Pipe plugs are designed to perform three essential functions:
- Blocking a pipeline
- Conducting an air test in a pipeline
- Bypassing effluent in an active pipeline.
Blocking a pipeline becomes necessary during new installation or maintenance when either effluent needs to be temporarily stopped or when a new pipe is being air tested for leaks.
Air testing a pipeline is necessary when testing a new installation for leaks before placing it in service or when trying to locate a leak in an existing line.
Bypassing is necessary when the flow of effluent in a pipeline needs to be redirected, most commonly when maintenance or repair is required for a longer period of time when the flow cannot be stopped.
Most Muni Balls come with caps threaded onto the bypass on the front of the plug. The Muni Ball is the most versatile plug in Cherne’s product line because, with the cap on, it can be used for blocking. With the cap removed, it can be used for bypassing. And, with the cap adapted with air fittings, it can be used to perform an air test. Cherne offers a broad size range of Muni Balls from ¾” to 96” in diameter, with bypass tubes ranging from 1/2” to 24”.
Types of Bypassing
Cherne’s bypass plugs are designed for two types of bypassing. Pump bypassing and gravity bypassing.
Pump Bypassing:
Bypassing with a pump involves a Muni Ball being installed in a pipeline upstream from where maintenance or replacement work needs to be conducted. The plug is installed into the pipe, and a hose or pipe is attached to the bypass on the front of the plug. The hose is then connected to a pump on the intake side and another on the output side.
Then, effluent is pumped up and out of the manhole running downstream, and past where the work is being conducted, before it is routed back into another manhole where the effluent can continue. A blocking plug is installed on the upstream side of this manhole to prevent effluent back from flowing toward the work area.
Gravity Bypassing
This type of bypassing occurs when work needs to be conducted in an active manhole, but the flow cannot be blocked. In this instance, two Muni Balls are installed into both access pipes that feed into the manhole. A hose is connected between the bypasses of the two plugs so that the flow can continue while the manhole remains dry.
Proper Muni Ball Selection
To select the correct Muni Ball for your application, the following questions need to be answered:
- What is the inside diameter of the pipe you need to plug?
- How much volume must the bypass accommodate? This goes to the size of the bypass required. You can obtain this information from your project engineer.
- What are the back pressure requirements? In other words, how much pressure will the plug be required to hold?
- Pressure is most commonly measured by either Pound per Square Inch (psi) when the pressure is coming from air, or
- Feet of Head, if the pressure comes from liquid such as water or sewage.
- What is the access opening the plug needs to fit through to be installed? Most commonly, this would be the diameter of the manhole the plug must be passed through before it is installed. Many of Cherne’s Muni Balls have flexible hose bypasses that allow the plug to be bent up to 45 degrees to aid in installation
- What is the temperature of the media being blocked? Cherne’s Muni Balls are made of natural rubber because of their flexibility, memory, and durability. However, natural rubber should not be exposed to temperatures exceeding 125 degrees Fahrenheit, as it will begin to melt.
- Are there going to be any oils, hydrocarbons, or petrochemicals in the media the plug needs to be blocked? These may harm natural rubber and cause it to degrade. Please consult with the factory if your application involves blocking substances such as these.
Important Safety Considerations
Special care needs to be taken before and after a Muni Ball or any pneumatic plug is placed into service:
- Inspect the rubber body of the plug for punctures, bulges, cracks, corrosion, and leaks.
- Inspect the end plates of the plug for cracks, loose fit, missing or damaged eyebolts, rusty end plates and fittings, and damaged inflation fittings.
- If any of these appear, we recommend consulting the Cherne factory.
While installing the Muni Ball:
- Make sure an extension hose with an accurate pressure gauge is used to safely inflate the plug, monitor its air pressure while in use, and deflate the plug from a safe distance.
- Always ensure the pipe the plug is being installed in is inspected and debris such as gravel or broken glass is removed.
- Avoid installing the plug over any exposed rebar.
- Ensure the plug is inflated to the exact inflation pressure prescribed by the manufacturer.
After the work is completed, eliminate any back pressure in the pipe before deflating the plug. Do not attempt to remove the plug from the pipeline until it has been completely deflated.
Remember, most damage occurs to plugs when they are either being installed or removed from the pipe. A safety instruction manual is provided with each Muni Ball when it leaves the factory. Make sure you review it and understand all precautions.
A safe pipe plug usage video is available to all on line at Cherne Product Safety Video - YouTube. Please contact the factory for any questions by either calling 1-800-843-7584 (1-800-THE PLUG) or by emailing chernesupport@oatey.com.
About the author: Pete Rogers is an Inside Sales Specialist at Cherne Industries (part of the Oatey family of companies). He has been with Oatey Co. for more than 50 years. He can be reached at chernesupport@oatey.com.