What is Golden Joint in Piping?
A Golden Joint in Piping refers to the final weld joint when joining an existing pipe line spool to a new piping spool by Welding and its not possible to perform the hydro test of this pipe spool. For example, a joint under the column, joining the column drain to further piping system as shown in below diagram is not possible to perform the hydro test after welding due to huge size of the column, so these joints will be Golden Joints.
To ensure to joint integrity, extensive 100% weld inspection is performed by using NDT such as radiographic testing, PT or MPI and Visual Testing in place of Hydro Test or Pneumatic test. This brings extra cost to this specific joints, so the Joint is named as Golden Joint.
Golden joint is required if the location of the pipeline line is not possible to be hydrotested, so the client chooses several golden joints in several places that are estimated to be critical, and the welding of the golden joint must be witnessed by the QC for root, fill with penetrant testing and after full weld by performing radiography.
What is a Closure Weld Joint in Piping?
Closure weld or also called final weld according to ASME B31.1 or B31.3 is used for joining a new pipe or existing pipeline spools to a new pipe or piping components such as socket. One example of closure joint for example: a pipe construction started from two sides and then there is a final joint which is joining these two pipe spools. This is very common when laying cross- country pipelines. Other examples quite often observed in running plants where an existing piping system is connected to a new system.
What is a Tie-in Joint in Piping?
Tie-in joint means joining a new pipeline or branch connection to an existing line by fabrication (cutting & welding). Tie-in joints are very common in refineries and power plant where extensive piping is used and it required Tie-in joints to accommodate modifications to the lines. For example, in the below piping diagram, red line represents existing piping system, and a blue line is connected using Tie-in joint.
Tie-in joints are used during plant expansion activities to connect existing line to new lines and the point where this new joint will come, is known as Tie-in Joint. This Tie-in connection could be by inserting a new spool or installing a valve. Piping Tie-in are very common in plants for compressed air lines, fluid lines, steam or fuel gas process piping where using a Tie-in joint can increase the process efficiency or flow. There are four types of Tie-in joints as given below:
- Existing line Tie-in
- Line Isolation type
- Shut down type
- Hot tapping type
Difference between tie-in and golden joint
The main difference between a Tie-in joint and golden joint is the level of testing. A golden joint is where hydrostatic test is not possible as stated above while for Tie-in joint, hydro test can be performed thus no need to carry out extensive weld testing using NDT. So Tie-in joint is cheaper than a Golden joint. Both Tie-in and golden joint are used to join an existing piping system to a new piping system but in Tie-in joint there can be a connection via valve or some other components while in Golden joint it will be between the pipes only.