Quality Assurance Testing

Individualized Quality Plans and Certification
An individual quality plan is developed for each project at Mafi-Trench. The quality plan identifies all Customer inspection points (witnessed or observed). MTC has developed a production control traveler system that defines all manufacturing operations, Customer witness points, and includes all preliminary and final inspection points for our Quality Control (QC) Inspectors. A member of the QA department also reviews the travelers to ensure that all special project requirements have been included in the manufacturing process.

The QA department compiles a certification book for the equipment during the manufacturing process. Representatives from the customer can review the status of certificates for the equipment during the entire engineering, purchasing, manufacturing, and testing process. Prior to shipment the QA department completes an extensive shipping checklist to ensure that all critical requirements have been completed.

Testing/Inspection
Each turboexpander system designed and supplied by MTC undergoes rigorous testing and inspection to ensure the equipment will achieve the performance and reliability required by our customers. Each project contains its own unique testing requirements and MTC is well-equipped to address them. The QA Plans provide a general listing of some of the standard and optional testing that is available for each of our systems.

The inspection and testing of all equipment is performed under the approval of the engineering department and the Quality Assurance Manager. These functions are broken down into two categories: individual components and complete assembly. Individual component testing includes balancing of the shaft and impellers, various casing NDT procedures, resonance and overspeed testing of the impellers, etc… Special inspection requirements (e.g., radiography, ultrasonic testing, magnetic particle testing) are available as an option. MTC inspectors meet the requirements of applicable industry standards.

Mechanical testing demonstrates the functional reliability and mechanical integrity of the machine design, while functional testing demonstrates the performance of the auxiliary systems. Mechanical tests are performed on every expander unit supplied by Mafi-Trench. The mechanical test operates over the entire speed envelope of the unit (from slow roll to trip speed) with run times varying from 1-4 hours at maximum continuous speed (MCS). Performance testing is conducted to verify the aerodynamic performance of each new impeller design. Sufficient test data is taken to produce curves for design and off-design performance.

Full Power Testing
In 1996, Mafi-Trench conducted the first full power, full pressure closed loop test of a natural gas turboexpander destined for operation in the North Sea. This test was conducted due to the critical delivery stipulations required in the owner’s gas supply contracts. Rigorous onshore testing of critical components ensured that the offshore module that contained the turboexpander would perform as designed.

Since then, several other full power, full pressure closed loop tests have been performed by MTC, establishing this testing as a viable option for critical applications. The benefits of full power/full pressure testing can be summarized as follows:

• Mechanical testing across the full range of operating points provides maximum confidence for on-schedule commissioning.
• Full power overspeed trips verify the robust design of the expander.
• Compressor surge can be demonstrated to assure that there are no detrimental effects on the turboexpander.