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Dual Line Lubrication

DropsA S.p.A.
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Features and guidelines to the utilization of dual line systems

As we continue on our journey through the different types of lubrication systems: the next product review is the dual line lubrication solution.

Dual Line lubrication is a reliable and efficient solution that can be utilized in conjunction with manual pumps, electric pumps, and pneumatic pumps. Additionally, this solution can be used in combination with monoblocs, modular volumetric dividers, AP/AG/DM Solid Base, or modular DM.

Dual Line systems can function under high pressure and incorporates a modular structure that allows for simple configuration and expansion of a system, a feature that saves time and reduces maintenance costs.

This solution is suitable for heavy industry with large machines with multiple lubrication points including, but not limited to, the iron and steel industry, cement plants, offshore platforms, large cranes, and cargo handling equipment.

When to utilize a dual line system

A dual line system is ideal for use with:

- Large oil and grease total loss lubrication plants, air-oil plants (also in combination with satellite stations), recirculating lubrication plants (low flow rate).

- A large requirement of lubrication points (up to 300 points and installation runs of up to 100 meters (328 Feet)).

- Applications that require the proper monitoring of the amount of lubricant delivered to each point.

- Pneumatic, electrical, or manual systems (possible but not recommended)

- The necessity to section a plant into zones (multiple machines or lubrication points)

- The requirement to work in ATEX zones or marine environments (INOX 316).

How a dual line system works?

In the dual line system, there are two main lines that operate alternately, switching back and forth, by means of an inverter valve.

• A lubrication cycle is completed when both the main lines alternatively pressurize and release pressure.

• The dual line solution operates as a parallel system and each divider valve functions independently from one another. In the case of a lubrication point becoming blocked, the remaining points would not be affected and would continue to lubricate as normal.

The operating principle

- Line 1 is pressurized while Line 2 acts as a return.

- The pressurized lubricant enters through port A, pushes the two pistons B and C downwards filling dosing chamber D.

- Piston C is equipped with a stroke adjuster that serves to regulate the amount of lubricant that is dispensed. In fact, it is possible to adjust the stroke of piston C by altering the adjustment nut E in order to obtain the desired quantity of lubricant.

Piston B acts as a pilot valve, supplying one of the two dosing chambers with the dividers lubricant output.

Subsequently, by depressurizing Line 1 and pressurizing Line 2, the lubricant enters through port F by moving the B and C pistons upwards.

Piston B, moving upwards, opens a passage to outlet 2, the upper dosing chamber of the cylinder in which the piston flows.

Simultaneously, port A connecting Line 1 to the upper chamber is isolated.

When piston B reaches the end of its stroke, the lubricant under pressure begins to enter the lower chamber, moving piston C upwards, which forces the lubricant contained in the upper chamber D to exit through outlet 2.

When piston C finishes its upward stroke, the divider has completed the first half of the lubrication cycle and the lower D1 chamber will contain the same amount of lubricant that was previously contained in the upper D chamber.

At this point, the pressurization inversion device of the two lines actuates.

By depressurizing Line 2 and pressurizing Line 1, the movements described will be repeated in the opposite direction which will result in the lower chamber to deliver its contents out outlet 1, completing the lubrication cycle.

Simultaneously, the upper chamber D will fill with lubricant and return the dosing device to

its initial position.


For the use of the dual line lubrication systems, it is necessary to comply with the following sizing/usage rules:

- There must always be a pressure difference of at least 70 bar at the bottom of the line between the two lines.

- Best practice is to implement pressure switches at the end of the line for proper function and monitoring of the system.

- If a divider valve has stopped functioning and all the other valves are functioning properly, replacing the individual element can be achieved without altering the base or removing lines due to DropsA’s modular concept.

- If the required lubrication solution is extensive, position the pump in the middle of the system to effectively reduce strain on the pump application.

Keep in mind that when a lubrication solution is designed for a plant, it is not necessary to immediately know the amount of lubricant required, however, it is important to understand if all the end points require the same amount of lubricant or vary throughout the system.

In summary, a lubrication solution that is proportional to the plant will be managed through the setting of the number of cycles of the lubrication system.

Dual Line Lubrication
Dual Line Lubrication

Features and guidelines to the utilization of dual line systems

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