Proper Flange Bolt Torquing Guide
Correct bolt torque is critical for achieving leak-free flange joints. Under-torquing causes gasket blowout, while over-torquing can damage gaskets or warp flange faces.
螺栓扭矩为何重要
- Ensures uniform gasket compression
- Prevents flange leakage under operating conditions
- Compensates for gasket creep and relaxation
- Maintains joint integrity during thermal cycling
Class 150 Bolt Torque Values (ft-lbs)
| Size | Bolt Size | Quantity | Non-Lubricated | Lubricated |
|---|---|---|---|---|
| 1/2″ | 1/2″-13 | 4 | 45 | 35 |
| 1″ | 5/8″-11 | 4 | 85 | 65 |
| 2″ | 3/4″-10 | 4 | 150 | 115 |
| 4″ | 5/8″-11 | 8 | 85 | 65 |
| 6″ | 3/4″-10 | 8 | 150 | 115 |
| 12″ | 7/8″-9 | 12 | 250 | 190 |
Class 300 Bolt Torque Values (ft-lbs)
| Size | Bolt Size | Quantity | Non-Lubricated | Lubricated |
|---|---|---|---|---|
| 1/2″ | 1/2″-13 | 4 | 65 | 50 |
| 2″ | 3/4″-10 | 8 | 185 | 140 |
| 4″ | 3/4″-10 | 8 | 185 | 140 |
| 6″ | 7/8″-9 | 8 | 290 | 220 |
| 12″ | 1″-8 | 12 | 425 | 320 |
Class 600-2500 Torque Guidelines
Higher pressure classes require significantly higher torque values. Always refer to manufacturer specifications for Class 900, 1500, and 2500 flanges.
Bolt Torquing Procedure
- Clean: Remove dirt, rust, and old gasket material from flange faces
- Inspect: Check flange faces for damage or warping
- Lubricate: Apply anti-seize compound to bolt threads and nut faces
- Insert: Place gasket centered on flange face
- Hand-tighten: Snug all nuts finger-tight
- Pattern: Use star/cross pattern for even compression
- Sequence: Torque to 30%, then 60%, then 100% of final value
- Verify: Recheck all bolts after initial torque
Important Considerations
- Gasket Type: Different gaskets require different compression loads
- Bolt Material: ASTM A193 B7 vs B16 have different strength ratings
- Lubrication: Reduces required torque by 20-25%
- Temperature: Hot torquing may be required for high-temperature service
- Re-torquing: Consider re-torquing after thermal cycles
应避免的常见错误
- Using impact wrenches without calibration
- Torquing in circular pattern instead of star pattern
- Skipping the multi-step torque sequence
- Reusing damaged or stretched bolts
- Ignoring gasket manufacturer torque recommendations
Proper bolt torquing is essential for leak-free flange joints. Always follow established procedures and use calibrated torque tools.
您可能还喜欢
Orifice Flanges What They Are How They Work and When to Use Them
Orifice Flanges Guide Orifice flanges are specialized flanges designed for flow measurement in piping systems. They work in conjunction with an orifice plate to create a pressure differential that can be measured and converted to flow rate. What Are Orifice Flanges Orifice flanges consist of a matched pair of flanges with an orifice plate sandwiched […]
PED vs ASME vs API vs ISO Which PVF Standard Is Strictest
Comparing Global Flange Standards When working on international projects, engineers encounter multiple flange standards. Understanding the differences helps ensure compliance and optimal selection. PED Pressure Equipment Directive European Union Standard Scope: All pressure equipment sold in EU Classification: Categories I-IV based on pressure and volume Requirements: CE marking, notified body certification Materials: Must use EN […]
How to Read Flange Size Chart ASME Dimension Tables Guide
Flange Size Chart Reading Guide Understanding flange dimension tables is essential for proper flange selection, procurement, and installation. This guide explains how to read and interpret ASME flange size charts. Key Dimensions in Flange Charts 1. Nominal Pipe Size (NPS) The designated pipe size the flange connects to. Note that NPS does not equal actual […]