“VelociFoam employs polyurethane-based technology within a proprietary process to dramatically change the geotechnical stability, economics, safety, security and environmental footprint of pipeline installation.”
(See the FAQ for answer to questions about the safety and other properties of PU foam.)
The construction industry has long made use of lightweight polymers such as polystyrene and polyurethane foam, due to the higher mechanical strength-to-weight ratios and longevity the materials enjoy over traditional materials such as wood, stone and steel.
The VelociFoam method utilises 7 main properties, singularly and in combination:
- Tensile strength
- The layer of PU foam binds pipe sections to each other, across any kind of joint, imitating a fully restrained joint.
- Compressive strength
- The PU foam provides a very high level of mechanical protection to the pipe surface, from general granular soil backfill, and unintended larger objects.
- This property is actually a combination of many others in pure engineering terms. For VelociFoam, elasticity is important because it allows a continuous, repeated and totally predictable return of the PU foam mass to its original position after repeated mechanical loading cycles.
- Load spreading
- The cellular nature of PU foam means that loads of all kinds, both ‘blunt’ and ‘point’, are spread in a near-90° cone from the point of contact and into the foam mass. This is very important for applications where dynamic loading, such as vehicle traffic is a factor in pipeline engineering.
- PU foam has strong adhesion to most pipe surface, both metallic and polymer. This property is important when axial forces must be counteracted, particularly in thrust block applications.
- Water impermeability
- Of particular importance to metal pipelines, PU foam is generally almost completely watertight.
- Chemical Inertness
- PU foam is chemically inert once cured. This property, particularly in conjunction with water impermeability, means that VelociFoam is a very environmentally-friendly solution to many buried pipeline challenges.
How We Use PU Foam
Although there are variations on each, the VelociFoam method covers two main application areas:
- Linear Pipeline Sections
- Thrust Block / Pipe Bends
Linear Pipeline Sections
(By this term, we mean lengths of pipe installation using normal coupling joints, without specialised bends. These sections normally don’t exceed 1.5° angular deflection in each joint.)
The main functional requirements for use of PU foam on ‘straight’ sections of a pipeline are
- geotechnical stability
- mechanical protection
We spray a layer of PU foam onto the pipe in situ, in a continuous mass, across the joints. The depth of the PU foam is between 75 and 125mm, depending on pipe dimension and stability requirements.
The system provides axial stability both by ‘gluing’ pipe sections to each other across pipe joints, thus preventing axial movement inside the coupler, and by interacting with the surrounding soil masses, causing ‘friction’. The system provides lateral and vertical stability through a combination of interaction with soil masses: the weight of soil above the pipe / foam system and dilatancy induced by shear forces where the uneven foam surface and the surrounding soils interlock.
The system provides mechanical protection by placing a very strong layer of foam between the pipe and any object. This is discussed in more depth here.
Thrust Block / Pipe Bends
We spray consecutive layers of PU foam onto a pipe bend, to a calculated depth relative to the resultant thrust forces.