Pipe Stoppers – Types and Applications

Pipe stoppers (or often called pipe plugs or bungs) are devices inserted into a pipe to temporarily block flow, allow for testing of pipelines, to isolate sections of a pipe, or to prevent debris entering during construction or maintenance.

The key factors to consider when selecting the type of pipe stopper to be used include:

• The internal diameter of the pipe – most stoppers have a range of adjustment and the internal diameter of the pipe to be blocked must fall within the adjustment range of the stopper being used.
• The back pressure the stopper is required to withstand – different types and diameters of stopper have the ability to withstand different back pressures (the pressure of fluid or gas in a pipe that the stopper is required to withstand).
• How accessible the pipe to be blocked is and where in the pipe the stopper is to be located – if the pipe can be blocked at an accessible location a more rigid stopper can be used. If the location required to be blocked is more inaccessible often an inflatable stopper is inserted into a pipe and inflated once in place.
• Environment – different types of stoppers are able to withstand different chemical environments better than others. Some stoppers are designed to be used in applications where residues of acids or alkalis or petrochemical by products are likely to be present.
• Bypass – some applications using pipe stoppers require the stopper to have a bypass facility. A bypass is a passage through the stopper that allows a connection to be made to the stopper through which gas or fluid can be passed into or out of the pipe behind the stopper. This is often required for pressure testing sections of pipe between stoppers.
• Bracing options available – some stoppers with higher back pressures require bracing when in use. Consideration needs to be given to the most appropriate type of bracing to use for an application.
• Health and safety – during pressure testing or pipe blocking with higher back pressures careful consideration needs to be given to the positioning, selection and method statements / working practices adopted when using pipe stoppers. In higher back pressure applications stoppers should only ever be selected, installed and operated by trained personnel.

Main Pipe Stopper Types

Please see the below guide to the two main types of pipe stopper.

Mechanical expansion stoppers / plugs

Mechanical expansion pipe stoppers work by a bolt or wing nut being tightened to compress rubber ring seals that expand outward and grip the pipe wall, creating a seal. Mechanical expansion stoppers are available with and without bypass fittings and able to withstand a wide variety of back pressures and environments.

Common applications of mechanical stoppers include:

• Testing of drainage or plumbing pipework
• Short-term pipeline isolation
• Maintenance work with moderate back pressures
• Use in applications with chemical or petrochemical residues

The advantages of this type of stopper are that they offer a strong mechanical grip, a reliable seal, are relatively inexpensive, are useful for fixed diameter pipes and have a wide range of varieties available that cater for most testing requirements. Mechanical stoppers are relatively slow to install, have a narrower range of adjustment (compared to inflatable stoppers), are not best suited to imperfectly round pipes and have access limitations due to the rigidity of their form.

Inflatable pipe stoppers

Inflatable pipe stoppers work by a deflated bladder being inserted into a pipe. The bladder is then inflated in the pipe using compressed air and as the stopper expands it seals the pipe. Inflatable bladders are available in an extensive range of diameters with and without bypass functionality for a wide range of applications and back pressures.

Common applications of inflatable pipe stoppers include:

• Leak testing of pipe lines
• Sewer and drainage air testing
• Installation where access is limited or the location that needs to be blocked is some distance along a pipe away from an access point
• Use where the internal profile of pipes is irregular or not perfectly round
• Applications where the wider range of stopper adjustment allows one stopper to be used in a wide range of pipe diameters
• Specialist stoppers can be inserted into pipelines containing flammable products or vapours to allow mechanical processes or welding to take place safely

The main advantages of inflatable stoppers are they are quick to install, work in irregular pipes, offer accessibility advantages and are available in a wide range of sizes, types and back pressures. Inflatable pipe stoppers are limited in uses where risks of puncture exist and provision of an air supply is difficult. Inflatable pipe stoppers also need careful positioning, care during inflation (to avoid over or under inflation), appropriate bracing must be provided and ongoing monitoring of inflation pressures when in situ is required.

Allpipe offer an extensive range of both mechanical and inflatable pipe stoppers available from stock on same day or next working day collection or delivery that are suitable for most applications. Please contact us on 01603 489260 or e-mail us at salesandhire@allpipe.co.uk to discuss your requirements and we will be pleased to advise you on a stoppers or other pipe equipment.