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What is a Grease Fitting? The Functions and Maintenance of Zerks in Heavy Equipment

What is a Grease Fitting? The Functions and Maintenance of Zerks in Heavy Equipment

A close-up image of a pile of silver grease fittings

What is a Grease Fitting? The Functions and Maintenance of Zerks in Heavy Equipment

Reading time: 6 min

Lubrication is one of the most critical aspects of heavy equipment maintenance. On modern machines, grease fittings are crucial to the lubrication process, allowing for regular lubrication and helping to prevent corrosion.

Grease fittings, commonly called “zerks”, are small, metal nozzles attached to heavy equipment at strategic points where lubrication is necessary. They serve as conduits for grease, which is pumped into the Zerks under pressure.

Zerks allow operators to grease and lubricate their machines regularly and without much hassle. Adding grease to a zerk is as simple as using a grease gun to pump directly into the zerk. Zerks help seal the points on your machine so that grease does not leak out and contaminants do not accidentally enter the machine.

Due to their convenience and reliability, zerks have been a staple in machinery for many decades. Their widespread use is a testament to their effectiveness and the simplicity of their design.

Grease fittings come in various sizes and types, each designed for specific applications and equipment types. Common zerk designs include standard grease fittings, button-head fittings and flush-type fittings. Each type has its unique characteristics, such as the angle of entry for the grease gun, size and pressure ratings.

In this article, we’ll get into the functions and maintenance requirements of zerks in heavy equipment. Learning about these indispensable components will help you maintain the machines in your fleet, allowing you to improve the reliability of your fleet and reduce its maintenance costs.

The Functions and Roles of Zerks

The primary role of zerks in construction machinery like excavators, loaders and skid steers, is to ensure adequate lubrication at crucial points on the machine, notably at joints, bearings and pivot points.

In excavators, for example, zerk fittings are commonly found on the boom, stick and bucket joints. These are high-stress points that undergo significant movement and require regular lubrication to maintain smooth operation and minimize wear. 

Similarly, in loaders, grease fittings are strategically installed at pivot points in the articulation joint, which allows the front and rear of the loader to move independently, and on the bucket linkage.

Bearings, which are essential for allowing rotational movement in certain components, also have grease fittings. Proper lubrication of bearings is required to prevent metal-on-metal contact, reducing wear and the risk of overheating.

The Impact of Grease Type on Performance

The type of grease used with grease fittings significantly impacts the performance and longevity of the equipment. Different greases have varying properties like viscosity, water resistance and temperature tolerance. 

For example, grease with high water resistance is vital in environments where equipment is exposed to moisture, preventing the grease from being washed out and reducing rust and corrosion risk.

Temperature tolerance is another critical factor. Machinery operating in extremely cold or hot conditions requires grease that can maintain its lubricating properties under these extreme temperatures.

Using the wrong type of grease can lead to inadequate lubrication, increased wear and potential equipment failure.

Advantages Over Traditional Greasing Methods

The use of grease fittings offers several advantages over traditional greasing methods. For starters, zerk fittings allow for more precise and targeted lubrication. By directing grease exactly where it is needed, they ensure that critical components receive adequate lubrication without the mess and waste associated with manual greasing.

Furthermore, zerk fittings allow for regular and easy maintenance, enabling quick connection and disconnection of a grease gun, making the lubrication process more efficient and less time-consuming.

Lastly, the use of grease fittings helps in maintaining a consistent lubrication schedule. Regular lubrication through zerks minimizes the risk of component wear and tear, extending the overall lifespan of the machinery. 

Maintenance of Grease Fittings

Maintaining zerks is an essential aspect of heavy equipment maintenance. Key maintenance tasks involving zerks include regular lubrication, cleaning, inspection and unclogging.

  • Regular Lubrication: This is the most crucial maintenance task. The frequency of lubrication depends on the equipment's usage intensity and the operating environment. For machines in constant use or harsh conditions, lubrication might be necessary weekly or even daily. Conversely, equipment with lighter usage may only require monthly lubrication.
  • Cleaning: Before lubricating, it’s important to clean around the zerk to prevent contaminants from entering the machine. A quick wipe with a clean rag or brush will help clear any dust or dirt that’s built up around the grease fitting.
  • Inspection: Regular inspection of grease fittings for signs of wear, corrosion or damage is vital. This should be part of routine maintenance checks, conducted at least monthly or according to the equipment's service schedule.
  • Unclogging: Grease fittings can become clogged over time. If a fitting doesn’t accept grease, use a grease fitting cleaner tool to unclog it. Check for clogs during each lubrication cycle.

Consequences of Improper Lubrication

Excessive grease can lead to increased pressure within bearing housings and other components. This can cause seal damage, leading to grease leaks and contamination

On the other hand, insufficient lubrication leads to increased friction and wear on moving parts. This accelerates component degradation and can result in premature failures. It also increases the risk of rust and corrosion, particularly in harsh operating environments.

Installation and Replacement

Installing grease fittings requires a few basic tools: a fitting installation tool or a wrench that fits the fitting, a thread tap of the appropriate size and possibly a drill for creating new installation points. 

The basic technique involves cleaning the area, ensuring the thread size matches the hole, and screwing the fitting in place, usually by hand to start and then tightening with the tool. It’s crucial to avoid over-tightening, as this can strip the threads or damage the fitting.

Signs of Clogged or Faulty Fittings

A grease fitting may need replacement if it’s visibly damaged, corroded or if grease refuses to enter or leaks out of the fitting. If a fitting doesn’t accept grease, that’s a clear sign of clogging.

Replacing a Grease Fitting

To replace a grease fitting, start by removing the old fitting with a wrench or pliers and cleaning the area. Screw in the new fitting by hand and then gently tighten it with a wrench, being sure not to over-tighten it. Once installed, test the fitting with a small amount of grease to ensure it's functioning properly.

Final Thoughts

Maintaining your machine’s zerks is essential to keeping it well-lubricated and operating smoothly. The EquipmentShare Shop carries OEM and aftermarket hardware parts, including grease fittings for heavy equipment, making it easy to order replacement components and get them shipped directly to you. Can’t find exactly what you’re looking for? Reach out to our dedicated parts experts and get personalized assistance.

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