14.07.2022

What is a blind flange?


A blind flange is a solid flange as shown below. The purpose of these is to block off a section of
pipe or a nozzle on a vessel that is not used. (A nozzle is typically a pipe coming out of a vessel and
is usually flanged so it can be connected to valves or piping). Many times a nozzle will be blanked
off with a blind flange for pressure tests in a plant, or simply because the customer does not need
all the nozzles that were supplied on the tank.
The best practice is to use a standard gasket for these blinds. Blind flanges, just like standard pipe
flanges, can be raised face (RF) or flat faced (FF). If the flange is RF we would recommend a
standard ring gasket that is appropriate for the service and/or test. If it is FF we would TYPICALLY
use a full face gasket, because the most common reason the flange is FF is that it is not designed
to handle the bending forces that result when using a ring gasket or a RF flange against the FF
flange. Again, we treat a blind flange just like any other pipe flange.


A common request for gaskets with a blind flange is for a gasket with no ID; a gasket with a solid
center. The customer might ask for these solid gaskets with bolt holes or without. If the blind
flange is a standard ASME flange, the OD of the gasket will be the same as the OD of the standard
ring or standard full face gasket. Many times, the customer expects that the solid gasket will
protect the blind flange from the fluid in the system. They might be trying to save money by using
a carbon steel (CS) blind in chemicals that require a more expensive metal, so they want the
gasket to keep the fluids away from the low cost blind flange.


This practice of using a solid ID is NOT RECOMMENDED, however, for several reasons.
? The first is that the gasket will probably not completely stop the fluids from reaching the
blind flange. Keep in mind that we do not publish zero leakage for test results such as the
ASTM F37B Sealability; there is some small amount of permeation that occurs when
gaskets are at low compressive loads, like they are in the ASTM F37B test, but especially
when the center of the disc is under NO compressive load.
? Another issue is that the solid center of the gasket will be uncompressed and probably will
be affected by the fluids. Fiber gaskets, such as Style 3000, etc, will often be damaged in
the uncompressed area, even in fluids that are compatible with the gasket, including
water. Fiber gaskets are simply not meant to be immersed in fluids with no compression.
That means that the gasket may contaminate the process fluids when the uncompressed
area swells or breaks apart.
? There is also a VERY IMPORTANT SAFETY ISSUE: Because the center, uncompressed
portion of the gasket might be permeable over time, fluids and even fluid pressure can
build up between the solid gasket disc and the blind flange. This is because the pressure
will try to equalize on both sides of the solid gasket disc. This will even happen with a
GYLON gasket, despite the very tight sealing properties of the GYLON gaskets. Remember
the center is not under compressive loads. When the space behind the disc becomes filled
with fluid, this fluid is under pressure. If the system is shut down and brought back to zero
pressure, the fluid that is trapped cannot escape back through the solid disc fast enough.
So when the bolts are loosened to remove the blind flange, liquids or gases can spray out
of the connection. If this fluid is dangerous, toxic, or flammable, the mechanic can be in
danger.
For these reasons, GARLOCK recommends that gaskets for blind flanges be cut as standard rings or
full face gaskets, and not with a solid center.


Spectacle Blinds are another somewhat uncommon but important application for gaskets. A
picture of a spectacle blind is shown below. The name comes from the fact that the assembly
looks like eyeglasses, or “spectacles".


These are normally used in piping systems, usually between two standard flanges, and are
designed to block off a section of pipe. However these are used where the customer needs to
block this connection off somewhat frequently. They are typically used where there is piping
connected to both flanges, where you cannot simply drop a standard blind flange in, because the
flanges cannot be pulled apart far enough to drop in the blind flange.
In this case, the open side of the spectacle is used (with a gasket on each side) when the customer
wants the piping sections connected and operating normally. Then they will remove bolts, and
spin the blind side of the spectacle into the flanged connection, and install 2 new gaskets. The
reasons these are built this way is that the spacing between the flanges and the piping is now the
same whether the pipe is blanked off or open, because the open ring and solid blind are the same
thickness. This is the easiest way to be able to blank off a connection and then open it without the
issue of the having different spacing between the flanges.


