Frequently Asked Questions

The following are frequently asked questions that customers, engineers, fabricators, distributors, and others have asked when inquiring about insert flanges. If you have a question that is not addressed here please e-mail your question to (Click on a question to go to the answer) Each month the best question asked from you, the consumer, will be published as our Question of the Month, along with its comprehensive answer!

Question of the Month:
 

What are the major advantages of insert flanges?

The rotating bolting ring helps you align bolt holes more easily, to assemble flanges faster, and to reduce joint stress.

Only the insert needs to be constructed of an expensive alloy such as stainless steel, nickel, alloy 20 or Hastelloy. The bolting ring material can be of higher strength, lower cost, carbon steel.

As aspecialty flange, insert flanges are manufactured in smaller quantities, with tighter tolerances and an emphasis on quality not to be found on commercial flanges.

Insert flanges that are designed specifically for jacketed piping. With a hub machined for the exact pipe size and schedule of the jacket pipe required.

Insert flanges for jacketed pipe offer centering hubs to make assembly easy and assure concentricity of jacket and core piping.

When a custom size is needed, SIFCO's experienced salespeople and engineering department will aide in designing a flange to meet your need.

Roll-on insert flanges have the option of being connected to pipe without being welded. Using roller expansion technology insert flanges can eliminate the need for welding, for safe use in an explosive atmosphere.

The Roll-on insert flange also provides an alternative to using buttweld stub-ends and lap-joint flanges. By using the Roll-on or Slip-on insert flanges, fabricators have reported saving up to 25% in fabrication time.

Delivery time for insert flanges, especially when exotic material is required, is drastically reduced.

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Do SIFCO Insert Flanges conform to the design requirements of ASME B31.3?

What effect does the pressure in the jacket have on the insert or its pressure rating?

How do you weld the core pipe?

Do SIFCO insert flanges meet code?

What's the Maximum Allowable Working Pressure for SIFCO insert flanges?

What's the Maximum Allowable Working Pressure for the jacket pipe?

Can I order a size not listed in your catalog?

What's the lead time for manufacturing insert flanges?

Is your material domestic?

Do you manufacture the flanges at your site?

What is the effect of using spiral wound gaskets on 150# insert flanges?

How much temperature drop will occur from the back of the flange to the gasket surface?

What does SIFCO mean when they refer to their insert flanges as ASME Rated?

What is a T/D insert flange?

Okay, I'm interested in getting a quote on insert flanges, how do I go about doing this?

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Do SIFCO Insert Flanges conform to the design requirements of ASME B31.3?
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Yes! ASME B31.3, Process Piping, provides requirements for the design of flanges which are not listed as standards in Table 326.1, of the specification. These requirements are found in paragraph 304.5.1. This states that flanges may be designed in accordance with the Boiler Pressure Vessel Code, Section VIII, Div 1, Appendix 2 or Appendix Y, depending on whether the gasket OD is inside or outside the bolt circle. It also states that flanges may be qualified by the requirements of paragraph 304.7.2. This paragraph applies when Appendix 2 or Appendix Y are not applicable and states that the design is to be based on calculations consistent with the design criteria on B31.3 and substantiated by one or more of the following:

a) Extensive & successful service experience under comparable conditions with similarly proportioned components.

b) Experimental stress analysis similar to that described in BPV Code, Section VIII, Div 2, Appendix 6.

c) Proof testing in accordance with ASME B16.9, MSS SP-97, or BPV Code Section VIII, Div 1, UG-101.

d) Detailed stress analysis such as finite element.

Since SIFCO's insert flanges are very similar to ASME/ANSI B16.5 flanges, containing the same ring-type elements, they can be reliably designed to Appendix 2 of the BPV Code, Section VIII, Div 1. Additionally, SIFCO's insert flanges benefit by SIFCO's extensive and successful service experience as they have been in use for several decades.

What effect does the pressure in the jacket have on the insert or its pressure rating?
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This question is almost always asked when the jacket pressure exceeds the pressure rating class of the insert assembly.

The simple answer is that there isn't any effect at all. The insert assembly consists of an insert and a flange ring. The flange ring itself does not come into contact with the jacket nor is it's loading influenced in any way by the jacket or it's contents.

The insert itself, technically, could be considered a closure ring as described by the ASME Boiler & Pressure Vessel Code, Division 1, Appendix 9. The pressure loading would be in the form of a uniform annular ring bound on the O.D. by the jacket pipe I.D. and on the I.D. by the process (core) pipe O.D. This loading would attempt to bend the ring (insert), with the inner and outer edge fixed into a portion of a torus, where the deflection would be axial, toward the gasket side. However, the insert thickness, axial at this section, is usually considerably greater than the annular width. The bending and shear stresses resulting from jacket pressure would therefore be very small.

