Top Flange Manholes Supplier in China

As a vital access solution for industrial systems, flange manholes provide a secure and repeatable entry point for inspection, cleaning, and maintenance. Primarily designed for pressure vessels, storage tanks, and large-diameter pipelines, these manholes utilize a robust, bolted blind flange cover. This assembly works in tandem with a high-performance gasket to create an impermeable seal, ensuring containment under both high pressure and vacuum conditions. Fabricated from superior-grade materials, including carbon steel, stainless steel, and specialized alloys, they deliver exceptional structural integrity and long-term resistance to corrosion, guaranteeing operational safety and reliability in critical process environments.

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What is a Flange Manholes?

A flange manhole is a high-performance access assembly engineered to provide secure, repeatable entry into pressure vessels, bioreactors, storage tanks, and sanitary processing systems. The system comprises a precisely machined cover and a matching flanged nozzle on the vessel. A specialized gasket is compressed between these two faces by a series of high-strength bolts, creating a hermetic seal capable of withstanding significant internal pressure or vacuum. Designs often incorporate features like domed covers for enhanced strength and integrated sight glasses for process monitoring. This robust, removable design is critical in industries where process containment, operational safety, and regular internal access for inspection or cleaning-in-place (CIP) are non-negotiable.

What is a Flange Manholes Used For?

Critical Process Entry: Offers A Secure, Bolted Gateway Into Pressure-Rated Vessels, Reactors, And Tanks For Direct Internal Access.
High-Integrity Containment: Creates A Hermetic, Leak-Proof Barrier Using A Gasket And Bolting System To Reliably Contain High Pressures And Vacuums.
Operational Maintenance & Inspection: Enables Essential Procedures Such As Internal Cleaning, Component Repair, Process Monitoring, And Regulatory Inspections.
Product & Personnel Protection: Prevents The Accidental Release Of Process Media And The Ingress Of External Contaminants, Ensuring Both Operator Safety And Product Purity.

Why Choose Our Flange Manholes?

We combine controlled forging processes with advanced CNC machining to produce flange manholes that consistently meet strict industry standards for strength, accuracy, and long-term operational reliability.

Premium Material Integrity

We utilize only certified, high-grade materials, from 316L stainless steel for sanitary applications to specialized alloys for corrosive environments. Full material traceability reports (MTRs) are available, guaranteeing our manholes meet your exact chemical resistance and purity specifications.

Precision-Machined Sealing Surfaces

Every manhole is engineered with CNC-machined gasket surfaces to achieve exacting tolerances and a specified surface finish (Ra). This precision ensures uniform gasket compression, creating a reliable, leak-proof barrier that performs flawlessly under pressure and vacuum cycles.

Advanced Safety & Handling Features

Operator safety is paramount. Our designs can incorporate ergonomic features such as spring-assisted lifting davits for heavy covers, captive swing bolts to prevent loss of hardware, and robust locking mechanisms, ensuring safe and controlled access during maintenance.

Application-Specific Customization

We recognize every process is unique. We offer complete customization, including specific pressure ratings, custom diameters, various port types like sight glasses or sampling valves, and integrated spray balls for Clean-in-Place (CIP) systems to ensure a perfect fit for your operational needs.

What Distinguishes a Sanitary Manhole From an Industrial One?

Surface Finish & Design: Sanitary manholes feature a highly polished, crevice-free internal surface to prevent microbial contamination and facilitate cleaning. Industrial designs prioritize structural strength and may have rougher finishes.
Materials & Gaskets: Sanitary models are built from high-purity stainless steel (like 316L) with FDA-compliant gaskets (e.g., EPDM, Silicone). Industrial manholes use a broader range of materials, including carbon steel, based on chemical compatibility.
Application & Certification: Sanitary manholes are used in food, beverage, and pharmaceutical industries, adhering to standards like 3-A. Industrial manholes are designed for chemical plants and refineries, complying with codes like ASME for pressure containment.

What Are Key Maintenance Checks For a Flange Manhole?

