Chapter 004, Design of Vessel Supports

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The greatest distance between any two akjacent stiffening rings, in. The distance from the center of the first stiffening ring to the head tangent line plus one third of the head depth, in. The charts are from: Logan, P. Logan, P. Copyrighted Gulf Publishing Co. Used with permission. The basic wind speed shall be taken from the map on the following page. The basic wind speed is 80 mph. The minimum design wind pressure shall be not less than 10 lb. When records and experience indicates that the wind speeds are higher than those reflected in the map, the higher values of wind speed shall be applied.

The wind pressure on the projected area of a cylindrical tower shall be calculated by the following formula. Exposure B; in open terrain with scattered obstruction, Exposure C; in flat, unobstructed areas, Exposure D. Importance factor, 1. Area of platform 8 sq. Users of vessels usually specify for manufacturers the wind pressure without reference to the height zones or map areas.

For example: 30 lb. This specified pressure shall be considered to be uniform on the whole vessel. The total wind pressure on a tower is the product of the unit pressure and the projected area of the tower. With good arrangement of the equipment the exposed area of the wind can be reduced considerably.

For example, by locating the ladder 90 degrees from the vapor line. Values are fastest-mile speeds at 33 ft. Linear interpolation between wind speed contours is acceptable. Caution in the use of wind speed contours in mountainous regions of Alaska is advised. Wind speed for Hawaii is 80 and for Puerto Rico is 95 mph. Where local records or terrain indicate higher year wind speeds, they shall be used.

Wind speed may be assumed to be constant between coastline and the nearest inland contour. This standard is obsolete but still used in some codes and foreign countries. The wind pressure at 30 ft. The table below gives the wind pressures for various heights above ground for the areas indicated by the map.

The vessel is intended to operate in Oklahoma, which is in the wind pressure map area marked In this map area the wind pressures for various height zones are: In the height zone less than 30 ft. In the height zone from 30 to 49 ft. For cylindrical tower these values shall be multiplied by shape factor 0.

If many equipments are attached to the tower it is advisable to increase the shape factor according to Brownell up to 0. Users of vessels usually specify for manufacturers the wind pressure without ref- erence to the height zones or map areas. Usually the compression due to the weight is insignificant and is not controlling. The weight shall be calculated for the various conditions of the tower as follows: A.

Erection weight, which includes the weight of the 1. Operating weight, which includes the weight of the: 1. Test weight, which includes the weight of the: 1. The weight of different vessel elements are given in tables beginning on page Equipments: The period of the vibration should be limited, since large natural periods of vibration can lead to fatigue failure. The allowable period has been computed from the maximum permissible deflection. The so called harmonic vibration is not discussed in this Handbook since the trays as usually applied and their supports prevent the arising of this problem.

The actual vibration does not exceed the allowable vibration Reference: Freese, C. The triangular loading pattern and the shape of the tower shear diagram due to that loading are shown in Fig. A portion F, of total horizontal seismic force V is assumed to be applied at the top of the tower. The remainder of the base shear is distributed throughout the length of the tower, includ- ing the top. Overturning Moment The overturning moment at any level is the algebraic sum of the moments of all the forces above that level.

S A soil profile containing more than 40 feet of soft clay. Each form contains explanation, the applicable regulation, data and example calculation. Equipment attached to the vessel on the outside can cause unsymmetrical distribution of the loading due to the weight and result in bending stress. This unsymmetrical arrange- ment of small equipment, pipes and openings may be neglected, but the bending stresses exerted by heavy equipment are additional to the bending stresses resulting from wind or seismic load. Efficiency of welded joints.

Moment of eccentric load, ft. Mean radius of vessel, in. Stress value of material, or actual bending stress, psi Thickness of vessel, excluding corrosion allowance, in. Eccentric load, lb. Determine moment, M, and stress, S. By buckling of the whole vessel Euler buckling 2. By local buckling In thin-walled vessels when the thickness of the shell is less than one-tenth of the inside radius local buckling may occur at a unit load less than that required to cause failure of the whole vessel.

The out of roundness of the shell is a very significant factor in the resulting instability. The formulas for investigation of elastic stability are given in this Handbook, developed by Wilson and Newmark. Elements of the vessel which are primarily used for other purposes tray supports, downcomer bars may be considered also as stiffeners against buckling if closely spaced.

