3115182200 Accumulator Rubber Diaphragm

What Is the 3115182200 Accumulator Diaphragm?

The 3115182200 accumulator rubber diaphragm is a critical hydraulic component installed inside the accumulator housing of Atlas Copco and Epiroc COP series rock drills. This flexible membrane serves as the physical barrier between pressurized nitrogen gas on one side and hydraulic oil on the other, creating a sealed energy storage chamber that is fundamental to the percussion mechanism of every modern hydraulic drifter used in underground mining and tunneling.

Within the accumulator assembly, the diaphragm flexes thousands of times per minute as the rock drill operates. Each percussion cycle sends a pressure wave through the hydraulic circuit, and the accumulator diaphragm absorbs and releases energy to smooth these pulsations. Without a properly functioning diaphragm, the raw pressure spikes from the percussion piston would transmit directly through the hydraulic system, causing accelerated wear on valves, seals, hoses, and the drill steel coupling. The diaphragm essentially acts as a hydraulic shock absorber that protects every downstream component in the circuit.

Atlas Copco originally catalogued this part under number 3115182200, which has since been revised to 3115182201. Both part numbers reference the same physical component with identical dimensions and material specifications. The revision typically reflects minor manufacturing process updates or material batch certification changes. Our aftermarket replacement diaphragms are manufactured to match the latest revision specifications while maintaining full backward compatibility with the original part number. Whether your parts catalog lists 3115182200 or 3115182201, the diaphragm we supply is the correct replacement.

How Rock Drill Accumulators Work

Hydraulic rock drills like the Atlas Copco COP 1838 series generate percussion energy by rapidly cycling a heavy piston back and forth inside the drifter body. A high-pressure hydraulic pump delivers oil at pressures up to 230 bar, and a control valve alternates this flow to drive the piston forward into the drill steel and then retract it for the next blow. This percussion cycle occurs at frequencies between 40 and 70 Hz depending on the rock drill model and operating settings.

Each time the percussion piston reverses direction, it creates a sharp pressure transient in the hydraulic circuit. These transients — essentially hydraulic hammer effects — propagate backward through the system at the speed of sound in oil (approximately 1,400 m/s). Without proper damping, these pressure spikes would rapidly destroy seals, fatigue hose assemblies, and create cavitation in the hydraulic pump. This is where the accumulator and its diaphragm become essential.

The accumulator is a sealed pressure vessel divided into two chambers by the rubber diaphragm. The gas side is pre-charged with dry nitrogen to a specific pressure (typically 50-70% of the system operating pressure). When a pressure spike arrives from the percussion piston, the hydraulic oil compresses the nitrogen through the flexible diaphragm, storing the excess energy momentarily. As the pressure drops during the piston's return stroke, the compressed nitrogen pushes the oil back into the circuit, maintaining flow continuity and eliminating harmful pressure valleys.

This pressure-smoothing function has two critical benefits. First, it dramatically extends the service life of every hydraulic component in the rock drill system — from the high-pressure hoses running down the drill feed to the sensitive control valves in the drifter body. Second, it improves drilling efficiency by maintaining consistent percussion energy delivery. A rock drill with a properly functioning accumulator diaphragm delivers more uniform blow energy, resulting in faster penetration rates and straighter holes.

Technical Specifications

OEM Part Number	3115182200
Revised Part Number	3115182201 (supersedes original)
Short Reference	115182200
Component Type	Accumulator Rubber Diaphragm / Membrane
OEM Brand	Atlas Copco / Epiroc
Material Options	NBR (Nitrile Butadiene Rubber) or Polyurethane
Maximum Operating Pressure	230 bar (3,336 psi)
Temperature Range (NBR)	-30°C to +120°C (-22°F to +248°F)
Temperature Range (PU)	-20°C to +80°C (-4°F to +176°F)
Fluid Compatibility	Mineral hydraulic oil, synthetic esters
Manufacturer	Babacan Rubber — ISO 9001:2015
Quality Testing	100% pressure tested before shipment
Recommended Replacement	Every 1,000–2,000 operating hours

Compatible COP Rock Drill Models

The 3115182200 accumulator diaphragm is specified for use across the full range of Atlas Copco and Epiroc COP series hydraulic drifters. These rock drills are mounted on various carrier rigs for face drilling in tunneling and development headings, as well as long-hole production drilling in underground mines.

