Olet Fittings: Types, Uses and Applications of Weldolet, Sockolet, Threadolet, Latrolet and Sweepolet

If you have spent any time around a pipe rack or a fabrication shop, you have probably heard someone ask for a weldolet or a sockolet without ever really stopping to explain what the word means. Olet fittings are the small forged pieces that let a smaller branch pipe tap into a larger header pipe without the whole assembly turning into a welding project. They are called olet pipe fittings as a group, and the family includes weldolet, sockolet, threadolet, latrolet, sweepolet, nipolet, elbolet, flangolet, coupolet and a few less common cousins. Each one solves the same basic problem, connecting a smaller outlet to a bigger run pipe, but each does it a slightly different way depending on the pressure, the size, and how the branch pipe needs to end.

USA Piping Solution puts this guide together for engineers, buyers and QA staff who need a clear, accurate reference on olet fittings types rather than a sales pitch, and we are happy to help source or confirm specifications once you know which fitting you need.

Need olet fittings for an upcoming project? Request a quote from our team for material availability and lead time.

What Are Olet Fittings

Olet fittings are self reinforced forged branch connection fittings. They connect a smaller branch or outlet pipe to a larger header or run pipe without needing a separate reinforcing pad, which is the main reason engineers reach for them instead of a standard tee or a stub in connection. The pipe an olet fitting is welded onto is called the header or run pipe, and the pipe connected to the other side is called the branch or outlet pipe. In plain terms, olet fittings are fittings that provide an outlet from a larger pipe into a smaller one, or occasionally into a pipe of the same size.

It is worth knowing that Weldolet, Sockolet, Thredolet, Latrolet, Elbolet, Nipolet, Sweepolet, Brazolet and Coupolet are registered trademarks belonging to Bonney Forge, the company that popularized this style of fitting. Other manufacturers produce equivalent fittings that work the same way under different brand names, but engineers should still review any fitting against the applicable codes and standards rather than assume every branded name is identical.

Why Choose Olet Fittings Over a Standard Tee or Stub In Connection

Olet fittings earn their place on a pipe rack for a handful of practical reasons rather than tradition alone.

• Olet fittings handle higher pressure than a fabricated stub in or stub on joint
• Only two welds are needed for most olet fittings, compared with three for a standard tee
• Installation takes less time and inspection is simpler
• No separate reinforcing pad is required, since the fitting is self reinforced
• Less material is removed from the header pipe, which keeps the header stronger
• The design does not restrict the flow of fluid through the header
• Welding an olet fitting is generally easier than welding a standard tee

Olet Fittings Types Comparison Table

The table below lines up the header end, branch pipe end, size range and pressure class for the most common olet fittings types in one place, so you can compare them side by side before reading the detail on each one below.

Weldolet

Weldolet fittings are the most widely used olet fitting type, and for good reason. A weldolet makes a 90-degree branch connection and is well suited to high-pressure and high-temperature applications. Because both the header side and the branch pipe side use a bevel end, a weldolet is classed as a butt weld fitting. The self-reinforced design spreads out stress concentrations that would otherwise build up around a branch opening, and the fitting is available in full size or in a reducing configuration for a straight run of pipe. Weldolet fittings are commonly stocked from 2 inch through 24 inch, though the 2-inch to 8-inch range is the most economical and commonly ordered size band. Thickness follows the same schedule as the connected pipe.

Sockolet

A sockolet is built the same way as a weldolet on the header side, but the branch pipe end changes to a socket weld connection instead of a bevel. That socket accepts the branch pipe as a plain end, and the joint is completed with a fillet weld rather than a full penetration butt weld. Sockolet fittings are the standard socket weld olet used for smaller branch pipe and lower pressure lines, typically 1/2 inch through 4 inch, and are manufactured in 3000#, 6000#, and 9000# pressure classes. Because the header-side connection still requires a welded joint, a sockolet gives you an easy branch connection without giving up a solid tie-in to the run pipe.

