When selecting a marine flange, you need to pay attention to the following points:
1, marine flange bolt preload:
A, the pre tightening force of the marine flange can not be too large, it can not be too small. (large: the gasket Yahuai or extrusion; too small: not up to the initial seal gasket compression and implementation conditions.)
B, appropriate to improve the pre tightening of the marine flange, you can increase the sealing capacity of the gasket. (because the capillary porosity of the porous material is reduced)
C, the pre tightening force of the marine flange can be used on the pad, which can be used to reduce the bolt diameter and increase the number of bolts.
2, the use of the ship’s surface (sealing surface) type
A, plane type compression surface
The surface of the compression surface of a marine flange is a plane or a plane with a groove.
Advantages: simple structure, easy processing.
Disadvantages: large contact area, the need for a large preload ratio, bolt bearing large, so the flange and other parts of the requirements of high, bulky, easy to squeeze out of the gasket, sealing performance is poor. The use of P pressure less than 2.5Mpa, not the use of toxic, flammable and explosive medium.
B, concave and convex type
Marine flange is composed of a concave surface and a convex surface with the composition. Put in the concave washer.
Advantages: easy to medium, can prevent gasket extrusion.
Available in P = 6.4Mpa, DN = 800mm
C, trapezoidal groove pressing surface
Marine flange at the bottom of the groove can not afford the sealing effect is groove inside and outside cone and gasket contact trapezoidal form a seal, and elliptic or octagonal cross section of the metal gasket with.
D, conical compression surface
Usually used for high-pressure sealing, the disadvantage is that the required size accuracy and surface roughness requirements are high. Must be matched with lens gasket, commonly used in high-pressure pipeline.
A tenon groove sealing surface, the utility model has the advantages of neutral good, the seal pretightening pressure small, gasket is not easy extrusion is not affected by the medium erosion for flammable and explosive sealing requirements high. The disadvantage is the replacement is difficult, easy to damage the tenon.
Source: Yaang Pipe Industry(www.yaang.com)