You rely on flange bolts to achieve secure flange connections in piping systems. These bolts provide secure fastening that keeps joints tight under pressure. Flange bolts help create leak-proof seals and support high temperatures. Raised face designs also prevent gasket blowouts. In industries like oil, gas, chemicals, and power generation, a strong bolt ensures operational integrity and safety. The table below shows how flange bolts improve reliability in industrial applications:
| Feature | Description |
|---|---|
| Secure Seals | Flange bolts provide leak-proof seals that withstand high pressures and temperatures. |
| Design and Material | Raised face configurations enhance sealing performance and prevent gasket blowouts. |
| Application | Critical in oil and gas, chemicals, and power generation sectors for operational integrity. |
Key Takeaways
- Flange bolts create secure, leak-proof seals in piping systems, essential for high-pressure and high-temperature applications.
- Choosing the right material and grade for flange bolts is crucial. Options like stainless steel resist corrosion, while alloy steel offers strength in extreme conditions.
- Follow a specific torque sequence when tightening flange bolts. This method ensures even pressure on the gasket, preventing leaks and maintaining safety.
- Use the ASME B16.5 chart to select the correct flange bolt size and number for your piping system. This step ensures compatibility and reliability.
- Regularly inspect and maintain flange bolts to prevent failures. Proper installation and tightening practices are key to long-term performance.
What are Flange Bolts?
Flange Bolt Definition
You use flange bolts to connect two flanges securely in piping systems and machinery. A flange bolt has a cylindrical body with a threaded end and a non-tapered shank. The head of the bolt often features a circular flange at its base. This design helps spread the load over a larger area, which reduces the risk of damage to the connected parts.
Tip: Choosing the right material for your flange bolt matters. Alloy steel gives you high strength, stainless steel resists corrosion, and high-strength alloys work well in extreme conditions.
Here is a quick overview of how engineering standards define flange bolts:
| Definition | Description |
|---|---|
| Flange Bolt | A fastener used to connect two flanges, featuring a cylindrical body with a threaded end and a non-tapered shank. |
| Material Specifications | Alloy Steel for high strength, Stainless Steel for corrosion resistance, High-Strength Alloys for extreme conditions. |
| Applications | Used in automotive, construction, and general engineering. |
Function and Benefits
Flange bolts play a key role in creating secure, leak-free joints. When you tighten flange bolts, they clamp the gasket between the flange faces. This action compresses the gasket and forms a tight seal that prevents leaks, even under high pressure or temperature.
- Flange bolts help you manage dynamic loads and keep the joint strong, even when conditions change.
- The bolting pattern ensures the load spreads evenly, which increases the safety factor of the connection.
- You find flange bolts in high-stakes environments, such as nuclear power plants and chemical factories, where leak-proof joints are critical.
- These bolts also help reduce fatigue loading, which can cause joint failure over time.
Note: Flange bolts must meet strict strength grades. For example, Grade 8.8 bolts have a tensile strength of at least 800 MPa, while Grade 10.9 bolts reach 1040 MPa. For high-temperature use, alloy steel bolts like ASTM A193 Gr.B7 perform well up to 450℃.
By understanding the definition and function of flange bolts, you can make better choices for your piping and mechanical connections.
Types of Flange Bolts
When you select flange bolts for your piping system, you need to understand the different types available. Each type offers unique properties that suit specific environments and requirements. Let’s break down the main categories.
Material Types
You can choose flange bolts made from several materials. Each material affects the bolt’s strength and resistance to corrosion. The table below shows the most common options:
| Material Type | Corrosion Resistance Properties |
|---|---|
| Carbon Steel | Suitable for low and medium pressure, good mechanical properties, relatively low prices. |
| Stainless Steel | Excellent corrosion resistance, suitable for corrosive environments like chemical and food industries. |
| Alloy Steel | Good strength and corrosion resistance, suitable for high pressure and high temperature environments. |
- Zinc and cadmium coatings act as sacrificial barriers. These coatings protect the base metal from corrosion. You often see these coatings in marine environments or places with moisture and oxygen.