Longitudinal stiffeners increase the rigidity of the tower more effectively than circumferential stiffeners. If the rings are not continuous around the shell, its stiffening effect shall be calculated with the restrictions outlined in the Code UG c. A y - Cross sectional area of one circumferential stiffener, sq. The deflection due to the wind load may be calculated by using the formula for uniformly loaded cantilever beam.

Width of the tower with insulation, etc. Modulus of elasticity, psi Leneth of vessel, included skirt, ft. The maximum allowable deflection 6 inches per ft. Since the actual deflection does not exceed this limit, the designed thickness of the skirt is satisfactory. Hydrocarbon Processing November The summation of the stresses indicate whether tension or compression is governing. It is assumed that wind and earthquake loads do not occur simultaneously, thus the tower should be designed for either wind or earthquake load whichever is greater.

Bending stress caused by excentricity shall be summarized with the stresses resulting from wind or earthquake load. The stresses shall be calculated at the following locations: 1. At the bottom of the tower 2. At the joint of the skirt to the head 3. At the bottom head to the shell joint 4. At changes of diameter or thickness of the vessel The stresses furthermore shall be examined in the following conditions: 1.

During erection or dismantling 2. During test 3. During operation Under these different conditions, the weight of the vessel and consequently, the stress conditions are also different. Besides, during erection or dismantling the vessel is not under internal or external pressure. For analyzing the strength of tall towers under various loadings by this Handbook, the maximum stress theory has been applied.

Specifying Design Requirements for Pressure Vessels

The bending moment due to wind is decreasing from the bottom to the top of the tower, thus the plate thickness can also be decreased accordingly. Table A and Figure B are convenient aids to find the distance down from the top of the tower for which a certain thickness is adequate. From Table A, using factor m can be found the distance X down from the top tangent line within which the thickness calcu- lated for internal pressure satisfactory also to resist the wind pressure.

Figure B shows the moment diagram of a tower under wind pressure. The diagram can also be used to select the appropriate plate thickness at various heights. No allowance for corrosion. Minimum required thickness for internal pressure considering the strength of the long seams: ,. Required thickness: M-r , , R 2 it SE 12 2 x 3. For int. For simple vessels where the moment due to wind is small, the above calculation is satisfactory. Vessels which are subject to larger loadings may need closer investigation with respect also to economical viewpoints. The preliminary calculation of the required wall thick- ness shows that at the bottom approximately 0.

For economical reasons it is advisable to use different plate thicknesses at various heights of the tower. The thickness required for hoop tension 0. From diagram B, Page 70 can be found the required thickness and length of the intermediate shell sections. Using 8 ft.

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Chapter , Design of Vessel Supports - Kindle edition by Dennis Moss. Download it once and read it on your Kindle device, PC, phones or tablets. Vessels of Rectangular Cross Section. Vessels cannot be safely filled with water due to their design and support system; b. Vessels in which.

Piping 21, Say 10, lb. For weight of water content, see Page lb. Checking the stresses with the preliminary calculated plate thicknesses: Stress in the shell at the bottom head to shell joint: Plate thickness 0. The allowable stress for the plate material with 0. Thus the selected 0. Stress in the shell at 72 ft. Plate thickness 0. Stress due to wind. Shell Platform 30 x 8 lin. Therefore without further calculation it can be seen that the tensile stress 10, psi does not exceed the allowable stress 11, Stress in the shell at 40 ft.

No further calculation is required on the same reason mentioned above. It is attached by continuous welding to the head and usually the required size of this welding determines the thickness of the skirt. Figures A and B show the most common type of skirt to head attachment. In calculation of the required weld size, the values of joint efficiency given by the Code UW 12 may be used.

Efficiency of skirt to head joint. B Moment at the skirt to head joint, ft. Outside radius of skirt, in. Stress value of the head or skirt material whichever is smaller, psi. Required thickness of skirt, in. Weight of the tower above the skirt to the head joint, in operating condition. NOTE: Using extremely high skirt, the stresses at the base may govern. To calculate the required thickness of the skirt, in this case the above formula can be used.

The moment and weight shall be taken into considera- tion at the base and the joint efficiency will be 1.

Determine the required skirt thickness. Weil, N. Industrial Engineering for Industry, Vol. The number of anchor bolts. The anchor bolts must be in multiple of four and for tall towers it is preferred to use minimum eight bolts. Spacing of anchor bolts. The strength of too closely spaced anchor bolts is not fully developed in concrete foundation.

