As a wholesaler, you are critical to the success of the PVF industry.  Complimenting your offering with pipe flanges means you can:

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• Improve supply chain efficiency and customer service with various types & materials
• Meet diverse customer needs for both low pressure & high pressure piping systems
• Support your customization needs for specific project requirements 
• Provide consistent & compliant product to ensure system compatibility and reliability

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What is a Pipe Flange?

Pipe flanges connect piping and the components of a piping system such as valves, fittings, pipe with each other and specialty items using bolted connections and gaskets.  They can be installed in several fashions including:  welding, lapping or screwing.

There are several benefits to using a pipe flange including:  it provides a secure connection between pipes, valves & other equipment; it allows for quick disassembly by providing installation or modification access points; and it increases the strength at the joint.

The application and type of flange determine the way in which the connection is made.  Always consider the fluid being conveyed through a pipeline, the operating temperature, flange type, size, pressure class/rating and other specifications prior to installation.  This ensures safety during installation and operation of the piping system.

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Components of a Pipe Flange

A pipe flange has several components:  a unique bolt pattern, connection type (e.g. socket weld, threaded, slip on, etc.) and face.  They have varying bolt patterns that are based on the type of flange and its diameter.It is important to note that flanges do require a gasket to make the seal except for ring-type joint faces.

Pipe flanges can be manufactured from a casting (cast from a mold) or forging (using energy to change the shape of billet/ingot).  They also come in various pressure ratings:  150, 300, 600, 900, and pounds.  While they are available in several diameters, the larger flanges are available in the higher pressure class/rating.

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Types of Flange Facing

Flanges also have several types of facing which include:  flat face, ring-type joint, lap joint, tongue & groove and raised face.  The facing is the area that is used to seal the flange.

Industry Flat-Full Face Raised Face Ring-Type Joint Face Cast-Iron Equipment X High Pressure/High Temperature (up to °F/750°C) X Low-Pressure Water Pipe Systems X Process Plants (Chemical, etc.) X Oil & Gas X X Valves X

The face itself can be serrated or smooth.  There are several industries that traditionally require a specific type of facing.

Types of Pipe Flanges

There are several types of pipe flanges in a piping system; but there are 6 main types – blind, lap joint, slip on, socket weld, threaded and weld neck.  Each of them has properties that determine their use in commercial, industriall and institutional applications.  Always consult your project manager prior to installing any pipe flange into any application.

• Blind flanges have no center hole and are used to seal off a piping system.  As a result, one can easily execute pressure tests cost effectively. 

• Lap Joint flanges use a stub end (Type A, B or C) and slide over the pipe.  They are also known as loose-ring flanges and back-up flanges.  Lap joint is used with lapped pipe and allow for frequent cleaning and inspection through dismantling.  They are very durable and can be used because the fluid conveyed in the system does not come in contact with the flange.

• Slip On flanges, also known as hubbed flanges, are thinner than other flanges and are traditionally used in low pressure systems.  This type slips onto the pipe and the fillet weld is applied at both the top and bottom of the pipe flange.  These welds provide extra strength and prevent leakage.  While the installation is low cost and easy, the welding does add cost to its installation.

• Socket Weld flanges are designed for small size, high-pressure piping systems that do not carry corrosive fluids.  The pipe is inserted into the socket and a single fillet weld on the outside of the flange is applied.

• Threaded flanges are used in applications that are low pressure on smaller, thick walled pipes.  Given their threaded connection, they do make it easy to disconnect the piping system.

• Weldneck flanges have a long neck that is butt welded to pipe.  This type is also known as a weld bend flange.  Since the bore of the neck matches that of the pipe, it reduces erosion and turbulence.

Raised Face or Flat Faced?

There are other types of flanges including:  orifice, reducing, ductile iron backup, copper solder joint and many more.

What are the Applications of Pipe Flanges?