Grade Classification
The grade of a flange bolt determines its mechanical strength and where you should use it. You find grade 8 flange bolts in heavy machinery and industrial settings because they offer high strength and load-bearing capacity. Grade 5 flange bolts work well in automotive parts and general machinery. The chart below compares the tensile strength of common grades:
| Bolt Grade | Tensile Strength (psi) | Applications | Characteristics |
|---|---|---|---|
| Grade 2 | ~74,000 | Non-critical applications like furniture | Inexpensive, lower strength |
| Grade 5 | ~120,000 | Automotive parts, machinery | Moderate strength, durable |
| Grade 8 | ~150,000 | Heavy machinery, industrial applications | High strength, load-bearing |
| Grade 304 | ~70,000 | Construction, food processing | General corrosion resistance |
| Grade 316 | ~80,000 | Marine applications, chemical processing | Superior corrosion resistance |
| ASTM A193 B7 | ~125,000 | High-temperature applications | High heat and corrosion resistance |
Head Types
You encounter two main head types for flange bolts. The hex flange head bolt features a hexagonal head with an integrated flange. This design spreads the load and prevents damage to the flange. The serrated flange bolt has serrations under the flange. These serrations help prevent loosening in high-vibration environments.
| Head Type | Description |
|---|---|
| Hex Flange Head Bolt | Hexagonal head with integrated flange for better load distribution. |
| Serrated Flange Bolt | Serrations under the flange to prevent loosening. |
Bolting Patterns
The bolting pattern you choose affects how the load spreads across the flange. A well-designed pattern ensures the gasket receives enough compressive stress to prevent leaks. If the stress is too low, the joint may fail under pressure. You must keep the stresses within the limits of the materials to maintain a secure connection.
Tip: Always match the bolting pattern to the flange type and application. This step helps you achieve reliable sealing and long-term performance.
You now have a clear understanding of the types of flange bolts. Use this knowledge to select the right flange bolt for your next project.
Flange Bolt Applications
Piping Systems
You often see flange bolts used in piping systems to connect flanges and create secure joints. These bolts help you maintain leak-proof seals, especially in high-pressure and high-temperature applications. You can choose different flange types based on your needs. Welding neck flanges work well for high-pressure pipelines. Slip-on flanges make installation easy for low-pressure systems. Blind flanges seal the end of a pipe, which is important when you need to isolate sections for maintenance. Threaded flanges allow you to connect pipes without welding, making them ideal for low-pressure setups.
| Flange Type | Application Description |
|---|---|
| Welding Neck Flanges | Designed for high-pressure applications, providing a strong connection in pipelines. |
| Slip-On Flanges | Easy to install, used in low-pressure applications by slipping over the pipe. |
| Blind Flanges | Seals the end of a pipe, critical for isolating sections for maintenance. |
| Threaded Flanges | Ideal for low-pressure applications, featuring threads for easy connection without welding. |
You rely on flange bolts to keep your piping systems safe and efficient. These bolts help you meet industry standards and prevent leaks.
Automotive Uses
You use flange bolts in many automotive applications. These bolts hold engine assemblies together and resist corrosion from heat and fluids. Transmission systems need flange bolts that stay tight under dynamic conditions. Exhaust systems require bolts that allow movement but keep parts secure. Suspension systems depend on flange bolts for safety and stability.
| Application Area | Performance Requirements |
|---|---|
| Engine Assemblies | Must withstand high stress and resist corrosion. |
| Transmission Systems | Needs to maintain tightness under dynamic conditions. |
| Exhaust Systems | Should allow for movement while holding parts together. |
| Suspension Systems | Must provide safety and stability under various conditions. |
You choose flange bolts for automotive uses because they offer reliability and meet strict performance requirements.
Machinery and Structures
You find flange bolts in heavy-duty machinery and large structures. These bolts provide strength and stability for bridges and industrial equipment. You use flange bolts to distribute loads evenly across joints, which prevents stress points and reduces the risk of failure. The flange design gives you a wider surface area, making force distribution more efficient.
- Flange bolts are essential in heavy-duty construction, such as bridges and industrial machinery, ensuring overall stability.
- They provide superior strength and are designed to withstand high stress levels, making them ideal for securing large, load-bearing components.
- Flange bolts distribute loads evenly across joints, preventing stress points that could lead to failure.
- The flange design offers a wider surface area for efficient force distribution, crucial in large structures like bridges.
