In our previous blog, we talked about the most common flange types used in the industry. Today, we would like to discuss on another important aspect of a flange – flange face. Understanding flange faces plays a crucial role to ensure that the right fit, right gasket and safety can be applied.
Flange face is the surface where contact between two flanges occur. A sealing component is generally introduced between the mating surface, such as metal or gasket. Below is a compilation of flange facing types that are commonly recognized in the market.
1. FLAT FACE (FF)
As its names suggest, flat face flange has a flat face. This means that the gasket seat is on the same plane as bolting circle face. Flat face allows full contact across the whole face of the two mating flanges and uses full face gasket. Flat Face flange is used for equipment made from cast iron or other brittle materials hence is only applicable for low temperature and low-pressure applications. It is important to only mate flat face flange with flat face flange and not a raised face.
2. RAISED FACE (RF)
Most widely used flange. Raised face flange has a small raised ring area around the bore where the gasket will be seated. Raised face flange can concentrate more pressure on a smaller gasket area and increases the seal and flange’s joint pressure containment capability. Raised face is typically used for equipment made from forged steel.
The height of the raised face depends on the flange’s pressure class rating. Pressure class 150 and 300 will have the height of raised face approximately 1.6mm (1/16 inch) while pressure class 400, 600, 900, 1500 and 2500 will have the height raised to approximately 6.4mm (1/4 inch).
3. RING TYPE JOINT FACE (RTJ)
Ring type joint (RTJ) flange has an embedded circular grove on its raised face where gasket will seat. When two RTJ flanges are bolted and tightened together, the gasket inside the flange groove will be compressed and will form a tight metal to metal seal. Other benefit of RTJ flange is that the raised face protects the gasket from over compression. RTJ flange has a good pressure and temperature resistance and used for highly demanding applications.
RTJ uses a metallic sealing ring gasket that is suitable for high pressure and high temperature. The gasket comes in either oval or octagonal cross-sectional area. The latter has a better sealing property than the former but only applicable for latest flange design.
4. TONGUE & GROOVE (T&G)
Tongue and groove (T&G) flange consist of two parts: tongue and groove. The tongue has a raised surface while the groove has a matching depression (groove) machined to its face. Both parts need to be matched to seal connection. Tongue and groove can self-align and has a good sealing property.
5. MALE & FEMALE FACE (M&F)
Male and Female face (M&F) has similar design with T&G except that its raised surface and groove’s ID extend into the bore hole. The male face is commonly mistaken as a raised face due to their similarities. The typical depth of the female groove is 3/16 inch while the typical height of the male raised face is ¼ inch.
Both tongue and groove and male and female have good sealing and accurate gasket compression. Their downside is their high cost due to lack of commercial availability.
If you are looking for any flanges, you may want to contact us at (65) 6298 3211 or firstname.lastname@example.org. Wah Joo Seng can assemble, deliver and supply our hose assemblies with flanges! Check out our flange collections here!