04,Nov 2024
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A ring-type joint flange, or RTJ flange, is a specialized flange featuring a groove machined into its face to accommodate a metal ring-joint gasket. This design provides a reliable, safe, and leak-proof seal for pipelines in high-pressure settings, such as oil & gas, and power generation.
RTJ flanges are commonly made from durable materials like carbon steel, stainless steel, and various alloys.
The main components of an RTJ flange include the ring groove, bolt holes, metallic ring gasket, and flange face.
The ring groove is a precision-machined indentation located on the flange’s face. This groove is specifically designed to hold the metallic ring gasket securely in place, ensuring that the gasket can compress adequately when the flange is bolted.
The metal ring gasket, made from materials like soft iron, stainless steel, titanium, or other alloys, sits within the ring groove.
When the bolts connecting the RTJ flange are tightened, the flange faces come together, compressing the metallic ring gasket. The gasket deforms slightly, filling any microscopic gaps and creating a strong seal that prevents fluids from escaping the joint.
There are specific types of metallic ring gaskets compatible with RTJ flanges, most notably the following:
Considered the traditional choice for RTJ flanges, these come in oval and octagonal cross-sections and can withstand pressures up to 5000 psi.
Adopted from the R Type design, RX gaskets are slightly wider and can be interchanged with R Type gaskets. They are rated for pressures up to 5000 psi and excel in environments where consistent vibration or shock may otherwise compromise the seal.
BX Type gaskets are specially engineered for BX-type flanges, meaning, they are not interchangeable with R or RX types. These gaskets can handle up to 20,000 psi, making them ideal for extreme conditions.
Bolt holes are drilled into the flange to accommodate bolts that connect it to other components in the piping system. These holes are strategically placed to provide even distribution of force when the bolts are tightened.
The flange face is the flat surface where the RTJ flange meets another flange. Its finish and flatness are essential for achieving a good seal with the gasket.
Compared to other flange types, such as raised face (RF) flange and flat face (FF) flange, RTJ flanges are specifically designed to prevent joint leaks in extreme high-temperature and high-pressure environments.
This comes largely from its sealing mechanism – the metal-to-metal compression of the ring gasket and groove creates a secure, blowout-resistant seal.
RF and FF flanges, by contrast, are more suitable for lower to moderate pressure applications.
RF flanges have a small raised area around the bore, where a softer, flat, or semi-metallic gasket is compressed between the mating flanges to form the seal.
FF flanges, on the other hand, are completely flat with no raised area, and they generally use non-metallic gaskets like Viton or EPDM to achieve an effective seal.
One drawback of ring-type joint (RTJ) flanges is their cost. Creating the precise groove and metal gasket needed for an effective seal requires careful machining, which makes RTJ flanges generally more expensive than other options.
Another challenge you need to look into when choosing high pressure flange plates is the space required for maintenance. When you need to disassemble an RTJ flange – such as when repairs or replacements are due – the gasket can be tightly lodged in the groove, making it hard to remove without extra room for maneuvering.
Because of this, RTJ flanges are typically used in setups where there’s enough space for regular maintenance.
The exact dimensions of an RTJ flange face varies depending largely on the flange’s class
rating, nominal pipe size (NPS).
You can refer to the standard ASME B16.35 to determine the exact dimensions of pipe flanges with sizes NPS 1/2 through NPS 24. For flanges suited for larger pipes, refer to ASME B16.47, as this standard covers flanges in sizes NPS 26 and above [1].
As you navigate through the correct table, you’ll encounter groove dimensions, raised portion diameters, approximate distances between flanges, and so on.
On the other hand, for the dimensions of metallic flange gaskets for RTJ flanges, refer to the standard ASME B16.20, where ring gasket types R, RX, and BX are covered [2]. There, you’ll see exactly dimensions like outside diameter, height of ring, hole size, and so on.
Generally, flange gaskets last anywhere from 5 to 20 years [3]. However, a gasket’s lifespan depends on three key factors: gasket selection, quality, and proper installation.