All of this assumes that this ring section is unsupported between the inner and outer pipes. However, in actuality, it is fully supported across the ring section. The gasket side of the insert provides constant contact between the jacket and process pipes. This means that the only stresses caused by the jacket pressure on the backside of the insert are compressive. The jacket pressure would have to exceed the allowable compressive stress of the material used before this would cause a problem. This would be a rare case.

How do you weld the core pipe?
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Fabricating the core pipe is a simple process that involves welding the inner pipe to the insert flange in one of two ways:

1. Clamshell construction consists of welding the process pipe to the insert, and putting the clam shell section of the jacket pipe into position and welding together.

2. SIFCO also offers a Transit Hub, which offers an alternative to clam shell construction. A transit hub allows the jacket pipe to slide further along the hub, thus allowing access to the welding area of the process pipe at the other end of the spool.

Further explanation, along with illustrations are available in SIFCO's catalog.

Do SIFCO insert flanges meet code?
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Yes! All of SIFCO's flanges meet the ASME Boiler and Pressure Vessel Code and can be used with both process piping and pressure vessel applications.

However, the designer needs to understand the features, advantages, and possible limitations of the two major series of SIFCO's insert flanges. The 'Conventional' series of jacket insert flanges are based on flange thickness equal to the ANSI B16.5 flanges. Since the flange ring portion of the SIFCO flange is without a hub, some of the calculated pressure-temperature ratings, which are based on compressed asbestos gasket factors and low strength SA-307 Gr. B bolting, are lower than those for the ANSI flanges. These pressure/temperature ratings are listed in the SIFCO catalog and are also available upon request. However, the above series flanges have been used successfully for many years with high strength bolting and various types of gaskets. They were designed with economy in mind. Therefore, these insert flanges tend to find their way into piping applications although they can also be safely used in pressure vessel applications.

The 'ASME Rated' series of jacket insert flanges, on the other hand, have been designed with thickness sufficient to meet the ANSI B16.5 pressure/temperature ratings based on spiral wound gasket factors and SA-193 B7 high strength bolting. SIFCO lists these flanges in the catalog 'for ASME Code & Pressure Vessel Applications' since many pressure vessel designers prefer to use ASME/ANSI flange replacements that carry the full pressure/temperature ratings. These flanges are also suitable for the more critical piping applications.

What's the Maximum Allowable Working Pressure for SIFCO insert flanges?
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When determining the Pressure Rating for SIFCO insert flanges keep in mind there are two classifications, 'Conventional' and 'ASME Rated'.

Conventional

Due to the differences between SIFCO's 'Conventional' jacket insert flange design and standard ASME/ANSI B16.5 flanges, calculations were performed to establish a MAWP Table (Table 2 pg. 6 SIFCO catalog). In some cases, values exceed the ASME ratings, and in others, values are below the ASME ratings. These calculations conform to the procedures detailed in Appendix 2 of the ASME Boiler and Pressure Vessel Code, Section VIII, Division 1. They were based on the use of standard 1/8î thick asbestos-equivalent gaskets and carbon steel bolts to SA-307 B. Flanges are forged carbon steel to SA-105 and inserts covered by these ratings may be type 304, 316, 304L or 316L.

The MAWP on SIFCO's 'Conventional' jacket insert flanges have been established without calculating for flange protection due to over-bolting using SA-193-B7 bolts. The ASME code has specifically allowed the use of alloy steel bolts to SA-193-B7 with ASME B16.5 flanges without calculation. This is primarily because ASME B16.5 flanges cannot always meet the over-bolting protection requirements of the code, due to extremely high bolt strength.

Since the bolting and flange thickness of 'Conventional' SIFCO jacket insert flanges are identical to those of ASME/ANSI B16.5, but do not share the code's exemption, SIFCO's MAWP was calculated using carbon steel bolts to SA-307 B. For piping systems using SA-193-B7 bolts, that must meet the ASME Code requirements, SIFCO has designed insert flanges that meet code requirements.

ASME Rated

The ASME/ANSI B16.5 Pressure Temperature Ratings at material group 2.2 (Table 1 pg. 5 SIFCO catalog) can be used for the jacket insert flanges marked 'ASME Rated', for ASME Code and Pressure Vessel Application. Calculations conforming to the ASME Boiler and Pressure Vessel Code, Section VIII, Division 1, have been performed which determine minimum flange thickness to meet ASME/ANSI B16.5 MAWP. These calculations are based on the use of carbon steel to SA-515/516 Gr70 or SA-105 material for the bolting ring and stainless steel type 304, 304L, 316, 316L to SA-479 or SA-182 for the insert. The bolting is to SA-193-B7 and the gasket material is spiral wound. Any changes to the material, bolting, or gasket could change the required dimensions of the insert flange.

