There are different types of gaskets in the piping industry. To better understand each type, here’s all the information to know.
A gasket is a mechanical seal that consists of a ring for sealing a pipe joint or packing pistons. Gaskets are used in piping as sealing materials placed between connecting flanges in order to create static seals. They help prevent leakages, irrespective of the operating conditions.
The #1 function of gaskets used in piping is to secure the irregularities on each face of the flange. This prevents any form of leakage of service fluids from the flange joint.
Gaskets used in piping are far different from those used in other industries. This article highlights the different types of gaskets used exclusively within piping systems.
Why Gaskets Are Used in Piping
Flange joints are not expected to leak because even a small leak can have disastrous consequences. When a leak occurs at a flange, it leads to a significant loss of energy and product.
This is why every plant operator does everything in their power to prevent leakages of hazardous or toxic materials that may harm humans in particular and the environment at large. Gaskets assist in reliable sealing in order to prevent leaks from flange joints.
The gaskets employed in a given fluid depend considerable on some essential parameters like:
- Pressure
The material used in making the gasket must be capable of withstanding a given fluid’s entire design pressure range.
- Temperature
The material used in making the gasket must be capable of withstanding the whole design temperature range of a given fluid.
- Type of Fluids
The material used in making this gasket must be capable of handling different fluid types. But the gasket must be installed in a line that deals with more than a particular fluid type.
- Resistance to Corrosion
When exposed to the materials it handles, the material used in making this gasket must be highly resistant to corrosion. It must not be susceptible to corrosion due to environmental exposure.
- Availability
Gaskets used in piping must be readily available so that if a replacement is required, it can be done speedily without the risk of prolonged downtimes.
- Robustness
Gaskets used in piping must withstand every movement that occurs – or may occur – as a result of a considerable change in pressure and temperature.
- Cost
Gaskets can be pricey. However, this is not an excuse to use unreliable and cheap gaskets as this could be hazardous in the long run.
Types of Gaskets in Piping
Three major types of gaskets are used extensively in piping. They are:
- Metallic gaskets
- Non-metallic gaskets
- Semi-Metallic or composite gaskets
Let’s take a brief look at the gaskets used in piping systems.
Metallic Gasket
Metallic gaskets – a.k.a. RTJ gaskets or ring gaskets – are manufactured from metallic materials like low carbon steel, soft iron, stainless steel, Inconel, and Monel.
RTJ Gaskets are costly, robust, and require high-tension bolting. They are often used extensively in a high-pressure class flange, usually above 900 class. They also find use in a high-temperature environment.
Metal gaskets are designed to fit perfectly within a machined groove on the flange faces of both mating flanges. Two types of metallic gaskets are used with RTJ flange, i.e., Oval and Octagonal gaskets.
Non-Metallic Gasket
Non-metallic gaskets are generally made from materials like Teflon, Graphite, PTFE (polytetrafluoroethylene), CNAF (Compressed Non-Asbestos Fiber), and Rubber. Gaskets in this category are soft gaskets, which can be inside bolt circles or full face types.
Non-metallic gaskets are typically used in low-temperature environments and with low-pressure class flanges like 150 or 300 Class. Low tension bolting easily compresses these types of gaskets.
However, graphite gaskets – which are categorized as non-metallic gaskets – are used in temperatures as high as 500 degrees Celsius.
Non-metallic gaskets are readily available and considered the cheapest compared to the other types of gaskets used in piping.
Semi-Metallic or Composite Gasket
Semi-metallic or composite gaskets are made from a combination of non-metal and metal materials. The service requirement of this type of gasket depends significantly on the materials used in fabricating them.
Gaskets within the composite category include:
- Metal jacketed gasket
- Spiral wound gasket
- Kamprofile gasket
These gaskets are utilized in several temperature and pressure services. Composite gaskets are generally cost-effective, especially compared to their metallic counterparts.
However, composite gaskets require careful handling. They are often employed on male-female, tongue-and-groove, and raised face flanges.
Properties Gaskets in Piping Systems Must Possess
Selecting the type of gasket used in a particular piping section depends on these factors:
- Capacity to withstand the temperature-pressure of the piping system
- The serviceable life of the gasket
- Compatibility of the gasket material with the fluid in the piping system.
Understanding these requirements is highly essential as it helps in gasket selection. Gaskets are designed to maintain seals against every operational force for a specified period.
Here are the properties gaskets in piping systems must possess for 100 percent effectiveness:
- Resilience
Flanges are designed to move slightly relative to each other, especially under the overall influence of cycling pressure and temperature.
Gaskets must be capable of compensating appreciatively for such irregular movements from time to time.
- Temperature Resistance
Great gaskets, especially those utilized in piping systems, must be capable of withstanding the overall effects of the minimum and maximum temperatures in processes as well as the external atmospheric temperatures.
- Chemical Resistance
Gaskets must be able to withstand chemical attacks from the medium being processed. The gasket’s material must also not contaminate or interfere with the process medium.
- Creep Resistance or Stress Relaxation
When the gasket is subjected to extreme temperature and load, it mustn’t show considerable creep or flow. If it does, the bolts will relax and minimize the surface stress of the gasket. This results in leakage.
- Impermeability
No gasket used in piping systems must not be porous, i.e., it must be impermeable to the fluid or process medium.
- Anti-corrosion
The gaskets utilized must not trigger the action of corrosion on the flange faces. It must also not be prone to corrosion.
- Compressibility
In order to create an initial seal, gaskets must compress into the imperfections the flange showcases.
- Anti-stick
The gasket used in piping systems must possess anti-stick properties for easy removability after use.
Conclusion
Several types of gaskets are used in piping. The materials used in making specific gaskets depend considerably on the environments or applications in which they will be used.
Since there is a wide range of materials used in making these gaskets, multiple options are available for piping. This is why you should understand the types, uses, as well as applications of every gasket in piping in order to get the most out of the mechanical seals within your piping system.