- Proper torque application is vital to avoid uneven load distribution and stress concentrations.
- Correct torque ensures a balance between bolt tension and structural load, essential for high precision and durability.
You depend on flange bolts to keep machinery and structures safe, especially when you face high stress and heavy loads. You also use these bolts in high-temperature applications where durability matters.
Flange Bolt Selection
Choosing the right flange bolts ensures your piping connections have the necessary strength and sealing capabilities. You need to consider several factors to make the best choice for your application.
Load and Pressure
You must match the bolt to the load and pressure demands of your system. High-pressure piping requires bolts and flanges that can handle greater forces. Thicker flanges and the correct number of bolt holes help you achieve the necessary strength and sealing capabilities. The table below shows what you should check:
| Factor | Description |
|---|---|
| Types | Choose the right flange design, such as socket weld or flat flange, for your application. |
| Size | Follow standards like JIS, ANSI, or ASME B16.5 for dimensions and pressure levels. |
| Thickness | Use thicker flanges for higher pressure to prevent leaks. |
| Bolt holes | Check the size, pitch circle diameter, and number of holes for proper fit and pressure class. |
| Pressure class | Make sure the flange matches the maximum pressure in your system. |
| Materials | Select materials that suit your environment, such as stainless steel for corrosion resistance. |
Tip: Always verify the pressure class and bolt pattern before installation. This step helps you avoid leaks and failures.
Material and Grade
You need to select the right material and grade for your flange bolt. The material affects how long the bolt lasts and how well it resists corrosion. For example:
- Carbon steel bolts give you good strength at a low cost, but they need coatings in aggressive environments.
- Stainless steel bolts work well in chemical or marine settings because they resist corrosion.
- 304 stainless steel is a general-purpose choice, while 316 stainless steel offers better resistance to chlorides and high temperatures.
| Material Type | Advantages | Limitations / Considerations |
|---|---|---|
| Carbon Steel | Good strength, low cost | Poor corrosion resistance, needs coatings |
| Stainless Steel | Excellent corrosion resistance, good for harsh settings | Higher cost, needs careful fabrication |
| Cast Iron | Low cost, good stiffness | Weak corrosion resistance, limited pressure ratings |
You should always pick a grade that meets the necessary strength and sealing capabilities for your system.
Pattern and Standards
The bolt pattern and standard you follow ensure your flange bolts fit and perform as expected. You should use industry standards like ASME B16.5 for most piping flanges and ASME B16.47 for larger sizes. These standards cover pressure-temperature ratings, materials, dimensions, and testing requirements.
| Standard | Key Components |
|---|---|
| ASME B16.5 | Pressure-temperature ratings, materials, dimensions, marking, and testing for flanges and bolts. |
| ASME B16.47 | Covers larger flanges (NPS 26 to NPS 60), thickness, weight, and fastening requirements. |
Note: Following the correct standard helps you achieve safe, leak-free connections and ensures compatibility with other components.
By considering load, pressure, material, grade, and the right standard, you can select flange bolts that keep your system safe and reliable.
ASME B16.5 Flange Bolts Chart and Dimensions
Understanding flange bolt dimensions is essential for safe and reliable piping connections. You use the ASME B16.5 flange bolt chart to select the correct bolt size, number, and length for each flange class. This chart helps you match your flange and bolt to the pressure and size requirements of your system. When you follow these standards, you ensure compatibility and safety in your piping projects.
Below is a commonly used Flange Bolt Chart in the ANSI/ASME B16.5 standard. You can download our Flange Bolt Chart File here.
Dimension Chart Overview
A typical flange bolt chart includes several important details. You will find the nominal pipe size, the number of bolts, the bolt diameter, and the recommended bolt length. Some charts also show the metric equivalents and the required wrench size. You use these charts to check that your flange bolt dimensions meet ASME B16.5 and ASME B16.47 standards.