Forging vs. Casting: Which is Better for Shackles?


This question, “Forging vs. Casting: Which is better?” is one that I have been asked many times when it comes to rigging products. To properly explore the answer, let’s first consider the process of each.


Forging and casting are two very different manufacturing methods. When something is cast, the material is heated above its melting temperature and poured into a mold where it solidifies. When something is forged it is physically forced into shape while remaining in a solid state – although it is frequently heated.


As an engineer, I have always known that forgings normally have less surface porosity, finer grain structure, higher tensile strength, better fatigue life/strength, and greater ductility than castings. In other words, forgings are generally better for shackles. The basics of why are pretty simple. When you melt metal to cast it, the grain size is free to expand. When it cools back to a solid, the grain structure is courser and more random, decreasing its strength.


I did some research on the internet and found an excellent research paper* written by members of the Industrial & Manufacturing Engineering Department at the University of Toledo, shared by the Forging Industry Association. This paper compares a single type of product made both ways. Read it here.




Forged parts had a 26% higher tensile strength than the cast parts. This means you can have stronger shackles at a lower part weight.






Forged parts had a 26% higher tensile strength than the cast parts. This means you can have stronger shackles at a lower part weight.




Forged parts have a 37% higher fatigue strength resulting in a factor of six longer fatigue life. This means that a forged shackle is going to last longer.




Cast iron only has 66% of the yield strength of forged steel. Yield strength is an indicator of what load a shackle will hold before starting to deform.




The forged parts had a 58% reduction in area when pulled to failure. The cast parts only had a 6% reduction in area. That means there would be much greater deformation before failure in a forged part.




To further illustrate the point, see the below photos from our in-house testing:


These forged CM shackles show significant deformities before failure. If you were hanging a load overhead from a shackle, wouldn’t you want that shackle to warn you before it failed? Or do you like surprises?


All CM shackles are forged; and they’re forged right here in America at our Chattanooga, Tennessee Operations. Safer and made in America? I think that I will stick to forgings. What will you do?


* The title of the research paper is “Fatigue Performance Comparison and Life Predictions of Forged Steel & Ductile Cast Iron Crankshafts” written by Jonathan Williams, Farzin Montazersadgh, and Ali Fatemi, Graduate Assistants and Professor, respectively, Mechanical, Industrial & Manufacturing Engineering Department, The University Of Toledo – Toledo, Ohio.


CS Blind Flanges and Weld Neck Flange manufacturer in India


Flanges are used to connect 2 ends of a pipe or to end a pipe. They are available in various materials. Carbon Steel Flanges are one such type of flange that is usually made up of carbon steel. This material provides properties such as resistance to corrosion, excellent durability, and finishing in goods. They are available in various types. For instance,Carbon Steel Blind Flanges are used to terminate the pipe. High grade raw material is used to manufacture these flanges. They have a carbon content in the range of 0.25% to 0.60%. Due to the high volume of carbon and manganese, the fabrication of the product is excellent and ductility is also good.


There is another type of flange that is known as killed Carbon Steel Forged Flanges. They are destroyed in the melting process. Due to the addition of manganese, silicon, and aluminum during the production of steel, deoxidation takes place. Carbon Steel Plate Flanges are welded onto the pipe which helps in bolting and connecting one pipe to the other. It displays good ductility, and toughness. These Carbon Steel Pipe Flanges also work well in low temperatures. They are used in fuel and water pipelines. The cost of these flanges ranges between Rs 398 to Rs 689.


To strengthen and harden the steel and cast iron alloy Carbon Steel Slip On Flanges are passed through a process known as quenching. They are used in various construction, engineering, and petrochemical industries. The outer diameter of the slip on flange is also welded. Carbon Steel Weld Neck Flanges have a neck extension at the end. This type of flange is directly buttwelded to the pipe to provide a natural connection. Carbon Steel Flanges manufacturers in India recommend the use of these flanges when the conditions are critical and severe.


