Project Tag: Non Destructive Testing (NDT)

Marine Outfall ROV Inspection

The Brightwater Marine Outfall was constructed and deployed in 2008 and came online in September 2012. Shortly after leaving the shoreline near Point Wells, WA, the pipeline branches into two parallel 84” HDPE outfall pipelines; diffuser ports are located on the last 250 linear feet of each pipe along with steel access gate structures. Semi-annual …

SS Montebello ROV Assessment

Global Diving and Salvage Inc. has been contracted by the United States Coast Guard to determine if oil is present aboard the sunken ship S.S. Montebello,which sits 900 feet below the ocean surface approximately 6.5 miles off the coast of Cambria,California.

The S.S. Montebello sank after a Japanese submarine torpedoed the large oil tanker on December 23,1941. The vessel broke apart landing upright with her bow separated from the majority of the wreckage. To date,no signs of leakage have been detected,and from previous visual inspections by submarine,the cargo section appears to be intact.

The possibility of future oil release has prompted the U.S. Coast Guard to contract Global to determine the integrity of the cargo section and its contents. Coast Guard Capt. Roger Laferrier,acting as the Federal On-Scene Coordinator,states,“The California coast is a vital national resource that we must protect.” Additionally,he explains,“Working in concert with our state and local partners,it is our duty to ensure we gain good information about the Montebello so we can do our best to protect the marine environment.”

Global’s Cougar XT ROV will be used as the platform which will support the inspection,both visual and sonar,thickness gauging,backscatter tooling operations,physical sampling of the tank contents,and sediment sampling from the general area. Global has teamed with T & T Bisso to provide engineering support and 3D modeling on the vessel. Additionally,Tracerco has been subcontracted to utilize their neutron backscatter tool,a non-invasive sensing device,which will be used to determine the presence of oil and oil/water interface.

“This sampling and observation operation will provide the answers needed to truly assess what threat,if any,the Montebello poses,” said Capt. Chris Graff from California Department of Fish and Game’s Office of Spill Prevention and Response,who will be serving as the State On-Scene Coordinator.

“Global Diving & Salvage is pleased to work in collaboration with the United States Coast Guard,other federal and state agencies,and our teaming partners to assist in the assessment of the vessel in a safe and efficient manner” says Devon Grennan,President of Global Diving & Salvage,Inc. “The project provides a unique opportunity to take a proactive approach towards mitigating potential pollution threats,and Global is proud to be a part of it.”

Marine Terminal Inspection

Our inspections included underwater thickness measurements,cathodic protection readings,flooded member tests,underwater digital still and video imagery. To complete necessary inspections,some areas required the use of 20,000psi high pressure water cleaning.

We provided the client with a complete detailed report including photographs,CAD drawings,and recommendations.

Platform Inspection

Our inspection of the this platform included high pressure cleaning of weld locations for inspections and concurrent black-water photography for the client’s records.

Subsea Pipeline Spool Piece Installation

We were hired to replace a pipeline spool exiting on one leg of the production platform Grayling located in Cook Inlet. The project required taking ultrasonic thickness readings and blackwater video pictures of various components.

The project involved removing pipe sections,measuring replacement pieces,and installing the new surface-fabricated steel pipe replacement pieces. Hydraulic stud stretchers and hydraulic impact wrenches were used to take apart and replace the flange bolts. Re-tightening the flange bolts required following an exact torque sequence.

The two replacements were completed in approximately a working depth of 140 feet of sea water.

Red Dog Mine Dock Inspection and Maintenance

We performed inspection and maintenance services on the Red Dog Mine’s dock and loading cells. The project involved underwater video and photographic inspections of the sheet piles,along with underwater welding to install additional passive anodes. During inspection,the dive team discovered loose bolts attaching the diffuser assembly. Cell calibration and reference cells were included in the dive package,plus underwater welding and burning equipment,a support vessel,a flyaway dive system,underwater video and still photography equipment,a portable generator,and a digital thickness machine.

New York Water Supply

Phase 1

We were contracted by Roundout Constructors to perform detailed inspection and measurements of an existing horizontal drift and submarine door,removal of existing plumbing components,remove and replace a 24-inch gate valve encased in concrete. The work was performed in an access shaft of the Delaware Aqueduct system,owned and operated by New York City’s Department of Environmental Protection. The drift and valve are located in approximately 685 feet of water,at the bottom of an 13-foot diameter shaft,north of New York City.