Gasket & Seal Integrity: Routinely inspect the gasket for hardening, cracking, or chemical swelling. A compromised gasket is the primary cause of leaks and must be replaced immediately to ensure a proper seal.
Bolting & Torque Values: Verify all bolts and nuts for signs of corrosion or thread damage. Ensure they are tightened to the correct torque specification in a star pattern to apply even pressure across the flange face.
Sealing Surface Condition: Carefully examine both the cover and neck flange sealing surfaces for scratches, dents, or residue buildup. Any surface imperfection can create a leak path and must be cleaned or repaired.

Explore Our Types of Flanges Manhole

Rotating Arm Manhole

Engineered for ergonomic access, this manhole features an integrated rotating arm that allows the cover to be swung open with minimal effort. This design enhances operator safety and is ideal for frequently accessed, side-mounted applications on tanks and vessels.

Stainless Steel Manhole

Manufactured from high-grade stainless steel, these manholes provide exceptional corrosion resistance and a hygienic surface. They are the standard choice for applications in the food, beverage, pharmaceutical, and chemical industries where product purity is paramount.

Crane Arm Manhole

Also known as a davit arm, this assembly includes a heavy-duty lifting crane to handle large, high-pressure covers safely. It is an essential solution for large-diameter tanks, ensuring that maintenance access is both safe and efficient for personnel.

Horizontal Tank Cover Manhole

Specifically designed for side-shell mounting on horizontal tanks, this manhole provides reliable access below the liquid line. Its robust construction ensures a pressure-tight seal and can be equipped with lifting aids for convenient operation during inspection.

Vertical Tank Manhole

The standard access solution for vertical storage tanks, typically mounted on the roof for atmospheric entry or on the lower shell for full internal access. These manholes are engineered to meet specific pressure and material requirements of the vessel.

Cleaning Hole

Often called a handhole, this is a compact access point designed for cleaning, flushing, or product sampling without requiring full personnel entry. Its smaller size makes it a cost-effective and convenient solution for routine maintenance tasks on equipment.

Carbon Steel Covers

A durable and cost-effective choice, our carbon steel manhole covers provide robust performance for a wide range of general industrial applications. They are ideal for water storage, oil and gas, and process systems where high strength is a key requirement.

Emergency Vent Covers

This critical safety device is designed for rapid emergency pressure relief. It remains closed during normal operation but automatically opens to vent excess internal pressure or vacuum, protecting the tank from catastrophic, pressure-related failure.

Nominal Size (DN / Inch)	Pressure Rating (bar)	Clear Opening ID (mm)	Min. Cover Thickness (mm)	No. of Bolts	Bolt Circle Dia. (mm)	Bolt Size (Metric)	Approx. Weight (kg)
DN400 / 16"	10	400	18	16	520	M20	85
DN500 / 20"	10	500	20	20	630	M22	125
DN600 / 24"	10	600	24	24	740	M24	180
DN700 / 28"	6	700	26	24	850	M27	255
DN800 / 32"	6	800	30	28	960	M30	340
DN900 / 36"	6	900	34	32	1070	M30	450

The data above is for general reference purposes. We manufacture a complete range of flanged manhole for various pressures, temperatures, and materials (Carbon Steel, Stainless Steel, etc.). All designs can be customized to meet specific codes and application requirements. For complete technical data sheets or custom configurations, please contact our engineering department.

Key Application Industries of Flanges Manholes

Chemical & Petrochemical

Essential for providing secure, pressure-rated access to chemical reactors, process vessels, and storage tanks containing volatile or corrosive substances.

Food & Beverage Processing

Used on sanitary stainless steel tanks, fermenters, and mixing vessels where hygienic, sealed access is critical for production and clean-in-place (CIP) procedures.

Water & Wastewater Treatment

Provides safe and secure entry into anaerobic digesters, clarifiers, and other large sealed vessels used in municipal and industrial water treatment facilities.

Bulk Storage & Terminals

Integral to large-scale atmospheric and low-pressure storage tanks at oil terminals and tank farms for secure access during inspection and maintenance operations.

