Here are some guidelines for developing Tie-In procedures (both Cold-Tie-Ins and Hot-Tap Tie-Ins)
How to do a Tie-In
To start, let’s define the terminology. Making a “New” piping connection to older existing Piping or Equipment is called a “Tie-In”. This term is used by (I’m sure) more than 95% of the piping profession. The balance of the piping related world may use “Tie-Point” or some other term. Regardless of which of these terms you use they mean the same. For the purpose of this article and any subsequent training we will use the term “Tie-In”.
There are three basic conditions that exist when doing a “Tie-In.”
1. The first condition is when a Tie-In is to be made and the line can be shutdown and made safe for welding or other work. This is called a “Cold” tie-in.
2. The second condition is when a Tie-In must be made but the line cannot be shutdown. This is called a “Hot-Tap” tie-in.
3. Some Hot-Tap tie-ins also require a procedure called “Stopple”. This is where a second Hot-Tap 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.
Cold Tie-In
What is a “Cold” Tie-In? A “Cold Tie-In” is just the shutting off of a piping system, draining and making it safe so it can be opened up and the new line attached. This attachment is normally by a flanged connection.
Will the presents of Piping Tie-Ins require any special procedures or special “Fabrication and Installation Specifications”? There are a number of questions that come up regarding this and can only be answered by a detailed review of the specific situation.
The following are issues that need to be resolved. Example:
• Who are you in the overall picture of this Tie-in? Are you the Client? The primary engineering company planning the Tie-in? Or are you the Mechanical Contractor who will be overseeing the actual Tie-in?
• What is covered in the normal Piping Fabrication and Installation Procedure?
• Are you sure you will be doing “cold” tie-ins?
• What is the line size, Flange rating and wall schedule of the tie-In?
• What is the commodity normally in the line?
• How far to the closest valves up stream and downstream of the Tie-in Point?
• Can the upstream and downstream piping be shut-off, drained and steamed out?
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 simple 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 and is this commodity safe for doing a Hot-Tap?
• What is the operating pressure and can the Hot-Tap machinery handle this pressure safely?
• What is the operating temperature and 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 Construction and the Installation Contractor 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?
Tie-In Planning
1. Identify each Tie-In schematic location on P&ID - Process Engineer
2. Review with Piping - Process & Piping Design
3. Create a Tie-In Index (or List) with key information about each Tie-In - Piping Design & Process Engineer
4. Review with Client - Process Engineer
5. Go to the Field to locate physical point of Tie-In - Piping Design/Process
6. Meet with plant personnel and review Tie-In requirements - Piping Design, Process, Plant Operations, Safety
7. Discuss different types and configurations of Tie-Ins - Piping Design, Process and Plant personnel
8. Establish physical Tie-In location point and type - Piping Design & Plant Personnel
9. Define if the line can be shut –down, when, how long, draining, depressurize, steam-out and other safety issues - All personnel
10. Visually inspect the existing pipe. Are more extensive tests needed to determine condition and suitability for the Tie-In? - Piping Design and Plant personnel
11. Mark or tag the selected Tie-In point - Piping Design & Plant Personnel
12. Photograph the Tie-In point - Piping Design
13. Draw sketch and take all required measurements - Piping Design
14. Determine locations of all existing upstream and downstream block valves, vents and drains - Piping Design
15. Determine the location of all existing upstream and downstream anchors and guides - Piping Design
16. Based on selected Tie-In location and type determine if additional vents or drains will now be required - Piping Design, Plant Operations
17. Include new vents or drains (if any) on sketch (these become new Tie-Ins) - Piping Design
18. Get plant personnel to sign off on all data collected in the field - Piping Design & Process Engineering
19. In the office modify the P&ID as required - Process Engineer
20. Convert all field sketches into appropriate production drawings (Isometrics) - Piping Design
21. Prepare a Plot Plan style “Tie-In Location Key Plan”
22. Update the Tie-In List as required - Piping Design
23. Review all Tie-Ins with Pipe Stress for effect on existing system piping and new system piping - Piping Design
24. Finalize (check, correct and approve) all Tie-In isometric drawings - Piping Design
25. Insure that this process is followed for all Tie-Ins - All participants
Tie-In List
A "Tie-In" List will normally have a Title Block area, a “Technical Data" area and an area to identify Revisions.
The Title Block Data area should have the following:
- Document Title (Example- "Piping Tie-In List")
- Document Number
- Sheet No. (At the top of each page)
- Project Name
- Project Number
- Unit Number
- Unit Name
- Unit Lead Name
- Piping Lead Name
A Technical Data area should have the following [indicates responsibility]:
- Tie-In No. [Piping]
Existing line (or equipment) being tied into:
- Existing Line No. [Piping]
- Existing Piping Plan [Piping]
- Existing P&ID [Piping]
- North Coordinates [Piping]
- East (or West) Coordinate [Piping]
- Center line Elevation [Piping]
- Existing Line Size [Piping]
- Pipe Wall Schedule [Piping]
- Material [Piping]
New line:
- P&ID No. [Piping]
- Line No. [Piping]
- Line Size [Piping]
- Tie-In Connection Type [Piping]
- Commodity [ [Piping or Process]
- Operating Pressure (1) [Piping or Process]
- Operating Temperature (1) [Piping or Process]
- Hydrotest Pressure [Piping]
Construction:
- Pre-weld Inspection [Construction]
- Post-Weld Inspection complete & tested [Construction]
Schedule Data:
- Required Completion Date [Project/Client]
- Schedule Shut-down [Project/Client]
- Actual Completion [Construction]
Other:
- Remarks [any group]
Revision Box
- Revision Number
- Revision Description
- Prepared By (Name) [Piping]
- Checked By (Name) [Piping]
- Company Approval (Name) [Project]
- Client Approval (Name) [Client]
Notes:
(1) This should be the same as the existing line so you do not need it twice
