Lap Joint Flange Definition and Details

Lap Joint Flanges have all the same common dimensions as any other flange named on this page however it does not have a raised face, they used in conjunction with a “Lap Joint Stub End“.These flanges are nearly identical to a Slip On flange with the exception of a radius at the intersection of the flange face and the bore to accommodate the flanged portion of the Stub End.
Their pressure-holding ability is little, if any, better than that of Slip On flanges and the fatigue life for the assembly is only one tenth that of Welding Neck flanges.They may be used at all pressures and are available in a full size range. These flanges slip over the pipe, and are not welded or otherwise fastened to it. Bolting pressure is transmitted to the gasket by the pressure of the flange against the back of the pipe lap (Stub End).

Lap Joint Flange Application

Lap Joint flanges have certain special advantages:
Freedom to swivel around the pipe facilitates the lining up of opposing flange bolt holes.
Lack of contact with the fluid in the pipe often permits the use of inexpensive carbon steel flanges with corrosion resistant pipe.In systems which erode or corrode quickly, the flanges may be salvaged for re-use.

Lap joint pipe flanges slide directly over the pipe and are most commonly used with stub end fittings. A pipe is usually welded to the Stub End and the Lap Joint pipe flange is free to rotate around the stub end. The benefit of this is that there will not be any issues with bolt hole alignment. Lap Joint pipe flanges are often used for applications that require frequent dismantling.

Lap Joint Flanges(Loose Flanges) are used with a corresponding stub-end that “inserts” in the inside of the flange. The main benefit of this type of flange, is that once the pipe welds to the insert stub-end, the flange then can rotate for easier alignment of the bolting holes. However, lap joint flanges and their stub-ends’ ability to hold pressure is about the same as slip-on flanges. They are not suitable for situations with a high external or changing loads of force. They do provide an advantage in a piping system that needs frequent dismantling for inspection or to remove build-ups.

Lap Joint Flange Standards:

ASME B16.5 Pipe Flanges and Flanged Fittings
ASME B16.47 Series A Steel Flanges NPS 26 Through NPS 60
API 605/ASME B16.47 Series B Steel Flanges NPS 26 Through NPS 60
BS EN 1759 Flanges and their joints. Circular flanges for pipes, valves, fittings and accessories, class-designated. Steel flanges
EN 1092 Circular flanges for pipes, valves, fittings

BS 4504 Circular flanges for pipes,valves and fittings
JIS B2220 Steel pipe flanges

DIN 2641 PN6 Loose (Lapped Joint) Flange Plain Collar 

DIN 2642 PN10 Loose (Lapped Joint) Flange Plain Collar 
DIN2655 PN25 Loose (Lapped Joint) Flange Plain Collar
DIN2656 PN40 Loose (Lapped Joint) Flange Plain Collar
GOST 12822 Steel loose flanges with welded ring for Pnom from 0,1 to 2,5 MPa (from 1 to 25 kgf/cm<(hoch)2>). Design and dimensions

Lap Joint Flange Pressure Rating:

America Series:Class 150 ,Class 300, Class 600, Class 900A ,Class 1500,Class 2500.

Europe Series:PN2.5,PN6,PN10,PN16,PN25,PN40,PN63,PN100,PN160,PN250,PN320,PN400.

Lap Joint Flange Facing Types

America Series:Flat face(FF),Raised face(RF),Tongue(T),Groove(G),Female(F),Male(M),Ring type joints face(RJ/RTJ)

Europe Series:Type A(Flat Face),Type B(Raised Face),Type C(Tongue),Type D(Groove),Type E(Spigot),Type F(Recess),Type G(O-Ring Spigot),Type H(O-Ring Groove)

Lap Joint Flange Material 

Carbon Steel Blind Flange:
A105 GradeⅠ Carbon Steel Blind Flange
A105 GradeⅡ Carbon Steel Blind Flange
Alloy Steels Blind Flange:
A182 Grade F1 Alloy Steel Blind Flange
A182 Grade F5 Alloy Steel Blind Flange
A182 Grade F7 Alloy Steel Blind Flange
A182 Grade F9 Alloy Steel Blind Flange
A182 Grade F11 Alloy Steel Blind Flange
A182 Grade F12 Alloy Steel Blind Flange
A182 Grade F22 Alloy Steels Blind Flange
Low-Temperat Steel Blind Flange:
A350 Grade LF1 Low-Temperat Steel Blind Flange
A350 Grade LF3 Low-Temperat Steel Blind Flange
A350 Grade LF4 Low-Temperat Steel Blind Flange
A350 Grade LF6 Low-Temperat Steel Blind Flange
A350 Grade LF8 Low-Temperat Steel Blind Flange
Stainless Steel Blind Flange:
A182 Grade F304 Stainless Steel Blind Flange
A182 Grade F304H Stainless Steel Blind Flange
A182 Grade F304L Stainless Steel Blind Flange
A182 Grade F316 Stainless Steel Blind Flange
A182 Grade F316H Stainless Steel Blind Flange
A182 Grade F316L Stainless Steel Blind Flange
A182 Grade F321 Stainless Steel Blind Flange
A182 Grade F321H Stainless Steel Blind Flange
A182 Grade F347 Stainless Steel Blind Flange
A182 Grade F347H Stainless Steel Blind Flange

Industrial Processes : Die forging,Machining.

Application for Lap Joint flange(LJ flange) /Loose flanges :Natural gas,chemical,petroleum,ship building,marine,paper making, metallurgy, electric, power, boiler , etc.

Hebei haihao group, as a first class manufacturer of Lap Joint flange(LJ flange) /Loose Flange in China,supplys a variety of steel flanges to satisfy our customers’ specifica requirements,which include different size,different schedule,different pressure and different finish faces. Our products are produced strictly according to the required standard. Our raw material for Lap Joint flanges(LJ flange) Loose Flanges all are purchased from big steel companies which can make sure the material in a high quality.