Every year, compressors experience unnecessary shutdowns caused by the limitations of aging no-flow protection technology. For decades, the natural gas compression industry has relied on digital no-flow shutdown devices to protect compressors from lubrication system failures. While these technologies represented significant advancements in their time, traditional spring-and-magnet designs were developed around proximity switch technology that was introduced more than 60 years ago.
Over time, increasing compressor discharge pressures, piston slap-back within divider blocks, vibration, contamination, extreme temperature variations, and growing runtime demands have exposed the limitations of these legacy no-flow devices. Originally introduced more than 30 years ago, these systems were not designed to address the performance and reliability challenges of today’s force-feed divider block lubrication systems.
Patton Lubricator Products (Patton) has introduced the WatchDog Lube No-Flow Protection System (WatchDog) to solve these problems.
“Our objective was not simply to replace an existing no-flow device, but to eliminate the primary causes of nuisance shutdowns while improving long-term reliability in demanding compressor environments,” said Curtis Roys, president of Patton. “We rebuilt compressor protection technology from the inside out to create a more reliable, more durable, and more intelligent shutdown device specifically engineered for modern divider block lubrication systems.”
In force-feed lubrication systems, proximity switches are commonly installed on divider block assemblies when used with control panels. These switches monitor the movement of the divider block and send a contact closure signal to the PLC or control panel with each cycle. This signal resets the alarm circuit and allows the lubrication system to continue delivering oil to cylinder and packing wear components.
If the PLC or control panel does not receive a contact closure within a predetermined period, it will shut down the compressor to protect these critical components from damage due to inadequate lubrication. However, if a proximity switch fails for any reason, the contact closure signal will not be transmitted. In that situation, the control panel or PLC may shut down the compressor even if the lubrication system is functioning correctly.
Traditional proximity switches provide contact closure signals to the control panel, but without local visual confirmation that the divider block is cycling properly, technicians may find it difficult to verify switch operation and identify the cause of a shutdown.
“We recognized these problems could not be solved by simply modifying older technology. The sensing architecture, alarm circuitry, environmental sealing, and durability all required complete redesign,” said Roys. “The result was a compact, stainless-steel, computer-designed protection device engineered specifically for compressor divider block systems.”
How It Works
Unlike traditional devices, the WatchDog senses divider block piston movement through controlled magnetic field detection without direct mechanical contact. As the piston completes its fully designed stroke, the sensor detects movement at a precise distance from the nose of the device. Once the piston is detected, the contacts close and instantly send a switch closure to the internal circuitry or control panel.
Housed in a stainless-steel enclosure, the WatchDog features a large, 360-degree LED cycle indicator. During normal operation, the LED flashes green, providing technicians with clear visual confirmation that the divider block is cycling correctly. If a shutdown alarm is activated, the LED flashes red, allowing technicians to quickly identify system problems and troubleshoot more efficiently.
“Its low-mass design makes the WatchDog particularly well suited for installation in the high-vibration environment typical of divider block systems,” said Roys. “The unit is fully sealed and utilizes magnetic field-sensitive technology to detect divider block piston movement. When the piston comes within a specific sensing distance, the switch activates without requiring direct mechanical contact. This design delivers accurate and reliable detection while keeping magnets and springs out of the lubrication oil.”
Roys continued, “As a result, the WatchDog maintains dependable performance across a wide range of operating conditions, including cold environments and applications involving higher-viscosity lubricants. The electrical connection uses a quick-disconnect mounted on a 270-degree rotatable head, allowing for optimal cable routing and easier installation access.”
Patton designed the WatchDog as a plug-and-play replacement for existing no-flow devices, minimizing installation time and simplifying upgrades. “Existing no-flow devices can be replaced directly by following the WatchDog wiring instructions,” said Roys. “Its magnetic field-sensitive operation provides fast, consistent contact switching, while the snap-action response ensures reliable contact engagement during every divider block cycle.”
Contacts are self-cleaning and designed to operate across a broad voltage range of 5 to 28 VDC, making the WatchDog compatible with virtually any control panel. Because the unit is externally powered, batteries are not required, eliminating battery maintenance concerns and providing long-term reliability without user-serviceable components.
“With a 90-second shutdown alarm circuit and a 1-amp continuous switching capacity, the WatchDog delivers dependable lube no-flow shutdown protection for all compressor divider block systems,” said Roys.
Its alarm circuit is designed for fail-safe operation in both normally open and normally closed configurations, ensuring that compressor protection is maintained regardless of wiring method and even in the event of power loss.
“Backed by a two-year warranty, the WatchDog represents the next generation of compressor lube no-flow protection,” said Roys. “As reciprocating compressors continue operating at higher pressures, longer runtimes, and under increasingly demanding service conditions, dependable lubrication system protection becomes more important than ever. The WatchDog Lube No-Flow Protection system represents Patton’s commitment to advancing divider block technology through practical engineering solutions designed to improve reliability, simplify troubleshooting, and protect critical compressor components.”