COP 1238K

The COP 1238K is a compact hydraulic drifter designed for light to medium-duty face drilling applications. It is commonly mounted on smaller Boomer rigs used in narrow-vein mining and secondary development headings. The accumulator in this drill operates at moderate pressures and the diaphragm experiences lower cycle counts compared to the larger COP 1838 variants, but regular replacement remains critical to maintain drilling accuracy and component longevity.

COP 1638HD and COP 1638HD+

The COP 1638 family represents Atlas Copco's medium-duty rock drill platform. The HD designation indicates heavy-duty internals designed for harder rock formations, while the HD+ adds further enhancements to percussion power and service intervals. Both variants rely on the 3115182200 diaphragm for accumulator function. These drills are typically found on Boomer M-series rigs in mid-scale tunneling projects and mine development.

COP 1838 Series (HD, HD+, HE+, ME, MUX, MUX+)

The COP 1838 is the workhorse of Atlas Copco's underground drilling fleet and the most widely deployed drifter in global mining operations. Multiple variants exist to suit different drilling requirements:

• COP 1838+ — Standard high-performance face drilling drifter
• COP 1838HD — Heavy-duty variant for abrasive hard-rock formations
• COP 1838HD+ — Enhanced heavy-duty with optimized percussion frequency
• COP 1838HE+ — High-efficiency model with improved energy transfer ratio
• COP 1838ME — Medium-energy variant balancing power and component life
• COP 1838MUX — Multi-purpose drifter for varied rock conditions
• COP 1838MUX+ — Enhanced MUX with extended service intervals

All COP 1838 variants use the same accumulator housing and therefore require the identical 3115182200 diaphragm. For detailed COP 1838 parts information, see our COP 1838 spare parts page.

COP 1840+

The COP 1840+ represents the evolution of the COP 1838 platform with increased percussion power for demanding underground applications. It delivers higher blow energy while maintaining the same accumulator configuration, making the 3115182200 diaphragm a direct-fit component.

COP 2238HD

The COP 2238HD is a production-class rock drill designed primarily for long-hole drilling applications on Simba rigs. With the highest percussion energy output in the COP range, this drifter places maximum demand on the accumulator system. The diaphragm in COP 2238HD applications may require more frequent replacement due to the higher cycle pressures and continuous operation typical of production drilling.

Diaphragm vs Bladder Accumulators

Hydraulic accumulators used in rock drills come in two primary configurations: diaphragm type and bladder type. Understanding the difference helps maintenance personnel select the correct replacement parts and appreciate why the accumulator design matters for drilling performance.

Feature	Diaphragm Accumulator	Bladder Accumulator
Separator Element	Flat or domed rubber membrane	Enclosed rubber balloon/bag
Gas Volume Ratio	Lower (compact design)	Higher (larger gas volume)
Response Speed	✓ Extremely fast — ideal for percussion	Fast but slightly slower
Pressure Rating	✓ Excellent — up to 350 bar	Good — typically up to 350 bar
Cycle Life	✓ Very high for thin membranes	High but bladder flex fatigue possible
Maintenance	✓ Simple membrane replacement	Full bladder replacement required
Size / Weight	✓ Compact and lightweight	Larger for equivalent capacity
Typical Application	Rock drills, compact cylinders	Larger hydraulic systems, presses

Atlas Copco selected the diaphragm-type accumulator for COP series rock drills because the compact design fits within the drifter body and the membrane provides the ultra-fast response times needed to smooth percussion pulsations at frequencies above 50 Hz. The 3115182200 diaphragm is specifically engineered for this high-frequency, high-pressure cycling environment.

Material Selection: NBR vs Polyurethane

The choice between NBR (nitrile butadiene rubber) and polyurethane for accumulator diaphragms depends on the specific operating conditions of your mining operation. Both materials are available for the 3115182200 diaphragm, and each offers distinct advantages.

