What are SAE Flanges? If this question confounds you, this is the right place to get answers.
SAE Flanges is a range of high pressure hydraulic flange which is made in accordance to SAE J518 standards. The acronym SAE stands for Society of Automotive Engineers. These flanges are used on oil hydraulic systems in many fields (shipbuilding, mobile hydraulic equipment, machine tools, earth moving machines, etc… ) and where there is passage of oil under pressure.
Flanges are made from normalized forgings and are usually of two kinds of material, steel ST52.3 and stainless steel AISI SS316L.
SAE Flanges come in two series, SAE code 61 (3000 series) and SAE code 62 (6000 series). For code 61 (3000# series), they are available in all nominal sizes between DN10 (3/8″) and DN125 (5″). For code 62 (6000# series), they are available in all nominal sizes between DN10 (3/8″) and DN80 (3″)
The standard pressure ranges from 34 to 345 bar for code 61 (3000 series) and 200 to 414 bar for code 62 (6000 series). Please take note that the pressure information of the flange and connected equipment combinations may vary from each other. For example: if a pipe connected to the flange has a lower working pressure, it will result in an overall lower working pressure of the system. Therefore, please consider the lowest pressure as the maximum working pressure of this combination.
The standard working pressure of carbon steel SAE flanges is between -40°C and +120°C. For stainless steel, the standard working pressure is between -60°C and +50°C. Working Pressure for SAE Flanges made from stainless steel and used at elevated temperatures have to be:
Reduced by 4%: +50°C to < +100°C
Reduced by 11%: +100°C to < +200°C
Reduced by 20%: +200°C to < +250°C
How SAE Flanges work:
A complete set comprises of a flat side flange and an o-ring side flange. The o-ring side flange contains a groove seat to place a rubber o-ring (normally made of NBR material). The complete set forms a seal between a flat surface and o-ring held in a recessed circular groove in the other half. Tightening the bolts draws the two halves together and compresses the O-ring.
Due to this usage of the o-ring, flanges with o-rings has an advantage over metal to metal flanges as all-metal flanges are more prone to leakage because they must be tightened to a higher, yet narrower torque range. This makes metal to metal flanges more prone to strip threads or crack.
A complete set of flange is tightened using socket head cap screws & spring washers according to recommended torque. The screw lengths are usually shorter than the overall SAE flanges length but this is normal in accordance to SAE J518 standard. Also, as per SAE J518, there are no requirements for hex nuts for securing the flanges.