Oil Analysis in Hydraulics | Key Metrics & Tips

Oil analysis in hydraulic systems combines practical relevance with sound engineering: it makes the internal condition of power units, cylinders, and valves visible before failures or performance losses occur. Especially in applications such as concrete demolition and deconstruction, building gutting and cutting, rock demolition and tunnel construction, as well as natural stone extraction, tools and drives from Darda GmbH operate under high load and in dusty, wet, or variable environments. Whether concrete demolition shears, hydraulic wedge splitters, hydraulic power packs, combination shears, or steel shears: the hydraulic fluid is the central functional element. Its systematic examination provides the basis for condition-based maintenance, longer service life, and stable performance in tough construction site operations.

Definition: What is meant by Oil Analysis in Hydraulics

Oil analysis in hydraulics refers to the methodical examination of the hydraulic fluid to assess cleanliness, aging, and wear. The focus is on metrics such as particle count and size (cleanliness class), water content, viscosity, oxidation and aging indicators (e.g., acid number), additive condition, as well as wear metals from pump, valves, or cylinders. Analytical methods range from optical particle counting and water determination to infrared spectroscopy and elemental analysis. The results are evaluated in trends to detect changes early and to initiate measures such as filtration, fluid conditioning, or component inspection in a targeted manner.

Objectives and benefits of oil analysis in hydraulic use

Oil analyses serve early risk detection, securing maintenance intervals, and root-cause analysis when anomalies occur. For tools and power units from Darda GmbH—for example concrete demolition shears, hydraulic wedge splitters, hydraulic power packs, concrete demolition shears, and multi cutters—the fluid condition analysis provides a reliable view of wear, leakage paths, dust ingress through fine dust, and moisture loads. The goal is stable operation under varying loads, temperatures, and media exposure as encountered in concrete demolition, tunnel heading, or natural stone extraction.

Typical test parameters and what they indicate

The selection of metrics depends on design, fluid type, environment, and duty profile. The following parameters have proven particularly meaningful:

Particle count and size (cleanliness state): Quantifies hard solid particles (e.g., quartz dust from concrete, abrasion from steel). Elevated values stress seals, valve spools, and bearings.
Water content: Free or dissolved water promotes corrosion, additive depletion, and cavitation. In humid environments (e.g., tunnel construction) this metric is especially critical.
Viscosity: Deviations from target viscosity affect lubrication, volumetric efficiency, and damping behavior. A decrease often indicates fuel or solvent fractions; an increase indicates oxidation and ingress of fine particles.
Acid number and oxidation indicators: A mirror of fluid aging; rising values indicate thermal-oxidative stress and additive fatigue.
Wear metals: Iron, chromium, copper, tin, or aluminum point to specific component groups (pumps, piston rods, bushings, bearings).
Soot, sludge, varnish: Polymerization products and deposits impair valve dynamics and tight clearances, especially at high speeds or temperature spikes.
Air and gas content: Entrained air leads to foaming behavior, compressibility, and so-called micro-dieseling, which accelerates fluid aging.

Sampling: procedure and typical sources of error

The significance of any oil analysis stands and falls with sample quality. The goal is a representative, clean sample under defined conditions.

Proven procedure

Draw the sample with the system at operating temperature, preferably in circulation.
Select the sampling location to avoid stagnant zones and dead legs (e.g., downstream of the return-line filter is not representative).
Use clean, suitable containers; pre-rinse; avoid cross-contamination.
Label the sample clearly (unit, fluid type, operating hours, date, temperature, last maintenance).

Minimize sources of error

Avoid external ingress of dust, rain, or cleaners—especially when working with concrete demolition shears and hydraulic wedge splitters outdoors.
After a filter change or fluid change, allow a short operating period before drawing a trend sample.
Observe pressure and safety regulations; never sample from high-pressure lines without appropriate equipment.

Evaluation and diagnosis: from finding to root cause

Diagnosis is performed over time and in conjunction with operating data. Individual values are snapshots; patterns and trajectories provide the decisive clues.

Particle image and wear mechanisms

Abrasive wear: Many sharp-edged particles (quartz, metal). Cause: dust ingress, inadequate filtration, damaged seals.
Adhesive wear: Metallic rubbing particles, often larger. Cause: poor lubrication, viscosity too low, overload.
Fatigue: Flaky particles. Cause: alternating loads, pressure spikes, resonances.
Corrosion: Oxidized particles, high water content. Cause: moisture, condensate, long downtimes in humid environments.

Component relation

Pumps: Increase of iron and chromium along with viscosity change; possible cavitation or poor lubrication.
Valves: Fine particles, varnish formation; sluggish switching times with contamination.
Cylinders: Chromium and iron; dust ingress via piston-rod guides when working in concrete and rock dust.
Quick couplers and lines: Fiber and rubber constituents; indication of hose aging or assembly abrasion.

Oil analysis in the context of products and applications

With concrete demolition shears and hydraulic wedge splitters, impact loads, dust, and changing temperatures act directly on the hydraulic fluid. In concrete demolition and special demolition, fine mineral dust is generated that can enter the system in cases of inadequate sealing or improper sampling practices. In rock excavation and tunnel construction, moisture raises the water content, while low temperatures (e.g., special winter operation) increase viscosity.