It is advisable to set the anchor bolts not closer than about 18 inches. To hold this minimum spacing, in the case of small diameter vessel the enlarging of the bolt circle may be necessary by using conical skirt or wider base ring with gussets. Diameter of anchor bolts. Computing the required size of bolts the area within the root of the threads only can be taken into consideration. The root areas of bolts are shown below in Table A.

For corrosion allowance one eighth of an inch should be added to the calculated diameter of anchor bolts. For anchor bolts and base design on the following pages are described: 1. An approximate method which may be satisfactory in a number of cases. A method which offers closer investigation when the loading conditions and other circumstances make it necessary. Size Root Area sq.

Diameter m. Stress psj Specification Number Diameter in. The required area of bolts shall be calculated for empty condition of tower. From Table A. Page 77 the root area of 2" bolt is 2. Adding 0. The bearing surface of the base ring shall be large enough to distribute the load uniformly on the concrete foundation and thus not to exceed the allowable bearing load of the foundation.

The thickness of the base ring shall resist the bending stress induced by wind or earthquake. Approximate Width of Base Ring in. Approximate Thickness of Base Ring in. Area within the skirt, sq. Circumference on O. Safe bearing load on concrete, psi. See Table E, on Page 80 Cantilever inside or outside, whichever is greater, in. Dimensions, as shown on sketch above. For minimum dimensions see Table A on page 77 Moment at the base due to wind or earthquake, ft. Weight of vessel during operation or test, lb. Then A. Thus the width and thickness of the base ring are satisfactory.

The stresses should be checked also for test condition. It is obvious then that the area of the bolting and the area of the base ring are related. As the anchor bolt area increased, the base ring area can be decreased. With the design method given here, the minimum required anchor bolt area for a practical size of base ring can be found.

The strength of the steel and the concrete is different, therefore, the neutral axis does not coincide with the centerline of the skirt. Design procedure: 1. Determine the value of k 2. Calculate the required size and number of anchor bolts. See page 77 Table B 3.

Sizing Vessels Using Limit Analysis.

Determine the inside and outside diameter of the base ring 4. Check the stresses in the anchor bolts and foundation 5. If the deviation between the allowable and actual stresses are too large, repeat the calculatibn 6.

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Calculate the base ring thickness 7. Use greater value, M x or My. Relationship between max. Tensile load on anchor bolts, Ft lb. Tensile stress in anchor bolts, Sa, psi. Thickness of a ring which has an area equal to the area of anchor bolts, ts, in. Compression load on the concrete, Fc, lb.

Compressive stress in the concrete at the bolt circle. Relationship between tension in steel and compression in concrete. Base ring thickness without gusset plate, tB, in. Base ring thickness with gusset plate, tB, in. Total area required for anchor bolt sq. Constants, see Table D on the preceding page.

Diameter of anchor bolt circle, in. Diameter of anchor bolt circle, ft. Compressive stress in the concrete at the outer edge of the base ring, psi. Compressive stress in the concrete at the bolt circle, psi. Constant, see Table D on the preceding page. Moment at the base due to wind or earthquake ft. M x or M y whichever is greater. See Table F on the preceding page. See Table E. Radius of bolt circle, in. Tensile stress in anchor bolts, psi. Maximum allowable stress value of base plate, psi. Weight of the tower at the base, lb.

See Table D on the preceding page. Page 80 of base ring. Then the constants from. F , To decrease the thickness of the base ring, use gusset plates. Use Wi in. The anchor bolt size and base plate shall be calculated as described on the fore- going pages. All contacting edges of the plates shall be welded with continuous' fillet weld. The leg size of the fillet weld shall be one half of the thinner joining plate thickness. Anchor bolt diam. Petroleum Refiner, June Shell and Tube Heat Exchangers 2.

Flange Design 3. Rotation of Hub Flanges 4. Fixed Tube Sheet Design 5. Flanged and Fluted Expansion Joints 6. Pipe Segment Expansion Joints 7. Pipe Segment Expansion Joints 8. Vertical Vessels Supported by Legs 9. Mechanical Design of Self- supported Steel Tanks 1 1. Vibration Analysis of Tall Towers Design of Rectangular Tanks It is a well organized presentation of subjects, each complete in itself. Ample charts and tables make important data clear at a glance.

The problems are solved by quick step-by-step calculations, illustrations and examples. About the Author. Kanti K. Mahajan is a registered professional engineer in the states of Kansas, California and Texas. He received his bachelor and master of science degrees in mechanical engineering from the University of Houston. He has been involved with the field of heat exchanger and pressure vessel design for the past seventeen years.