Why Choose Our Flange Manholes?

End-to-End Engineering Control: From initial design and FEA analysis to final forging and CNC machining, we manage the entire production process to deliver a perfectly integrated and reliable manhole assembly.
Rigorous Testing & Validation: Every manhole undergoes a strict quality protocol, including hydrostatic testing, Positive Material Identification (PMI), and detailed dimensional checks to certify leak-proof performance and material integrity.
Guaranteed Code & Standards Adherence: We manufacture manholes to meet and exceed international standards, including ASME Section VIII, PED, and 3-A sanitary standards, providing full documentation for your compliance needs.
Bespoke Design & Application Matching: Our engineers collaborate with you to create fully tailored manholes, adjusting materials (e.g., Hastelloy, Duplex), dimensions, surface finishes, and adding features to perfectly suit your process environment.
Dedicated Lifecycle & Technical Support: Our commitment extends beyond delivery. We provide expert technical support, from initial specification to long-term maintenance advice, ensuring the ongoing safety and reliability of your vessel access system.

What Our Client Says

Understand from our clients what they say about doing business with us and the unique value addition we provide.

"We required a sanitary flange manhole for our new bioreactor. The 316L unit we received exceeded our expectations. The internal polish was impeccable, making our CIP validation straightforward. All material traceability and compliance documents were provided. A top-tier product for critical applications."

Elena Petrova

PLANT SAFETY MANAGER

"Our project required a custom-sized flange manhole made from Hastelloy to handle a highly corrosive medium. The engineering team provided excellent support, delivering a solution that fit perfectly. The robust build quality and precise machining give us confidence in its long-term reliability."

David Chen

LEAD MECHANICAL ENGINEER

Comprehensive Guide to Flange Manhole

What pressure ratings are available for Manholes?

Flange manhole pressure ratings are not one-size-fits-all; they are engineered for specific applications. Ratings can range from full vacuum and atmospheric service for storage tanks to high-pressure designs for ASME-coded vessels, often exceeding 25 bar (365 PSI). The final rating is a function of the manhole’s diameter, material selection, cover thickness, and the quantity and size of the bolts used.

How do Flange Manholes seal?

A flange manhole creates a seal by compressing a specialized gasket between two precision-machined flange faces—one on the vessel’s neck and the other on the cover. A series of bolts, when tightened to a specific torque in a star pattern, applies a uniform clamping force. This compression causes the gasket material to fill the microscopic imperfections on the flange surfaces, creating a robust, leak-proof barrier.

What standards apply to Flange Manholes?

The applicable standards depend heavily on the industry and location. For pressure applications, the ASME Boiler and Pressure Vessel Code (BPVC) Section VIII is the primary design standard in North America. In Europe, the Pressure Equipment Directive (PED 2014/68/EU) is required. For sanitary applications in food and pharma, designs must often comply with 3-A Sanitary Standards or EHEDG guidelines.

How often should the manhole gasket be replaced?

There is no fixed schedule; replacement depends on use. Gaskets should be inspected every time the manhole is opened. Replace the gasket if you see any signs of hardening, cracking, brittleness, discoloration, or permanent deformation, as these indicate it can no longer provide a reliable seal.

What documentation is typically supplied with a flange manhole?

A standard documentation package for a pressure-rated manhole includes general arrangement drawings, Material Test Reports (MTRs) for all pressure-retaining parts, and a pressure test certificate if a hydrostatic test was performed. For more critical applications, a full manufacturing data book with welding procedures and welder qualifications can also be provided.

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Flange Manhole - Engineered For Your Process

Our expert team is ready to assist in engineering the ideal flange manhole for your specific process. From standard ASME-rated units to fully custom designs with unique alloys or integrated features, we guarantee every solution meets the highest standards of safety and reliability. Contact us today to review your project and receive a detailed, no-obligation proposal.

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Frequently Ask Questions

Q: What is the difference between a flange manhole and a simple cover plate?

