Sering kita melihat valve yang terpasang di system perpipaan namun kita banyak yang masih bingung perbedaan penggunaan dari berbagai type valve ini.
Dibawah ini disajikan tanya jawab tentang valve. Semoga bermanfaat dan bertambah ilmunya.
1. What are the steps in selection of valve?
Ans : What to handle, liquid, gas or powder, fluid nature, function, construction material, disc type, stem type, how to operate, bonnet type, body ends, delivery time, cost, warranty.
2. What are functions of valves?
Ans : Isolation, regulation, non-return and special purposes.
3. What are isolating valves?
Ans : Gate, ball, plug, piston, diaphragm, butterfly, pinch.
4. What are regulation valves?
Ans : Globe, needle, butterfly, diaphragm, piston, pinch.
5. What are non-return valves?
Ans : check valve,
6. What are special valves?
Ans : multi-port, flush bottom, float, foot, pressure relief, breather.
7. What materials are used for construction of valves?
Ans : Cast iron, bronze, gun metal, carbon steel, stainless steel, alloy carbon steel, polypropylene and other plastics, special alloys.
8. What is trim?
Ans : Trim is composed of stem, seat surfaces, back seat bushing and other small internal parts that normally contact the surface fluid.
9. Which standard specifies trim numbers for valve ?
Ans : API 600.
10. What are wetted parts of valve?
Ans : All parts that come in contact with surface fluid are called wetted parts.
11. What is wire drawing?
Ans : This term is used to indicate the premature erosion of the valve seat caused by excessive velocity between seat and seat disc, when valve is not closed tightly.
12. What is straight through valve?
Ans : Valve in which the closing operation of valve is achieved by 90degrees turn of the closing element.
13. What pressure tests are carried out on valves?
Ans : Shell-hydrostatic, seat-hydrostatic, seat-pneumatic
14. What are available valve operators?
Ans : Handlever, handwheel, chain operator, gear operator, powered operator likes electric motor, solenoid, pneumatic and hydraulic operators, Quick acting operators for non-rotary valves (handle lift).
15. What are two types of ball valve?
Ans : Full port design and regular port design, according to type of seat, soft seat and metal seat.
16. What are ball valve body types?
Ans : Single piece, double piece, three piece, the short pattern, long pattern, sandwitch and flush bottom design.
17. Why ball valves are normally flanged?
Ans : Because of soft seat PTFE which can damage during welding.
18. What are butterfly valve types?
Ans : Double flange type, wafer lug type and wafer type.
19. What are types of check valve?
Ans : Lift check valves and swing check valves.
20. What are non-slam check valves?
Ans : Swing check valve, conventional check valve, wafer check valve, tilting disc check valve, piston check valve, stop check valve, ball check valve.
21. Where stop check valve is used ?
Ans : In stem generation by multiple boilers, where a valve is inserted between each boiler and the main steam header. It can be optionally closed automatically or normally.
22. Where diaphragm valves are used ?
Ans : Used for low pressure corrosive services as shut off valves.
23. What is Barstock Valve?
Ans: Any valve having a body machined from solid metal (barstock). Usually needle or globe type.
24. What is BIBB Valve?
Ans: A small valve with turned down end, like a faucet.
25. What is Bleed Valve?
Ans: Small valve provided for drawing off liquid.