Troubleshooting a Centralised Lubrication System, Fault by Fault

Lubrication systems are simple machines, which is why symptom-first troubleshooting works well on them. There are only a handful of things a pump-line-distributor system can do wrong, and each leaves a distinct signature.

Start from what you observe, not components. Don't pull the pump apart just because it looks mechanical. This guide runs symptom by symptom, with a summary table near the end for your phone at the machine.

Symptom 1: Pressure never reaches action pressure

In a volumetric oil system, nothing downstream happens until the main line reaches the distributors' action guarantee pressure. That figure is per family, not universal: 8–12 kgf/cm² on the 34-type and RH-2, 12–15 kgf/cm² on the 35-type and RH3. Check the number for the distributors you actually have. Below their threshold, the metering valves don't fire. A gauge that climbs partway and sags, or never climbs at all, means zero delivery: the fault sits on the supply side.

Low reservoir. Obvious enough, but the real question is why the level switch didn't alarm. An empty tank with no alarm means two faults, not one: the tank, and a switch that failed or was never wired in. Fix both (see symptom 6).

Suction-side air leak. A pump pulling air through a loose fitting or cracked pickup can't prime. It churns froth instead of moving oil. Look for a fitting anyone recently disturbed.

Burst or disconnected main line. If the pump moves oil but the line won't hold pressure, the oil is going somewhere. Check behind covers, the chip pan, and under the machine for the puddle. A disconnected push-in fitting after maintenance is a classic culprit.

Worn pump. Least common, and the most expensive conclusion to reach. If the reservoir is full, the suction side tight, and the line intact end to end, the pump is no longer making rated pressure. Bench-test it or replace it.

Symptom 2: Pressure builds almost instantly

Here's the counterintuitive one: a system that snaps to full pressure faster than it used to is just as sick as one that never gets there. Pressurising a line takes time, filling metering chambers, compressing residual air, and flexing tubing.

If the gauge hits action pressure almost instantly, it's pressurising a tiny trapped volume. The main line is blocked or crushed close to the pump, and everything beyond that point gets nothing while the gauge reads perfect.

Record your system's healthy time-to-pressure at commissioning, as we argue in the commissioning checklist. Against that baseline, both too-slow and too-fast become obvious. First check: follow the main line for a crush point. A guard screwed down through a tube path is a repeat offender.

Symptom 3: One point dry while the others are fine

On RH3 units the signal pin turns a silent outlet into a visible one. Watch it during a commanded cycle.

This is the volumetric architecture's blind spot. Each outlet meters independently, so one starved point can coexist with a healthy gauge and normal consumption. Usually nobody spots it directly; they see a hot bearing, a scarred way, or a whining ballscrew, and work backward from there.

Two mechanisms account for nearly all cases. Either the feed tube is pinched, kinked, or swollen shut, or the metering valve is jammed, overwhelmingly from contamination: grit from a dirty top-up or an open lid, lodged in a precision valve.

Checks depend on the hardware. On an RH3 inspecting distributor, watch the signal pin during a commanded cycle: the pin's behaviour shows whether the fault is upstream or downstream. A pin that never moves points at the valve; one stuck extended points at a blocked line.

On a plain unit with no indicator, swap-test instead: move the suspect tube to a known-good outlet, or vice versa, and run a cycle. The new pairing tells you which side is at fault.

Symptom 4: Progressive system alarms or stalls

A series-progressive distributor turns any single blocked point into a full stop. The pistons fire in sequence, so the sequence halts at the blocked outlet, and the cycle-monitoring alarm (if fitted) trips.

The fix uses the same mechanism in reverse: crack outlet fittings one at a time with the pump running. When cycling resumes, the last fitting you opened is the blocked line. Full reasoning, and the monitoring logic, is in progressive distributors and PLC monitoring.

One more check before you assume a blockage: SD-series blocks need 1.4 MPa at the inlet to shift the pistons. A tired pump or a supply leak below that threshold can mimic a blocked point. Verify supply pressure first, crack fittings second.

Symptom 5: The reservoir empties faster than it used to

Consumption is worth trusting, but read it carefully. There are three different explanations.

First, the settings changed: check the timer interval and dose against the lube card. An interval shortened during troubleshooting and never restored is a common find.

Second, a leak. A weeping fitting or split tube dumps oil that never reaches a bearing, becoming an extra, unmetered "point." Follow the smell and check for wet spots below tube runs.

Third, on machine-tool way lube specifically, nothing may be wrong at all. Way and ballscrew oiling is total-loss by design, so consumption is the system working. What looks new is sometimes just more spindle hours, or a normal rate someone's noticing for the first time. Know your baseline before hunting a leak; we cover that, and how it interacts with timer settings, in total-loss lubrication and timer setup.

Symptom 6: The alarms that never fire

This is the quietest fault of all: a protective switch that isn't protecting anything. A reservoir level switch, or the optional pressure switch on the TZ pump at 5 or 10 kgf/cm², only helps if it's wired into the alarm chain and the machine reacts when it opens. An unwired switch is decoration.

Test it on a schedule, not just at commissioning. Lift the level float, or run the reservoir low during an attended cycle, and confirm the machine annunciates. If fitted, confirm a lube-pressure fault appears on the control when the line can't make pressure.

The summary table

The root cause behind the root causes

Run enough of these diagnoses and a pattern emerges. Most jammed metering valves, and a fair share of blocked progressive outlets, trace back to contamination entering through the reservoir's top: dirty transfer containers, the wrong funnel, lids left open over a weekend of grinding dust.

The fix is boring discipline: dedicated clean containers, closed lids, correct oil from a sealed source.

If you've worked through a symptom and the system still won't behave, or the same fault keeps returning, contact us with your pump and distributor models and what you've observed, and we'll help you run it to ground.