as well as power plants, agriculture, and fisheries. Recently, because of increasing concern over the aging of facilities and piping systems, piping systems are re quired to have longer lives. However, metal valves an d piping systems will be corroded by seawater or chemicals no matter how expensive they are. We can expect that valves and piping systems have longer lives even at affordable prices when the characteristics of thermoplastic valves are made full use of wise ly. For this reason, the following sections introduce effective ways to use thermoplastic valves. Table 1 Valve types and features Types and characteristics of Thermoplastic Valves Ball Precautions for using thermoplastic valves include: to use them within the usable range of temperature and pressure, to select a material suitable for the chemical, to select a valve Diaphragm type suitable for the application, to avoid piping stress, and to adhere to the construction procedures. There are wide-ranging types of thermoplastic valves, and they can be categorized into various types such as ball valves, Butterfly diaphragm valves, butterfly valves, and gate valves. Table 1 shows the types and characteristics of them. The following are the advantages and precautions for use of each type of Gate valves.

Advantages and precautions for use of Ball Valves Ball valves are highly versatile and have advantages such as that they can be opened or closed quickly, that the degree of opening is easy to see, and that pressure loss is extremely small. The precautions for use include that they are unfit for flow rate or pressure control and unsuitable for volatile fluids (the pressure in the cavity increases abnormally) (Figure 1). As a concrete example of problems, Photo 1 shows a deformed seat. This problem occurred because an internal part was pushed

out by the running fluid to deform the seat when the valve was used at an intermediate degree of opening. The necessary countermeasure is not to use valves at an intermediate degree of opening. Photo 2 shows an example of problems in which part of fluid that was encapsulated in a closed valve vaporized and then the valve was damaged due to abnormally increased pressure. There is a dead space in the cavity because of the str ucture of the valve. This damage was caused by vaporization of a volatile fluid, such as hydrogen peroxide water and sodium hypochlorite. As for a countermeasure, the damage can be prevented by using vented-type ball valves to let the pressure in the dead space escape to piping.

Opened Position Closed Position

Vented-type Ball

Upstream Downstream

Cavity Flow Direction Figure 1 Ball Valve Ball

Photo 1 Seat deformation Photo２ Broken Valve

１ ASAHIAV | Technical Report | How to choose, How to use and Trouble Case Study for Thermoplastic Valves

Advantages and precautions for use of Diaphragm Valves Opened Position Closed Position Diaphragm valves are designed for the heavy and chemical industries and can be used general chemical solutions. The

advantages include the high sealing performance, the outstanding open/close durability, and the suitability for flow rate control. The precautions for use include the necessity of consideration to pressure loss and the unsuitability for the use with large-diameter piping (Figure 2).

Cushion (EPDM ) PVDF Cushion Cover PTFE Diaphragm Figure 2 Diaphragm Valve Insert Metal Part (SUS304) Photo 3 shows an example of problems in which metal parts corroded by penetrating chlorine gas prevented the valve from functioning. This problem

occurred because chlorine gas penetrating the diaphragm corroded Photo 4 Blisters inside a diaphragm valve and damaged the metal parts. An effective countermeasure for fluids EL-PVDF Valves that generate corrosive gas is to attach a cushion cover made of PVDF that can prevent hydrochloric acid and chlorine gas from penetrating the diaphragm. Photo 3 Metal Parts Corroded

Photo 4 shows another example of problems in which blisters were generated by chlorine gas inside a diaphragm valve. This problem occurred because chlorine gas penetrated the resin surface. The generation of blisters can be reduced by using a special thermoplastic valve for electrolysis (EL-PVDF), which can suppress the penetration of chlorine gas.

Advantages and precautions for use of Butterfly Valves

Opened Position Closed Position Butterfly valves are suitable for large-size-diameter piping and have advantages such as that the disc can be opened or closed by rotating 90 degrees, that the flow rate can be controlled,

and that the face-to-face dimension is short and the weight is light. The precautions for use include that cavitation easily occurs at a low degree of opening, and that the valves are not suitable for use at an intermediate degree of opening because the disc is guided to the closing direction, and that attention should be given to the interference between the disc a nd pipes or flanges from the installation of the piping (Figure 3).

Figure 3 Butterfly Valve

Photo 5 shows an example of problems in which the seat of a valve curled up to damage the flange surface. This problem occurred because the valve was installed without the valve face to face extended, curling up the seat to get it caught. It is important to widen the gap between the flange faces until it becomes larger than the gap between the valve faces when piping is installed.

