Essential Guide to Furukawa Hydraulic Breaker Diaphragms & Membranes

Hydraulic breaker diaphragms (also referred to as accumulator membranes) are critical wear components in Furukawa rock hammers. Installed inside the hydraulic accumulator, the diaphragm separates nitrogen gas ($N_2$) from high-pressure hydraulic oil. Its primary function is to store energy during the piston return stroke and release it instantly to maximize impact power while dampening hydraulic shock waves to protect the excavator pump.

When a diaphragm tears or degrades, nitrogen gas escapes, causing reduced blow energy, erratic hammering, and intense hydraulic hose vibration. Replacing worn membranes with high-grade, oil-resistant rubber diaphragms restores peak performance and guards against costly accumulator cylinder damage.

Below is a complete size specification chart and cross-reference guide for Furukawa F-Series and HB-Series Hydraulic Breaker Diaphragms.

Furukawa Diaphragm Size & Specification Reference Chart

Item No.	Brand	Model / Part Name	Outer Diameter & Specification Size (mm)
1	FURUKAWA	F-1 Diaphragm	82 × 19
2	FURUKAWA	F-2 Diaphragm	100 × 17
3	FURUKAWA	F-3 Diaphragm	109 × 16
4	FURUKAWA	F-4 Diaphragm	120 × 24
5	FURUKAWA	F-5 Diaphragm	130 × 22
6	FURUKAWA	F-6 Diaphragm	109 × 16
7	FURUKAWA	F-9 Diaphragm	130 × 22
8	FURUKAWA	F-12 Diaphragm	140 × 40
9	FURUKAWA	F-15 Diaphragm	149.3 × 43.2
10	FURUKAWA	F-19 Diaphragm	149.3 × 43.2
11	FURUKAWA	F-22 Diaphragm	169 × 36.6
12	FURUKAWA	F-27 Diaphragm	169 × 36.6
13	FURUKAWA	F-35 Diaphragm	190 × 40.3
14	FURUKAWA	F-45 Diaphragm	209 × 52
15	FURUKAWA	F-70 Diaphragm	237 × 41
16	FURUKAWA	F-300 Diaphragm	109 × 16
17	FURUKAWA	HB-1G Diaphragm	65 × 10
18	FURUKAWA	HB-2G Diaphragm	82 × 19
19	FURUKAWA	HB-3G Diaphragm	100 × 17
20	FURUKAWA	HB-5G Diaphragm	100 × 17
21	FURUKAWA	HB-8G Diaphragm	120 × 24
22	FURUKAWA	HB-10G Diaphragm	140 × 40
23	FURUKAWA	HB-15G Diaphragm	149.3 × 43.2
24	FURUKAWA	HB-18G Diaphragm	149.3 × 43.2
25	FURUKAWA	HB-20G Diaphragm	169 × 36.6
26	FURUKAWA	HB-30G Diaphragm	190 × 40.3
27	FURUKAWA	HB-40G Diaphragm	209 × 52
28	FURUKAWA	HB-50G Diaphragm	237 × 41
29	FURUKAWA	HB-200 Diaphragm	135 × 26
30	FURUKAWA	HB-400 Diaphragm	165 × 20
31	FURUKAWA	HB-700 Diaphragm	165 × 20

Material & Performance Requirements

Because hydraulic breaker accumulators undergo continuous rapid flexing under high pressures, premium replacement membranes feature:

• High-Flex Hydrogenated Nitrile Rubber (HNBR) / NBR Rubber: Formulated for superior tear strength, fatigue resistance, and gas impermeability to prevent nitrogen migration.
• Extreme Heat & Fluid Compatibility: Resistant to high hydraulic oil temperatures (up to 120°C / 248°F) and harsh anti-wear hydraulic oil additives.
• Precise Molding Tolerances: Engineered to match OEM shell dimensions exactly, preventing pinch damage or seal degradation during installation.

Signs Your Breaker Diaphragm Needs Replacement

1. Loss of Impact Power: The breaker loses strike force or operates sluggishly despite full hydraulic flow from the base machine.
2. Excessive Hose Violent Vibration: Severe shaking in the supply and return hydraulic lines indicates the accumulator is no longer absorbing hydraulic pulsation.
3. Nitrogen Gas Loss: The accumulator repeatedly loses $N_2$ charge pressure over short operating intervals.
4. Oil in Gas Chamber: Hydraulic oil drips from the nitrogen charging valve during pressure checks.

Best Practices for Replacement

• Depressurize Completely: Always release all nitrogen gas pressure from the accumulator gas valve before disassembling the accumulator shell.
• Clean the Chamber Shell: Inspect the interior accumulator cavity for rust, metal shavings, or scale before placing the new diaphragm in position.
• Use Correct $N_2$ Gas Charge: Re-fill the accumulator exclusively with pure Nitrogen gas ($N_2$) to the factory-specified pressure rating. Never use oxygen, shop air, or flammable gases.