Sockolet vs. Weldolet

What is a Sockolet?

In short—a sockolet is similar to a welded joint, but its branch pipe connects to the main pipe through the joint.

1. Features and Structure

Suitable for small-diameter branch pipes (generally ≤ 2")

Branch pipe ends are socket welded

Main pipe ends are butt welded or fillet welded

Commonly used in high-pressure, small-diameter, low-vibration systems

2. Common Manufacturing Standards

ASME B16.11

MSS-SP-97 (General Standard for Olet Fittings)

3. Common Materials

Carbon steel: A105 / A350 LF2

Stainless steel: 304 / 316

Alloy steel: F11 / F22

4. Advantages of Sockolet

Faster installation, suitable for small-diameter branch pipes

Less welding work, reducing leakage risk

Highly suitable for high-pressure systems (Class 3000 / 6000 / 9000)

What is a Welddolet?

Welddolets are the most common branch pipe fittings, belonging to butt welded connections, and are available in a full range of sizes.

1. Features and Structure

Both branch and main pipes are butt-welded.

Used for medium to large diameter branch pipe connections (2"–24" or above).

Weld strength is consistent with the base material, resulting in high load-bearing capacity.

2. Common Manufacturing Standards

ASME B16.9

MSS-SP-97

3. Commonly Used Materials

Carbon steel: A234 WPB

Stainless steel: 304 / 316

Low-temperature steel, alloy steel, etc.

4. Advantages of Weldolet

High strength, able to withstand high pressure and high temperature

More uniform stress distribution

Can replace tees, reducing costs

Sockolet vs. Weldolet

Item	Sockolet	Weldolet
Connection	Socket Weld	Butt Weld
Applicable Diameter	Class 3000 / 6000 / 9000	Medium to large diameter (2"–24"+)
Pressure Rating	Class 3000 / 6000 / 9000	SCH STD～XXS (depending on main pipe wall thickness)
Strength	Medium, higher than general socket joints	Very high, close to the strength of the base material
Welding Process Requirements	Lower, easy to install	Higher, requires skilled welders
Applicable Operating Conditions	High pressure, small diameter, low vibration	High pressure, high temperature, large diameter
Cost	Higher (precision machining)	Lower (widely used)
Maintenance	Fewer welds, lower risk	Longer welds, higher welding quality requirements

Sockolet vs. Weldolet: Installation Process

1. Sockolet Installation Steps

Insert the branch pipe into the socket;

Control the insertion gap (generally 1.6mm);

Perform fillet welds;

Weld the main body to the main pipe.

2. Weldolet Installation Steps

Drill a hole in the main pipe;

Align the Weldolet bevel with the main pipe;

Perform a full penetration butt weld;

Butt weld the branch pipe to the other end of the Weldolet.

Sockolet: Simpler installation, less welding required ⇒ Suitable for small-sized systems with high manifold pressure.

Weldolet: Requires skilled welders ⇒ More suitable for medium to large-sized, critical system piping.

Sockolet vs. Weldolet: Load Capacity

Welded fittings have the advantage of welded connections, and therefore can generally withstand greater loads than socket fittings. Socket fittings rely solely on the friction of the gasket under the sleeve for sealing, which is suitable for lighter loads. However, for larger, heavier pipes and higher pressures, welded fittings provide a stronger and more durable load-bearing connection.

How to Choose?

If you are a purchasing or engineering professional, you can quickly choose based on the following principles:

1. Choose Sockolet

Branch pipe diameter ≤ 2"; High system pressure but small pipe diameter; Faster installation desired; Limited welding space.

2. Choose Weldolet

Branch pipe diameter ≥ 2"; High temperature, high pressure, and highly corrosive systems; Requires a high strength rating for the base material; Oil, gas, boiler, and chemical applications.