The short-lived experiment with rubber tires on railways


For all their design innovations, railways still retain one fundamental weakness — they put metal wheels onto metal tracks.


Not just inefficient as there is limited grip between two such smooth surfaces, but noisy as well. So why don’t they use something different? It won’t surprise you to learn that railway companies have tried. And sadly failed.


It’s mainly a Frenchman we have to thank for the best attempt to deal with the metal upon metal, and that was tire magnate, Andre Michelin who upon returning from an unpleasant train trip instructed his engineers to develop something better.


Unsurprisingly for a tire manufacturer, they came up with a tire for railways.


The special pneumatic tyres, fitted with metal flanges in order to keep the coach on the rails, had a wooden hoop inside them so if they punctured, they only deflated slightly to prevent derailment.


At the time it was claimed that this type of tyre had an adhesion three times greater than steel wheels, and so the test trains could accelerate faster and brake later than conventional steam trains of the era.


The pneumatic tires absorbed shocks and bumps, and were considerably quieter in use — a boon it was said for passengers, but surely also for people living near to the railways.


It also didn’t take too long for someone to think that if trains could run on road tires, why not combine the road and rail vehicles into one. And thus the Micheline Railcar was born — basically a bus that ran on railway tracks.


Quieter than steam with its diesel engine, it could also be started up faster than a steam locomotive and didn’t need trained operators to handle it. Anyone able to drive a bus could manage the Micheline.


Tests were carried out in France, but in 1932, a Micheline Train was brought to the UK for evaluation. It was tested by the LMS on the line between Bletchley and Oxford, but did not prove to be a success.


There were other attempts — the Coventry Pneumatic Rail-Car, built by a Coventry car manufacturer for example. Which did have the advantage of looking exceptionally sleek as well.


Despite all the claims at the time of long life for the tires, they did wear out quickly, and also where a train carriage of the time needed just four wheels, a comparable carriage fitted with pneumatic tyres could need as many as 20 wheels.


The extra cost of building the carriage, and the ongoing maintenance meant the concept was doomed. It was the wrong sort of wheel on the tracks.


On the 30th November 1951, a debate in Parliament asked why defunct railway lines couldn’t be bought back into use by combined rail-road trains, but no one seemed interested anymore, and the Beeching Cuts would have probably killed the idea off anyway.


So to this day, we put up with steel on steel, and the inherent weakness that entails.


Forged Wheels vs Cast Wheels


When looking to purchase OEM Wheels, there are many different factors to consider. In addition to things like size and style, it is also important to understand the difference between forged wheels and cast wheels. This refers to the two main ways that OEM wheels are manufactured during the production phase.


A forged wheel is manufactured from a billet, or a large square piece of solid metal. The billet is heated to extreme temperatures and pressurized to take its shape. This thermal cycle process causes forged wheels to be stronger than cast wheels due to grain refinement. Consistent forging makes for stronger structural integrity with less material compared to a cast wheel, however the process costs more, rendering forged wheels the more expensive option.


Forged wheels offer several advantages. The manufacturing process results in a stronger wheel by eliminating cavities, porosity, and shrinkage. Due to its tighter grain structure, forged wheels are also mechanically stronger, ensuring better wear resistance over time. You also get better performance and handling because of this process.


The cast wheel manufacturing process involves heating up aluminum until it reaches a molten state. The molten aluminum is then poured into a mold where it is cast into its final shape with the help of a vacuum. After the cast cools down, it is trimmed and drilled to perfection. The casting process is quick and inexpensive but has the disadvantage of rendering a weaker material than a forged wheel.


In addition to the advantage of being the less expensive option, cast wheels offer other upsides. Casting wheels offers a wide range of alloys to choose from. There are also no limits to casting weight and the process makes it much easier to produce complicated parts. Contrary to popular belief, a properly cast wheel can weigh more than a forged wheel and the build quality is more than enough for street and light track use.

keine Angabe