I will explain the basics of spiral gasket.
Add a high pressure line of 1 MPa or more.
You’re thinking of a gasket that can withstand 1 MPa, right? okay, right?
If you are in charge of a continuous plant, you probably know that spiral wound gaskets are for high pressure.
However, the person in charge of the batch plant is unexpectedly unaware of the existence of spiral wound gaskets.
This is because there is almost no reaction under high pressure exceeding 1 MPa.
A world without high-pressure gas facilities and almost no pressure.
That’s the batch plant.
That’s why we grow up without knowing the existence of spiral wound gaskets, and when it comes time to handle spiral wound gaskets, we end up in trouble.
As the basics of spiral wound gaskets, we have summarized what you should know at a minimum.
The reason why spiral wound gaskets can withstand high pressure
Spiral wound gaskets are for high pressure.
Joint sheet gaskets, etc. cannot withstand high pressure and break. I would call it crushing.
Since the joint sheet is made of rubber or PTFE, it is natural that it is weak.
It is somewhat strange that even a gasket can withstand high pressure.
If you notice that gaskets have the following classifications, that question will be answered.
- joint sheet
- metal gasket
If the gasket is molded from metal, it is natural that it can withstand high pressure.
Spiral wound gasket is metal
Spiral wound gaskets are basically made of metal and molded into the following shapes.
It’s a “V” shape.
When pressure is applied here, the “V” expands.
The shape of the “V” expands and the gasket presses against the flange surface.
This is the same as V-packing.
Spiral wound gaskets are “V” shaped.
As with V-packing, stacking multiple layers gives strength and durability.
Even if only metal is overlapped, the force is not properly transmitted in the overlapped metal part.
This is because metal deformation is not uniform.
Therefore, we will put cushioning material in between.
The metal part is called the hoop, and the cushioning material part is called the filler.
I always get confused and don’t know which is the hoop or the filler.
Speaking of metals and cushioning materials, you can easily understand.
Spiral gasket shape
There are a total of 4 patterns of spiral gasket shapes.
There are four types: basic, with inner ring, with outer ring, and with inner and outer rings .
Inner and outer rings are available as options.
In any case, it is OK to choose the gasket according to the type of flange.
The shape of the spiral wound gasket matches the type of flange.
The basic shape is a “groove flange”
The basic type can be used for groove type flanges.
It looks like the image below.
It is a method to make a groove firmly with the flange and to fix it firmly by inserting a spiral gasket in the groove.
In the sense of “holding”, it is the same concept as the O-ring.
Even if the spiral wound gasket is deformed under high pressure, the flange groove acts as a guard and the amount of deformation is suppressed while sealing is possible.
If you can use a groove type flange , you should choose the basic type.
The groove type flange is also called MF type.
With inner ring is “Inset type flange”
The inner ring type is used for the inset type flange.
It looks like the image below.
The inner ring has the purpose of reinforcing the strength of the gasket, but also has the purpose of guarding like the groove type flange.
If you cannot or do not need to use a groove type flange and want to use an inset type flange , select a type with an inner ring.
The inset type flange is also called TG type.
Outer ring type is “raised face/flat face flange”
The outer ring type is used for flat face flanges and flat face flanges.
It looks like this:
Since it has an outer ring, it is stronger than the basic type.
Even if the spiral wound gasket is deformed, it ends when the outer ring touches the flange bolt.
The advantage is that there is no need for special flange processing such as a groove type or an inset type.
However, it is a fairly half-baked existence.
The reason is because there is a lower inner and outer ring.
For inner and outer rings, “raised face/flat face flange”
The inner/outer ring type is the same as the outer ring type and is used for raised face and flat face flanges.
The advantage of the outer ring is the same, but since it has an inner ring, it is stronger and more secure than the one with the outer ring.
It would be safer to choose one with inner and outer rings than one with outer rings.
Spiral gasket material
Lastly is the material.
The material is decided based on the metal (hoop), cushioning material (filler), and reinforcing material (inner and outer rings).
metal (hoop)
Metal (hoop) is metal, so you can choose from general-purpose metals.
It is enough if you know SUS304 and SUS316L.
Keep in mind that you can use high-grade metals such as titanium.
This is because using high-grade metal means that the device itself that handles it under high pressure is high-grade metal,
This is because it is at a level that can be said to be almost completely unusable in a batch plant.
Cushioning material (filler)
There are several types of cushioning materials (fillers).
- expanded graphite
- PTFE
- Inorganic material
It’s the same idea as the joint sheet.
Expanded graphite is treated in the same way as general-purpose joint sheets and is used for non-corrosive utility lines.
PTFE is used in corrosive process lines.
Inorganic materials have no merit other than being cheap, so if you are worried about it, you should choose expanded graphite. Except in special cases.
Reinforcing material (inner and outer rings)
The reinforcing material (inner and outer rings) is the same as the metal (hoop).
The point is that carbon steel is also an option for the reinforcing material.
If the outer ring is not in a corrosive atmosphere, carbon steel is sufficient.
If you choose carbon steel for the inner ring, it will be limited to utility applications.
Carbon steel is positioned as the inner ring in contrast to the expanded graphite filler.
For process applications, it is better to choose SUS304 or SUS316L.
reference
There is a regular room to decide the gasket by trial and error.
Spiral wound gaskets are handled in the same way, but they are high pressure and dangerous, so I would like to understand the principle and be able to choose a safe one.
Related article
Related information
lastly
I explained the basics of spiral wound gaskets.
Why spiral wound gaskets can withstand high pressure, Materials and shapes.
Batch-type chemical plants are rarely used under high pressure, so it is sufficient to understand the basics of spiral wound gaskets.
Please feel free to post your worries, questions, and questions about the design, maintenance, and operation of chemical plants in the comments section. (The comment section is at the bottom of this article.)
*I will read all the comments and answer them seriously.