How to Do a Tie-In

How to do a Tie-In The question: What methods and techniques are used to break into pipelines? I know that the easiest way would be to a blind flanged tie-in point or if a line is to be modified post a flange/valve then it is easiest to make a new spool between two flanges. My question relates to when you have to put a new tie-in into a pipeline and the above isn't viable, i.e. there is no option but to break into the line. I told one option on a gravity drain line for example would be to cut the line then put a bung into the pipe to stop drains backing up, make up the new spool then weld them back together. With piping I am aware it isn't always as simple as this as sometimes welding isn't an option either. I know you could also use an o'let for branching. My answer: To start, let's correct the terminology. The term you used "to break into (a) pipeline" is called a "Tie-In" by more than 95% of the piping profession. The balance of the people use "Tie-Point" or some other term. Regardless of which of these terms you use they mean the same. There are two basic conditions that exist when doing a "Tie-In." The first condition is when a Tie-In must be made and the line can be shutdown and made safe for welding or other work. This is called a "Cold" tie-in. The second condition is when a Tie-In must be made and the line cannot be shutdown. This is called a "Hot-Tap" tie-in. Some Hot-Tap tie-ins also require a procedure called "Stopple". This is where a second HotTap is made downstream of the first one. The flow is routed through the first tie-in while an articulated plug is inserted into the second Hot-Tap to blank off the flow. Various kinds of work can then be done to the remaining pipe. The "Cold" tie-in is simple to design and install. With only a few exceptions you can handle them the same as you would for any new piping. The exceptions include: · Make a proper survey of the condition of the existing pipe material. Is it too corroded to join the new pipe to? · The existing line can be shut down but can the environment around the existing pipe be made safe for any required welding? The "Hot-Tap" tie-in is more complicated. There are many, many questions and issues that need to be resolved. These include: · Will the tie-in be a plain tie-in or a more complex "Stopple" tie-in? · Will this be a single tie-in point or a multiple tie-in point? · Will the tie-in be made with a "split-Tee" branch or an "O-Let" branch? · Is there proper space available for the piping fittings and the valve? · Is there proper space for the Hot-Tap machine and the Hot-Tap operators?

· What is the commodity? Is this commodity safe for doing a Hot-Tap? · What is the operating pressure? Can the Hot-Tap machinery handle this pressure safely? · What is the operating temperature? Can the Hot-Tap machinery handle this temperature safely? · Can flow be maintained (required for cooling) during the cutting part of the Hot-Tap process? · What is downstream (direction of flow) of the Hot-Tap that might be damaged by the cuttings from the Hot-Tap process? · Has there been proper consultation with one or more "Hot-Tap" Specialty Contractors? Issues for all tie-ins: · Has Process Engineering reviewed and approved the location and type of tie-in? · Has Plant Operations reviewed and approved the location and type of tie-in? · Has the Installation Constructor reviewed and approved the location and type of tie-in? · Has the tie-in location been tagged for easy and proper identification? · Have the proper drawings been prepared and checked? · Has the proper material been ordered?