Flange Bolt Hole Orientation

Single line: 12" and smaller Double line: 14" and larger

Figure 4-27. Orifice flange drawing symbols.

BOLTS

To complete any flanged assembly, two additional items are required: bolts and gaskets. Bolts obviously hold mating flanges, nozzles, or valves together. The pressure rating of a flange will determine the size, spacing, and number of bolts required. As the nominal pipe size and pressure ratings change so will the diameter, spacing, and number of bolts.

Flanges are designed to match the bolt circle and bolt hole dimensions of other flanges that are of the same diameter and pressure rating. Bolt hole arrangements may seem inconsequential, but, when one considers the fact that components of a piping system may be fabricated in one country then shipped to another country for assembly, bolt alignments become increasingly important. It is critical that drawings convey the exact orientation of flanges to the fabricator. Otherwise, bolt holes may not align properly. ANSI standards require all flanges straddle either the horizontal, vertical, or north-south centerlines of pipe and equipment, unless otherwise noted on a drawing.

To assure that bolt holes on flanges, nozzles, or valves align properly, holes are equally spaced around the flange. One column on the Taylor Forge Forged Steel Flanges Dimensioning Chart found in Appendix A indicates the number and diameter of the bolt holes on flanges. Notice bolts are found in quantities of four, that is, 4, 8, 12, 16, etc. The following formula makes bolt hole location and alignment quick and simple.

Using this formula shows holes on an eight-hole flange to be spaced 45° apart. By straddling the centerline, holes will be positioned 221/2° on each side of the centerline (see Figure 4-28).

Bolts are available in two types, machine or stud. Machine bolts have a "head" on one end and threads on the other. Stud bolts have threads throughout their entire length and require the use of two nuts. Stud bolts are the most commonly used type and are available in two grades, A-193-B7 and A-193-B16. B7 grade bolts are used for temperatures to 1,000°F. B16 bolts are used when temperatures exceed 1,000°F (see Figure 4-29).

GASKETS

The primary purpose of any flanged assembly is to connect piping systems in such a manner as to produce a leak-free environment. Hazardous and combustible materials and extreme pressures and temperatures require the utmost in safety precaution. Creating a leak-proof seal between two connecting metal surfaces in an industrial setting is almost impossible. Therefore, gaskets perform a vital function in plant safety.

Formula For Flange Hole

4 BOLT FLANGE 8 BOLT FLANGE

Figure 4-28. Bolt hole spacing.

Using a gasket material softer than two adjoining flanges is an excellent way to eliminate the possibility of a fluid escape. Gaskets can be made of materials such as asbestos, rubber, neoprene, Teflon, lead, or copper. When bolts are tightened and flange faces are drawn together, the gasket material will conform to any imperfections in the flange faces to create a uniform seal.

Figure 4-30 demonstrates the three types of gaskets that can be found in piping systems. They are full face, flat ring, and metal ring. Full face gaskets (Figure 4-31) are used on flat face flanges. Flat ring gaskets (Figure 4-32) are used on raised face flanges. Metal rings (Figure 4-33) are used on ring-type joint flanges.

A gasket's thickness must be accounted for when dimensioning the piping system. The typical gasket has a thickness of V%" (3.175mm). At every occurrence of a flange bolting to a nozzle, two flanges joining one another, two valves joining one another, or a flange connecting to a valve, a gasket thickness must be added to the length of the pipe components. Figures 4-34 and 4-35 show that a flat-ring gasket does occupy space. Though it's only V%" thick, a gasket cannot be ignored.

Figure 4-36 depicts the gap between ring-type joint flanges. The ring-type joint section of the Welded Fittings-Flanges Dimensioning Chart, gives the gap measurement as the G dimension. This dimension will vary

Flange Bolt Hole Orientation
Figure 4-30. Gaskets. Courtesy of Flexitallic, Inc.

Figure 4-29. Stud and machine bolts.

900 Flange Stud Chart

Figure 4-33. Metal rings for ring-type joint flanges. Courtesy of Flexitallic, Inc.

Piping Gasket Symbols Chart

Figure 4-31. Full face gaskets.

Figure 4-34. Flat ring gasket and flange. Courtesy of Flexitallic, Inc.

Flexitallic Gasket With Explosion Rings

Figure 4-34. Flat ring gasket and flange. Courtesy of Flexitallic, Inc.

Figure 4-31. Full face gaskets.

Figure 4-32. Flat ring gaskets. Courtesy of Flexitallic, Inc

Figure 4-35. Flat ring gaskets between flanges. Courtesy of Flexitallic, Inc.

Figure 4-33. Metal rings for ring-type joint flanges. Courtesy of Flexitallic, Inc.

Figure 4-36. Ring-type joint gap spacing.

depending on the size and pound rating of the flange. This is an important consideration to keep in mind when dimensioning piping runs that have ring-type joint connections.

