Saturated steam application

Transcription

1 Saturated steam application

2 Saturated steam table 2

3 Saturated steam table Saturated steam has a fixed pressure & temperature related table. 3 barg saturated steam temperature is C 5 barg saturated steam temperature is C 10 barg saturated steam temperature is C 15 barg saturated steam temperature is C 20 barg saturated steam temperature is C

4 Metal seated valve Bronze gate valve Malleable iron/ductile iron gate valve Forged steel gate valve Cast steel gate valve Bronze globe valve Malleable iron/ductile iron globe valve Forged steel globe valve Cast steel globe valve Bronze check valve Malleable iron/ductile iron check valve Forged steel check valve Cast steel check valve

5 Metal seated valve High performance or eccentric butterfly valve can be used for saturated steam application Metal seated ball valve can be used for saturated steam application

6 Bronze valve for saturated steam

7 Cast iron valve for saturated steam

8 Cast iron family Gray iron, or grey cast iron, is a type of cast iron that has a graphitic microstructure. It is named after the gray colour of the fracture it forms, which is due to the presence of graphite. Since the carbon content is high, it becomes brittle if given tension. Malleable iron is cast as white iron, the structure being a metastable carbide in a pearlitic matrix. Through an annealing heat treatment, the brittle structure as first cast is transformed into the malleable form. Carbon agglomerates into small roughly spherical aggregates of graphite leaving a matrix of ferrite or pearlite according to the exact heat treatment used. Ductile iron, also known as ductile cast iron, nodular cast iron, spheroidal graphite iron, spheroidal graphite cast iron and SG iron, is a type of graphite-rich cast iron. While most varieties of cast iron are weak in tension brittle, ductile iron has much more impact and fatigue resistance, due to its nodular graphite inclusions.

9 Cast iron vs Malleable iron vs Ductile iron As for the casting process, the production for malleable iron & ductile iron are made similar with the normal casting iron Ductile iron has a inoculation process. Inoculation means we will add the spheroidizing agents during melting and pouring process to make the graphite into ball shape. The production of malleable iron includes a special heat treatment process, which can make the graphite into cottony shape. Malleable iron & ductile iron are generally superior to grey irons, regarding their yield strength. The max yield strength of ductile iron is 40k psi (grey iron is not very malleable or strong it fractures/breaks easily) Malleable iron & ductile iron are more flexible and elastic than other cast irons. It has higher strengths, greater elongation and better resistance to impact than grey iron (so it is better than grey iron in handling temperature expansion problem such as in steam application) The malleable iron & ductile iron family offers the design engineer a unique combination of strength, wear and fatigue resistance and toughness as well as excellent ductility characteristics

10 Carbon content in iron & steel

11 Malleable iron/ductile iron valve for saturated steam

12

13 Forged steel valve for saturated steam Class 800 forged steel valve with standard A-105 type of material can stand saturated steam without problem! For example: 20 barg of saturated steam temperature is C At C class 800 forged steel valve can stand bar pressure

14 Cast steel valve for saturated steam Class 150 or class 300 cast steel valve with standard A216- WCB type of material can stand saturated steam without problem! For example: 20 barg (290 psig) of saturated steam temperature is C (417 F) At 400 F (204 C) class 300 cast steel valve can stand 635 psi (43.8 bar) pressure

15 Valve s seat material for saturated steam Valve s seat ring Steam is very abrasive! To prevent wear of the internal part of the metal seated valve the valve s seat ring have to be stellited

16 Valve s seat material for saturated steam If the valve s seat ring is stellited The trim material no 8 is choosen!

17 Soft seated valve Ball valve has soft seat can be used for saturated steam application But the pressure-temperature rating is based on the soft seat material Concentric butterfly valve cannot be used for saturated steam application

18 Ball valve seat pressure temperature rating PTFE seat material (T) At 10 bar pressure it can stand 210 C temperature 10 bar saturated steam temperature is only C Even though 18 bar saturated steam temperature is 210 C PTFE seat of a ball valve can stand 10 bar saturated steam only!

19 Ball valve seat pressure temperature rating PTFE seat material (blue line) At 10 bar pressure it can stand 210 C temperature PTFE seat of a ball valve can stand 10 bar saturated steam only ANSI class 150 ball valve is suitable for this job!

20 Superheated steam application

21 Superheat steam Saturated steam Superheat tubes Superheated steam is created by further heating wet or saturated steam beyond the saturated steam point in a water tube steam boiler. This yields steam that has a higher temperature and lower density than saturated steam at the same pressure. Superheated steam is mainly used in propulsion/drive applications such as turbines, and not so much is used for heat transfer applications.

22 Superheat steam Superheat steam does not have a fixed pressure-temperature relationship like saturated steam!

23 Forged steel valve for superheated steam For example: Application: Superheated steam, 500 C & 40 bar If we look at the A-105 forged steel material P/T-chart At 510 C temperature the class 1500 valve can stand 35.5 bar pressure only

24 Forged steel valve for superheated steam For example: Application: Superheated steam, 500 C & 40 bar If we look at the A182-F22 forged steel material P/T-chart At 510 C temperature the class 1500 valve can stand 130 bar pressure!

25 Cast steel valve for superheated steam For example: Application: Superheated steam, 400 C (753 F) & 40 bar (580 psi) If we look at the A216-WCB cast steel material P/T chart At 750 F temperature the class 300 valve can stand 505 psi pressure only

26 Cast steel valve for superheated steam For example: Application: Superheated steam, 400 C (753 F) & 40 bar (580 psi) If we look at the A217-WC1 cast steel material P/T chart At 750 F temperature the class 300 valve can stand 530 psi pressure only

27 Cast steel valve for superheated steam For example: Application: Superheated steam, 400 C (753 F) & 40 bar (580 psi) If we look at the A216-WCB cast steel material P/T chart At 750 F temperature the class 600 valve can stand 1,010 psi pressure

28 Valve s seat material for superheated steam Superheat steam is very abrasive If the valve s seat ring + the valve s disc are stellited The trim material no 5 is choosen!