In centralized lubrication systems, distributors or central lubrication distributors are devices that meter the lubricant delivered by a pump to the lubrication points during the lubrication cycle or within a predetermined time period. The intended amount of lubricant supplied per lubrication cycle should not be affected by the type of lubricant (oil, semi-fluid grease, or grease), the system pressures, the operating temperature, or the type of system.
The main distributor types used in centralized lubrication systems are:
- Single-line distributors
- Progressive distributors
- Dual-line distributors
- Throttle distributors
- Injection lubricators, micropumps
Depending on the manufacturer, these components are referred to by different names, e.g., distributor, metering element, metering valve, etc. In terms of design, a distinction can be made between static and dynamic distributors, which in turn differ in their construction depending on the lubricant used.
Static Design
In static distributors, the main line and lubrication line are hermetically separated by sealing elements during pressure build-up in the main line. This prevents "pushing through" 1) from the main line to the lubrication line, even if the pressure build-up is slow (quasi-static).
1) Piston distributors meter lubricant quantities of 0.01 cm³ to 2.5 cm³ per lubrication pulse.
With these small quantities, minor leaks in the distributor lead to undesirable additional lubricant quantities. Depending on the degree of leakage, the oil viscosity, the pressure, and the pressurization time, the target quantity can be exceeded. Exceeding the target quantity is referred to as "pushing through."
Dynamic Design
In dynamic distributors, the main line and the lubrication line are separated from each other only by a small gap during pressure build-up. The pressure build-up must occur as abruptly (dynamically) as possible. Under unfavorable conditions – slow pressure rise (≥ 1 s to max. pressure) – these distributors can "push through."
Pre-lubrication distributor (static)
Each distributor outlet may only be assigned to one lubrication point. Distributing the lubricant downstream of the distributor outlet to multiple lubrication points is strictly prohibited.
Design
Depending on the metering capacity, the distributors differ in their design. Multi-port distributors have a die-cast zinc housing, which is installed in the main line. Single-port distributors, also known as metering units, are mounted on distributor manifolds).
The distributor outlets are connected to the lubrication points via pipelines. Pipes with an outer diameter of 4 mm are most commonly used for the lubrication point lines.