A: A manhole is a complete, engineered system where the neck becomes an integral part of the vessel. A cover plate, or blind flange, is just one component—a lid used to blank off an existing flanged opening. A manhole assembly is designed as a pressure-retaining system, whereas a simple cover plate is just a blank for a nozzle.

Q: What information do I need to provide for a quote?

A: To get an accurate quote, you should provide the required clear opening diameter, the vessel’s operating pressure and temperature, the material of construction (e.g., carbon steel, 316L stainless steel), the required design code or standard (e.g., ASME), and any special features needed like hinges, lifting davits, or sight glasses.

Q: What materials are flange manholes typically made from?

A: Common materials include Carbon Steel (e.g., SA-516-70) for industrial applications and Stainless Steel (304L, 316L) for corrosive or sanitary environments. For highly aggressive media, specialty alloys like Duplex, Hastelloy, or Inconel can be used.

Q: What is the correct way to tighten the bolts on a flange manhole?

A: Bolts should be tightened gradually in a “star” or “criss-cross” pattern using a calibrated torque wrench. This method ensures that clamping force is applied evenly across the gasket surface, which is critical for achieving a leak-proof seal and preventing flange distortion.

Q: How do I choose the correct gasket material?

A: Gasket selection depends on three main factors: chemical compatibility with the process media, the operating temperature range, and the pressure. Common materials include EPDM for general use, PTFE (Teflon) for high chemical resistance, and Viton for high temperatures and chemicals.

Q: Can flange manholes be customized?

A: Yes, absolutely. Manholes are frequently customized to meet specific application needs. Common customizations include adding hinges for easier opening, spring-assists or lifting davits for heavy covers, integrated sight glasses for process viewing, and sampling ports.

Q: What design standards apply to flange manholes?

A: For pressure applications in North America, they are typically designed according to the ASME Boiler and Pressure Vessel Code (BPVC) Section VIII. In Europe, the Pressure Equipment Directive (PED) is the governing standard. For food and pharmaceutical use, designs may need to comply with 3-A or EHEDG sanitary standards.

Q: What is the difference between an industrial and a sanitary flange manhole?

A: An industrial manhole prioritizes strength and pressure containment. A sanitary manhole, used in food or pharma, also requires a highly polished internal surface (low Ra value) and a crevice-free design to prevent bacterial growth and facilitate easy cleaning.

Top Flange Manholes Supplier in China

What is a Flange Manholes?

What is a Flange Manholes Used For?

Why Choose Our Flange Manholes?

Premium Material Integrity

Precision-Machined Sealing Surfaces

Advanced Safety & Handling Features

Application-Specific Customization

What Distinguishes a Sanitary Manhole From an Industrial One?

What Are Key Maintenance Checks For a Flange Manhole?

Explore Our Types of Flanges Manhole

Rotating Arm Manhole

Stainless Steel Manhole

Crane Arm Manhole

Horizontal Tank Cover Manhole

Vertical Tank Manhole

Cleaning Hole

Carbon Steel Covers

Emergency Vent Covers

Flange Manhole Specifications Chart

Key Application Industries of Flanges Manholes

Chemical & Petrochemical

Food & Beverage Processing

Water & Wastewater Treatment

Bulk Storage & Terminals

Why Choose Our Flange Manholes?

What Our Client Says

Comprehensive Guide to Flange Manhole

What pressure ratings are available for Manholes?

How do Flange Manholes seal?

What standards apply to Flange Manholes?

How often should the manhole gasket be replaced?

What documentation is typically supplied with a flange manhole?

Latest Blog Posts

Flange Manhole - Engineered For Your Process

Frequently Ask Questions

Q: What is the difference between a flange manhole and a simple cover plate?

Q: What information do I need to provide for a quote?

Q: What materials are flange manholes typically made from?

Q: What is the correct way to tighten the bolts on a flange manhole?

Q: How do I choose the correct gasket material?

Q: Can flange manholes be customized?

Q: What design standards apply to flange manholes?

Q: What is the difference between an industrial and a sanitary flange manhole?

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