Flange And Bolt Chart Selection Guide | Hebei Wotu Fastener Manufacturing Co., Ltd.
A flange and bolt chart is usually used to confirm bolt diameter, bolt count, bolt circle, hole size, and matching nut or washer requirements before ordering fasteners for a flanged joint.
The key decision is not only “which bolt fits the flange,” but which standard, pressure class, material, coating, and joint condition the assembly must satisfy. A small mismatch in bolt length, thread engagement, or hole pattern can delay installation even when the nominal flange size looks correct.
Brand: Wotu Surface: zinc plated Specifications: in stockM6/M8/M10/M12/M14/M16/M20 Chinese national standardfull range of specifications, support nonstandard thickness, tooth pitch customized Matching: can be matched with bolts of the same specification, flat washer, spring washer complete set of shipment Packaging: 25kg cartons, whole wooden pallets
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Brand: Wotu Surface: color zinc plated, blue-white zinc plated, black oxide, hot-dip galvanized, various surface treatments available Specifications: Comply with DIN934, GB/T6170, GB/T6172.1, GB/T6177.1 standards, in stock M6-M64 full range of specifications, support nonstandard customized Packaging: woven bag inside/25kg export carton, full-container wooden pallet wrapped with film, supports private-label, neutral export packaging
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Brand: Wotu Surface: overall hot-dip zinc plating treatment Specifications: Comply with DIN and GB standards, in stock M6-M48 full range of specifications, length 20mm-300mm, supports nonstandard customized. Packaging: woven bag inside / 25kg export carton, film-wrapped wooden pallet; supports neutral packaging and customer private-label customization.
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Brand: Wotu Surface: Natural black oxide treatment, customized hot-dip galvanized, zinc plated as required Specifications: Follow Chinese national standard GB/T799-1988, in stock M12-M48, total length 120mm~1500mm, nonstandard customized diameter, bending length, total screw length available Matching: Nuts, flat washers and spring washers of the same specification can be supplied in complete sets. Packaging: Bundling and packaging, using wooden pallets and film-wrapped export packaging in large quantities
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Brand: Wotu Surface: quenching and tempering heat treatment + high temperature black oxide anti-rust treatment Specifications: Comply with DIN934, GB/T6170 standards, in stock M6-M48 full range of specifications, nonstandard sizes can be customized Packaging: 25kg carton/woven bag inner packaging, whole wooden pallet wrapped with film for export packaging, supports neutral/private-label customization packaging
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Brand: Wotu Surface: natural black oxide / hot-dip galvanized / blue-white zinc plated, multiple processes available Specifications: Based on common industry drawing parameters, suitable for pipe diameter 25mm~139.7mm, screw diameter M10~M24, total length can be nonstandard customized Matching: can be matched with nut, flat washer and spring washer of the same specifications for complete shipment Packaging: Bundling and packaging + 25kg export carton, full-container wooden pallet wrapped with film, supports private-label export packaging
Read MoreFlange bolting criteria
For flange bolting, selection should compare bolt diameter, length, thread form, material grade, coating, compatible nuts, washers, and packaging by joint or project quantity. If dimensions come from a chart, verify them against the flange drawing before turning them into a purchase order.
| Criterion | What To Check | Why It Matters | Buyer Tip |
|---|---|---|---|
| Flange standard and pressure class | Match the chart to the flange standard shown on the drawing, such as ASME, EN, JIS, or another project standard, and confirm the pressure class or PN rating. | Bolt circle diameter, hole count, hole size, and bolt diameter can change between standards even when the nominal pipe size looks similar. | Ask: Which flange standard, size, and pressure class should the bolt chart follow for this joint? |
| Bolt diameter, length, and thread form | Verify the specified bolt diameter, thread pitch, and effective length against the flange thickness, gasket type, washer use, and nut engagement requirement. | A bolt that is too short may not give full nut engagement; a bolt that is too long can interfere with nearby parts or waste space in compact piping assemblies. | Ask: Is the required length measured for stud bolts with two nuts, machine bolts, or another fastening arrangement? |
| Number of bolts and bolt circle layout | Compare the chart’s bolt quantity, bolt hole diameter, and bolt circle diameter with the flange drawing before ordering. | Small layout differences can prevent the bolts from passing through both flanges, especially where replacement parts are mixed from different standards. | Ask: Can you confirm the bolt hole count and bolt circle diameter from the actual flange drawing or specification? |
| Material grade and coating compatibility | Select the bolt and nut material grade, coating, or surface finish according to the operating environment and the mating flange requirements. | Strength, corrosion resistance, galling risk, and tightening behavior depend on the chosen material and finish, not only on the bolt size in the chart. | Ask: What service environment, temperature exposure, and corrosion requirement should the flange bolts meet? |
| Gasket and tightening method | Confirm the gasket type, washer use, lubrication condition, and tightening sequence required by the project or equipment specification. | A flange and bolt chart gives dimensions, but sealing performance also depends on gasket compression and controlled tightening practice. | Ask: Does the assembly require a specified torque method, bolt lubrication condition, or tightening sequence? |
The most important distinction is between a flange dimension chart and a fastener order specification. A flange chart can show the number of holes and the nominal bolt size for a flange standard, but it does not always define the bolt grade, finish, nut style, washer type, or final bolt length required for the actual joint.