The purpose of the project was to inspect and verify the condition of the drift and submarine door,remove several pieces of plumbing and replace a valve to allow de-watering of the system.

Prior to start of the project on-site,all aspects of the project had to be performed in a full-scale mock-up,to demonstrate the methodology and constructibility of the tasks. Full-size mock-ups were designed and built addressing the salient points of the project. Highly specialized tooling had to be designed and work plans drawn up simply to get to the work location. All the tools,equipment and personnel had to come and go via an 13-foot diameter shaft. To complicate matters,the top of the shaft was enclosed by a concrete structure with doors on opposing sides,10-feet wide by 15-feet high,that limited access. We designed and built all of the mock-ups,specialized tooling and equipment in our Seattle office. The mock-up demonstrations were carried out at a local shipyard in shallow water. Access to the shaft and drift required the specialized design of components and rigging to move tooling into place. A track system was designed to allow for adjustment in both the X and Y axis,allowing for a consistent,repeatable point to be moved in and out of the drift. A fast-scanning sonar head was mounted to a purpose built cart,combined with some tactile measurements,we were able to achieve measurement of the 70 feet long drift to within +/- 1/8”. The track system and cart were also designed to accommodate the core drill base which allowed for sample cores to be taken at any radial location along the drift.

Sections of the existing 24-inch manganese bronze piping: elbow,tee and needle valve were removed. Piping was cut using a remotely operated rotary mill. Approximately 25,000 pounds of piping was removed. A 24-inch gate valve,encased in concrete to above the valve bonnet was completely exposed using a combination of hydraulic splitting and ultra high pressure water blasting to remove approximately 7 cubic yards of concrete. 1 ¾” holes were cored over 6-feet deep to accept the hydraulic splitters. A detailed plan of the hole spacing and splitting sequence was planned and performed on a mock-up of the valve and concrete encasement in our yard in Seattle to ensure that there would be no stress on the active valve during the concrete removal. This was critical,because the allowable work periods would not have let us return to the project until late fall of 2009. The valve was exposed and removed,and we then completed installation of the new hydraulically operated valve.

Working at 685 feet of water required the use of saturation diving. The complete system was moved into the building that housed the shaft. Every component had to be moved through a 10-foot wide door. This system was set up to accommodate 6 divers. The system is equipped with re-breathers,enabling the reuse of the helium component of the breathing gas mixtures.

Phase 2

In preparation for the upcoming bypass tunnel installation Global Diving & Salvage,Inc. was further contracted to install a mechanical plug to isolate the dewatering shaft from the Delaware Aqueduct in upstate New York. At the bottom of the shaft is a horizontal drift that was used for access during the original construction. The drift has a bronze hemispherical submarine door to isolate the aqueduct from the shaft. Depending on the demand,this door can see up to 1,100 feet of head pressure.

To install the pumps and plumbing required to support the bypass operation the shaft will need to be dewatered. To provide an added safety measure,saturation divers installed a mechanical plug approximately 50 feet into the drift.

The plug weights over 23,000 pounds,is five feet wide by seven feet tall and approximately four feet thick. It has a mechanical seal as well as two grout actuated seals to seal the perimeter. To withstand the over two million pounds of force the plug may see a series of struts were mechanically anchored into the drift walls around the perimeter of the bulkhead.

Highly specialized tooling and fixtures were developed for this project in order to assist the diver in the installation of the plug and its components. Divers were transported to and from the work site by an eight foot diameter diving bell. Given a shaft diameter of only thirteen feet,all materials and tools had to be lowered prior to the bell being launched and had to be retrieved after the bell was recovered.

A detailed rigging plan was developed to allow for the loads to be lowered in the center of the shaft then pulled over to the side wall to allow room for the bell. A track system was installed along the floor of the drift to allow the divers to move the equipment and materials to the plug location.

A remote operated hydraulic crane was also designed and fabricated by Global specifically for this project. The crane,operated from the surface,assisted the diver in handling and installing the various pieces of the plug,some of which weighted up to 500 pounds.