Why do we straddle bolt holes in flanges?
Purpose The purpose of this check is to ensure that the flange hole shape can be manufactured using standard pierce equipment.
How many bolt holes in a flange?
Generally, higher pressure class flanges will have more bolt holes and/or larger bolt hole diameters. A 2″ Class 150# flange has 4 holes and a 2″ Class 300# flange has 8 bolt holes.
How do you check flange orientation?
Position, or check, vertical orientation of both end flanges using the carpenter’s level, as illustrated. Using two equal diameter pins located in two adjacent bolt holes, orient the flange on one end so that the carpenter’s level resting on the pins indicates level.
How many bolt holes in a 150 flange?
Diameters and bolt circles for standard ASME B16. 5 flanges – 1/4 to 24 inches – Class 150 to 2500.
| Nominal Pipe Size NPS (inches) | Class 150 | |
|---|---|---|
| Diameter of Flange (inches) | Diameter of Bolt Holes (inches) | |
| 3-1/2 | 8-1/2 | 0.75 |
| 4 | 9 | 0.75 |
| 5 | 10 | 0.88 |
What does straddle centerline mean?
All Flange Bolt Holes Straddle the Centerlines. This means: For vertical flange sealing surfaces (the flange surface is vertical and the pipeline runs horizontally), the bolt holes should span both sides of the vertical line and the horizontal centerline.
How do I choose Bolts for flange?
STUD BOLT MATERIALS. The most common materials for stud bolts (for flanges) are ASTM A193 (grade B7, B8, B8M, B8T), ASTM A453 (grade 660), ASTM A320 (grade L7, L7M), and ASTM A182 (duplex and super duplex bolting). For aggressive fluids and environments, stud bolts can be coated with Xylan, Xylar and other materials.
What is flange PCD?
What is PCD? The PCD of a flange is one of the critical dimensions. PCD (Pitch Circle Diameter) is the diameter of a circle that goes through each of the bolt holes.
How many bolts does a flange need?
Flange Bolting Chart
| 150 LB. Flanges | ||
|---|---|---|
| Nominal Pipe Size | # Bolts or Studs | Dia of Bolts or Studs |
| 8 | 8 | 0.88 |
| 10 | 12 | 1.00 |
| 12 | 12 | 1.13 |
Why do bolt holes on flanges straddle center lines?
Here’s a copy/paste from Yahoo answers, of all places. Looks right to me. “Bolt holes on flanges straddle the center lines (one on each side of the center line) for a very simple reason, To assure proper alignment of flanges from piece to piece there needs to be a simple method of consistently orienting the bolt holes.
How to orient bolt holes on flanges?
Looks right to me. “Bolt holes on flanges straddle the center lines (one on each side of the center line) for a very simple reason, To assure proper alignment of flanges from piece to piece there needs to be a simple method of consistently orienting the bolt holes. By using a simple spirit level it is possible to set the hole orientation.
How do you level a flange with bolt holes?
A bolt can be placed in each of two holes and a level is place on them. The flange is rotated until the bubble in the level is centered. This places the two bolt holes equidistant from the center line. A simple but low tech way of getting the job done regardless of the location.”
How do you place a bolt on a level?
A bolt can be placed in each of two holes and a level is place on them. The flange is rotated until the bubble in the level is centered. This places the two bolt holes equidistant from the center line.