To complete a centralized lubrication system design, the designer must tie the pump and delivery system together and synchronize their operation with a combination of control and signal devices.
The type of controller and signal devices used will depend on the budget, the level of system protection required, the type of pump and distribution system employed and the ability of the host machine to interpret and act upon the control signals.
How Controllers Work
A lubrication-system controller is often described as the system’s “brain.” Most controllers are multi-function, stand-alone devices housed in a control panel. The exceptions to this can be found in single-point lubricators (SPLs) and some smaller electro-mechanical oil-delivery pumps that have built-in circuit-board-style controllers that can be programmed through an LCD touch screen or a series of mechanical switches. These are usually simple control devices that activate the lube pump and speed up or slow down the flow rate of the pumped lubricant.
Turning the pump on and off is the controller’s primary function. In the case of a pneumatically powered pump, the controller opens an electrically operated air solenoid valve to allow air into the piston and fire the pump. With electrically driven piston and gear pumps, the motor is electrically energized, allowing the pumping action to commence. Once the controller receives a signal informing it that the pump has fired, a given time has elapsed, a lubricant line pressure has been achieved or a distribution block cycle has been completed, the pump’s power source is shut down until the next lubrication cycle commences. (The only exception to this is a recirculating-oil system that is powered up on machine startup and runs continually until it is turned off when the machine is idled or shut down.) Lubrication cycles can be controlled by a counter that determines the number of machine or production operations, by a programmed or set timer or by a condition signal—for example, an amperage draw meter indicating energy draw increases on a machine system motor because of a mechanical friction rise due to lack of lubrication. (This is a popular control mechanism that measures the amperage of the conveyor drive and take-up motors to activate and deactivate the “power and free” conveyor chain and pin lubricators used in automotive assembly plants.)
A controller’s secondary function is to take an emergency signal, shut down the system and activate an alarm. The alarm can be a simple light or buzzer wired directly to a solenoid in the control panel that, in turn, will activate an alarm email or work order—or both—in the CMMS/EAM maintenance management software.
A controller’s level of sophistication can range from a manual on/off device, to a simple count-driven on/off device, all the way up to a very sophisticated programmable PLC/computerized PC device. The controller sophistication is usually underwritten by the lube system’s consequence of failure where public safety is a concern—i.e., in the nuclear or chemical industries, etc.—or where production losses are major concerns when lubricated equipment is a production constraint, or where machine failure leads to high downtime.
How Signal Devices Work
Signal devices used for control and system protection can be mechanical, hydraulic, pneumatic or electrical in design—and active or passive in operation.
Different delivery-system designs will use controls differently. For example, in most single- or dual-line system designs, the pump must continue to operate until the line pressure has reached an end-of-line line pressure of at least 800 psi, allowing the injectors to fire. Once attained, a pressure-signal switch informs the controller to shut off the pump, which, in turn, also reverses a flow valve allowing the lubricant to return to the reservoir and the injectors to reset. A timer then counts operations or elapsed clock time and tells the controller to start the process all over again. In this system type, the pressure switch can also be coupled to a time-out switch set to signal an alarm state if the system doesn’t achieve its line pressure (due to a broken line or no lubricant) in a specified time period.
Progressive-divider lubrication-delivery systems can employ simple counters attached to the top piston in a primary delivery block. Once every outlet in the block has fired lubricant, the top pin will have moved in and out of the block once—thus signaling one complete operation of the block. The counter is linked to a controller that actuates the pump based on the number of required block cycles. Progressive blocks also utilize passive hydraulic blocked-line indicators that actuate when hydraulic lock up occurs in a line-blockage situation, causing a pin to “pop” out and indicate which line is blocked, thus speeding up the troubleshooting process (see Fig. 1).
The bottom line is that there are many control and protection devices available to the customer. Be sure to consult with your suppliers to ensure that you have the right system and right level of control your systems need.
The November/December issue will address the maintenance of automated lubrication systems. LMT
For more information on automated lubrication delivery systems and/or ICML or ISO lubrication certification training, contact Ken Bannister directly. Telephone: (519) 469-9173;