He is currently a principal mechanical engineer with the Fluor Engineers, Inc. The British Standard adopted this method with slight modification and further refinement. The design method of this Handbook is based on the revised analysis mentioned above. The loading conditions are different for a full or partially filled vessel. The stresses in the vessel vary according to the angle included by the saddles. The load due to the weight of the vessel is combined with other loads.

Reaction of the saddles. It is a recommended practice to design the vessel for at least a full waterload. Internal Pressure. Since the longitudinal stress in the vessel is only one half of the circumferential stress, about one half of the actually used plate thickness is available to resist the load of the weight. External pressure. If the vessel is not designed for full vacuum because vacuum occurs incidentally only, a vacuum relief valve should be provided especially when the vessel outlet is connected to a pump.

Wind load. Impact Loads. Experience shows, that during shipping, hardly calculable im- pact loads can damage the vessels. When designing the width of the saddles and the weld sizes, this circumstance is to be considered. The use of only two saddles is preferred both statically and economically over the multiple support system, this is true even if the use of stiffener rings is necessary. The location of the saddles is sometimes determined by the location of openings, sumps, etc. If this is not the case, then the saddles can be placed at the statically optimal point.

Thin walled vessels with a large diameter are best supported near the heads, so as to utilize the stiffening effect of the heads. Long thick walled vessels are best supported where the maximal longitudinal bending stress at the saddles is nearly equal to the stress at the midspan. This point varies with the contact angle of the saddles. The distance between the head tangent line and the saddle shall in no case be more than 0. Code Appendix G Vessels supported by saddles are subject to: 1.

Longitudinal bending stress 2. Tangential shear stress 3. Use formula with fac- tor K 3 if ring used in plane of saddle. The maximum bending stress S j may be either tension or compression. Computing the tension stress in the formula for Sj, for factor K the values of Kj shall be used. Computing the compression stress in the formula for Sj, for factor K the values of Kg shall be used. Use stiffener ring if stress Sj exceeds rhe maximum allowable stress. In unstiffened shell the maximum shear occurs at the horn of the saddle. When the head stiffness is utilized by locating the saddle close to the heads, the tangential shear stress can cause an additional stress S3 in the heads.

This stress shall be added to the stress in the heads due to internal pressure. When stiffener rings are used, the maximum shear occurs at the equator. The combined circumferential stress at the top edge of the wear plate should also be checked. If the shell is not stiffened, the maximum stress occurs at the horn of the saddle. This stress is not be to added to the internal pressure-stress. In a stiffened shell the maximum ring-compression is at the bottom of shell.

Use stiffener ring if the circumferential bending stress exceeds the maximum allowable stress. Yield point 38, psi. Joint Efficiency : 0. Compression at the Shell Governs Ring Outside. Stress at the Shell Ring Outside. Stress at the Tip of the Ring Ring Inside.

Standard Welding Procedure Specifications (SWPS)

Stress at the Shell Ring Inside. Stress at the Tip of the Ring Ring Outside. Compression at the Shell Governs Ring Inside. The first part of the formulas for Sg gives the direct stress and the second part gives the circumferential bending stress. If the governing combined stress is tensional, the stress due to internal PR pressure, — — shall be added. Determine the width of shell that is effective t o resist the circu mferential bending moment.

Divide the stiffener ring into rectangles and calculate the areas a of each rectangles, including the area of shell section within the effective width. Multiply the areas a with the distances Y from the shell to the center of gravity of the rectangles. Summarize the results and denote it AY. Determine the neutral axis of the stiffener ring, the distance C from the shell to the neutral axis r - A 5. Determine the distances h from the neutral axis to the center of gravity of each rectangle of the stiffener. See example calculations on the following pages. The saddle at the lowest section must resist the horizontal force F.

The effective cross section of the saddle to resist this load is one third of the vessel radius R. The average stress shall not exceed two thirds of the compression yield point of the material. See example below. The thickness of the web plate is satisfactory for horizontal force F.

The base plate and wear plate should be thick enough to resist longitudi- nal bending over the web. The web plate should be stiffened with ribs against the buckling. In this saddle for the anchor bolts slots are to be used instead of holes. The length of the slots shall be determined by the expected magnitude of the movement. The table below shows the minimum length of the slot. The design based on: 1. Drill and tap! At the sliding saddle the nuts of the anchor bolts shall be hand-tight and secured by tack welding. The maximum tensile stresses S, and S 2 , respectively, plus the tensile stress due to internal pressure shall not exceed the allowable tensile stress value of head material.