Bolt length depends on flange thickness, gasket thickness, washer use, nut height, and required thread projection. Two flanges with the same nominal pipe size may need different fastener sets if the pressure class, sealing arrangement, or coating requirement changes.
Start with the flange standard and pressure class, not only the pipe size. ASME, DIN, EN, JIS, and other flange systems can use different hole patterns and bolt dimensions for similar nominal sizes. If the standard is unclear, confirm the bolt circle diameter, number of holes, hole diameter, and flange thickness from the drawing.
Check the joint stack before deciding bolt length. Include both flanges, gasket, washers, nut height, and the amount of thread that should extend beyond the nut. Ordering from a chart alone can result in bolts that are technically the right diameter but too short for safe assembly or too long for nearby clearance.
Match the fastener material and coating to the service environment. Indoor dry assemblies, outdoor pipe racks, hot-dip galvanized structures, and corrosive environments can call for different finishes or materials. Coating thickness can also affect nut fit, so confirm whether matching nuts need oversize tapping or another compatible treatment.
A practical next step is to send the flange standard, nominal size, pressure class, bolt quantity per joint, required bolt diameter and length if known, material grade, coating, and nut or washer requirements. If the flange chart is being used to build a bill of materials, include the drawing or joint section so the fastener set can be checked against the real assembly.
| Criteria | Importance | Description | Example Options |
|---|---|---|---|
| Flange standard and pressure class | Critical because similar nominal pipe sizes can have different hole patterns and fastener dimensions. | Identify the governing flange system and class before reading bolt size, bolt count, bolt circle, or hole diameter from a chart. | A drawing based on one flange standard should not be matched to a bolt row taken from another standard solely because the nominal size is the same. |
| Bolt diameter and hole pattern | Critical for physical fit and correct load distribution around the joint. | Check bolt count, bolt circle, hole diameter, and clearance rather than relying on nominal pipe size alone. | The correct set must place every bolt through the corresponding flange holes without forcing the pattern or contacting the hole edges. |
| Bolt length and thread engagement | Critical for assembly security and avoiding installation delays. | Calculate the full joint stack, including both flanges, gasket, washers, nut height, and the intended thread projection. | A bolt that matches the charted diameter can still be unsuitable if a thicker gasket or added washer leaves too little thread in the nut. |
| Material and coating compatibility | Important where moisture, corrosion, temperature, or contact between dissimilar materials affects the joint. | Select the bolt, nut, and washer materials and finishes as a compatible set; coating thickness may affect thread fit. | An outdoor coated assembly may require a different fastener finish and matching nut treatment than an indoor dry assembly. |
| Nut, washer, and packaging requirements | Important for complete installation and accurate project quantities. | Specify compatible nuts and washers and state whether fasteners should be counted or packed by joint, flange, or project batch. | A purchase order may call for one complete set per joint rather than a loose quantity of bolts without nuts and washers. |
Related Options
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No. A chart may identify the hole pattern, bolt count, and nominal bolt size, but it may not define the required bolt grade, coating, nut, washer, or length. Confirm the chart against the flange drawing and the complete joint stack.
Different flange standards and pressure classes can use different bolt circles, hole sizes, bolt counts, and flange thicknesses. Gasket type, coating, and service conditions can also change the required length or material.
Add the thickness of both flanges, the gasket, washers, and the nut, then allow the required thread projection beyond the nut. Check the result against nearby clearance and the fastener's available threaded length rather than selecting length from nominal pipe size alone.
No. A larger diameter may not pass through the flange holes or may interfere with the bolt circle, gasket, tools, or adjacent equipment. It can also change the intended joint design, so any substitution should be checked against the flange drawing and applicable engineering requirements.
Provide the flange standard, nominal size, pressure class or drawing, bolt quantity, bolt diameter and length if known, material grade, coating, and the required nuts and washers. Include the gasket or joint-stack details when bolt length is uncertain.
Please share the flange standard and size, pressure class or drawing, bolt diameter and length if known, plus the required material grade, coating, nuts, and washers.
