1. What are the common size ranges for SSAW pipes?
Answer: SSAW pipes are known for their large diameters. The typical outside diameter (OD) range is from 20 inches (508 mm) up to 100 inches (2540 mm) or even larger. The wall thickness can also vary significantly based on the design pressure and structural requirements.
2. What are the limitations or disadvantages of SSAW pipes?
Answer: The main disadvantages are:
The spiral weld seam is generally longer than a longitudinal seam, which can be considered a potential weak point over a greater length.
They may have a slightly rougher internal surface compared to seamless pipes, which can increase flow friction.
For high-pressure, critical applications, seamless or LSAW pipes are often preferred due to their more uniform stress distribution.
3. How is the quality of the weld on an SSAW pipe ensured?
Answer: Quality is ensured through rigorous Non-Destructive Testing (NDT) methods. The primary technique used online is Ultrasonic Testing (UT), which continuously inspects the entire weld seam for defects like cracks, lack of fusion, or porosity. Additional tests like X-ray inspection may also be performed.
4. What types of protective coatings are applied to SSAW pipes?
Answer: To prevent corrosion, SSAW pipes are often coated. Common coatings include:
FBE (Fusion Bonded Epoxy): A thin, durable thermosetting powder coating.
3LPE/3LPP (3-Layer Polyethylene/Polypropylene): A multi-layer system with FBE, a copolymer adhesive, and an outer polyolefin layer for superior protection.
Bituminous Coatings: For less aggressive environments or water pipelines.
Galvanization: Applying a zinc coating for general structural use.
5. Why is SSAW pipe popular for piling and foundation work?
Answer: SSAW pipes are excellent for piling because:
Their large diameter provides high load-bearing capacity and bending resistance.
The spiral weld can contribute to increased torsional strength.
They are a cost-effective solution for creating deep foundations for bridges, buildings, and offshore structures. The pipe can be driven into the ground and then filled with concrete.