The maximum compression stresses S, and S 2 , respectively, plus the tensile stress due to internal pressure shall not exceed the allowable compression stress value of head material. It does not exceed the stress value of the girth seam: 17, x 0.

Standard Welding Procedure Specifications (SWPS)

All dimensions are in inches 2. The design is based on conditions: a. Minimum tensile strength of lug material 70, psi. Direction of force is in the plane of lugs. Use wear plate if necessary to eliminate buckling due to normal or sudden loading. To design the lugs the entire load should be assumed to act on one lug. All possible directions of loading should be considered during shipment, storage, erection, handling. When two or more lugs are used for multileg sling, the an- gle between each leg of the sling and the horizontal should be assumed to be 30 degrees.

These are expressed as percentage of the rating in the axial direction. The above dimensions and recommendations are taken from C. Thus the maximum allowable safe load shall be reduced proportionally to the increased stress. If the allowable load for a single vertical rope is divided by the cosecant of the angle between one side of the rope and the horizontal, the result will indicate the allowable load on one side of the inclined sling.

Example: The allowable load for a rope in vertical position is lb. The table shows the load-bearing capacity of ropes and chains in different positions. Multiplying with the factors shown in the table the allowable load for a certain rope or chain, the product will indicate the allowable load in inclined position. An obround opening is one which is formed by two parallel sides and semicircular ends.

The opening made by a pipe or a circular nozzle, the axis of which is not perpendicular to the vessel wall or head, may be considered an elliptical opening for design purposes. Openings may be of shapes other than the above. See Code UG In place of two smaller openings a single opening may be used, provided it is of such size and location as to afford at least an equal view of the interior.

Compressed air as used here is not intended to include air which has had moisture removed to the degree that it has an atmospheric dew point of F or less. UG e. UG c. UG b. For other types see Code, Fig. Depends on plate thickness, welding pro- cedure. NOTES: 1. Thank you for your interest! To view the Global Flood Map, please enter your information below one-time registration per device. If you'd like to receive any email subscription s , make your selections below to have the latest news from FM Global delivered directly to your inbox. FM Global has provided this link for your convenience only and it is not responsible for the content, links, privacy or security of the website.

Please review the terms of use and privacy policy of the third party site if you have specific questions regarding their collection, use and storage of your personal information. Construction Sprinklers Water Supply Extinguishing Equipment Electrical Boilers and Industrial Heating Equipment Hazards Each stirrer can be raised by hand into a convenient position for easy vessel removal or insertion. PTWS D is capable to perform a staggered start for each of the six positions.

Vessel Centering System The PTWS D features a rigid and precise three-point individual centering system for each dissolution vessel picture shows view from below.

Vertical Pressure Vessel Hydrostatic test analysis as per ASME Guidelines using ANSYS Workbench

The vessels are held in position by three adjustable noses and are inserted into the instrument support framework. The access points for sampling as well as the openings for the tools are contained in an auxiliary, low evaporation, vessel cover. Each USP Borosilicate glass vessel has a batch code on top of the flange for easy visibility and positioned placement inside the water bath cover. Lift Mechanism The upper drive is motorized and electronically controlled it offers eight programmable positions: an upper cleaning and instrument qualification position and lower working positions are programmable depending on the type of stirring tool used.

The upper position offers ideal access to the stirring tools and vessels for a change of tools and cleaning steps between the dissolution tests. The electronically driven lift mechanism is located centrally above the water bath.

Saudi Aramco DeskTop Standards

Where steel pipe is threaded and used for steam service at pressure above psi, or for water service above psi with water temperature above F the pipe shall be seamless hav- ing the minimum ultimate tensile strength of 48, psi and weight at least equal to Sell 80 of ANSI B A person who receives a notice of violation pursuant to NAC C. An appeal of any action taken by the Mechanical Compliance Section pursuant to subsection 3 must be made in accordance with the provisions of NAC C. UW UW- 12 d category A welds in vessel sections or heads or connect seamless vessel sections or heads None 0. To eliminate the necessity of additional reinforcement by using thicker plate for the cylinders at the junction in some cases may be more advantageous than the application of compression rings. Except as otherwise provided in subsections 3 and 4, the Enforcement Section shall charge and collect the following fees:. See tables on page 28 for maximum allowable pressure for flanges.