Type Traditionally Used In Blind

• Creating piping system access points
• Permanent seal to a piping system
• Pipe pressure testing
• Temporary seal for system repairs

Lap Joint/Loose Ring

• Frequent dismantling for maintenance
• Low-pressure applications

Slip-On/Hubbed

• Cooling water lines
• Firefighting water lines
• Oil, gas & steam process lines

Socket Weld

• Hydraulic pipes

Threaded

• Applications that are flammable, hazardous, or explosive & cannot be welded due to safety concerns
• Restricted space where welding is not feasible
• Small pipe sizes

Weld Neck/Weld Bend

• Conveyance of volatile and hazardous fluids
• Piping systems with bends that are repeating
• System conditions that have wide fluctuations in pressure & temperature

Flanges are available in several alloys including:  copper, brass, stainless steel, carbon steel, titanium, aluminum, superalloys, tool steel and alloy steel.  Each alloy carries specific attributes:

Alloy Attributes Alloy Steel

• Iron-based with <4% Chromium
• Resistant to wear & tear
• Strong

Aluminum

• Ideal for lightweight requirements
• Great weight-to-strength ratio
• Corrosion resistant due to surface microscopic oxide layer

Brass

• Highly conductive
• Copper, Tin and Zinc alloy
• Nonmagnetic
• Corrosion resistant
• Resists higher heat & electric conductivity compared to other metals

Carbon Steel

• Low & high carbon steels available
• Ductility, impact strength, wear resistance and hardness determine its need

Copper

• Nonmagnetic
• Compared to other materials, can sustain greater loads
• Corrosion resistant
• Can handle high-temperatures

Stainless Steel

• Corrosion resistant
• Durable
• Withstands pressure & high temperatures

Super Alloys

• Tolerates severe conditions
• Material makeup includes Nickel & Cobalt
• Resists acid corrosion & high temperatures

Titanium

• Lightweight
• Strength is exceptional
• High heat resistance
• Very costly

Tool Steel

• Made from tool steel billets/ingots
• Impact resistance & robustness is strengthened because it includes carbon & other alloys that react with iron
• Durable

Merit offers several types of flanges in various alloys:

Brass

• Domestic
  
  • Leaded
  • Lead Free
• Import
  • Leaded 
  • Lead Free
• Classes 150, 250 & 300

Stainless Steel

• ANSI  
• MSS
• 150 LB
• 300 LB
• Weldneck
• Blind
• Threaded
• Plate (Tube OD Slip-on, Bling, IPS Slip-on Bevel x Square and IPS Slip-on Square x Square)
• Slip-on
• Socket Weld
• Lap Joint

Chrome-Plated Brass

• Floor

Ductile Iron

• Standard
• Galvanized

PIPE FLANGES FREQUENTLY ASKED QUESTIONS

• Can a stainless steel flange be put with carbon steel pipe?  Absolutely not, it would cause galvanic corrosion.  Always consult your project team to ensure a proper, safe installation.
• Does Merit's offering of pipe flanges come with flange protectors?  Yes.
• Do ANSI Flanges come in raised face (RF) and flat-faced (FF)?  Yes, Merit's ANSI Flanges are raised face.  The raised face can be machined off to make it the flat-faced style.
• Can a flange be identified without stampings on the sides?  Yes, traditionally, the bolt dimensions, OD and thickness can identify which class the flange is.

The Major Advantages of Flanges and Flange Fittings

Hydraulic connections mate pipes, hoses or tubes together or to components such as cylinders, pumps, valves or ports in other equipment. They are used in to complete a leak free hydraulic fluid system. These components combine to ensure the system is free of leaks or other failure under high pressures. Because of certain connection configurations and applications, flange fittings or separate flanges are the best or sometimes only practical solution to make an efficient and leak free connection.

Flange connections are typically used in applications that will encounter exceptionally high pressures when using pipe or tubing with an OD over 7/8 inches. They may be

bolted together to mate two sections of pipe (tube or hose), or bolted or screwed into the component to secure a flange fitting or section of pipe. Flanges can also be disassembled for easy access to modify the system, clean or inspect it. Certain flanges may also be permanently welded together or to the port section of the component (motor housing, valve port, etc.). More commonly, a flanged joint is made by bolting two flanges together with a gasket in-between to ensure a secure seal.

