Introduction to Pressure Vessel and Design

Pressure Vessel - Introduction

1. Pressure Vessel INTRODUCTION

2. What is Pressure Vessel Pressure vessels are the containers of fluid static or flowing, internal and/or external under internal and/or external pressure. Closed vessels containing fluid under pressure are termed closed pressure vessels. Boilers and their components and heat exchangers with water or steam as the internal fluid (water tubes, steam drum, etc.) or external (fire tube, furnace tube, etc.) or both sides (tubes in steam feed water heaters) are specific types of pressure vessels. Open vessel is defined as the enclosure open to the atmosphere of spherical, cylindrical, rectangular, or other geometry or in combination, holding any material or fluid such as tanks, bunkers, etc , which are under pressure due to static head or flow. In general, pressure vessels designed in accordance with the ASME Code, Section VIII, Division 1, are designed by rules and do not require a detailed evaluation of all stresses.

3. Uses of Pressure Vessels Industrial compressed air receivers Domestic hot water storage tanks Diving Cylinders Recompression chamber Distillation towers Autoclave Oil refineries and petrochemical plants Nuclear reactor vessel Pneumatic & Hydraulic Reservoir Storage vessel for liquefied gas

4. Difference between Boiler and Pressure Vessel   Boiler Pressure Vessel Introduction Boilers are special type of closed vessels in which fluid mainly water is heated. Heated fluid is then used for different purposes. Basically a closed container with a pressure difference between inside and outside the container. The inside pressure is usually higher than the outside except for some isolated situations. Uses The main function of a Boiler is to either produce hot water or steam. Mainly used to store gases and liquids at high pressure. Area of use Different sectors like food industries, beer brewing process, domestic purposes, commercial and industrial uses, textiles, thermal power plants, power sectors, sugar plants etc. Different sectors like gas and oil industries, chemical industry and power plants, distillation towers use Pressure Vessels for various purposes.

5. Difference between Boiler and Pressure Vessel   Boiler Pressure Vessel Main Components A Furnace is an essential part of a Boiler where fuel is burned to produce heat. The main components of a pressure vessel are shell casing, nozzle, support or saddle and head or end closures. Types Different types of Boilers are Fire tube boiler, Water tube boiler, High pressure and low pressure Boiler, Horizontal and Vertical Boiler, Externally and Internally Fired Boilers etc. Different types of pressure vessels are autoclaves, high pressure vessels, process vessel, expansion tank,  heat exchanger , vacuum tanks, ASME pressure vessel, Boilers, thin walled pressure Vessel etc. Materials used Steel. Alloy steel, copper, brass, wrought iron etc are used. Steel, nonferrous materials(aluminium, copper), metals(like titanium, zirconium)plastics, composite, concrete etc.

6. Types of Pressure Vessel

7. Vertically supported cylindrical pressure vessel Horizontally supported cylindrical pressure vessel Tower-vertical cylindrical pressure vessel Cylindrical Pressure Vessel ? ? ?

8. Spherical Pressure Vessel

9. Rectangular Pressure Vessel

10. Cylindrical Pressure Vessel Head shapes are frequently either hemispherical or dished ( torispherical ) Easy to manufacture Make better use of the available space.

11. Spherical Pressure Vessel Required thinner wall compare to cylindrical pressure vessel at equivalent diameter and pressure. Used for large gas or liquid container, gas cooled nuclear reactors and containment buildings for nuclear plant.

12. Pressure Vessel Components and Material

13. Component

14. Component Shell primary component that contains the pressure shells are welded together to form a structure that has a common rotational axis. Most pressure vessel shells are cylindrical, spherical and conical in shape

15. Component & Material Head Located at the both end of the shell Heads are typically curved rather than flat Curved configurations are stronger and allow the heads to be thinner, lighter, and less expensive than flat heads.

16. Component Type of Head Heads are usually categorized by their shapes. Ellipsoidal, Hemispherical, Torispherical , Conical, Toriconical Flat

17. Component Support To support the load from pressure vessel and fluid inside it and at the same time can support the external load from environment such as wind and earthquake. The design depend on size and orientation of the pressure vessel.

18. Support Component & Material

19. Skirt Normally used for tall, vertical, cylindrical pressure vessel. A support skirt is a cylindrical shell section that is welded either to the lower portion of the vessel shell or to the bottom head (for cylindrical vessels). Skirts for spherical vessels are welded to the vessel near the mid-plane of the shell. The skirt is normally long enough to provide enough flexibility so that radial thermal expansion of the shell does not cause high thermal stresses at its junction with the skirt. Support

20. Support Leg Used for small vertical cylindrical pressure vessel. Normally welded to the lower portion of the shell. Ratio between leg length to pressure vessel diameter is 2:1 Also typically used for spherical pressurized storage vessels Made from structural steel column or pipe section Cross bracing between the leg is typically used to help absorb wind and earthquake loads.

