Mechanical Engineering Intern
Schlumberger - Houston, TX
Completions Houston Product Center
June 2019 - September 2019
At Schlumberger, I worked as a Sustaining Engineer Intern on the Safety Valves Team. The safety valve on a deep sea drill is the most critical line of defense, powered by hydraulics to seal the drill and stop operations in case of emergency or environmental damage. The sustaining engineers group troubleshoots the immediate failures of safety valves in the field and makes design changes accordingly.
For my internship, I overtook a departing employee’s project to investigate and redesign a high pressure seal for the hydraulic piston. As seen above, the layered o- and v-rings showed heavy damage after only a few hydraulic actuation cycles. The piston head failure resulted in several global instances of leaked gas into the sea and was a high profile problem that received company-wide pressure to address by the end of the year.
My role included:
1) Identifying failure modes causing the subsea gas leaks from a hydraulic piston head seal in deep sea safety valves
From images, previous test reports, and acquired field samples, my first objective was to characterize the cause of failure. The seal was initially verified to a safety factor of 4+ for pressure and temperature, yet there were immediate extrusions and cuts after the first actuation cycle in several tests. I determined the final cause to be the surge of fluid cutting through the Teflon o-ring when the safety valve is initially pressurized. The 10,000psi pressure differential is released all at once during the first piston movement, which caused the gas to rush through the seal and damage it.
2) Redesigning a piston-head face seal to a Teflon-coated metal c-ring to withstand both low and high pressure sealing
There is little to no control over the pressurization of the safety valve when implemented at deep sea drilling site, so the seal required redesign to withstand potential fluid surges up to 10,000psi. The piston must seal also at low pressures; a metal o-ring was insufficient for a low pressure differential. I worked closely between the sustaining team and the Schlumberger HQ Seals Team to research materials and o-ring variations. The final design features a Teflon-coated metal c-ring: the Teflon coating supports sealing at low pressures and the open c-ring allows fluid pressure release in multiple channels.
3) Testing and qualifying the new seal design for 600 hydraulic actuation cycles at 10,000psi and 350F
I designed three testing procedures to verify and validate the seal for implementation. The first setup tests only the piston and hydraulic chamber portion to full pressure; the second test is to full pressure and temperature; the third test is the entire safety valve at full pressure and temperature for 600 hydraulic actuation cycles to simulate the lifetime of the product.
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Working closely with the product designers, the testing engineers, the machinists, and the specialist seal team was a great opportunity to learn from a wealth of engineering knowledge. This internship was an invaluable experience around the adaptability and extreme conditions required of energy resources.
