What follows is an abbreviated project profile on Stella Maris’ custom-designed IWOCS HPU, 5k/10k Unit, which was custom-designed for Cross Solutions.

Client: Cross Solutions

Project: IWOCS HPU, 5k/10k

The Task: Cross Solutions, a division of Cross Group, based out of Houma, Louisiana, called upon Stella Maris to design and build an IWOCS HPU capable of supplying LP hydraulic control fluid at pressures up to 5,000 psi, as well as HP pressure hydraulic control fluid at pressures up to 10,000 psi. The unit was to be used in the commissioning, testing and intervention of subsea wells and control equipment – and the unit structure needed to be designed, built and approved to meet the stringent DNV 2.7-1 standard. The unit was also to be provided with a self-contained reservoir to hold clean control fluid, returns from testing and operations and to allow for cleanliness levels to be maintained throughout the life of the system.

Design/Fabrication: Two 3.6 GPM, 10,000 psi check ball piston pumps with Class 1 Div 1 25HP 460 VAC electric motors were selected for the HP supply. HP system accumulation was provided by two five-gallon 10,000 psi stainless steel piston accumulators. Each of the HP accumulators were provided with independent isolation and bleed valves along with pressure relief devices on the gas end. Two 6.0 GPM, 6,000 psi check ball piston pumps with Class 1 Div 1 25HP 460 VAC electric motors were selected for the LP supply. LP system accumulation was provided by two 10-gallon 6,000 psi bladder accumulators rated for water service. Each of the LP accumulators were provided with independent isolation and bleed valves along with pressure relief devices on the gas end. Extra space on the skid was provided for future addition of two 10-gallon 6,000 psi bladder accumulators.

The 316 stainless steel reservoir consisted of two chambers: one return compartment, and one supply compartment. The reservoir had a combined volume of 550 gallons. A recirculation pump was provided for recirculation of the control fluid to maintain high cleanliness levels as well as fill capability as new fluid is required to be added in the system. Sample points on each reservoir compartment were provided to check and sample fluid periodically. Visual level gauges were provided to monitor levels in each compartment. An electronic level switch was provided on the supply compartment to disable the HP and LP pumps’ operation during a low level condition.

The unit was designed for manual controls with minimal connections for field hookup. The motor starters for the unit were provided on the skid, housed in Class 1 Div 1 explosion-proof enclosures. A manual high voltage distribution panel was provided to isolate the HP, LP and Recirculation motor starters. Each HP and LP pump was provided with a three-way selector switch for hand, off and automatic states. Each HP and LP pump start and stop operation in automatic mode is controlled by an independent adjustable pressure switch. The LP pump discharge header and HP pump discharge header were provided with separate PSVs for overpressure protection.

The HP accumulator discharge was provided with redundant stainless steel filters with five micron elements. Also provided on the HP discharge was a flow meter and totalizer assembly to monitor fluid flow and total volume used in gallons per minute and gallons, respectively. The HP discharge header consisted of two 10,000 psi regulated circuits, each with two outlets and associated three-way valves and pressure gauges.

The LP accumulator discharge was provided with redundant stainless steel filters with five micron elements. Also provided on the LP discharge was a flow meter and totalizer assembly to monitor fluid flow and total volume used in gallons per minute and gallons, respectively. The LP discharge header consisted of two 5,000 psi regulated circuits, each with four outlets and associated three-way valves and pressure gauges.

The HP and LP discharge flow meters, three-way valves, pressure gauges and regulators were mounted on a centrally-located 316 stainless steel control plate to provide for easy monitoring and control of the IWOCS unit. The HP outlets, LP outlets and flushing return bulkheads were all located on one common bulkhead plate.

The flushing returns header was provided with a flow meter and totalizer assembly to monitor fluid flow and total volume used in gallons per minute and gallons, respectively. It was also provided with a spin on returns filter to minimize contamination and improve cleanliness of the system.

Testing: Each pressure circuit was hydrostatic tested to 1.5 times the design working pressure. Stella Maris also provided 460VAC 3 phase power to test the function of each circuit, pump and verify flow rates with returns piped to the flushing returns header. All testing parameters were logged and documented on our FAT documentation.

To learn more about the intricacies of this or other design-and-build projects, or to discover how Stella Maris can design and build a custom system to fit your company’s unique needs, contact us at 337-504-5128.