There are two primary types of flanges:

• SAE Code 61 flanges are used for applications requiring working pressure of 3,000 to 5,000 PSI
• SAE Code 62 flanges are used for applications requiring working pressure of up to 6,000 PSI

The hydraulic flange standard is ISO , which includes SAE Code 61 and 62 or SAE J518 UNC thread North American Standard, along with International standards with metric threads.

NOT Interchangeable

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It is important to note that the two flange style codes (61 and 62) are not interchangeable due to their pressure ranges and their different bolt patterns.

As shown in this diagram of overlapping code 61 and code 62 4-bolt flanges the dimensional placement of holes are close, but not identical. Note the difference in the bolt-hole’s center-to
-center dimensions.

As shown in the flange diagram and chart below,  the distance 

between hole centers for dimension A in a 2 inch Code 61 versus a Code 62 flange varies by as little as 0.062 inches and for dimension B is offset by a significant 0.75 inches.

There is also another style that must be accounted for and not interchanged with Code 61 or 62 flanges. This other 4 bolt flange often found in the field is made for Caterpillar equipment and called (not surprisingly) a Caterpillar flange. This style is almost an exact match to the SAE Code 62 4-bolt flange with one major difference:

The flange head on an SAE Code 62 has a thickness which ranges from 0.305 inches on the 1⁄2 inch flange to 0.495 inches on the 2 inch flange, where the Caterpillar flange head thickness is 0.560 inches for all 4-bolt flanges. Hence an important distinction as to why they should not be interchanged.

Although many SAE 4-bolt hydraulic flanges might look alike or that different flanges and fittings might appear to be compatible, that is usually not the case. SAE Code 61, SAE Code 62 and Caterpillar 4-bolt flanges have dimensional variations and slight differences in configuration, plus the differences in allowable working pressure, do not allow them to be used together or interchanged. Take the example from on the The Fluid Power Safety InstituteTM website:

A diesel mechanic was installing a new hydraulic motor onto a machine. While reconnecting the hydraulic hose he inadvertently used a 4-bolt split flange that did not line up with the holes on the motor housing. Suspecting the holes in the motor were not tapped in the proper place he filed the holes in an attempt to have them line up with the flange. He essentially modified a 6,000 PSI SAE Code 62 4-bolt flange to mate with a 3,000 PSI SAE Code 61 motor.

This was an unfortunate mistake and one that could have been catastrophic to the system if it had been the other way around; modifying a 3,000 PSI bolt flange with a 6,000 PSI motor. An obvious system failure would have occurred, or worse a system failure that blew the assembly off causing severe damage or physical harm. This is a prime example of the importance of using only matched and properly rated components. This example illustrates the importance of properly matching flanges with each other or to

the intended component. To recommend guidelines for avoiding the mismatching of 4-bolt flanges, the Fluid Power Safety Institute (FPSI) developed the table below for common types and sizes.

Benefits of Flanges

Though there are specific applications where flanges and/or flange fittings are the only practical choice (particularly in larger, high pressure piping applications), flanges sometimes provide benefits to the piping system that traditional hydraulic fittings do not. For example, in those larger OD applications flanges are often able to be connected to pipe (tube or hose) and component ports more easily than threaded fittings or adapters. In many severe service applications on mobile construction equipment flanged connections are best for:

1.   Ease of assembly in tight spaces where wrenches might not have clearance if installing traditional fittings and they are more easily assembled with moderate torque.
   
   
2.   Hard to reach areas where flexibility is required, eliminating the need for adapters in the tube, pipe
   or hose line.
   
   
3.   Large hose, tube or pipe connections where shock, vibration, high pressure and/or pressure surges are present, which could more easily damage a traditional large hydraulic fitting.
   