What's the Maximum Allowable Working Pressure for the jacket pipe?
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When calculations are performed on the pressure of the jacket pipe the insert flange is not included because references to pressure temperature are limited to the pressure temperature of the process pipe only. Insert flanges are not a limiting factor to the pressure of the jacket pipe. If calculations were performed on the pressure of the jacket pipe the flange would not be included in these calculations.

Can I order a size not listed in your catalog?
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A custom order is always welcomed at SIFCO, we'll be happy to help you with any questions you may have regarding your specific project.

The sizes and classes in the catalog are listed due to their frequency of request and are not meant as a capacity range. Insert Flanges can be manufactured in all ANSI B16.5 classes and sizes.

What's the lead time for manufacturing insert flanges?
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If the order is already in stock, the flanges can be shipped usually the same day in which it is ordered. However, if the order is not in stock, we require approximately two weeks for manufacturing and shipping.

Is your material domestic?
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Most raw materials inventoried are from domestic USA mills. If domestic material is required, this requirement must be made known when ordering and quoting to assure receiving 'domestic only' material. Material Test Reports (MTR's) are produced for internal purposes on every shipment.  If placing an order it is always good to specifically request MTR's to guarantee that they will be included with your shipment if needed>

Do you manufacture the flanges at your site?
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The insert flanges are manufactured at SIFCO's facility in Media, Pennsylvania, from the finest craftsmanship. The offices, manufacturing facility, and warehouse are all at one location for easy communication between sales, manufacturing and shipping.  For some types of standard flanges, such as carbon steel slip-ons, weld-necks, and plate flanges, SIFCO acts as a distributor through our network of local and global flange companies.  We always pledge to give you the best quality for the best price!

What is the effect of using spiral wound gaskets on 150# insert flanges?
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Spiral wound gaskets have been around for a long time, have a good record, and can be used to seal a wide variety of fluids and vapors. They do however require large bolting forces to achieve adequate sealing.

It is a well known fact that these forces, particularly those required during a hydrostatic test, will theoretically overstress certain size 150# ASME/ANSI flanges. Piping and pressure vessel engineers and designers deal with this condition in several different ways.

When some occasional leakage can be tolerated, many engineers will allow the situation to exist knowing that ASME/ANSI flanges are accepted by most of the codes without being subjected to a stress analysis as long as the design pressure and temperatures do not exceed the pressure/temperature ratings established. The long history of the usage of ASME/ANSI flanges has shown that this can be a safe approach as long as the flange and bolting materials operate in a temperature range that maintains their ductile state. Other conditions should also be considered, such as fatigue.

Some engineers will include restrictions in their specifications on the use of 150# flanges, particularly slip-ons, or require that only 300# or higher are permitted.

Another approach is to reduce the required bolting forces by using spiral wound gaskets designed to specifically address the problem of overstressing 150# flanges. At least one gasket manufacturer now offers a line of this type of gasket and the required seating forces are approximately half that of the regular line.

SIFCO's conventional jacket insert flanges have been successfully used with many types of gaskets, including spiral wound. However, when the specifying engineer or end user does not have this kind of specific experience on which to rely, SIFCO recommends their ASME rated jacket insert flanges when using spiral wound gaskets.

When used on pressure vessels, Insert Flanges are subjected to the requirements of the ASME Code, Section VII, Div. 1, Appendix 2. Conditions, which would normally overstress ASME/ANSI flanges, are not permitted to overstress the insert and flange ring.

Although the use of spiral wound gaskets is common with the conventional jacket insert flange, calculating pressure/temperature ratings must be accomplished without protection from over-bolting, using low strength bolting such as SA-307 GR B, and gasketing factors of m=2 and y=1200.

Many engineers and end users specify the conventional jacket insert flange with spiral wound gaskets because of their successful history, but the development of SIFCO's ASME rated insert flanges have made it possible to meet the ASME Code requirements when using high strength bolting and spiral wound gaskets.

How much temperature drop will occur from the back of the flange to the gasket surface?
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When introduced to insert flanges, this is a frequent concern of process engineers and piping designers. A definitive answer is not possible since there are an infinite possibility of combinations and conditions. It is not feasible for a manufacturer to conduct tests and studies to provide answers to all of these conditions. However, the following guidelines can be offered.