When selecting a gasket, ensure it’s compatible with the design pressure and temperature, and the type of media in your application. In other words,, gaskets intended for high-pressure environments should be made from materials that can handle the stress.
Otherwise, if you use a gasket that’s not compatible, it may become brittle and lose its sealing effectiveness.
The quality of the gasket also has a big impact. Less expensive gaskets may likely be of lower-quality, which degrades faster under demanding conditions. You are better off investing in flange gaskets from trusted manufacturers as these are designed to hold up a secure seal over the long run.
Lastly, make sure installation is done right the first time. Properly aligning the flanges and applying the correct torque when tightening the bolts can minimize stress on the gasket. This reduces the risk of leaks, extends the gasket’s lifespan, and helps avoid costly issues later on.
The main difference between RF (raised face) flanges and RTJ (ring-type joint) flanges is their sealing mechanism and pressure handling.
RF flanges use a soft gasket on a raised surface for a flexible seal. RTJ flanges, meanwhile, use a metal ring gasket in a machined groove for a tight, metal-to-metal seal.
Let’s take a closer look at how these flanges compare and when you should choose one over the other.
An RF flange has a slightly elevated surface where the gasket sits. This design helps focus pressure on a smaller area, creating a reliable seal with soft gaskets. RF flanges are the most common flange facing type.
Common Uses: Chemical plants, water treatment facilities, and oil pipelines.
An RTJ flange has a machined groove that holds a metal ring gasket. When bolted, the ring deforms to create a metal-to-metal seal. This design handles extreme pressure and temperature better than RF flanges.
Common uses: Oil refineries, steam pipelines, and petrochemical plants.
So how do RF and RTJ flanges compare? Here’s an overview of their differences:
| Feature | RF Flange (Raised Face) | RTJ Flange (Ring-Type Joint) |
| Sealing Mechanism | Soft gasket seal | Metal-to-metal ring gasket |
| Pressure Capacity | Moderate (up to 2500 PSI) | High (over 20,000 PSI) |
| Temperature Handling | Moderate (up to 750°F with carbon steel) | High (over 1000°F with suitable materials) |
| Thickness | Thinner due to soft gasket use | Thicker to support metal ring seal |
| Gasket Material | Soft materials like graphite, PTFE | Metal ring (soft iron, stainless steel) |
| Installation | Simple, easier to align | Requires precise alignment |
| Cost | Lower due to simpler design | Higher due to machining and metal gasket |
| Maintenance | Easier, with accessible gaskets | More complex, requires groove inspection |
| Application Suitability | Chemical, water, and moderate-pressure pipelines | Oil, gas, and extreme-pressure pipelines |
RTJ flanges are thicker than RF flanges. The added thickness supports the pressure from the metal ring gasket.
According to ASME B16.5 standards, surface heights vary:
RF flanges use soft gaskets like graphite or PTFE. This makes them easier to install and replace. However, they are more prone to leakage under high pressure.
RTJ flanges rely on metal ring gaskets for a metal-to-metal seal. This helps them provide superior leak prevention under high pressure and temperature.
RF flanges are simpler to install because the raised face helps align the gasket.
RTJ flanges demand precise alignment of the ring gasket in the groove. A small misalignment can cause leaks or gasket damage.
You should use RF flanges if:
You should choose RTJ flanges if:
No, you cannot connect RF and RTJ flanges directly. They have different sealing surfaces:
RTJ flanges need a metal ring that fits into a machined groove.
Mixing them will cause leaks and may damage the flanges.
At Longan Flange, we specialize in delivering high-quality steel flanges that are fully compliant with ASME, DIN, BS, JIS, and GOST specifications. You can trust they’ll perform effectively in various applications and environments.
We also produce custom, non-standard products tailored to your unique setup. Contact us today and let’s talk about how we can support you and your pipe flange needs.
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Tel: +86-15258415825
+86-15858538689
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