Ductile Iron Blank Flanges: Types, Applications, Benefits & Selection Guide

• TruForm

You must have ordered Ductile iron DI blank flanges or at least heard about it if you work in the piping, water infrastructure or industrial fabrication industry. It’s straightforward: one solid, round disc without a bore. However, its simplicity is what makes it one of the most useful and prolific parts in any pipeline. It plugs the end of a pipe, cements the end of a branch line or allows engineers to pressure test a system before putting it into operation.

Here, we’re going over all the details on ductile iron DI blank flanges and what they can do, but without a lot of jargon.In this guide, we’re going to get down to the details of what ductile iron blank flanges are and what they can do, without the jargon overload.

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What Is a Ductile Iron Blank Flange?

A ductile iron DI blank flange (also known as a blind flange) is a solid, unbored flange plate that is bolted to the flanged end of a pipeline to completely close the pipeline with no opening, no flow. Its ductile iron structure provides it with the strength of resisting high internal pressure and rough site handling without cracking, whereas plain grey cast iron is not.

Most Ductile Iron DI Blank Flange manufacturers make these flanges to standards like EN 1092-2, ISO 7005-2, and EN 545 that apply to dimensions, pressure ratings and drilling patterns, which ensures that it fits equally well on all suppliers.

Types of Ductile Iron Blank Flanges

Different types of ductile iron blank flanges are mentioned below:

By pressure rating (PN class): PN10, PN16 and PN25 are the most commonly used ratings which indicate the bar pressure that the flange can endure. PN40 may be required for higher pressure industrial lines. 

By drilling pattern: Blank flanges are available as either predrilled (holes drilled to match the holes of the mating flange) or fully solid/undrilled (installed flanges are drilled to the exact field requirements by the installer). 

By size: Standard nominal diameters are normally from DN50 to DN1200, from small distribution pipes to large trunk mains.

By coating/finish: Flanges are furnished in epoxy, zinc or bitumen coating, depending on the environment, for corrosion resistance; particularly crucial for underground or coastal applications.

Applications of Ductile Iron DI Blank Flanges

Various applications of ductile iron blank flange have been discussed here. 

• Water and wastewater networks – sealing dead-end pipelines and isolating sections during maintenance. 
• Sewage and drainage systems – closing off manholes/chambers or unused sewage/drainage outlets. 
• Firefighting and hydrant lines – blanking off unused outlets of fire mains when not in use. 
• Industrial process piping – segregating plant components for planned maintenance or further development. 
• Pressure testing – temporarily closing down a section to allow the engineers to test for leaks prior to commissioning.

In the event that a pipeline is being sealed, isolated, tested or future proofed, it’s likely a blank flange was performing that task in the background. 

Benefits of Choosing Ductile Iron DI Blank Flanges

Ductile iron blank flanges have the following benefits:

• High strength-to-weight ratio – can resist high pressure and mechanical force without adding too much weight. 
• Corrosion resistance – will not rust or corrode even in underground or marine applications with proper coating. 
• Long service life – extended lifespan of decades with minimal maintenance, thus reducing lifecycle cost. 
• Design flexibility – multiple pressure classes and sizes to fit virtually any pipeline spec. 
• Cost-effective – usually less expensive than stainless steel of equal pressure and durability.

Apart from the benefits of the product, it is extremely important to choose an appropriate ductile iron blank flange supplier.

Selection Guide for Ductile Iron Blank Flange

Before ordering the ductile iron DI blank flange, here are some things to keep in mind: 

1. Match pressure rating to your system. Check operating pressure of your pipeline and the test pressure (which is typically higher) and then choose the appropriate PN value, which is 10, 16, 25 or 40. An under-specification is a safety hazard, while over-specification only adds to wasted expense. 
2. Confirm the standard. There are three main standards that are recognised worldwide: EN 545, EN 1092-2 and ISO 2531 but make sure you know exactly what your project, client and local regulation require prior to ordering. 
3. Check the drilling pattern against the mating flange. Bolt hole count and PCD (pitch circle diameter) should be precisely matched – there should be no variation or it will cause delays and rework at site when the flange is delivered. 
4. Consider the installation environment. For sites that are underground or marine, or have been exposed to chemicals, a simple mill finish is not enough; these require a proper protection: epoxy, zinc or bitumen coating. 
5. Verify certification and testing. Request material test certificates, pressure test reports and ISO 9001 quality documentation, especially for municipal, industrial or export orders where compliance is a condition of the order. 
6. Factor in lead time and logistics. Large diameter or custom size flanges are more time consuming to cast and finish so please obtain production and shipping dates in advance for projects where the date is important. 
7. Work with an experienced supplier. There is a considerable difference in dimensional accuracy and casting quality between manufacturers which is where it pays to differentiate through a trusted, certified name.

Analysis of Ductile Iron DI Blank Flange exporters or Ductile Iron Blank Flange supplier should be done properly before choosing or ordering any product.

Why Choose Truform Techno Products

Buyers select Truform Techno Products as Ductile Iron DI Blank Flange supplier for the following reasons: 

• ISO 9001:2015 certified manufacturing, with every flange produced to EN 545, EN 1092-2/ISO 7005-2 and ISO 2531 standards.
• A team of professional metallurgists and 20 + years of industry experience.
• Production capacity of 10,000 MTPA with bulk municipal orders and customised specifications.
• Wholesale ductile iron blank flange exporter and supplier to 40+ countries around the world.

Frequently Asked Questions

What are some applications of ductile iron? 

Because of ductile iron’s strength, ductility and resistance to corrosion, ductile iron is used extensively beyond flanges, including pipes and sewer pipe, pipe fittings, manhole covers, valves, fire hydrants, pumps and general engineering castings. 

What are the different types of flanges and what are their applications? 

Flanges are commonly used as weld neck flanges (high pressure pipelines), slip on flanges (low pressure systems), blind/blank flanges (sealing pipe ends), socket weld flanges (small diameter pipes), lap joint flanges (systems which have to be dismantled often), and threaded flanges (where there is no welding). 

What is FF & RF in flanges? 

FF (Flat Face) and RF (Raised Face) are used to describe gasket contact area. The FF flanges feature a flush flat face (typical of cast iron fittings) whereas the RF flanges have a raised ring around the bore which provides a more secure seal, normally for steel piping.

What is the ASME standard for flanges? 

Flanges range in size from NPS½ up to NPS60, with ASME B16.5 for NPS½ to NPS24 and ASME B16.47 for NPS60 and above. These are the main US standards, other than widely used EN and ISO standards, particularly in Europe and Asia. 

What is the difference between blind flanges and blank flanges? 

Blind flange and blank flange are used interchangeably to refer to a flange without a bore that plugs a pipe end. In ASME standards, the term “blind flange” refers to the same flange as “blank flange,” which is widely used in the trade sector, particularly within the EN/ISO market.

Final Thoughts

While perhaps not the most eye-catching part of a pipeline, ductile iron DI blank flanges are crucial, sealing, isolating and protecting pipeline systems around the world in water, industrial and infrastructure projects. When selected properly, the right pipeline type and pressure rating can keep your pipeline safe, up to code, and leak-free for years.

Ductile iron DI blank flange may not be the attractive or eye-catching part of pipeline system but it is important for sealing and isolating the pipeline systems. Moreover, the flange protects the pipeline system in water, industrial and infrastructure projects. Selection of a right ductile iron DI blank flange supplier plays a crucial role in the quality of products delivered and helps to form robust water infrastructure. Selecting the right pipeline and pressure rating can keep the pipeline and entire infrastructure safe and leak-free for years.

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