Tees and welding in chemical process pipelines

A three-way connection is better. The inside of the tee connector is relatively smooth, with no joints. Direct open welding results in uneven weld positions inside the tube, which can affect the liquid. Especially for certain special fluids, nodes or protrusions can cause many problems.

Opening directly on the main pipe is not allowed in cases where the design temperature exceeds 425 degrees, there are mechanical vibrations, pressure fluctuations, or sudden changes in temperature, the branch pipe experiences thermal deformation, the design pressure is 20 kilograms or more, or the design temperature exceeds 250 degrees. I think it’s better to use a tee!

Actually, welding is also an option, and it’s convenient too! To connect the components, a tee fitting is needed: L

Depending on the medium, if there isn’t excessive pressure or no special requirements, it’s simpler and saves material to just drill a hole and weld the pipe directly: lol

There is only one welding surface for direct opening connections, while tee connections have three such surfaces. For pipeline connections, the fewer sealing surfaces there are, the better; in normal situations that are not characterized by high temperatures or pressures, direct opening is more convenient

At the pressure pipeline connections that must be reported to the boiler inspection agency, tees are definitely used~! ~~~The rest can be decided depending on the circumstances~~~

The original poster is being too vague; they should specify the medium as well as the operating pressure and temperature, so that others can help come up with suggestions.

The medium is mainly chlorosilane; the pressure is below 10 kilograms and the temperature is below 150 degrees. Alternatively, the pressure is above 10 kilograms and the temperature is above 150 degrees

This condition is convenient for installation; of course, a tee is the best choice. If the conditions aren’t too strict, just go ahead and ask :) Also, are there any special requirements in the design guidelines for your project?

A tee is generally used; only when the branch pipe is too small and no tee size is available is it necessary to make a hole. :Victory: This is what is generally done in design work; after all, there are many human factors involved in welding, and it’s not reliable! !

Medium and high-pressure pipelines have strict requirements for piping welding; generally, tees must be used； Low-pressure pipelines can be constructed using hole-welding, a method that is widely used in practical projects. It allows for faster progress during piping work, reduces the number of welds required, and minimizes leaks.

It seems this issue has nothing to do with chemical blind plates. It is better to use a tee when high pressure, high temperature, or special media impose requirements on fluid flow. It should also be possible to speak directly when other requirements are not high. Especially when preparing on-site, it is more convenient to use a spigot.

Opening directly on the main pipe is not allowed in cases where the design temperature exceeds 425 degrees, there are mechanical vibrations, pressure fluctuations, or sudden changes in temperature, the branch pipe experiences thermal deformation, the design pressure is 20 kilograms or more, or the design temperature exceeds 250 degrees. I think it’s better to use a tee! Agree!

With the increase in static sealing points at the tee connection, the risk of medium leakage must be taken into consideration

Check the requirements; if they’re not high, welding will suffice, while for higher requirements, a tee should be used.

It can’t be answered simply; the question is too broad

The tee is much better, based on our workshop’s experience

Installation of blind flanges HG/T 20570.23—95 1 Classification and selection of blind flanges 1.0.1 Blind flanges are primarily used to completely isolate the process medium, thereby preventing disruptions in production that could result from improper closure of shut-off valves, or even accidents. In terms of appearance, they are generally divided into 8-character blind plates, plug plates, and gaskets (the plug plate and the gasket are mutually blind-connected). 1.0.2 Blind plates should be installed at the locations where separation (isolation) is required, such as at the equipment connection ports, in front of and behind isolation valves, or between two flanges. It is generally recommended to use 8-character blind flanges ； Plug plates (circular blind plates) can also be used for one-time-use components such as suppression and purging. 2 Installation of blind flanges 2.0.1 Locations where blind flanges need to be installed 2.0.1.1 During the initial preparation phase before starting up the system, when strength tests or leak tests are conducted on the pipelines, and it is not possible to carry out these tests simultaneously with those on the connected equipment (such as turbines, compressors, gasifiers, reactors, etc.), blind flanges must be installed at the connections between the equipment and the pipelines. 2.0.1.2 For various process material pipelines that connect outside the boundary zone to inside it, when the plant is shut down, if such pipelines are still in operation, a blind flange shall be installed at the isolation valve. 2.0.1.3 When the unit consists of multiple series, the main pipeline coming from outside the boundary area is divided into several branch pipelines that lead to each series, and blind plates are installed at the isolation valves of each branch pipeline. 2.0.1.4 When the device requires regular maintenance, inspection, or mutual switching, and the associated equipment needs to be completely isolated, a blind plate should be installed at the shut-off valve. 2.0.1.5 When the pressurization pipelines and purge pipelines (such as nitrogen pipelines and compressed air pipelines) of Process I are connected to equipment, a blind plate shall be installed at the shut-off valve. 2.0.1.6 Drain the low points of equipment and pipelines; if the process medium needs to be collected in a unified system, install blind flanges after the shut-off valves. 2.0.1.7 Blind plates or plug valves should be installed behind the valves on the exhaust pipes, drainage pipes, and sampling pipes of equipment and pipelines. Except for materials that are non-toxic, do not pose a health risk, and are not explosive. 2.0.1.8 When the facility is constructed in phases, blind plates are installed at the isolation valves for interconnected pipelines to facilitate subsequent construction work. 2.0.1.9 When the unit is operating normally, blind plates should generally also be installed on those auxiliary pipelines that need to be completely isolated. 2.0.1.10 Situations where blind plates are required for other process requirements. 2.0.2 Examples of blind plate settings 2.0.2.1 The graphical representation of blind plates on PI diagrams is in accordance with the industry standard \"Graphic Symbols for Piping and Fittings in Piping and Instrumentation Diagrams\" (HG20559.3—93). The 8-character blind flange pattern used in these regulations is shown in Figure 2.0.2–1. 2.0.2.4 When the device is produced in multiple series, the arrangement of blind plates is shown in Figure 2.0.2–2. 2.0.2.3 The installation of blind flanges on the punching pipeline and replacement pipeline is shown in Figure 2.0.2–3. 2.0.2.4 The installation of blind flanges for draining the lowest points of equipment pipelines is shown in Figure 2.0.2–4. 2.0.2.5 When the device is constructed in phases, the placement of blind flanges is shown in Figure 2.0.2–5. 3 Precautions for installing blind plates 3.0.1 Install as few blind plates as possible, provided that the process requirements are met. 3.0.2 The blind flanges specified in 3.0.2 must indicate whether they are to be opened normally or closed normally. 3.0.3 Whether the blind plate should be installed upstream or downstream of the isolation valve shall be determined based on the isolation efficiency, safety requirements, and process requirements.