NBR (Nitrile Butadiene Rubber)

NBR is the traditional material choice for hydraulic accumulator diaphragms and is the standard specification for the 3115182200 component. Its key properties include:

• Excellent resistance to mineral-based hydraulic oils
• Wide operating temperature range: -30°C to +120°C
• Good flex fatigue resistance at high cycle frequencies
• Proven track record in mining hydraulic systems worldwide
• Lower material cost compared to polyurethane

NBR is the recommended choice for most standard COP rock drill applications where the hydraulic oil temperature stays below 100°C and the drill operates under normal production conditions.

Polyurethane (PU)

Polyurethane diaphragms offer specific advantages in demanding applications:

• Superior abrasion resistance — up to 5x greater than NBR
• Higher tear strength and resistance to extrusion under pressure
• Better performance in contaminated hydraulic systems
• Extended service life in high-cycle applications
• Operating temperature range: -20°C to +80°C (narrower than NBR)

Polyurethane is recommended for operations where hydraulic oil cleanliness is difficult to maintain, or where the rock drill operates at maximum percussion settings for extended periods. The trade-off is a narrower temperature range and higher unit cost.

For an in-depth comparison of these materials in mining contexts, read our article on NBR vs polyurethane diaphragms for Atlas Copco rock drills.

Installation Procedure

Replacing the accumulator diaphragm in a COP series rock drill requires careful attention to cleanliness and assembly torque specifications. The following procedure applies to all compatible COP models listed above. Always consult the specific service manual for your drill model for detailed torque values and special tool requirements.

Step-by-Step Replacement

1. Depressurize the system. Shut down the rock drill and carrier rig. Release all hydraulic pressure by cycling the control valves with the engine off. Use the accumulator charging kit to safely bleed the nitrogen pre-charge to zero pressure.
2. Remove the accumulator assembly. Disconnect the hydraulic connections to the accumulator housing. On most COP models, the accumulator is accessible from the top or side of the drifter body. Remove the mounting bolts and carefully extract the assembly.
3. Disassemble the accumulator. Remove the accumulator cap bolts following the manufacturer's recommended loosening sequence (typically a star pattern). Separate the two halves of the accumulator housing to expose the diaphragm.
4. Remove the old diaphragm. Carefully peel the worn diaphragm from its seating surfaces. Inspect the housing bore for scoring, corrosion, or debris. Any damage to the seating surface will prevent the new diaphragm from sealing properly.
5. Clean all components. Thoroughly clean the housing halves, seating surfaces, and gas-side cavity with clean hydraulic oil. Remove any rubber fragments, dirt, or corrosion products. Dry the nitrogen side completely.
6. Install the new 3115182200 diaphragm. Position the new diaphragm on the seating surface, ensuring it sits flat and centered with no wrinkles, folds, or pinched areas. The diaphragm must cover the full sealing area uniformly.
7. Reassemble the accumulator. Align the housing halves and install the cap bolts hand-tight. Torque the bolts in a star pattern to the specified value in three equal increments to ensure even clamping force on the diaphragm.
8. Pre-charge with nitrogen. Using a proper accumulator charging kit, slowly charge the gas side with dry nitrogen to the specified pre-charge pressure (refer to the service manual for your specific COP model — typically 90-120 bar depending on the drill variant).
9. Reinstall and test. Mount the accumulator back on the rock drill, reconnect hydraulic lines, and start the system. Check for leaks at all connections. Monitor the accumulator pressure gauge during a short test drilling cycle to confirm proper function.

Maintenance and Service Intervals

Proper maintenance of the accumulator diaphragm directly impacts rock drill performance, component longevity, and drilling productivity. Atlas Copco recommends the following maintenance schedule for accumulator systems in COP series drifters:

Interval	Action
Every shift (8-12 hours)	Check accumulator pre-charge pressure via gauge. Pressure drop greater than 10% indicates a diaphragm leak.
Every 250 hours	Measure pre-charge pressure with calibrated gauge. Compare to baseline. Inspect for oil weeping at accumulator housing joints.
Every 500 hours	Full accumulator inspection. Depressurize system and visually inspect the diaphragm for cracks, bulging, hardening, or permanent deformation. Check seating surfaces.
1,000–2,000 hours	Preventive diaphragm replacement. Replace the 3115182200 diaphragm regardless of visual condition. Service interval depends on drilling intensity and operating conditions.

For more information about recognizing diaphragm failure, see our guide on 5 signs your rock drill diaphragm needs replacing.

Key Features

Frequently Asked Questions