Threaded Flanges Guide: Flanged vs Threaded Pipe Connections for Industrial Piping

Threaded flanges are used when a pipe connection needs a flange face and bolt pattern, but welding is not practical, allowed or economical. Instead of welding the flange to the pipe, the bore of the flange has internal threads. The pipe is screwed into the flange, and the flange is then bolted to the matching flange, valve, pump or equipment nozzle.

For buyers and engineers, the key question is often not just “what is a threaded flange?” but flanged vs threaded: which connection style is better for the pressure, maintenance plan, material and site conditions? This guide explains how threaded flanges work, where threaded flanged connections make sense, and how to compare flanged vs threaded pipe options before ordering.

Selection point	Threaded flange	Welded or standard flanged connection	Practical buying note
Установка	Screws onto an externally threaded pipe	Usually welded, then bolted to the mating flange	Threaded flanges reduce hot work and are useful for field modification.
Best pressure range	Common in low to moderate pressure service	Better for high pressure, high temperature and severe cyclic loading	Always confirm class rating, pipe schedule and service temperature.
Техническое обслуживание	Can be removed without cutting the pipe if threads are still in good condition	More permanent after welding	Good for inspection points, small bore piping and temporary systems.
Leak risk	Depends strongly on thread quality and sealant	Depends on weld quality, gasket and bolt load	Thread inspection is as important as flange inspection.
Typical sizes	Often used for small bore lines	Available across a wider size range	For larger sizes, welded flange types are usually preferred.

What Are Threaded Flanges?

A threaded flange is a pipe flange with an internal pipe thread inside the bore. The matching pipe end has an external thread. During installation, the flange is tightened onto the pipe, then bolted to another flange or equipment connection. This creates a detachable bolted joint without requiring a flange-to-pipe weld.

In industrial purchasing, the same idea may appear under several phrases: threaded flange, screwed flange, threaded pipe flange, threaded flanged connection or threaded flange fitting. The important detail is the same: the flange connection uses threads at the pipe side and bolts at the flange face.

Why Use Threaded Flanges?

The main advantage is simple installation. Threaded flanges can reduce welding work, shorten maintenance time and avoid hot work permits in certain field conditions. They are especially useful when the project involves small bore pipe, non-critical low-pressure service or equipment that may need to be removed for inspection.

Common benefits include:

• No flange-to-pipe welding: installation can be faster when pipe threading is already part of the specification.
• Convenient disassembly: maintenance teams can remove the flange if the thread is not damaged or seized.
• Lower field work risk: avoiding welding can help in areas where heat, sparks or access limitations are a concern.
• Good for small bore piping: threaded flanges are common in instrument lines, utility lines and auxiliary systems.

Flanged vs Threaded: What Is the Difference?

The phrase flanged vs threaded can be confusing because a threaded flange is still a flange. In most engineering discussions, it means comparing two pipe-end connection methods: a bolted flanged joint and a threaded pipe joint. A threaded flange actually combines both: the pipe side is threaded, while the external connection is flanged and bolted.

When comparing threaded vs flanged, ask where the joint must open. If the connection needs a gasketed bolted joint for valves, pumps or equipment, a flange is required. If the pipe itself only needs a simple connection and does not need a flange face, a threaded coupling or threaded fitting may be enough.

Flanged vs Threaded Pipe: When to Choose Each

Flanged vs threaded pipe selection should be based on pressure, temperature, vibration, corrosion, maintenance frequency and installation environment. Threaded pipe connections are compact and inexpensive for small systems, but they can be sensitive to thread wear, sealant quality and repeated assembly. Flanged pipe connections are easier to inspect visually at the gasket face and are preferred for many industrial pipe runs that require reliable disassembly.

Choose threaded flanges when the pipe is small, the service is not severe, welding should be avoided, and the system still needs a bolted flange interface. Choose welded flanges such as weld neck, slip on or socket weld flanges when the line has higher pressure, higher temperature, vibration, hazardous media or stricter inspection requirements.

Where Threaded Flanged Connections Are Used

Threaded flanged connections are often found in water systems, compressed air, instrument piping, fire protection lines, low-pressure utility lines, test systems, temporary pipework and maintenance-heavy installations. They can also appear around pumps, small vessels, filters and valves where compact assembly is important.

For stainless steel service, material selection matters. 304 stainless steel threaded flanges can suit general corrosion environments, while 316 or 316L stainless steel is often selected for chemical, marine or chloride exposure. Carbon steel threaded flanges may be suitable for general industrial service when coating, medium and temperature are compatible.

Limitations of Threaded Flanges

Threaded flanges are useful, but they are not the correct answer for every system. Thread roots can create stress concentration. Threads can also loosen under vibration if the assembly is not designed and tightened correctly. For high temperature service, thermal cycling can affect thread sealing and joint stability.

Before using threaded flanges, confirm:

• Pipe thread standard and tolerance
• Pressure class and temperature rating
• Pipe schedule and wall thickness after threading
• Material grade and corrosion allowance
• Thread sealant or sealing method
• Whether welding is prohibited, optional or required by the project specification
• Inspection requirements for the finished connection

Threaded Flanges vs Socket Weld Flanges

Socket weld flanges are another common small bore option. Unlike threaded flanges, a socket weld flange requires fillet welding around the pipe. This generally creates a stronger and more permanent connection than a threaded joint, but it requires welding work and inspection. If hot work is acceptable and higher joint strength is needed, socket weld may be preferred. If quick assembly and no welding are the priority, threaded flanges may be better.

How to Order Threaded Flanges

A clear inquiry helps avoid wrong threading, wrong rating or wrong material. When requesting a quotation, include nominal pipe size, pressure class, standard, material grade, thread type, face type, coating or finish, quantity and any certificate requirements.

For example, a complete description might be: ASME B16.5 Class 150 threaded flange, 1 inch NPT, raised face, ASTM A105, black coating, with EN 10204 3.1 certificate. For stainless steel, specify 304, 304L, 316 or 316L and confirm whether the thread needs special protection during packing.

FAQ About Threaded Flanges

Are threaded flanges the same as threaded pipe fittings?

No. Threaded pipe fittings connect pipe to pipe or pipe to equipment through threads. Threaded flanges have a threaded pipe side but also provide a bolted flange face.

Are threaded flanges suitable for high pressure?

They can have pressure classes like other flanges, but severe high-pressure, high-temperature or high-vibration service often favors welded flange types. Always check the project standard and service conditions.

What is the main difference in threaded vs flanged connections?

A threaded connection relies on pipe threads for assembly. A flanged connection relies on bolts, gasket compression and flange faces. A threaded flange uses both principles in one product.

Can Songhai supply stainless steel threaded flanges?

Yes. Songhai Flange can support stainless steel and carbon steel threaded flanges according to common industrial standards, with material, class, size and face type confirmed before production.

Final Thoughts

Threaded flanges are a practical solution when a piping system needs a detachable flange connection without welding the flange to the pipe. The best use cases are small bore, low to moderate pressure, maintenance-friendly systems where fast installation matters. For more demanding service, compare flanged vs threaded options carefully and confirm the standard, material, pressure class and thread details before placing an order.