HNBR Sealing Gasket For Pressurized Manholes

Linde Polymer Tec Co.,Ltd. is one of the most experienced manufacturers and suppliers of hnbr sealing gasket for pressurized manholes in China, also supports customized service. Please feel free to buy high quality hnbr sealing gasket for pressurized manholes for sale here from our factory.

HNBR sealing gasket for pressurized manholes

High temperature and high pressure resistance·Long-term leakage prevention

In high-risk industries such as petroleum, chemical, and pharmaceutical industries, pressurized manholes are the "life channels" for equipment maintenance, and the reliability of the gasket directly determines the safety and cost of operation. HNBR (hydrogenated nitrile rubber) pressurized manhole gaskets are developed for high temperature, high pressure, and highly corrosive working conditions .

Key words: HNBR gasket for pressurized manhole, pressurized equipment seal, HNBR rubber gasket

 "three highs" performance beyond traditional NBR**

HNBR (hydrogenated nitrile rubber) is an upgraded version of nitrile rubber (NBR). Through the hydrogenation process, its temperature resistance, media resistance and aging resistance are greatly improved:

✅ High temperature resistance: -40℃~+180℃ (up to 200℃ for a short time), far exceeding the 120℃ limit of NBR

✅ High pressure resistance: static seal ≤40MPa, dynamic seal ≤10MPa, adapt to pressure operation requirements

✅ Strong corrosion resistance: oil resistant, acid and alkali resistant, solvent resistant (such as aromatic hydrocarbons, ketones), life span is 3~5 times that of NBR

✅ Anti-fatigue: Compression permanent deformation rate <15% (70℃×22h), long-term elastic sealing

Scenario-based pain point solutions**:

▸ Traditional NBR pads harden and crack in high temperature oil medium after 3 months , while HNBR pads have a lifespan of more than 2 years

▸ Frequent disassembly during pressure plugging can lead to seal failure . Pre-compression design + anti-creep properties make it stable after repeated use.

▸ Chemical media corrosion causes leakage risk , passed ISO 16923 media resistance test, suitable for 95% of industrial scenarios

1. Multi-layer composite technology: HNBR main body + fiber reinforcement layer + metal skeleton (optional), anti-deformation ability increased by 40%

2. Precise tolerance control: ±0.1mm thickness error, adapted to ASME/GB/T 2501 manhole standard (covering full sizes from DN150 to DN600)

3. Food grade optional: FDA certified, suitable for pressurized manholes in pharmaceutical and dairy equipment

4. Visual identification: molded LOGO + material/pressure level coding for easy traceability and maintenance

**Technical parameters** (partial): Refers .Different TDS based on Different Hardness needs

Application scenarios: covering 90% of industrial pressure equipment

Petrochemical: reactor manholes, tower inspection ports, pipeline blind plates (such as PTA units, ethylene cracking furnaces)

Energy and power: coal-fired boiler manholes, gas tank observation ports (suitable for complex environments of pulverized coal + steam)

Pharmaceuticals and food: CIP/SIP online cleaning manhole (FDA certified, resistant to 135°C high temperature steam sterilization)

Environmental protection equipment: hazardous waste treatment tanks, biogas reactors (resistant to hydrogen sulfide + acid and alkali dual corrosion)

Three core advantages of the source factory

40 years of experience in seal R&D: ISO 9001/14001 certified, in-depth cooperation with Sinopec, BASF and other companies

Customized service: support processing according to drawings, special medium testing (such as HF acid, liquid ammonia), 48-hour rapid proofing

Q1: How to choose HNBR and fluororubber (FKM) sealing gaskets in pressurized manholes?

A1:

HNBR advantages: resistant to high temperature of 180℃ + high pressure of 40MPa, compression set <15% (20% for FKM), cost only 60% of FKM, suitable for pressurized scenes with oil/water as the main medium (such as reactor in refinery).

FKM advantages: Resistant to ultra-high temperatures of 250°C and strong oxidants (such as concentrated sulfuric acid), but with weak dynamic sealing performance (pressure ≤ 8MPa), suitable for static and highly corrosive scenarios (such as chemical storage tanks).

Data support: A comparative test of an ethylene plant showed that the life of HNBR in 150°C hot oil is 1.8 times longer than that of FKM (Source: Sealing Technology Journal 2024).

Keywords: HNBR vs FKM, selection of pressurized manhole sealing materials

Q2: How does the compression rate of the HNBR gasket of the pressurized manhole affect the sealing performance? **

A2:

Optimum compression rate: 15%~20% (according to ASME PCC-2 standard). Too low will lead to insufficient springback, and too high will easily lead to creep failure.

