Types of bushings for flanges - application and advantages (ASA, MSS)

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What do you think is the main cause of most man-made disasters? Errors in calculations? Cataclysms? Crooked hands of workers? Evil fate? Everything is fair. But I will add one more factor - details! One small, poorly installed, or simply poor-quality part can destroy the entire system and lead to large-scale troubles.

A clear example of this is the Boston disaster in 1919. There, due to rivets that could not withstand the load, a tank with molasses with a capacity of 10 million (!!!) liters burst. As a result, 21 people drowned in the sweet syrup and another 115 were injured, and the streets of Boston could not be cleared of the sticky mass for a long time.

Therefore, my article today is devoted to a detail that seems modest at first glance, the name of which is the HDPE bushing for the flange. Its mission is a strong connection of pipes and fittings. Is it worth mentioning how many floods and gas leaks could have been avoided if pipe connections had been more reliable?

Using a bushing for a flange

A flange sleeve and a free sleeve can be used together as an alternative way to create a flange connection, instead of a collar flange.

The two components will be combined if:

• A sleeve that is actually a piece of pipe with one end flared outward and the other end prepared to be welded to a pipe of the same hole size (NPS = nominal pipe size), material, and wall thickness. The most widely used tool for making bushings is a flaring machine, which is capable of expanding the end of a pipe and then cutting it to the desired length.
• A loose flange that is used to bolt two lengths of pipe together.

Advantages of flange bushing

Using a flange sleeve has the following two advantages:

Reduce flange connection costs

Typically, the loose flange is made from a lower grade material than the sleeve and piping system material, reducing the overall weight of the high quality material used for the flange connection.

Example:
For 316 stainless steel pipe, instead of using an all 316 steel collar flange, the combination of a 316 stainless steel sleeve and a carbon steel loose flange will be similar, but the overall weight of the stainless steel material will be lower, and the cost will be lower as well.
In fact, flange bushings can minimize the weight of high-quality material in stainless steel, duplex and nickel alloy piping, reducing costs. Of course, the larger the diameter and class of flanges, the higher the savings!

Flange installation assistance

The loose flange can be rotated on the pipe, making it easier to align the bolt holes of the mating flanges.

It should be noted that bushings are becoming popular in high pressure applications as well (whereas they were used for low pressure applications previously).

Installation methods

The flange is installed on the sleeve using a slip-on method. There is no need to weld the flange, but it must be bored out strictly for the reinforcing expansion of the sleeve, designed for additional reliability of connecting the collar. It is this expansion that bears the main burden. The regulatory document for bored flanges is GOST 12822.80.

Installation of a plastic sleeve and flange on a polyethylene pipe

After installing the steel flange, the bushing shank is welded to the pipe using special welding equipment. The flange is connected to the flange of another pipe or to a shut-off valve element using bolts and nuts.

There are many videos on the Internet that allow you to connect pipelines using HDPE bushings with your own hands.

Types of flange bushings

The bushings are available in three different types, called "Type A", "Type B" and "Type C":

• The first type (A) is manufactured and processed according to a standard loose flange (both products must be used in combination). The mating surfaces have the same structure to ensure a smooth application on the surface.
• Type B must be used with standard flat flanges.
• Type C can be used with either elbow or flanges and are made from pipes.

Machining the bushing for a flange

Flange bushings can be ordered with different end finishes:

• Beveled ends;
• Square ends;
• Flanged ends;
• Grooved ends;
• Threaded ends (injection type only).

Materials for flange bushings

Flange bushing sizes

The table shows the sizes of MSS and ANSI flange bushings in inches.

Types of bushings/model parameters and price

Polyethylene bushings are designated by the abbreviation SDR.
SDR is a parameter indicating the ratio of the outer size of the pipe to the wall thickness. The lower this indicator, the thicker the wall of the product and vice versa. When marking plastic products, a combination of PE is added.

Bushings vary in size and manufacturing method.

Manufacturing methods:

• Casting.

Such models are made from polyethylene grades PE 80 and PE 100 by casting into a special mold, followed by mechanical processing.

• Welding of individual parts.

In this method, a piece of plastic pipe and a disk made of solid polyethylene are connected to each other using wedge, air, or contact welding.

HDPE bushings come in short, long and semi-long.

Let's look at the most popular types of products.

PE 100 sdr11

A part made of P100 polyethylene with an outer diameter to wall ratio of 11. The standard sizes of extended bushings with a flange collar are given in Table 1.

The average price for the largest PE 100 sdr11 bushing in specialized organizations reaches 250 thousand rubles.

Important! Working pressure of PE100 bushings: Water -1.6MPa, gas - 1.0MPa

PE 100 sdr17

Cast HDPE fitting, similar to the first one, but with different standard sizes (shown in Table 2).

The price of the model depends on the diameter, varying on average from 100 rubles to 450 thousand rubles.

Bushing with welded shank

This model is a prefabricated (welded) part. The components are a piece of polyethylene pipe and a collar. To produce this type of product, pipes with an SDR value of 11, 13.6, 17, 21.26 are used. Diameter range - from 90 to 630mm. It can be short or long.

Thanks to a wide range of electric welded fittings for a flange with a welded shank, they are used in all types of HDPE pipelines

The average cost of a bushing with a welded shank is from 300 to 21,000 rubles.

Short bushing PE100 sdr11

A short polyethylene sleeve is used in the same conditions as an elongated one, but due to less material consumption, its price is an order of magnitude lower.
It is easier and more convenient to work with short products, especially in hard-to-reach places. This is important when installing pipelines with large diameters. The required length of the shank is adjusted by the length of the PE pipe.

The main standard sizes are in table 3.

Average price - from 300 to 14,000 rubles

Short bushing PE100 sdr17

Available in the main sizes shown in table 4.

Price range - from 320 to 54,000 rubles.