| Size in Inch | Size in mm | No of Bolts | Bolt Size UNC | RF Stud Length | ISO Stud Size | Machine Bolt Length |
|---|---|---|---|---|---|---|
| 1/2 | 15 | 4 | 1/2 | 55 | M14 | 50 |
| 3/4 | 20 | 4 | 1/2 | 65 | M14 | 50 |
| 1 | 25 | 4 | 1/2 | 65 | M14 | 55 |
| 1 1/4 | 32 | 4 | 1/2 | 70 | M14 | 55 |
| 1 1/2 | 40 | 4 | 1/2 | 70 | M14 | 65 |
| 2 | 50 | 4 | 5/8 | 85 | M16 | 70 |
| 2 1/2 | 65 | 4 | 5/8 | 90 | M16 | 75 |
| 3 | 80 | 4 | 5/8 | 90 | M16 | 75 |
| 3 1/2 | 90 | 8 | 5/8 | 90 | M16 | 75 |
| 4 | 100 | 8 | 5/8 | 90 | M16 | 75 |
| 5 | 125 | 8 | 3/4 | 95 | M20 | 85 |
| 6 | 150 | 8 | 3/4 | 100 | M20 | 85 |
| 8 | 200 | 8 | 3/4 | 110 | M20 | 90 |
| 10 | 250 | 12 | 7/8 | 115 | M24 | 100 |
| 12 | 300 | 12 | 7/8 | 120 | M24 | 100 |
| 14 | 350 | 12 | 1 | 135 | M27 | 115 |
| 16 | 400 | 16 | 1 | 135 | M27 | 115 |
| 18 | 450 | 16 | 1 1/8 | 145 | M30 | 125 |
| 20 | 500 | 20 | 1 1/8 | 160 | M30 | 140 |
| 24 | 600 | 20 | 1 1/4 | 170 | M33 | 150 |
You can see how the number of bolts increases with the flange size. The bolt diameter and length also grow as the pressure and pipe size increase.
Class 150
You use the class 150 flange for low-pressure applications. The flange bolt chart for this class shows the standard bolt sizes, lengths, and quantities for each nominal pipe size. This information helps you select the right bolt for your flange.
| Nominal Pipe Size, NPS | Diameter of Bolts, in. | Length of Bolts, L |
|---|---|---|
| 1/2 | 1/2 | 55 |
| 3/4 | 1/2 | 65 |
| 1 | 1/2 | 65 |
| 1 1/4 | 1/2 | 70 |
| 1 1/2 | 1/2 | 70 |
| 2 | 5/8 | 85 |
| 2 1/2 | 5/8 | 90 |
| 3 | 5/8 | 90 |
| 4 | 5/8 | 90 |
| 5 | 3/4 | 95 |
| 6 | 3/4 | 100 |
| 8 | 3/4 | 110 |
| 10 | 7/8 | 115 |
| 12 | 7/8 | 120 |
| 14 | 1 | 135 |
| 16 | 1 | 135 |
| 18 | 1 1/8 | 145 |
| 20 | 1 1/8 | 160 |
| 24 | 1 1/4 | 170 |
You can also check the number of studs and their lengths for each pipe size:
| Nominal Pipe Size | Number of Studs | Diameter of Studs (inches) | Length of Stud – RF (inches) |
|---|---|---|---|
| 1/2 | 4 | 0.5 | 2.25 |
| 3/4 | 4 | 0.5 | 2.5 |
| 1 | 4 | 0.5 | 2.5 |
| 1-1/4 | 4 | 0.5 | 2.75 |
| 1-1/2 | 4 | 0.5 | 2.75 |
| 2 | 4 | 0.625 | 3.25 |
| 2-1/2 | 4 | 0.625 | 3.5 |
| 3 | 4 | 0.625 | 3.5 |
| 4 | 8 | 0.625 | 3.5 |
| 5 | 8 | 0.75 | 3.75 |
| 6 | 8 | 0.75 | 4 |
| 8 | 8 | 0.75 | 4.25 |
| 10 | 12 | 0.875 | 4.5 |
| 12 | 12 | 0.875 | 4.75 |
| 14 | 12 | 1 | 5.25 |
| 16 | 16 | 1 | 5.25 |
| 18 | 16 | 1.125 | 5.75 |
| 20 | 20 | 1.125 | 6.25 |
| 24 | 20 | 1.25 | 6.75 |
You see that as the pipe size increases, both the number and size of bolts increase. This ensures the flange can handle higher loads.
