Plugs are used for the temporary blocking, closing of gravity pipelines, or for the leakage tests of newly constructed pipelines. Correct plug selection in testing and temporary blocking operations is extremely important for the success of the application.
Certain criteria should be considered for the correct plug selection. These are:
1. The Diameter of the Pipe Where the Plug Will Be Used
- If the plug to be selected will be used in more than one pipe diameter, a multi-size plug should be preferred.
- If the plug will be used in a single pipe diameter, a single-size plug should be selected.
https://www.youtube.com/watch?v=xuBP1BGwrH4
- Care should be taken to ensure that the internal diameter of the pipe where the plug will be used is within the usable diameter range of the plug.
Note: In cases where the plug will be used in critical applications, a higher model of the suitable plug should be preferred to stay on the safe side.
Example:
- Internal Pipe Diameter: 400-500–600 mm
- Working Pressure: 0.5 bar
- Suitable Plug Model: PP300600 (1.5 bar model)
If the application is critical and difficult, instead of the PP300600/1.5 bar plug, the PP300600/2.5 bar or PP375800/1.5 plug model should be used to stay on the safer side.
2. Back Pressure / Test Pressure
Back Pressure
Back Pressure: It refers to the maximum water head that the plug can withstand. In other words, it is the pressure generated by the water accumulating behind the plug.
Test Pressure: It is the pressure value applied during the leakage tests of newly constructed pipelines. This value is specified in the EN 1610 standard or defined in the project specifications.
For plug selection, back pressure and test pressure refer to the same information. This information is indicated on the plug’s label or specified in the data sheet of the purchased plug.
For more detailed information: https://www.plugco.net/pipe-plug-inflation-presure-and-back-pressure
3. Media Resistance
The type of fluid the plug will be exposed to is important in plug selection.
• When the plug is exposed to a non-chemical fluid, plugs produced from standard flow, SBR+NR rubber, and reinforced cord fabrics can be used.
• However, if the plug will be exposed to chemical fluids such as gas or oil, plugs manufactured from Nitrile (NBR) rubber with high chemical resistance must be preferred.
• To give another application example, if the pipeline is a potable (clean) water line, the plug should be manufactured with rubber that is not harmful to health.
• If the application involves high temperatures, the raw material of the plug should be selected from heat-resistant materials.
• Plugs can be manufactured to meet specific application requirements.
4. Requirements of the Application Where the Plug Will Be Used
Another critical piece of information in plug selection is the specific details of the application. Based on this information, the most suitable plug selection will be made.
Inflatable plugs are generally used for the following similar applications:
Repairing broken or faulty pipelines by temporarily blocking them: During the repair, actively flowing fluid is transferred from one location to another using a by-pass plug.
Use of by-pass plugs: In such applications, a by-pass plug must be used.
Water discharge: To ensure water is transferred more quickly and easily, or to prevent the pressure of the water accumulating behind the plug from exceeding the back-pressure limit, the water should be discharged with the help of a pump.
By-pass plug used for dewatering
In leakage tests of newly constructed pipelines: If there is an opening such as a manhole to add water on the line to be tested, a non-bypass inflatable plug can be used.
Both ends of the pipe are blocked with PP model plugs, and the test is performed by filling water through the manhole.
Related Video: https://www.youtube.com/watch?v=LSbb7va-bo4
Leak Testing for New Pipe Line with Water
In leakage tests without openings or manholes: If there is no opening or manhole on the line, 2 PTP model plugs or a combination of 1 PP model and 1 PTP model plug are used to fill the line with water or air.
Testing with PTP (By-pass) plugs: The leakage test is conducted by filling the test area with water or air through the bypass line of the PTP model plug.
Related Video: https://www.youtube.com/watch?v=we2e-5p8QUw
Leak Testing for New Pipe Line with Air
Model PP or PTP plugs are used in the repair of faulty pipelines and manholes, depending on the specific characteristics of the application.
If a manhole is to be repaired: The temporary blocking of the pipe is performed using a PTP model plug.
Dewatering process: The accumulated water is discharged with the help of a motor (pump) by using the bypass line available on the PTP model.
Manhole Repair bu Using the PTP
In some applications, the access point diameter (manhole diameter) may be smaller than the pipe diameter.
Example: The manhole diameter may be 500 mm and the pipe diameter 1200 mm. In this application, the deflated diameter of the plug to be used must be smaller than 500 mm. The deflated diameter of the PP6001200 product recommended for a 1200 mm pipe is 586 mm, which is larger than the entrance.
In such special applications, a conical plug with foldable features is recommended. Because conical plugs are foldable, they are used as a solution in applications where the manhole diameter is smaller than the deflated diameter of the plug. A conical plug is used when the condition D_manhole > D_pipe plug is met.
Frequently Asked Questions About Pipeline Tests and Plug Selection
1. What are the basic criteria to consider when selecting a plug?
The pipe diameter, the back pressure (or test pressure) it will withstand, the type of fluid it will be exposed to, and the specific requirements of the application.
2. What is the difference between a multi-size plug and a single-size plug?
Multi-size plugs can be used in multiple pipe diameters, whereas single-size plugs are designed for only one specific, fixed pipe diameter.
3. What does “Back Pressure” mean?
It is the maximum water head that the plug can withstand; in other words, it is the pressure generated by the water accumulating behind the plug.
4. What type of rubber plug should be used in lines exposed to chemical fluids or oil?
Plugs manufactured from Nitrile (NBR) rubber with high chemical resistance must be preferred.
5. What should be the characteristics of plugs used in potable water lines?
The rubber used must not contain harmful substances and must be suitable for drinking water.
6. In which cases is a by-pass (PTP model) plug necessary?
It is used to transfer the flow in the line to another location (bypass), discharge the water accumulating behind the plug, or to fill test water/air in lines without manholes.
7. What solution should be applied if the manhole entrance is narrower than the pipe diameter?
Conical plugs with foldable features should be preferred.
8. How should plug selection be made for critical and difficult applications?
To stay on the safe side, a higher model (higher pressure resistance or suitable diameter range) of the appropriate plug should be preferred.
9. According to which standards are pipeline leakage tests performed?
They are generally performed according to the values specified in the EN 1610 standard or defined in the project specifications.
10. For which fluids are standard SBR+NR rubber plugs suitable?
They are suitable for non-chemical, standard flow fluids (generally domestic wastewater or rainwater).