12 Oct 96″ Surge Tower Rehabilitation Isolation Plug
THE PROBLEM:
Our customer, a hydropower operator and their consulting engineers, came to us with their problem: the need for a temporary water pressure isolation device to allow rehabilitation on existing pipe works, as well as the removal and eventual re-build of a surge tower at an existing hydro-electric plant in North America. As is the case with many aged infrastructure projects, the piping system into which the bulkhead was to be installed was severely corroded and eroded, as well as potentially quite out of round. The installation location was extremely remote with widely varying temperatures. Product installation had to be timed seasonally with partial demolition occurring prior to installation, for what could be several months, up to a year.
The need was for a product to provide fail-safe leak-tight service for construction contractors in potentially confined spaces. The bulkhead in question would need to be nearly eight feet in diameter to handle sealing service of over 50 psig, as well as self-restrain itself in the same degraded infrastructure against all generated loads due to pressure.
WHAT IS A SURGE TOWER/TANK?
THE PROBLEM AND THE SOLUTION
THE SOLUTION:
Mechanical Research & Design, Inc. worked with the customer, their engineers, and subcontractors to provide an effective design and fabricated product that were able to pressure test onsite prior to delivery. The final solution was a dual redundant seal bulkhead, or large mechanical/inflatable plug with integral restraint. The bulkhead utilized dual, redundant seals, one SEALFAST® mechanical seal and one SEALFAST® inflatable seal, both engineered specially, to seal on highly-corroded pipe surfaces. The mechanical seal, the primary fail-safe seal, was a SEALFAST® active compression type seal, using manually torqued seal nuts to expand the seal in place, providing no-maintenance, long term, and safe sealing. The inflatable seal was a SEALFAST® extended-reach design seal, perfect for increased seal range requirements as well as out of round piping conditions, lower temperatures, and inflatable via air, bottled gas, or water. The restraint system utilized proprietary traction pads that were manually torqued, in sequence, and custom spaced during design, to handle the eroded conditions of the pipe (variable thin wall thicknesses, extreme corrosion), maximize performance, and maintain worker safety.
Mechanical Research & Design, Inc. worked with the customer to provide special instruction on assembly of the multi-piece assembly in a pipe of unknown out of roundness and few datums (i.e. – the challenges of installing a long cylinder straight and aligned within another cylinder). Special monitoring devices were added to the tool, additionally, to confirm pressures between the seals for redundancy as well as the provision of a large bypass to facilitate safe removal and overpressure monitoring and regulation.
The final, assembled product was also tested in a large scale test structure. mimicking installation challenges, offering functional practice, redundancy checks, and pressure testing to confirm the structure, sealability, as well as restraint at elevated pressures.