Class 300
The class 300 flange is designed for higher pressure than class 150 flange. You will notice thicker walls, larger outside diameters, and bigger bolt circles. The flange bolt chart for class 300 flange shows that you need more and larger bolts compared to class 150.
| Feature | Class 150 Flange | Class 300 Flange |
|---|---|---|
| Maximum Pressure Rating | Up to 285 psi | Up to 740 psi |
| Wall Thickness | Thinner | Thicker |
| Outside Diameter | Smaller (9 inches for 4-inch flange) | Larger (10.75 inches for 4-inch flange) |
| Bolt Circle Diameter | Smaller | Larger |
| Bolt Hole Size | Smaller | Larger |
You must always check the flange bolt chart for class 300 flange before selecting your bolts. This step ensures your connection meets the higher pressure requirements.
Class 400
You use class 400 flanges in even higher pressure systems. The flange bolt chart for this class provides detailed dimensions for each nominal pipe size. You see larger bolt circles and thicker flanges.
| NPS | O (mm) | O (inch) | T (mm) | T (inch) | X (mm) | X (inch) | Ah (mm) | Ah (inch) | ro (mm) | ro (inch) | Q (mm) | Q (inch) |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 1/2 | 95 | 3.75 | 14.3 | 0.56 | 38 | 1.50 | 21.3 | 0.84 | 3 | 0.12 | 23.6 | 0.93 |
| 3/4 | 115 | 4.62 | 15.9 | 0.62 | 48 | 1.88 | 26.7 | 1.05 | 3 | 0.12 | 29.0 | 1.14 |
| 1 | 125 | 4.88 | 17.5 | 0.69 | 54 | 2.12 | 33.4 | 1.32 | 3 | 0.12 | 35.8 | 1.41 |
| 1-1/4 | 135 | 5.25 | 20.7 | 0.81 | 64 | 2.50 | 42.2 | 1.66 | 5 | 0.19 | 44.4 | 1.75 |
| 1-1/2 | 155 | 6.12 | 22.3 | 0.88 | 70 | 2.75 | 48.3 | 1.90 | 6 | 0.25 | 50.6 | 1.99 |
| 2 | 165 | 6.50 | 25.4 | 1.00 | 84 | 3.31 | 60.3 | 2.38 | 8 | 0.31 | 63.5 | 2.50 |
| 2-1/2 | 190 | 7.50 | 28.6 | 1.12 | 100 | 3.94 | 73.0 | 2.88 | 8 | 0.31 | 76.2 | 3.00 |
| 3 | 210 | 8.25 | 31.8 | 1.25 | 117 | 4.62 | 88.9 | 3.50 | 10 | 0.38 | 92.2 | 3.63 |
| 3-1/2 | 230 | 9.00 | 35.0 | 1.38 | 133 | 5.25 | 101.6 | 4.00 | 10 | 0.38 | 104.9 | 4.13 |
| 4 | 255 | 10.00 | 35.0 | 5.75 | 146 | 5.75 | 114.3 | 4.50 | 11 | 0.44 | 117.6 | 4.63 |
| 5 | 280 | 11.00 | 38.1 | 7.00 | 178 | 7.00 | 141.3 | 5.56 | 11 | 0.44 | 144.4 | 5.69 |
Class 600
Class 600 flanges are used in systems with even higher pressure. You will see more bolts, larger diameters, and longer lengths in the flange bolt chart for this class. The increased bolt size and number help the flange withstand greater forces. Always check the flange bolt chart for class 600 before installation.
Class 900
When you work with class 900 flanges, you deal with very high pressures. The flange bolt chart for this class shows a significant increase in both the number and size of bolts. You must use the correct bolt dimensions to ensure the flange can handle the pressure safely.
Class 1500
Class 1500 flanges require even more robust bolting. The flange bolt chart for this class lists the largest bolt diameters and the longest lengths so far. You need to follow the chart closely to prevent leaks and failures in these high-pressure systems.
Class 2500
Class 2500 flanges are used in the highest pressure applications. The flange bolt chart for this class specifies very large bolts and precise bolt hole dimensions. For these flanges, the bolt hole diameter is always 1/8 inch larger than the bolt diameter. This detail ensures a proper fit and safe operation under extreme pressure.
Tip: Always use the correct flange bolt chart for your flange class. This step ensures your flange bolt dimensions match the requirements of ASME B16.5 and ASME B16.47. You protect your system from leaks and failures by following these standards.
