In the PN series of chemical flanges, common sealing surface types include protruding surface (RF), full flat surface (FF), concave convex surface (MFM), tenon groove surface (TG), ring connection surface (RJ), etc. Each type has unique characteristics and applicable scenarios, as follows:

1. Raised Face (RF)

● Features:

The sealing surface is a smooth convex surface, with a simple structure and easy processing.

Suitable for general media and pressure conditions, with moderate sealing performance.

It needs to be used in conjunction with gaskets, which are prone to being squeezed to both sides and require a large amount of bolt force to tighten.

● Applicable scenarios:

Suitable for low and medium pressure pipeline systems with nominal pressure PN ≤ 25MPa.

Commonly used for pipeline connections in non corrosive media such as water, steam, and air.

Widely used in general working conditions in industries such as petroleum, chemical, and power.

2. Full Flat Face (FF)

● Features:

The sealing surface is completely flat, without any protrusions or indentations.

The structure is simple and the processing cost is low, but the sealing performance is poor.

It needs to be used in conjunction with thick gaskets or special gaskets (such as metal coated gaskets).

● Applicable scenarios:

Suitable for low-pressure, non critical sealing applications with nominal pressure PN ≤ 1.6MPa.

Commonly used as matching flanges for cast iron equipment, valves, or low-pressure vessels.

Suitable for scenarios where the medium is non-toxic, non corrosive, and does not require high sealing requirements.

3. Male Female Face (MFM)

● Features:

The sealing surfaces of a pair of flanges are concave and convex, with the convex surface embedded in the concave surface.

The stopper on the outside of the concave surface can prevent the gasket from extruding outward, and the sealing performance is better than that of the protruding surface.

Gasket replacement is convenient, but the structure is complex and the processing cost is high.

● Applicable scenarios:

Suitable for medium pressure pipeline systems with nominal pressure PN ≤ 6.3MPa.

Commonly seen in pipeline connections with nominal diameter DN ≤ 800mm.

Suitable for medium pressure working conditions of general media such as oil and chemicals.

4. Tongue and Grove Face (TG)

● Features:

The sealing surfaces of a pair of flanges are mortise and tenon shaped and groove shaped, with gaskets placed in the grooves.

The gasket will not be squeezed out, the force is uniform, and the seal is reliable.

The structure is complex, requiring high machining accuracy, and it is difficult to replace the gasket.

● Applicable scenarios:

Suitable for high-pressure, high-temperature, or flammable and explosive medium pipelines with nominal pressure PN ≤ 20MPa.

Commonly found in critical sealing applications with nominal diameter DN ≤ 800mm.

Widely used in hazardous medium pipelines in industries such as petroleum, natural gas, and chemical.

5. Ring Joint Face (RJ)

● Features:

The sealing surface is a trapezoidal groove or octagonal groove, used in conjunction with a metal ring gasket.

The metal ring gasket forms a "line contact" with the groove surface, with high sealing pressure and reliable effect.

Suitable for ultra-high pressure, high temperature, or highly corrosive media, but at a higher cost.

● Applicable scenarios:

Suitable for ultra-high pressure pipeline systems with nominal pressure PN ≥ 6.3MPa.

Commonly used for pipeline connections in high-temperature, high-pressure, or highly corrosive media such as hydrogen and liquefied gas.

Key equipment widely used in industries such as oil, natural gas, and nuclear power.

Key points for selecting sealing surface types

● Medium characteristics:

Corrosive media: Stainless steel or alloy steel materials are preferred, and corrosion-resistant gaskets (such as polytetrafluoroethylene gaskets) are used in combination.

Flammable and explosive media: Priority should be given to using mortise and tenon surfaces (TG) or ring joint surfaces (RJ) to ensure reliable sealing.

High temperature medium: Priority should be given to using RJ or metal gaskets to prevent gasket aging.

Pressure and temperature:

Low voltage, room temperature: You can choose to use either RF or FF.

Medium pressure and medium temperature: can choose between concave convex surface (MFM) or mortise and tenon surface (TG).

High pressure and high temperature: Ring connection surface (RJ) or trapezoidal groove sealing surface must be selected.

Economy and operability:

Cost sensitive scenarios: Prioritize the use of structurally simple protruding surfaces (RF) or full flat surfaces (FF).

Scenarios that require frequent disassembly: Priority should be given to using concave convex surfaces (MFM) or convex surfaces (RF) that facilitate gasket replacement.