Pipe flanges are a foundational component in oil and gas, petrochemical, and other industrial piping systems, connecting and isolating pipeline segments for maintenance, inspection, and system integrity. Coastal Flange has manufactured and supplied pipe flanges since 1985, serving engineers and procurement teams with in-stock inventory and custom manufacturing across steel material grades.
Learn more about lap joint pipe flanges and their applications in different piping systems.
What Are Lap Joint Pipe Flanges and How Do They Work?
A lap joint flange consists of a backing flange and a stub end. The stub end is welded to the pipe, and the lap flange slides over the pipe and rotates around the stub end. Because the lap flange is never fixed to the pipe, bolt holes align without rotating the pipe itself.
Unlike most flange types, the lap joint flange does not contact the process media. The stub end is designed for process contact, while the backing flange is used to secure the bolted connection.
Lap Joint Flanges vs. Slip-On Flanges
A slip-on flange is a single piece that is welded directly in place, which is suited for low-pressure, permanent connections. The lap joint flange stub end assembly is used when:
- A pipeline requires frequent inspection, cleaning, or component replacement
- Dissimilar materials are needed between the flange and the pipe interface
- Bolt-hole alignment is difficult with the piping geometry
Design Considerations for Lap Joint Pipe Flanges
The right flange lap joint depends on material grade, governing specification, and dimensional requirements.
Material Grades
Coastal Flange manufactures the lap flange in carbon steel, stainless steel, and alloy grades:
- Carbon steel. This suits oil and gas pipelines and general industrial service where cost efficiency is a primary driver.
- Stainless steel. This is selected for waterworks distribution systems and applications requiring oxidation resistance.
- Alloy steel. Steel alloys can be used for elevated-temperature service, high-pressure petrochemical applications, and aggressive corrosive conditions.
Because the lap flange does not contact the process fluid, engineers can pair a carbon steel backing flange with a stub end in a different material to reduce overall material cost in corrosive-service installations. This is just one of the reasons the flange lap joint remains a practical choice in piping systems.
Specifications, Sizes, and Dimensions
At Coastal Flange, we can provide lap joint pipe flanges to meet various standards and specifications. ANSI requirements can be met for the following classes of lap joint flanges:
We can also provide lap joint flanges that meet ASME B16.47 specifications for larger-diameter, high-pressure applications or flanges in custom dimensions for specialty projects.
Applications and Benefits of Lap Joint Pipe Flanges
In oil and gas, the lap joint flange and stub end design allows maintenance teams to isolate and access pipeline segments more easily. In petrochemical or waterworks applications, lap joint flange and stub end assemblies can simplify pressure zone repairs with minimum disruption to the broader network.
Some key advantages of using lap joint pipe flanges can include:
- Free rotation. The backing flange rotates independently, eliminating bolt-hole misalignment during installation and reassembly.
- Dismantling access. The assembly attaches and separates without welding or pipe modification, reducing downtime during inspections.
- Material flexibility. Different grades for the stub end and backing flange can support corrosion requirements and procurement budget needs.
- Broad specification coverage. Find flanges for ANSI, ASME, and AWWA specifications from a single source, simplifying purchasing across multi-specification projects.
Lap Joint Pipe Flanges by Coastal Flange
Coastal Flange stocks and manufactures lap joint flanges in carbon steel, stainless steel, and alloy to meet ANSI, ASME, and other specifications. Our Houston, TX facility provides direct access to rail, truck, air, and water transportation for faster delivery. Every order is backed by our in-house QC department and ISO 9001:2015 certification, from standard stock to custom-engineered dimensions.
Browse our product catalog to find lap joint flange options for your project or submit an RFQ to confirm availability, lead time, and pricing.
