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hydraulic specialty inc wet line kits for trucks

Heavy Duty Truck Wet Line Kit: What Are They & How Do They Work?

Heavy duty trucks are essential to the everyday lives of Americans. They are relied on to transport heavy construction materials and debris from work sites, utilized in major infrastructure improvements and needed for common maintenance services. They come in many shapes and forms, but the common element between them is the use of hydraulics to perform their respective tasks. 


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What Is A Wet Line Kit & What Does It Do? 

A heavy duty truck wet line kit refers to the combination of components that, when paired together, form a hydraulic system that can power a variety of heavy duty truck functions. They can be fitted on any truck or tractor that has a PTO (power take off) provision. The purpose of the wet line kit is to transfer the power generated in the truck’s transmission to a hydraulic system where it can be used to propel very heavy loads and perform specific tasks. 


Who Uses Wet Line Kits?

Wet line kits can be seen on a variety of truck and trailer combinations, but the most common heavy duty trucks that utilize this equipment are: 

  • Dump trucks – they use a hydraulic system to raise the front end of the dump box to offload material
  • Moving (walking) floor trailers – uses a hydraulic system to offload bulk material from within the trailer, off the rear of the trailer
  • Side Dump trailers – uses hydraulic rams that tilt the body to dump bulk material to the right or left side of the trailer
  • Low Boy trailers – hydraulics cylinders raise and lower the deck of a trailer
  • Log Loading trailers – these trailers use hydraulics to operate an articulating arm with a rotating grapple to load logs onto and off of a trailer deck


Components Of A Wet Line Kit

Several customizations can be made to a wet line kit, but they all have the same basic components.

  1. PTO – This refers to the power take off. It is mounted to the transmission and contains a series of gears on the inside. Once engaged, the gears of the transmission turn the gears of the PTO, which in turn rotates the hydraulic pump.
  2. Hydraulic Pump – The hydraulic pump performs one function, moving oil from the reservoir, through the hydraulic system and back to the reservoir.  This movement of oil when directed to an actuator is what moves the load.  Resistance to moving the load along with hoses, fittings and components is what creates pressure in the hydraulic system.
  3. Directional Valve – This is what directs oil flow to an actuator, like a cylinder or a motor. 
  4. Relief Valve – This is what limits the pressure in the hydraulic system so that it does not exceed what the system was designed for.
  5. Filtration – Before the hydraulic fluid completes the trip back to the tank, it can be passed through a filter. Filtration removes dirt and particles that can build up, causing wear, and a reduction in pressure and flow.
  6. Hydraulic Tank – This stores the hydraulic fluid and provides an opportunity for the hydraulic oil to cool, losing some of the heat generated by the system doing work.


There are two types of wet line kits:

Two-Line Kit

These kits do not include a dedicated return line, the hydraulic fluid must pass back and forth along the same two lines to execute the hydraulic task. This results in the inability of the hydraulic oil to be filtered or cooled since both of those require a dedicated return line. Without filtration, a two line system can result in more contamination wear.  Idling the system with the PTO running can also result in the pump overheating since oil can only recirculate within the pump alone. 


Three-Line Kit 

These kits generally are a longer lasting, more efficient system. They have a dedicated return line that can be passed through a filter, which removes dirt and particles that can cause system wear. The dedicated return line also allows the hydraulic fluid to continuously circulate through the entire system, even in a hold or idling position. This will eliminate the possibility of overheating the pump in this condition.


High Quality Wet Line Kit Installation

Whether you need a new wet line installation, or just replacement parts or service, visit us at Hydraulic Specialty, Inc. With years of experience, you can trust us with any wet line installation, service or replacement needs.