Photo 5 Curling-up the Seat

ASAHIAV | Technical Report | How to choose, How to use and Trouble Case Study for Thermoplastic Valves ２

Advantages and precautions for use of Gate Valves Gate valves, designed primarily for water, are suitable for buried piping and have advantages such as that fluid resistance when fully opened is extremely small and that the structure allows large-size-diameter

valves to be manufactured. The precautions for use include the impossibility of emergency interception due to long open/close time and the unsuitability for use at an intermediate degree of opening. Figure 4 shows an example of troubles in which increased operating torque due to Cantilever occurred the influence of in-pipe flow velocity brought about a malfunction. This problem occurred because the disc-gate was inclined by the action of fluid stress of the high-speed flow in

Large Flow Large Flow the piping. It is necessary to avoid using the valve at an High Velocity intermediate degree of opening when the flow rate and flow velocity are high. Fully Closed Position Middle Open Position Image View Figure 4 Increased operating torque

Installation of Thermoplastic Valves and precautions

To use thermoplastic products for the long term, they must be so installed as to avoid excessive action and stress such as tension, compression, bending, and imp act on piping and valves. Photo 6 shows an example of troubles in which the body of a PVC ball valve was damaged due to piping stress. This problem occurred because piping stress caused by misalignment acted on the valve. It is necessary to install piping with axis misalignment and parallelism values kept within specified Photo 6 Damaged by misalignment ranges. Optimal materials for Thermoplastic Valves ifferent materials are used for valves, depending on the application. Bodies and casings are made of resin and can be influenced D by chemical solutions and atmosphere, which means that it is important to select optimal materials. Screws and other parts th at should have high strength are made of metals. If the y can be influenced by gases or atmosphere even though there is no contact with liquids, corrosion resistance metals should be selected. Seals are made of elastomer such as rubber and have contact with liquids, which means that the selection of materi als is important. Tables 2 and 3 show the general tolerances of resins and sealing materials used for valves. Table 2 Chemical resistance for valve body material Table 3 Chemical resistance for valve sealing material Acid Alkaline Acid Alkaline Material Oil Material Weak Strong Weak Strong (Wet) Weak Strong Weak Strong EPDM Good○ △ Excellent◎ Excellent◎ × × U-PVC Excellent◎ Good○ Excellent◎ Good○ × NBR △ × Good○ Good○ × Excellent◎ C-PVC Excellent◎ Good○ △ × × FKM Excellent◎ Good○ △ × × △ PP Excellent △ Excellent Excellent Good○ ◎ ◎ ◎ Excellent◎Excellent ◎ Good○ △ × △ PVDF Excellent Excellent Good Good○ ◎ ◎ ○ △ Excellent◎ Good○ Good○ △ Good○ △ PTFE Excellent◎Excellent ◎Excellent ◎ Excellent ◎ Excellent◎ Excellent◎ Selection of Thermoplastic Valves With thermoplastic valves, Table 4 Working Temp. & Working Pressure Movie manual working conditions (working Different thermoplastic valves have different pressure and temperature) Material installation instructions depending on the type. In are specified for each material U-PVC 0℃〜 50℃ 1.0 {10.2｝ addition, various connection methods have their own and type. Table 4 shows precautions. For this reason, ASAHI YUKIZAI has C-PVC 0℃〜 90℃ 1.0 {10.2｝ representative examples. produced and uploaded movie manuals for installing PP -20℃〜 80℃ 1.0 {10.2｝ What you should mind when piping on the web of http://asahiav.jp/en/, so that selecting a valve is that, as PVDF -20℃〜 100℃ 1.0 {10.2｝ customers can understand important points for shown in Figure 5, working [Ref.] Ball Valve Type21a construction and execute construction work properly. pressure may decrease in the

temperature range beyond 1.0

} { } Conclusion 2 ordinary temperatures. DF PV ur idea is that you can contribute to the society F C O D PV Therefore, operating pressure PV C- C PV C through enhanced longevity of piping, which is PP U- PV at each temperature must be 0.5 C- {5.1} resulting from the usefulness as valves and piping checked without fail. VC PP -P （MPa）{kgf／cm U systems, such as corrosion resistance and light weight of thermoplastic valves that cannot be realized with Allowable WorkingAllowable Pressure 0.0 -40 -20 0 20 40 60 80 100 120 metal valves, if you know the strength and weakness of Fluid Temperature（ ℃） resins, use different types depending on the Table 5 Valve Working Temp vs. Pressure application, and execute construction work properly [Ref.] Ball Valve Type21a not to apply excessive force on thermoplastic valves. ３ ASAHIAV | Technical Report | How to choose, How to use and Trouble Case Study for Thermoplastic Valves