A Staff Feature
I EQUIPMENT A
W O R K B O O K
AND
DESIGN
F E A T U R E
E C
A Short-Cut Method for Calculating Design of Bolted Flange Connections Lap flange specifications in easy steps AN
EASIER WAY to do a difficult
task turns u p every day. Some of the most complicated math calculations can be reduced to a simple chart or graph. Lengthy design calculations for lap-joint flange connections can now be determined in a matter of minutes. Days of study which have sorely tried the soul of the most adept design engineer can be a thing of the past. All that is needed are the size of vessel, design temperature and pressure, type of material in gasket, bolts and flange, and a copy of the MCA Manual M-I—a series of graphs, definitions of terms, and a stepwise procedure for use. This manual was prepared after 3 years of work by a subcommittee of the Chemical Industry Advisory Board of the American Standardization Association and published by the Manufacturing Chemists' Association. Ten months ago, I / E C reported on the work done by M C A toward standardization of pumps and heat exchangers
[IND. ENG. CHEM.
tions and effort for flange diameters ranging from 26 to 144 inches and for pressures in direct relation to selection of materials. It provides maximum flexibility, uniform design results, and interchangeability for the same nominal service. Various relative component parts are thus standardized. T h e method is adaptable to all suitable materials: steel, aluminum, copper, nickel, titanium, and alloys such as stainless steel and bronze. T h e gasket material may also be a combination of metal and a softer material without changing the result. Time Sover In the normal course of a year's operation, several hundred lap
flanges might be designed for a large chemical plant. Each of these designs ordinarily requires 3 to 4 hours of calculating and checking plus many hours of study and estimation. Now this time can be reduced to about 10 minutes by using M-I. Savings on the order of 1500- to 1600-design hours per year may thus be realized. M-I can be used by lesser qualified personnel—such as draftsmen—and engineers alike with equal accuracy. Stepwise Procedure
S. E. Bergh, a senior technical associate at Du Pont and technical consultant to the subcommittee, recently described the M-I method to
49,
No. 6, 59A(1957)]. Manual M-I in Use
Two basic types of flanges are in general use—ring and hubbed. M-I provides the design engineer a graphic method for ring-type flanges on unfired vessels. Work on a design method for hubbed flanges is under consideration. For a given service, standardization should provide the same nominal sizes, boltcircle diameters, number of bolts, bolt diameters, and other mating characteristics for all four possible combinations. The manual's graphic method minimizes time-consuming calcula-
Typical ring flange. This new method saves many hours of calculating time
I/EC
ORKBOOK
FEATURES
59 A
Μ Ι Κ Η
I/EC
EQUIPMENT AND DESIGN
•
A Workbook Feature
Final step in flange thickness d e t e r m ination uses a g r a p h simi lar to this
designed for confidence
Picco
C0 = gasket yield stress/design pressure Ci = allowable vessel stress/ design pressure C2 = allowable vessel stress/ allowable bolt stress C3 = allowable vessel stress/ allowable flange stress The new procedure uses only graphs from this point, with these steps : Determine factors governing the design, lap thickness and extension, general or practical minimum case, and pressure or gasket yielding by entering the joint parameters into the proper graph. Guiding rules for selection of the size and number of bolts in the joint are given in the new procedure. When the size de termined is not available, select the closest (larger) available size. The procedure provides an overbolt cor rection, KB. Flange moment arm, h„ is found by use of another graph. Having the selected bolt size and flange moment arm, outside flange diam eter is calculated from a given for mula. Flange factor Κ then equals flange outside diameter/flange in side diameter. The final dimension, flange thick ness, is found by plotting previously determined components on a graph similar to the one reproduced in this article. The result is a lap flange conforming to ASME Codes. Copies of Manual M-I are avail able, at $1.25 each, from the Manu facturing Chemists' Association, Inc., 1625 Eye St. N.W., Washington 6, DC.
resins
Trust is warranted in Picco Resins. Carefully manufactured in large quantities, Picco Resins assure uniformity and high quality. PENNSYLVANIA INDUSTRIAL CHEMICAL CORPORATION Clairton, Penna. 60 A
INDUSTRIAL AND ENGINEERING CHEMISTRY
I / E C as " . . . . an especially im portant contribution because of its very simplicity." Bergh pointed out that the use of M-I permits the de signing of joints in six easily followed steps. The size, operating conditions, and materials of construction are selected. A basic calculation of joint param eters is made from these data. The parameters are :
Our authors like to hear from readers. If you have questions or comments, or both, send them via The Editor, I/EC, 1155 16th Street N.W., Washington 6, D.C. Letters will be forwarded and answered promptly.
