Weldolet, Sockolet, Threadolet

Weldolet, Sockolet and Threadolet are olet pipe fittings that can supply an outlet from a larger pipe to a smaller one (or one of the same size).

(Sockolet as above picture, one one end welded to run pipe, another end welded to branch pipe.)

There are 13 types pipe olets fittings, and sockolet, weldolet and threadolet are mostly common used. Their names depend on how they are connected to the branch. Weldolet has a butt welded connection, threadolet has threaded connection, and sockolet has welded connection.

What is Weldolet

Weldolet is the most common among all pipe olet. It is ideal for high pressure weight application, and is welded onto the outlet of the run pipe. The end are bevelled to facilitate this process, and therefore the weldolet is consider a butt weld fitting.


Weldolet is a branch butt weld connection fitting that is adhered to outlet pipe to minimizes stress concentrations. And it provides overall reinforcement.Normally it has the same or a higher schedule than the run pipe schedule, and offers a variety of forged material grades, such as ASTM A105, A350, A182 etc.

Weldolet Dimensions and Weight

Weldolet dimensions ranges from 1/4 inch to 36 inch for run pipe diameter, and 1/4'' to 2'' for branch diameter. Although big brand diameter could be customized.

What is Sockolet

Sockolet is used for 90 degree self-reinforcing branch accessory, and is suitable for small instrument connection or small branch pipe. It has the same basic design as “weldolet” or “threadolet”, but its branch connection is socket weld type.


The sockolet has full size or reduced size. Full size means to take a branch of same size as the pipe, for example, 3 inch to 3 inch. Reducing size is when the branch size is less than the running pipe size, for example, 3 inche to 1inch.


The sockolet is classified as socket weld fitting, and are available in class 3000,6000 and 9000 pressure temperature rating.

Sockolet Dimensions and Weights

Same as weldolet dimensions up to 48 inch for run pipe, and 2 inch for branch pipe.

What is Threadolet

A threadolet is similar to sockolet. However the main difference is the fitting has a female threaded connection, and the branched pipe is screwed on the fitting. This makes the 90 degree branch a full size or reduced straight pipe.

Threadolet end is generally NPT type (National Pipe Thread) in accordance with American standard. Typically, it is welded to holes drilled or burned in the pipe. Threadolet considered to a threaded fitting, and it is manufactured in 3000 and 6000 classes.

Differences between Weldolet, Sockolet, Threadolet

The mainly differences are the connection surface, weldolet ends in plain or beveled to weld on the the branch pipe, sockolet ends in socket type that to insert branch pipe. Threadolet is insert branch pipe and with screw connection. So they have different advantages:

Weldolet: Compatible with higher pressure and simple connection, cost lower. Thickness in SCH STD, SCH XS, SCH 160 to SCH XXS.
Sockolet: Compatible with higher pressure but cost is higher. Pressure ratings in 3000#, 6000#.
Threadolet: Easy to replace and maintain, cost is higher. Pressure ratings in 3000#, 6000#.

Octal Supply Weldolet, Sockolet, and Threadolet

For Weldolet
Standard: ASTM A234, MSS SP-75, ASTM A403
Run Pipe OD: 1/2”, 1”, 2”, 3”, 4”, 6”, 8”, 10”, 12”, 16”, 20” to 48”.
Branch Pipe OD: 1/2'', 3/4'', 1'', 1 1/2'', 2''
Thickness: SCH STD, SCH XS, SCH 160, SCH XXS.

For Sockolet (and Threadolet)
Standard: ASTM A105, ASTM A182, ASTM A403
Main Pipe OD: up to 48”
Branch Pipe OD: 1/2'', 3/4'', 1'', 1 1/2'', 2''
Pressure Ratings: 3000#, 6000#

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