You now have a clear overview of how to use the flange bolt chart for each class. Always check the chart before selecting your bolts. This practice keeps your piping connections safe and reliable.
What is the Flange Bolt Torque Sequence?
You need to follow a specific flange bolt torque sequence to create a reliable seal between flanges. This sequence helps you apply even pressure to the gasket and prevents leaks. If you tighten bolts in a random order, you risk uneven compression and possible gasket failure.
The recommended flange bolt torque sequence uses a star or criss-cross pattern. You should tighten bolts in several passes, increasing the torque each time. Here is the step-by-step process:
- Tighten all bolts to about 30% of the final torque value. Use a star or criss-cross pattern so you spread the load evenly.
- Increase the torque to 60% of the final value. Repeat the same pattern for each bolt.
- Tighten all bolts to 100% of the final torque value. Continue using the star or criss-cross pattern.
- For a final check, go around the flange in a circular sequence (clockwise) and confirm each bolt reaches the correct torque.
- In high-pressure or high-temperature systems, you may need to re-torque the bolts after the system runs for a while. This step usually happens 4 to 24 hours after initial tightening.
Tip: Always use a calibrated torque wrench for each pass. This tool helps you achieve the correct tension and protects the gasket from damage.
You can see that the flange bolt torque sequence is not just about tightening bolts. You follow a pattern and use multiple passes to make sure the gasket compresses evenly. This method keeps your flange connection strong and leak-free.
Why is the Flange Bolt Torque Sequence needed?
You might wonder why you cannot just tighten flange bolts in any order. The answer is simple: the flange bolt torque sequence helps you create a safe and leak-free connection. When you follow the correct sequence, you apply even pressure to the gasket. This even pressure keeps the seal strong and prevents leaks.
If you skip the proper flange bolt torque sequence, you risk many problems. Uneven tightening can crush the gasket in one spot and leave gaps in another. This can cause leaks, which are dangerous in industrial piping systems. You also increase the chance of damaging the flange or the bolts themselves.
Here are some key reasons you need to use the correct sequence:
- You prevent leaks by making sure the gasket gets even pressure.
- You avoid damaging the flange or bolts from too much force in one area.
- You keep your piping system safe and reliable.
If you do not follow the right torque sequence, you may face serious consequences. The table below shows what can happen:
| Consequence | Description |
|---|---|
| Safety Hazards | Leaks of flammable, toxic, or high-pressure fluids can lead to fires, explosions, and injuries. |
| Environmental Damage | Release of pollutants can lead to regulatory fines and reputational damage. |
| Production Losses | Unplanned shutdowns for repair can result in significant loss of production and revenue. |
| Increased Maintenance Costs | Frequent repairs and labor costs can escalate due to improper torque application. |
| Equipment Damage | Leaking fluids can damage surrounding equipment or infrastructure. |
Tip: Always use a calibrated torque wrench and follow the recommended pattern. This step helps you avoid costly mistakes and keeps your system running smoothly.
You see that using the correct flange bolt torque sequence is not just a best practice. It is a critical step for safety, reliability, and long-term performance in any flange connection.
Common Flange Bolt Torque Sequence
You need to follow a reliable flange bolt torque sequence to achieve a tight, leak-free seal. The most common method you will use is the crisscross, or star, pattern. This approach helps you apply even pressure across the gasket and prevents the flange from warping. You see this method used widely in the oil and gas industry because it gives you the best results for both safety and performance.
When you tighten a flange bolt, you should not apply full torque in one step. Instead, you use a staged process. This method lets you gradually compress the gasket and avoid uneven stress. Here is a simple way to follow the crisscross pattern:
- Start by tightening each bolt to about 30% of your target torque. Use the star pattern, moving across the flange rather than around it.
- Next, increase the torque to 60% of the final value. Repeat the same crisscross order.
- Finally, tighten each bolt to 100% of the required torque, again following the star pattern.
- After you finish the main tightening, make a final pass around the flange in a circular order. This step checks that every bolt is at the correct torque.
Tip: Always use a calibrated torque wrench for each stage. This tool helps you avoid over-tightening and protects the gasket.
You can use this flange bolt torque sequence for most standard flanges. The process works well for both small and large connections. By following these steps, you help ensure that your flange stays secure and leak-free under pressure.
