What Are Service Plugs And What Features Should I Look For In One?

Hydraulic service plugs from Hydrastar

A service plug is a resistant device that can be placed in an open hydraulic pipeline or chamber inlet or outlet to stop leaks, spillages, and unintentional drainage. They are used when a machine has stopped and is being maintained and should never be used on a running hydraulic system, or one that is cooling after having recently been shut down.

Service plugs come in many different shapes and sizes to fit different types of hydraulic pipe and nozzle. They are usually a simple, high-resilience piece of moulded rubber shaped into a wedge, with a broad top ridge for easy removal. They’re used in industrial, plumbing, and catering machines, but are most popular for use in hydraulic control and maintenance.

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What Features Should You Look For In Your Hydraulic Service Plugs?

High Temperature And Pressure Resistance

One of the main problems you’ll encounter if you use oily rags and cloth to block off pipes and valves is that fabric offers limited resistance to the viscous fluid left inside hydraulic machinery.

Hydraulic systems retain their high internal temperatures for a long time after deactivation and depressurization, sometimes for days. This means that ambient heat can make fluid more malleable, making it more difficult to control. Toxic hydraulic fluid can also seep out of cracks left by temporary or inadequate stoppage solutions.

It’s therefore crucial that your service plugs can take the strain. A good service plug should resist temperatures of up to 100°C, be made of a sturdy material such as PVC or rubber, and form a complete temporary seal around the O-ring entrance to pipes and chambers.

Hydrastar recommends our range of YELLOC service plugs.


You should be able to clean, dry, and wipe down your service plugs in between uses. This is to prevent fluid retention and cross-contamination. If dirt and dust get into hydraulic fluid, it can easily damage delicate internal mechanisms, and clog pipelines.


Not every off-the-shelf service plug will fit every machine. Service plug manufacturers keep this in mind, making their plugs from material that can easily be cut or sheered to the right size. While the wedge design helps fit service plugs to a variety of hydraulic ports, a good service plug should allow you to modify it to optimize performance.

Service Plugs From Hydrastar

If you’re an engineer or administrator looking for a better solution for your hydraulic maintenance issues, contact Hydrastar. We offer a versatile range of YELLOC professional-quality service plugs to buyers in the UK, alongside thousands of other hydraulic parts, pieces, and pumps.

Next Steps

At Hydrastar, we are experts in pneumatic systems. We can provide you with the high-quality components and specialist advice you need to sustain highly efficient pneumatic systems. To find out more, please call 01353 721 704.

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