Getting the jacketed medium (usually heat) as close to the gasket surface of the flange is the obvious first choice. There are several methods for terminating jackets at flanged connections. The most common method is to end the jacket at a closure ring short of the back of a non-reducing (line size) flange so that attachment welds to the pipe can be made to both the hub of the flange and the closure ring so there is space for nuts and bolt heads. Another method is to terminate the jacket right at the back of a reducing flange hub.

SIFCO's reducing insert flanges simulate this second method, bringing the jacket medium directly against the back of the insert portion and provide similar thermal performance to that of solid ASME/ANSI slip-on flanges while offering assembly and rotational advantages. However, many times it is not possible to use reducing (oversize) flanges.

When line size flanges are required, the jacket medium cannot be brought as close to the gasket surface because of wrench clearances. In the case of Insert flanges, the insert length must be extended to provide room for nuts and bolt heads. This amounts to about the same distance as a jacket closure ring would have to be placed for the same reasons. Here the advantage in thermal performance clearly goes to the insert flange. The mass of metal in the insert acts as a heat conduit up to the gasket surface, drastically reducing the temperature drop along the process pipe wall. One study indicated that the temperature drop with piping using a closure bar was three times as much as those using a non-reducing insert flange.

The insert flange allows the designer to efficiently bring the jacket fluid up against the back of the flange assembly in either reducing or non-reducing styles, minimize heat transfer loss and assembly time, as well as provide the convenience of rotating flanges.

     Reducing Insert Flange       Non-Reducing Insert Flange             Slip-On Flange

What does SIFCO mean when they refer to their insert flanges as ASME Rated?
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Standard one-piece pipe size flanges conforming to the ASME/ANSI B16.5 standard, 'Pipe Flanges and Flanges Fittings', are pressure rated for various temperatures. This allows piping and pressure vessel designers to select from a specific material, and to determine whether that flange has a high enough pressure and temperature rating for their required design conditions.

Custom designed flanges made to mate with these standard ASME/ANSI flanges do not necessarily meet those pressure/temperature ratings published in B16.5. However, by using sufficient flange and insert thickness and subjecting these specialty flanges to a series of calculations for each of the pressure/temperature ratings listed in B16.5, the manufacturer may claim that their flanges can be safely used at those same pressure and temperature conditions given for the standard flanges. It is having successfully performed this series of calculations that SIFCO refers to as 'ASME Rated', i.e., their flanges meet the same pressure/temperature ratings as the ASME/ANSI B16.5 standard flanges.

SIFCO's 150# and 300# Insert Flanges listed 'ASME Rated' and all pressure classes above 300# are 'ASME Rated'. Those 150# and 300# conventional jacket insert flanges not listed 'ASME Rated', are also pressure/temperature rated. However, those ratings may be less than the ASME/ANSI B16.5 ratings for the equivalent pressure class. These P/T ratings are listed in the catalog and are also available upon request.

What is a T/D insert flange?
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T/D is an old trade name for a Speedline Insert Flange. It was short for tapered designed, designating Speedline's specific design. Though Speedline went of business circa 1982 we still get this question from companies that have not updated their descriptions. SIFCO's Roll-on Insert Flange will satisfy the requirement of a T/D insert flange.

Okay, I'm interested in getting a quote on insert flanges, how do I go about doing this?
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First, you need to know if your application is for jacketed or single pipe.  Single pipe is simple, just know what your flange size needed is, and what size the pipe should be (usually the same size as the flange but can reduce down in size).  Then specify the weight class (usually 150 lbs.), along with the material of the insert and the material of the flange (usually 316L insert and carbon steel flange). (You can download the PDF portion of our catalog for single pipe by clicking here)

If requesting a quote for jacketed pipe it is easiest to see our complete line of cut sheets first. (You can download them in PDF format by clicking here.) If you cannot find a series number just name the weight class, determine if you need the insert flange to be a CONVENTIONAL or ASME RATED series, then specify the flange size first, then the core pipe size second, and then the jacket pipe size third. (Example: 150 lbs. 2" x 2" x 3" mean 2" flange by 2" core pipe by 3" flange).  Next, specify the grade of material for the insert and flange. (Remember, the core and jacket pipe only weld to the INSERT, therefore, it is much more economical to use a carbon steel FLANGE portion with your alloy of your insert matching the alloy of the pipe)  Finally, determine if you need a slip-on or buttweld core pipe design and give us the appropriate schedule for the jacket pipe for a slip-on, and the core and jacket pipe schedules for a buttweld design.  Remember, if you already know the series number by looking in the catalog, we would still need the sizes, schedules of pipe, and grade of material.  If you have further questions feel free to pick up the phone, toll-free and call SALES at 1-800-877-4326 (or toll call at 610-494-1800), email us at sifco@insertflanges.com, or fax us at 610-494-1803 . We are eagerly awaiting your call!