Measuring method: Use a micrometer to measure the thickness before and after compression. For example, a 5mm thick pad is qualified when compressed to 4.0~4.25mm.

Case: A pharmaceutical factory had leakage during steam sterilization due to a compression rate of only 10% (used by old NBR pads). After adjustment, the HNBR pads had no problems for 3 years.

Technical details: Provide "Compression Rate Calculation Formula" for download (including Excel template, SEO long-tail keyword: compression rate calculation of pressurized sealing gasket).

Q3: What is the difference between API 6A certified HNBR pads and ordinary pads? **

A3:

Certification requirements: Pass API 6A Annex F (-46℃~+121℃ temperature cycle +70MPa pressure test), suitable for wellhead equipment and high-pressure valves.

Measured data: The leakage rate of a certain API 6A gasket is less than 0.01cc/min (0.5cc/min for ordinary gaskets) after 3000 cycles at 150°C and 35MPa.

Purchase suggestion: API certified models are a must for the oil and gas industry, while ISO 16923 (chemical) or FDA (food) certifications are available for other industries.

Q4: How to prevent the HNBR pad from being washed away by the medium when replacing it under pressure? **

A4:

Three-step operation method:

① Reduce the pressure to ≤1.6MPa and use a special clamp to fix the manhole cover;

② Loosen the bolts diagonally (1/4 turn each time) to release residual stress;

③ Insert a wedge-shaped tool to separate the flange to avoid damaging the sealing surface by prying directly.

Q5: What does the "15% compression set rate" of HNBR pad mean? **

A5:

Definition: After compression at 70℃×22h, the thickness recovery rate is ≥85% (the smaller the value, the better).

Comparison: NBR pad deformation rate > 30% (loses elasticity after hardening), silicone pad > 25% (not oil resistant).

Lifespan impact: For every 5% increase in deformation rate, the lifespan is shortened by 40%. Example: A thermal power plant uses HNBR pads with a deformation rate of 12%, and the lifespan is 28 months (the industry average is 18 months).

Q6: What is the minimum order quantity for customized special-shaped HNBR pressure manhole pads?

A6: According to the size of the provided drawing and the materials used for the machine.

Q7: How long can HNBR pads be used in liquid ammonia media? **

A7:

Measured data: passed ISO 1817 liquid ammonia immersion test (70℃×168h), volume change rate ≤3%, hardness change ±5 Shore A.

Life prediction: Continuous contact with liquid ammonia (-33℃~+100℃), design life is 24~36 months (depending on the frequency of pressure fluctuations).

Risk warning: It is recommended to perform preventive replacement every 18 months. The "Liquid Ammonia Equipment Seal Maintenance Cycle Schedule" is provided.

Q8: What is the torque tightening standard for HNBR pads for pressurized manholes? **

A8:

Reference standard: According to the ASME B16.5 flange torque table, the torque of HNBR gaskets needs to be 15% higher than that of NBR gaskets (due to the high hardness of the material).

Example: DN200 PN16 flange, recommended torque 450 N·m (tighten diagonally three times, increasing by 30% each time).

Tool recommendation: Use a digital torque wrench to avoid over-tightening and causing the gasket to squeeze out (recommended wrench model: CDI 300N·m).

Q9: Can HNBR pads be used in pressurized manholes in vacuum systems? **

A9:

Applicable conditions: vacuum degree ≤-0.1MPa (absolute pressure), temperature ≤150℃, medium free of particulate impurities.

Special design: Our vacuum-specific HNBR pads are equipped with a **metal support ring** (1.5mm thick) to prevent collapse under negative pressure, and pass ISO 28769 vacuum leakage test (leakage rate <1×10⁻⁶ Pa·m³/s).

Keywords: Vacuum pressure manhole gasket, HNBR metal support ring

Q10: How to verify the authenticity of HNBR pads through third-party test reports?

A10:

Must check indicators:

① Infrared spectrum (IR): HNBR characteristic peaks are at 2920cm⁻¹ (CH₂), 1630cm⁻¹ (C=C residue <1%);

② Mooney viscosity (ML1+4 100℃): 45~65 (too high is reclaimed rubber);

③ Density: 1.03~1.08g/cm³ (NBR≈1.2, FKM≈1.8).

Inspection suggestions: SGS, TÜV and other institutions are recommended.

Hot Tags: hnbr sealing gasket for pressurized manholes, China hnbr sealing gasket for pressurized manholes manufacturers, suppliers, factory, Round Rubber Gasket, Viton Rubber Gasket, Vacuum Cleaner Friction Disc Motor Gasket, Automatic Transmission Oil Pan Gasket, Sprayers Seal Gasket, Car Lift Rubber Pads