This article originally appeared in Crane Hot Line.

Many buyers looking for a new hydraulic swivel/slip ring combination unit have an objective of saving money and creating an assembly that surpasses the requirements of the application but is not over-engineered. There are three main styles of slip ring and hydraulic swivel combination units. Below is a look at each combination and their pros and cons.

Fully Integrated

These combo units integrate the slip ring directly into the end of the hydraulic swivel. Externally, the unit looks to be just a hydraulic swivel with the telltale signs of an electrical harness coming out both ends. The style is best used with minimal slip ring circuits and a critical requirement for sealing and protecting the slip ring components. It is commonly used in the forestry industry and military.

Pros:

• It’s the most robust, by a large margin.
• It employs the least amount of parts.

Cons:

• Due to its nature, only low amounts of slip ring circuits are cost effective.
• Removal of the slip ring can be trickier than the separated style.
• Additional engineering time is required.

Semi-Integrated

On semi-integrated combination units, the slip ring is mounted directly onto the end of a hydraulic swivel. However, the slip ring circuits are enclosed using a standard spun aluminum cover and not the swivel housing, like the fully integrated version.

This version is best suited for applications that have more slip ring circuits and less harsh requirements for sealing and protecting the electrical circuits, as well as designs with length restraints. The style is commonly used in the construction and railroad industries.

Pros:

• It fits the maximum amount of slip ring circuits into an application with length restrictions.
• It’s the most cost-effective style for large amounts of circuits.

Cons:

• It doesn’t have the robustness of the fully integrated style.
• It has similar engineering time requirements as the fully integrated version.
• The harness exit location is not free to change as the fully integrated version.

Separated Design

Combination units with a separated design have the hydraulic swivel and slip ring separated by a mounting tube and flange. This is the classic style that has been used for decades. The two units can be separated easily, and this style has the lowest heat transfer between the slip ring and swivel.

The separated design is best suited for applications with many slip ring circuits, low sealing, and protection requirements, as well as no stringent length requirements. This style also requires the least amount of upfront design work, so it’s well suited for low yearly requirements – for example, less than 10 per year. The style is also commonly used in the construction and railroad industries.

Pros:

• It requires the least amount of engineering effort to join the two together.
• We can lengthen the mounting tube if other components are in the way.
• The additional space between the two units helps reduce heat transfer.
• Disassembly is visually straightforward; most mechanics are familiar with this style as it’s been the standard for decades.

Cons:

• It uses the most parts.
• It’s typically the longest of the three.

Brady Haugo is a Senior Design Engineer at United Equipment Accessories.