   
4.   Making connections that allow for easy maintenance in rigid lines such as continuous pipes or metal tubes.
   
   
5.   Reducing the chance of components becoming loose in rigorous hydraulic applications. 

FLANGE FITTINGS & HOW THEY FIT IN

The fluid power industry is working to make a shift to using connections with an elastomeric, O-ring type seals to minimize leakage. Among other styles, these fittings include the SAE straight thread, face seal, ISO , SAE J518 (Code 61 and Code 62) flange fittings and flanges (Code 61 and Code 62), where the O-ring seal is compatible with the fluid. As covered above, when fitting tube-to-tube (or pipe or hose) a captive

flange is often used. Captive flanges simply slip over the flared tube and are connected to mating flange or other component. Captive flanges are commonly used with MJ-Flange Straight fittings (aka flange adapters), where there is smooth clearance to slide over the fitting allowing the flange head on the fitting to seat into it. Yet split flanges are used when 45° or 90° flange fittings are used (i.e. MJ- Flange 45 or 90). Split flanges come in kits (either for Code 61 or 62) which include:

• Two halves of the flange that fit around the fitting where the fitting’s flange head meets
• The accompanying O-ring seal
• Four bolts and washers to secure the flange and fitting to its intended port

Flange fitting connections are easy to assemble and provide the best option in larger diameter applications, especially when under high pressure. They provide significant advantages versus threaded fittings in these larger, more severe applications, such as:

• Easier to assemble in tight spaces
• Easy to disassemble for maintenance of reconfiguring of the system
• Large connections of over 7/8 inch up to 5 inch O.D tube or pipe – for Code 61 only
• Less torque required for tightening the four bolts versus achieving proper torque for a comparable large size fitting
• Provides up to 6,000 PSI capability through 2″ size – for Code 62 only, 5,000 PSI for Code 61
• Single point of sealing between tube, pipe, hose and/or component port connection

SAE J518 MAXIMUM WORKING PRESSURE RATINGS
FOR CODE 61 AND CODE 62 FLANGE FITTINGS

MPa (Mega Paskels) — 1 MPa = 145 PSI

Among the category of flange fittings (or flange adapters) are flanges plugs, which are used to cap off or block the flow in the pipe. Flange plugs are basically a flange without a center hole which closes the end of a pipe when bolted to a standard mating flange. Depending on the system requirements these plugs are typically gas or liquid tight. For gray water subsurface irrigation they are sometimes used to force waste through perforated holes in the pipe, driven by system pressure.

Conclusion

Though many SAE 4-bolt hydraulic flanges look quite similar to each other, SAE Code 61, SAE Code 62, and Caterpillar 4-bolt flanges exhibit small dimensional and physical differences that cannot be interchanges. It’s imperative to make sure the flanges are of the same code and the hole alignments match exactly.

Flange connections use a gasket to ensure a secure seal and are best in conditions of exceptionally high pressures in piping systems of 7/8” OD or larger. They

are used to connect pipe-to-pipe, tube- to-tube, hose-to-hose, etc. Or a single flange is used to bolt a pipe directly onto a component.

Flange fittings (aka flange adapters) are used with split and 4-bolt flanges when the mating connection is a threaded JIC 37° flare or other connection type. High quality flange fittings are made to endure extremely high working pressures and tensile strength, and are designed to perform in a variety of clearance applications. The most popular sizes of flange fittings range from 1/2” to 4”.

When fittings are involved, captive flanges are commonly used with MJ-Flange Straight fittings where there is smooth clearance to slide over the fitting allowing the flange head on the fitting to seat into the flange. Yet split flanges are used with 45° or 90° flange fittings (i.e. MJ-Flange 45 or 90).

A 4-bolt flange connection that complies with SAE J518 and ISO -1 and -2 (Code 61 and Code 62) ensures a leak-free connection and is best in larger sizes under high pressure and for assemblies in tight spaces. These 4-bolt flange port connections allow for the connection of larger sizes and attain high pressures with the capability of assembling at low torques. When compared to equivalent size threaded ports these low torque assemblies are typically the best choice in tight spaces, especially where there is limited wrench clearance.

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