Flange Bolt Tightening
ASME B16.5 Recommendations
You need to follow the ASME B16.5 guidelines when tightening flange bolts in piping systems. These recommendations help you achieve proper sealing and prevent leaks. The standard provides minimum and preferred torque values for each nominal pipe size. You should always check the torque table before starting the tightening process.
| Nominal Pipe Size (in) | Minimum Torque (ft. lbs.) | Preferred Torque (ft. lbs.) |
|---|---|---|
| 0.50 | 9 | 14 |
| 0.75 | 12 | 17 |
| 1.00 | 14 | 21 |
| 1.25 | 16 | 24 |
| 1.50 | 19 | 28 |
| 2.00 | 33 | 49 |
| 2.50 | 45 | 67 |
| 3.00 | 49 | 73 |
| 3.50 | 30 | 45 |
| 4.00 | 33 | 49 |
| 5.00 | 41 | 61 |
| 6.00 | 46 | 69 |
| 8.00 | 66 | 99 |
| 10.0 | 64 | 96 |
| 12.0 | 93 | 140 |
| 14.0 | 134 | 201 |
| 16.0 | 120 | 181 |
| 18.0 | 132 | 198 |
| 20.0 | 124 | 187 |
| 24.0 | 173 | 260 |
Tip: Always use a calibrated torque wrench and follow the torque values in the table for each flange bolt.
Torque Sequence
You must use the standard tightening sequence to ensure even sealing. Start by tightening each bolt to about 30% of the final torque using a crisscross pattern. Increase to 60% and repeat the pattern. Finish by tightening to 100% of the recommended torque. Make a final pass around the flange in a circular order to confirm each bolt is at the correct torque.
- Begin with a star pattern for the first pass.
- Increase torque in stages.
- Complete with a circular check.
The correct tightening sequence helps you distribute clamping force evenly. This even distribution protects the gasket and maintains sealing. If you skip steps or tighten bolts randomly, you risk uneven stress and misalignment, which can cause leaks.
Safety and Leak Prevention
You protect yourself and your system by following best practices during flange bolt tightening. Most leaks in flange connections happen because of improper installation or maintenance. Faulty tightening can lead to hazardous leaks and injuries. Up to 85% of gasket failures result from user errors during installation.
Note: Always train personnel in proper tightening procedures and check torque tables before starting. Understand the assembly process and use the correct tightening sequence for every flange bolt.
- Regularly inspect tools and equipment.
- Choose the right gasket and ensure proper alignment.
- Avoid rushing the sealing process.
If you use the correct tightening sequence and follow ASME B16.5 recommendations, you improve sealing and reduce the risk of leaks or injuries in piping systems.
You ensure secure piping connections when you select the right flange bolts, use accurate dimension charts, and follow proper tightening steps. Adhering to ASME B16.5 and B16.47 standards improves the reliability of every flange connection by setting clear requirements for design and installation. Standardized tightening procedures and correct bolt choices help prevent leaks and mechanical failures, keeping your system safe and durable for the long term.
FAQ
What is the difference between a flange bolt and a regular bolt?
A flange bolt has a built-in washer-like flange under the head. This flange spreads the load and helps prevent damage to the connected parts. Regular bolts do not have this feature.
How do you know which flange bolt size to use?
You should check the ASME B16.5 chart for your flange class and pipe size. The chart tells you the correct bolt diameter, length, and number of bolts needed for a safe connection.
Can you reuse flange bolts after disassembly?
You should not reuse flange bolts in critical piping systems. Used bolts may have stretched or weakened. Always use new bolts to ensure a secure and leak-free joint.
Why do flange bolts need to be tightened in a specific sequence?
You need to tighten flange bolts in a crisscross pattern. This method spreads pressure evenly on the gasket. Even pressure helps prevent leaks and keeps the connection strong.
What tools do you need to tighten flange bolts correctly?
You need a calibrated torque wrench for accurate tightening. For large bolts, you may also use hydraulic torque wrenches. Always check the torque value in the ASME standard before tightening.
Related resource references:
https://www.extreme-bolt.com/flange-bolting-chart-asme-b16-5.html
https://eriks.co.uk/en/know-how-hub/blogs/sealing-polymer/talking-torqueing