Threadolet

A threadolet looks similar to a sockolet and weldolet at first glance, but the branch pipe end is female threaded rather than socket weld or bevel. Instruments and small branch pipes are simply screwed into the fitting, which makes a threadolet a convenient choice anywhere welding on the branch side is impractical, for example on instrument connections or small drain and vent lines. The thread preparation follows ASME B1.20.1, and threadolet fittings are typically available from 1/2 inch through 2 inch in 2000#, 3000# and 6000# pressure classes.

Latrolet

A latrolet fitting stands apart from every other olet fitting on this list because it is the only one that makes a 45-degree lateral branch connection rather than the usual 90-degree connection. That angled branch matters in services where a straight 90 degree tap would create a dead leg or disrupt flow, so a latrolet pipe fitting is often specified for drain lines, vent connections, and instrument taps that need to sit at an angle relative to the header. Latrolet fittings are available with threaded, socket weld and bevel end branch connections, generally 1/2 inch through 2 inch for the threaded and socket weld versions, with bevel end latrolet fittings available above 2 inch. Pressure classes follow the same 3000# and 6000# pattern as sockolet and threadolet fittings, and bevel end versions are rated the same as the connected pipe.

Sweepolet

A sweepolet is a contoured, integrally reinforced branch connection engineered around a low stress concentration factor, which gives it a longer fatigue life than a standard weldolet in the same service. Sweepolet fittings are typically specified once the header pipe rises above 24-inch NPS and the branch pipe rises above 8-inch NPS, though that threshold varies from one engineering standard to another. The contoured shape reduces pressure drop, supports free draining of fluid, and is friendlier to radiography inspection than a sharper-edged branch connection. Both ends are bevels, sized the same as the connected pipe schedule, and the fitting is most commonly seen in the 8 inch to 24 inch range.

Other Olet Fittings Types

A handful of additional Olet fittings round out the family, each suited to a narrower set of applications.

• Nipolet: joins a plain end header pipe to a small bore threaded or socket weld branch, commonly used for valve takeoffs, high point vents, and low point drains, 1/2 inch to 2 inch in 3000# and 6000#
• Elbolet: mounted on a 90-degree long-radius elbow, commonly used for instrument and thermowell connections, available with butt weld, socket weld, and threaded ends
• Flangolet: joins a large bore header directly to a flanged component, available 1/2 inch to 24 inch across the common flange pressure classes
• Coupolet: similar to a threaded half coupling, designed for fire protection sprinkler systems and other low-pressure piping, rated up to 300# in most cases
• Insert Weldolet: a contoured butt weld branch connection similar to a sweepolet but intended for less critical applications, 8 inch to 24 inch
• Brazolet: designed for brazed connections on copper or brass tubing, available with socket or threaded ends

How to Choose the Right Olet Fitting

Most specification decisions come down to three questions.

• Pressure rating: does the line call for a full schedule butt weld connection, or is a 3000#, 6000# or 9000# socket weld or threaded rating enough
• Connection angle: does the branch need to sit at 90 degrees to the header, or does the layout call for the 45 degree angle only a latrolet fitting provides
• End connection type: will the branch pipe be butt welded, socket welded, or threaded onto the fitting

Working through those three questions in order will point you to the right olet fitting type well before you ever need to compare specific dimensions.

Materials of Construction

Olet fittings are forged fittings, and the material grade is usually selected to match the header pipe material and the service temperature.

Installation Procedure

Installing an olet fitting follows a fairly consistent sequence regardless of which type is being used.

• Select the correct olet type for the required pressure, angle and end connection
• Prepare the header pipe surface, removing rust, scale and debris at the marked location
• Mark the branch location on the header pipe and confirm the hole size against the fitting
• Cut or bore the header pipe opening to match the fitting bore
• Position the olet fitting and complete the weld, following the applicable welding procedure specification
• Inspect the completed weld visually and by the required nondestructive method
• Pressure test the finished connection before the line is placed into service

Codes and Standards

Not sure which Olet fittings type fits your line? Contact us with your header size, branch size and pressure class and we will confirm the right fitting.

Request Olet Fittings from USA Piping Solution

USA Piping Solution can help you source or confirm olet fittings including weldolet, sockolet, threadolet, latrolet and sweepolet fittings across the material grades covered in this guide. Contact us with your header size, branch size and pressure class, or browse our full product range for related piping components.

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