4. Clamp-Type Repair
Mechanical clamps restore service strength without welding the host body — eliminating burn-through and hydrogen / cold embrittlement risk. Construction and process are correspondingly more complex, and cost is higher.
Figure 1 illustrates a typical clamp. The method suits temporary emergency response on oil and gas pipelines, primarily where the pipe is already leaking. For gas line emergency repair, the internal pressure must drop to ≤ 1/3 of design before work begins.
Clamp variants in service include:
- Bolted clamp — two-piece clamp bolted around the pipe, gasket-sealed
- Epoxy-injection clamp — the bolted clamp is augmented with high-strength epoxy injected between clamp and pipe, sealing leaks and transferring load through cured epoxy
- Hot-tap stop-flow clamp — for live operations requiring isolation
Clamps work well where leak control is the priority. For non-leaking but defective pipe, the construction effort and cost of a clamp installation are often disproportionate to the benefit, and composite repair becomes the more sensible choice.