Concrete demolition and special demolition: Elevated particle counts due to cement and quartz fractions; focus on fine filtration and seal condition.
Building gutting and cutting: Frequent coupling operations; pay attention to residual dirt, flushing procedures, and clean sampling.
Rock excavation and tunnel construction: Moisture load; keep an eye on water content and corrosion markers.
Natural stone extraction: Abrasive dust; regular cleanliness checks and fluid conditioning.
Special operations: Extreme temperatures or long downtimes; prioritize viscosity control and oxidation indicators.

Filtration and cleanliness management

The most effective measure against wear-relevant particles is appropriately designed filtration—matched to pumps, valves, cylinders, and the dynamics of the application.

Implementation building blocks

Full-flow and off-line filtration: Off-line improves fine cleaning in continuous operation without impairing full-flow dynamics.
Filter fineness and separation efficiency: Choose fineness to match valve and pump sensitivity; ensure high particle retention values.
Water removal: Water separators, drying elements, or vacuum dehydration depending on the findings.
Magnetic pre-separation: Reduces ferromagnetic particle load in systems with steel-intensive components.

Hydraulic fluid: selection, properties, and aging

The choice of fluid influences start behavior, wear protection, and energy efficiency. In mobile applications with changing temperatures, fluids with stable viscosity behavior and good cold-start characteristics have proven effective. Additive packages protect against oxidation, corrosion, and foam formation. Oil analysis monitors whether viscosity, additives, and aging markers remain within the target corridor.

Factors influencing fluid aging

Temperature spikes due to high load changes (e.g., during splitting or cutting).
Fine dust from concrete and rock as a catalyst for oxidation.
Air and gas content that favors micro-dieseling and stresses additives.
Water and condensate under changing outdoor conditions.

Trend monitoring and maintenance decisions

Single results are indicators; trends drive decisions. Continuous monitoring makes it possible to plan fluid changes, filter changes, and inspections as needed.

Practical sequence

Establish a baseline after commissioning or fluid change.
Take regular samples using the identical procedure (same interval, same location).
Evaluate results over time and link them to operating data (load, temperature, environment, interventions).
Define measures: refine filtration, check seals, flush, condition fluid, or inspect parts.

Common findings in practice and suitable responses

Elevated particle count with mineral character: Search for the source in dusty environments; check seals on cylinders and couplers; retrofit fine filtration; plan flushing cycles.
Water content above the target range: Initiate drying/dewatering; reduce ingress sources (condensate, washing processes); consider downtimes in humid environments.
Viscosity increase and elevated acid number: Fluid aging advanced; change the fluid and clarify the cause (temperature, air content); check cooling and deaeration.
Metallic wear signatures (Fe, Cr, Cu): Sharpen the component focus (pump, valves, piston rods); analyze pressure spikes and vibrations; improve filtration and oil-film stability.

Specifics for concrete demolition shears and hydraulic wedge splitters

These tools from Darda GmbH often work in close proximity to dust-generating material separation. Fine dust from cement and rock can enter the fluid via piston-rod guides, breathers, or coupling operations. Mechanical impact loads cause varying pressure spikes that promote particle mobilization and challenge seals.

Field recommendations

Draw samples soon after work phases with high dust load to capture peaks.
Regularly check and clean protective boots and wipers on piston rods.
Monitor filter condition; add a finer stage if trends show elevated fine particles.
With frequent coupling, keep couplers clean and standardize flushing procedures.

Measurement methods at a glance

Particle counting: Optical or porometric; provides cleanliness classes and size distribution.
Water determination: Sensor-based (online) or titrimetric; distinguishes dissolved and free water.
Viscosity: Measurement at defined temperatures; compare with the ISO VG of the fluid used.
Infrared spectroscopy: Captures oxidation, nitration, additive changes, and contaminants.
Elemental analysis: Assigns wear metals to component groups.
Membrane patch test: Qualitative view of sludge, varnish, and dark aging products.

Implementing an analysis program

An effective program is lean, reproducible, and tailored to risk.

Interval: Stage by operating hours, calendar time, or severity of use; begin with tighter intervals for critical missions.
Sampling plan: Define simple, clear instructions for sampling and documentation.
Thresholds: Set target corridors and response plans; prioritize trends, not single spikes.
Feedback: Results feed into maintenance and spare parts planning; learn from deviations.

Fluid care, flushing, and commissioning

Start clean, stay clean: good initial cleanliness reduces run-in wear and extends service life.

Pre-fill and flush: Flush components before assembly; minimize residual dirt.
Filtered filling: Use filling systems with fine filters; clean containers and funnels.
Control measurement: Early analysis after commissioning to establish the baseline and capture start-up particles.

Operating data and context information

Oil analyses gain value when linked to context data. For mobile hydraulic power units, stone splitting cylinders, concrete demolition shears, and tank cutters from Darda GmbH, load spectra, temperature profiles, coupling operations, as well as dust and moisture exposure are the most relevant influencing factors.

Key context factors

Location and environment of use (construction site, tunnel, plant hall).
Temperature profile (start, continuous operation, peaks).
Operating hours since the last fluid or filter change.
Special events (leakage, filter bypass, atypical noises).

Benefits for maintenance and operational safety

Professional oil analysis combines condition knowledge with practical measures. For the application areas mentioned for Darda GmbH, this results in increased availability, plannable service appointments, and consistent working behavior of the tools—from concrete demolition shears and hydraulic wedge splitters to combination shears and steel shears. The greatest effect is achieved through consistent trend monitoring, clean sampling, and targeted fluid care.