Valve Connection Types Explained: What Works Best and Where

• July 04,
• 0 comments

In practical engineering projects, valve selection depends not only on its control function but also—more importantly—on whether its connection type is compatible with the pipeline system. Different connection methods can significantly affect ease of installation, sealing reliability, structural integrity, and future maintenance.

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The way a valve connects to the pipeline plays a critical role in system reliability, ease of installation, and long-term performance. Different connection types are designed to suit different operating conditions. This article provides a practical overview of the most common connection methods used in industrial valves, helping you choose the right one based on real application needs.

Flange connection

The valve has flanges at both ends, which are tightly connected with the paired flanges at the end of the pipeline through bolts, and gaskets are placed between the flanges to realize sealing.

Features:

• One of the most widely used and reliable connection methods.
• Suitable for various sizes (from small to very large), various pressure levels (from low pressure to ultra-high pressure), various temperature ranges and media.
• Easy to install, dismantle and repair (valves can be replaced online).

Flange Standards:

There are various standards, and they must match those of the pipeline system. Common standards include:

• ANSI/ASME: American standards (Class 150, 300, 600, 900, , )
• EN / DIN: European/German standards
• EN -1 (replaces most DIN standards)
• DIN , , , , (older standards)
• JIS: Japanese standards (5K, 10K, 16K, 20K, 30K)
• BS: British standards (PN series, similar to DIN)

Flange Face Types:

• RF (Raised Face): Most common type; a slightly raised, circular sealing surface on the flange face.
• FF (Flat Face): Entire flange face is flat, with no raised section.
• RTJ (Ring Type Joint): A groove is machined into the flange face to fit a metal ring gasket for high-pressure sealing.
• TG (Tongue and Groove): One side has a raised tongue, and the other has a matching groove.
• M&F (Male and Female Face): Similar to tongue and groove but generally deeper and wider.
• LJ (Lap Joint): The valve and pipe are not integrally formed; used with a lap joint flange for ease of alignment and rotation.

Advantages: high strength, reliable sealing, very wide range of applications, easy to install, disassemble and maintain, high degree of standardization.

Disadvantages: relatively high cost (flanges, bolts, gaskets), large volume and weight, requires a large installation space

Image Source：whatispiping

Threaded connection

Valve ends with internal or external threads are connected by screwing into the external threads on the pipe or the internal threads on the fittings.

Type.

• Male thread (Male): Threads on the outside of the connection, such as bolts, threaded pipe.
• Female thread (Female): Threads on the inside of the connection, such as nuts, threaded valve ports.

Common thread standards

• NPT: American tapered thread (sealing by thread deformation).
• BSPT: British tapered thread (sealing by thread deformation).
• BSPP: British straight thread (need to be sealed by a washer or O-ring)

Advantages: easy to install and disassemble, relatively low cost, suitable for small size (usually DN50 or less), medium and low pressure occasions.

Disadvantages: sealing reliability is relatively low (especially NPT / BSPT rely on thread deformation seal), not suitable for frequent disassembly, in the vibration or temperature change occasions easy to leak.

Image Source：redfluid

Welding connection

The end of the valve is processed into a bevel, directly connected with the pipeline by welding (butt welding or socket welding) fusion.

Type:

• Butt welding: the two pipes or components of the end face to face, through the fusion of the weld connection, welded to form a high strength, excellent sealing of the permanent connection.
• Socket Welding: Valve end is socket, pipe inserted into it, in the socket outside the corner of the fillet weld connection. Mainly used for small size (usually DN50 or less) high-pressure pipeline. Installation is faster than flanges and threads, and sealing is better than threads.

Advantages:

• High connection strength, good sealing performance
• Suitable for high temperature and pressure, corrosive environment
• Compact structure, space-saving

Disadvantages:

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• Installation is not removable, maintenance is more complicated
• High welding quality requires professional operation
• Stress and corrosion problems may occur at the welding seam

Wafer Connection

A wafer connection is a compact design in which the valve is installed between two pipeline flanges without having flanges of its own. It’s held in place by the tightening force of flange bolts, with gaskets providing the necessary seal between surfaces.

Advantages:

• Saves installation space
• Lightweight and cost-effective
• Quick to install
• Compatible with various flange standards

Disadvantages:

• Disassembly requires complete removal of the flange bolts, not as convenient as flange connection maintenance;
• Sealing depends on bolt tightening force
• Not suitable for heavy or large diameter valves, limited structural strength andsupport.

 Lug Connection

In a lug connection, the valve body features multiple threaded lugs (ears) around its perimeter. These allow the valve to be bolted independently to each of the adjacent flanges, providing a more secure and isolated connection.

