Whether replacing worn gaskets or installing new valves,accurately determining flange size is one step in preventing costly leaks.In the industrial piping sector,even a few millimeters of error can lead to catastrophic failures.This article explains how to properly measure brides en acier inoxydable.
The Importance of Accurate Measurement
Before you begin,you must realize that flange size refers to more than just the outer diameter.It involves a set of specific dimensions that must align with international standards like ASME B16.5 ou EN 1092-1.If you miscalculate the size,the bolt holes will not align.Consequently,the gasket will not seat properly.This leads to uneven pressure distribution and eventual joint failure.
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Flange Size and Pressure Class Correlation
When identifying flange size,you must remember that dimensions change based on the pressure rating.For example,a 2-inch Class 150 flange has a different bolt circle than a 2-inch Class 600 flange.
As the pressure rating increases,the flange becomes thicker to handle higher internal stress.Additionally,the bolt holes often become larger or more numerous to provide greater clamping force.Consequently,if you only measure the bore,you might order a component that does not fit your existing stainless steel pipe fittings.Always verify the “Class” or “PN” rating before finalizing your measurements.
Essential Tools for Measuring Flange Size
- Vernier Calipers:
Ideal for measuring thickness and small diameters. - Large Outside Calipers:
Necessary for measuring the total outer diameter of large flanges. - Bolt Hole Gauge:
Helps determine the exact diameter of the holes. - Measurement Chart:
Used to cross-reference your findings with standard size tables.
Step-by-Step Guide to Measuring Your Flange
To find the correct flange size, follow this specific sequence.Always record your measurements in both millimeters and inches to avoid conversion errors.
Measure the Outside Diameter (OD)
Start by measuring the distance across the entire face of the flange.Place your calipers at the widest points of the outer circle.This measurement helps narrow down the potential size category but does not define the pressure rating.
Determine the Bolt Circle Diameter (BCD)
Measure from the center of one bolt hole to the center of the opposite hole. If you cannot reach the center, measure from the inner edge of one hole to the outer edge of the opposite one.
Count the Number of Bolt Holes
This may seem simple,but it is a vital part of the identification process.Standard flanges usually have holes in multiples of four (4, 8, 12, 16, etc.).The combination of BCD and the hole count usually reveals the pressure class (e.g., Class 150 vs. Class 300).
Measure the Bore Size (ID)
The Bore Size corresponds to the inside diameter of the flange.This should match the nominal size of the SS Pipe you are using.For example,a 2-inch pipe requires a flange with a matching 2-inch bore.
Check the Thickness
Measure the thickness of the flange at the edge. Thicker flanges generally indicate a higher pressure rating.
Professional Verification: Reading Flange Markings
Experts do not rely solely on calipers to determine flange dimensions.Each premium stainless steel flange features etched markings on its outer edge.
- Taille:
Look for a marking like “2” or “DN50.” - Rating:
You will see “150#,” “CL150,” or “PN16.” - Matériau :
It often shows the grade, such as “316L.” - Standard:
Look for codes like “B16.5” or “EN1092-1.”
Flange Size Reference Table (ASME B16.5 Class 150)
| Nominal Pipe Size (NPS) | Outside Diameter (OD) | Bolt Circle Diameter (BCD) | Number of Holes | Hole Diameter |
|---|---|---|---|---|
| 1/2 po | 3.50″ (89mm) | 2.38″ (60mm) | 4 | 0.62″ (16mm) |
| 1 pouce | 4.25″ (108mm) | 3.12″ (79mm) | ||
| 2 pouces | 6.00″ (152mm) | 4.75″ (121mm) | 0.75″ (19mm) | |
| 4 pouces | 9.00″ (229mm) | 7.50″ (190mm) | 8 | |
| 6 pouces | 11.00″ (279mm) | 9.50″ (241mm) | 0.88″ (22mm) |
International Conversion: NPS vs. DN
If your project involves equipment from different regions,you may encounter different sizing systems.The United States uses NPS (Nominal Pipe Size),while Europe uses DN (Diameter Nominal).
| NPS (Imperial) | DN (Metric) | Measurement Match? |
|---|---|---|
| 2 pouces | DN50 | Almost identical; check hole spacing |
| 4 pouces | DN100 | Common cross-over point |
| 8 pouces | DN200 | Major differences in bolt patterns begin |
Identifying the Flange Face Type
The shape of the flange face also impacts how you measure flange size.You must identify if the flange is a “Flat Face” (FF),”Raised Face” (RF),or “Ring Type Joint” (RTJ).
- Raised Face (RF):
These have a small elevated section around the bore.You should measure the diameter of this raised section separately. - Ring Type Joint (RTJ):
These contain a deep groove.You must measure the width and depth of the groove to select the correct metal ring gasket.
Troubleshooting Measurement Errors
If your measured Flange Size does not match any standard table,consider these possibilities.First,check if the flange is metric (DIN/EN) rather than imperial (ASME).European flanges use different hole spacings and diameters.Second,inspect the flange for a passive layer or coating that might add slight thickness.Finally,ensure the flange is not warped.A bent flange will give inconsistent diameter readings across different axes.
| Potential Error | Symptom | Solution |
|---|---|---|
| Metric vs Imperial | BCD is off by a few millimeters | Switch to an EN 1092-1 reference chart |
| Warped Face | OD varies at different points | Inspect the flange for mechanical damage |
| Debris Interference | ID measurement seems too small | Clean the bore of any scale or slag |
| Wrong Pressure Class | OD is correct but BCD is wrong | Check if it is a Class 300 or 600 flange |
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