21. Support Saddle Normally used for horizontal cylindrical drum at two location. A saddle support spreads the weight load over a large area of the shell, to prevent an excessive local stress in the shell at the support point. Only one saddle are anchor to the foundation, the other saddle support is free, for longitudinal thermal expansion.

22. Support Lug Lugs are welded to the pressure vessel shell. Typically limited to small vessel to medium vessel diameter (1 to 10 ft) and moderate high to diameter ratio 2:1 to 5:1. The lug are typically bolted to horizontal structure members to provide stability against overturning load; however, the bolt holes are often slotted to permit free radial thermal expansion of the drum.

23. Component Nozzle Cylindrical component that penetrate the pressure vessel shell or head. Nozzle end usually flanged to allow connection with others component and easy maintenance or access. Nozzle application: Attach piping for flow into or out of the vessel. Attach instrument connections, (e.g., level gauges, thermowells , or pressure gauges). Provide access to the vessel interior at manways . Provide for direct attachment of other equipment items, (e.g., a heat exchanger or mixer).

24. Material There are many parameters which may be investigated by practice, calculations and tests, shall be considered in the selection of suitable material for pressure vessels. These parameters are including the following aspects: Strength for design condition Strength for desired service life Resistance to corrosion in service environment for desired life Capabilities for fabrication processes Market availability Maintenance and repair Cost (first investment and operation cost)

25. Material Some national standards list acceptable materials with acceptable temperature ranges and design stresses . Design stresses are set using safety factors applied to material properties , which include: Yield strength at design temperature. Ultimate tensile strength at room temperature. Creep strength at design temperature.

26. Material Material Standard AA The Aluminium Association AISI American Iron and Steel Institute ANSI American National Standards Institute AMS Aerospace Material Specifications (SAE) ASME American Society of Mechanical Engineers ASTM American Society for Testing and Materials AWS American Welding Society CSA Canadian Standards Association SAE Society of Automotive Engineers

27. Material The range of materials used for pressure vessels is wide and includes, but is not limited to, the following: Carbon steel (with less than 0.25% carbon) Carbon manganese steel (giving higher strength than carbon steel). Low alloy steels. High alloy steels. Austenitic stainless steels. Non-ferrous materials (aluminum, copper, nickel and alloys). High duty bolting materials. Clad materials are accepted by national standards but often only the base material thickness can be used in design calculations.

28. Material Selection for Pressure Vessel Materials are generally selected by the user for whole of the plant and specifically, by pressure vessel designer/ supplier according to the following criteria. Corrosive or noncorrosive service Contents and its special chemical/physical effects Design condition (temperature) Design life and fatigue affected events during the plant life Referenced codes and standards Low temperature service Wear and abrasion resistance Welding and other fabrication processes

29. Material Selection for Pressure Vessel

30. ASME Pressure retaining parts must full fill requirements not only from material standards but also from pressure vessel codes. ASME VIII Subsection C determine the requirements for materials to be used in construction of pressure vessels and contains material tables with acceptable materials.

31. Allowable Materials ASME VIII

32. Properties of Material and Application

33. AISI and ASTM Material Specification ASME has adopted many of the ASTM material standards and the number of the ASME material standard is only distinguished by the additional letter S.

34. Video

35. Longitudinal Stress -  l Hoop Stress -  θ Radial Stress -  r Stress In Cylindrical Shell

36. Types of Stress in Pressure Vessel Longitudinal stress,  l Internal pressure, p Pressure area Pressure area Hoop stress  θ dr  θ  θ  r + d  r  r

37. Stress element Wall thickness t Radial stress  r Longitudinal stress  l (closed ends) A pressurized cylinder is considered a thin-walled vessel if the wall thickness is less than one-twentieth of the radius. < 1/20 t r Thin-walled pressure vessel Tangential stress  θ Hoop stress

38. Type of failure Such a component fails in since when subjected to an excessively high internal pressure. While it might fail by bursting along a path following the circumference of the cylinder. Under normal circumstance it fails by bursting along a path parallel to the axis. This suggests that the hoop stress is significantly higher than the axial stress . In order to analyse the thin walled cylinders , let us make the following assumptions : There are no shear stresses acting in the wall. The longitudinal and hoop stresses do not vary through the wall. Radial stresses   r  which acts normal to the curved plane of the isolated element are negligibly small as compared to other two stresses especially when 

39. Longitudinal Stress (Thin-walled) Longitudinal stress,  l Internal pressure, p Pressure area 1

40. Hoop Stress (thin-walled) Pressure area Hoop stress  θ 2 1 2 & :

41. Radial Stress In a thin-walled pressurized cylinder the radial stress is much smaller than the tangential stress and can be neglected. t  θ  θ P  r

42. Exercise

43. Exercise

44. Widescreen Test Pattern (16:9) Aspect Ratio Test (Should appear circular) 16x9 4x3