For each instance of a gasket or ring, gap spacing must be reflected in the dimensions shown on a piping drawing. Tick marks are used to indicate each location where a gasket or ring gap has been included in the dimensioning of the piping configuration. Tick marks are drawn approximately Vs" long and are placed on piping drawings near the location where a gasket or ring is to be installed. Figure 4-37 depicts two tick marks, one on each end of a valve, that have been included in the total dimension between the faces of the two flanges. The 10Vi dimension would be the sum total of one valve and two gaskets.

EACH SET OF FLANGES MUST HAVE A GASKET

Flange Straddle

TICK MARK USED TO REPRESENT THE GASKET

Figure 4-37. Dimensioning gaskets.

TICK MARK USED TO REPRESENT THE GASKET

DIMENSION INCLUDES FACE TO FACE DIMENSION OF VALVE PLUS THICKNESS OF TWO GASKETS

DIMENSION INCLUDES FACE TO FACE DIMENSION OF VALVE PLUS THICKNESS OF TWO GASKETS

Piping Gasket Symbols Chart

Figure 4-37. Dimensioning gaskets.

CHAPTER 4 REVIEW QUIZ

1. Name the seven forged steel flange pound ratings.

2. Name the four pressure classes for cast iron flanges.

3. What are the three flange facings discussed in this chapter?

4. What is the thickness of the raised face on a 600# raised-face flange?

5. Briefly describe five types of flanges depicted in this chapter.

6. Give O, T, and L dimensions of the following flanges.

SIZE/RATING O T L

62 Pipe Drafting and Design 7. What is the purpose of an orifice flange union?

8. Name the two types of bolts used to assemble flanges.

9. According to ANSI standards, which centerlines should flanges straddle on pipe and equipment?

10. List four materials used to manufacture gaskets.

EXERCISE INFORMATION

The fittings depicted in Figure 4-38 will be used to complete the exercises in Chapters 4, 5, and 10. To complete the exercises draw the symbols below using the following guidelines.

• Start from scratch and draw all symbols full scale.

• Draw symbols with a PLINE having a width of .56" (Vie") for single line symbols and a 0" width for double line fittings. Symbols requiring a full circular shape must be drawn with the PLINE command ARC option. These arcs can only be drawn with a 359° circumference.

• Create weld dots with a 1.75" diameter DONUT.

• Block each symbol individually using the block name indicated. (DO NOT include text with the blocked symbol.)

• Place a base point on one end of each fitting using MIDpoint, ENDpoint, or CENter OSNAP options.

• In the "Block Definition" dialog box check the Create icon from block geometry radio button.

After the symbols have been created and the drawing saved, start the exercise drawing and use AutoCAD Design Center to open the file FLANGES.dwg. Insert the required symbols into the appropriate locations.

14-300LT

14—3000D

12-300LT

8-300LT

6-300LT

12—3000D

10-300LT

10-3000D

6-3000D

4-300LT

4-3000D

6-150LT

6-1500D

4-150LT

4-1500D

Figure 4-38. AutoCAD flange drawing and filenames.

DRAW ALL VIEWS AS SHOWN 12"-300# RFWN

DRAW ALL VIEWS AS SHOWN 14"-300# RFWN

DRAW ALL VIEWS AS SHOWN 10w-300# RFWN

Ml 1 rn

DRAW ALL VIEWS AS SHOWN 18"-300# RFWN

n

-

(I

FITTING MAKE-UP

DRAW ALL VIEWS AS SHOWN 14"-300# RFWN

Pipeline Isometric Drawing Exercises

DRAW ALL VIEWS AS SHOWN 12"-300# RFWN

Flange Bolt Hole Orientation

EXERCISE 4-2

Valve Orientation Isometric DrawingsFlange Bolt Hole Orientation

CD CO

Flange Bolt Hole Orientation
+1 -1

Responses

  • Nathan
    How to mark flange holes?
    2 years ago
  • vilma
    How to draw 4 hole flange?
    2 years ago
  • NICOLE
    How to design flange and bolt holes?
    2 years ago
  • Lexie
    How construct a five hole flange?
    2 years ago
  • theodore
    How to make 7 hole flange?
    2 years ago
  • J
    Does an 8 bolt flange have the same 2 hole as a 12 bolt flange?
    2 years ago
  • Pansy
    How do we connect flange to the pipe using holes?
    1 year ago
  • AMALDA
    How to make bolt holes in flange?
    1 year ago
  • Sante
    How to determine number of holes in a steel flange?
    1 year ago
  • laila
    How marking a hole in piping flanges?
    1 year ago
  • tobias
    How to mark out gasket holes?
    1 year ago
  • rolando
    What is the meaning of bolt is streddle principal?
    12 months ago
  • asmara
    How do we make a flang with hole?
    12 months ago
  • pirkko suorsa
    How to make gasket of a 8 hole flange?
    12 months ago
  • stefan
    How to design of hole in flange?
    11 months ago
  • Mattia
    How to mark out a 4 hole flange?
    10 months ago
  • andwise
    How to do a drawing of 5 hole flanges?
    10 months ago
  • niklas
    Why flange holes to straddle to vertical?
    10 months ago
  • kristian
    How to pipe flange holes marking?
    10 months ago
  • Joel Hughes
    How to find flange Holes numbers and orriantation?
    10 months ago

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