Advantages:

• Allows one-sided pipeline disassembly without affecting the other side
• More robust than wafer-type: flange bolts are threaded directly into the valve body, distributing the load more evenly
• Suitable for dead-end service
• Flexible compatibility: lug hole patterns can be designed to match multiple standards such as ANSI or DIN

Disadvantages:

• Heavier and slightly more expensive than wafer-style valves
• Requires precise alignment between flange holes and lug holes during installation

Clamp (Tri-Clamp) Connection

Clamp connections use specially designed grooved or flanged valve ends, which are joined using a clamp—typically a two-piece assembly tightened by bolts. A gasket between the mating surfaces ensures sealing.

Advantages:

• Extremely fast to install and remove
• Easy to clean and inspect in-line; no dead zones (sanitary design)
• Allows for slight adjustments during installation

Disadvantages:

• Generally limited to low- and medium-pressure applications, especially in sanitary or hygienic systems.
• Requires matching pipe ends with flared lips or weld ferrules.
• The clamp itself can be a potential leakage point, though the gasket is seated in a defined groove.

Image Source：sanitaryfittings-cad

Conclusion

Each type of valve connection has its own advantages and limitations. Selecting the most appropriate connection method can not only improve system performance but also significantly reduce long-term maintenance costs. In real-world applications, a comprehensive assessment of factors such as operating conditions, available installation space, pressure class, and overall cost is essential to ensuring stable and efficient system operation over time.

Tianjin Union Valve is committed to providing a full range of high-performance valve products to customers worldwide, offering various connection types to meet the needs of both standard and demanding applications. With extensive engineering experience and strict quality control, Union Valve is your trusted partner. We offer not just products, but also professional technical support and customized solutions to help your project proceed smoothly and efficiently.If you have any other questions, please contact us.

Want more information on ANSI Standard Flange Check Valve? Feel free to contact us.

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There's a wafer check valve # 900 which is installed with four semi-attached stud bolts (Locations # 1,2,15,16).

The valve is installed on a high pressure gas piping system with design pressure 110 bar & operating temp. 54 C

Even though the outer diameter of the four holes (53.5mm) is larger than the diameter of the bolt (51mm), the inner diameter of the four holes (47 mm) is smaller than the diameter of the bolt (51mm).

Also it is believed that these holes are threaded through half of the hole groove.

I need to know if there's a standard for the design of such flanges ( half groove threaded holes ) and to confirm that there is NO overload on the other stud bolts.

 https://files.engineering.com/getfile.aspx?folder=87fc7e41-1c51-476f-85b0-c4f91b25ba32&file=100_.JPG
A,drawing would help but it looks like the top and bottom two studs are screwed into a tapped hole on the valve itself??

You need to look out measure how much those atuds are screwed into the valve. This needs to be at least the same depth as the nut on the other studs.

If this is the case then it's very odd but almost certainly still effective.

I'm not sure why those two studs are double bolted but it may be a way to screw the stud into the flange of the valve....

Remember - More details = better answers
Also: If you get a response it's polite to respond to it. Replying to Gator:
The manufacture is CONTROLFLUID SRL
It's an old modeled valve & i've tried contacting them to get the related data sheet with no reply.
Replying to LittleInch:
A drawing isn't available.
My concern that overload may exist on the rest of the bolts as these bolts are 1,2,15,16 ( sequence of torque tightening ) so the torque isn't well distributed
I think if these bolts were 1,2,3,4 then it might have been better in load distribution over the rest of bolts  https://files.engineering.com/getfile.aspx?folder=bf5fa783-56a4-479f-ac8c-127ca9f3&file=image001_(1).png
I can't see any issue here.

Is there an issue with this valve?

When you tighten no 1, 2, 15 and 16 just make sure you do both sides at the same time. Tightening uis a gradual process, so hand tight, then 25% of torque, then 50, then 85 then 100.

Or something like that.

You seem to be trying to find a legible which doesn't exist IMHO.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it. Looks like it was done to make installation and removal of valve easier since the lifting eye is centered between the threaded bolts, and may be easier for threaded bolts in this arrangement to be first to be installed during installation or last to be removed during removal of valve because valve can the be self supported from those 4 bolts even with all studbolts removed. it may even be the manufacturers standard design. Otherwise it was rigged in the field? But if they threaded 4 of same size holes of the studbolt holes in field then I believe then the diameters would then be larger not smaller, so it looks like it could be a manufacturer's design. I've seen similar design at an oil refinery. I meant the a couple of holes bigger than the rest. It was awhile back and could not find it in any specific standards. In the end, it was the manufacturer design to facilitate installation for a big flange. Worst, it used JIS Standard for main flange dimension, which took me awhile to figure that out. This valve was provided with tapped holes for the top and bottom two bolt positions on each side. There is a casting feature just visible at 12 o'clock (and presumably there is a similar one at 6 o'clock) that is preventing fitting a nut on the backface of the valve flanges in those positions, so tapped holes were required.

Curiously, wafer style bolting (one extra long set of studs) has been provided for the balance of the hardware for this double flanged style check valve instead of two sets of typical flange bolting.