Valve Locations: Population of our NRV s at MPT well pad area:

Transcription

1 Swing Check Valve Failure at Cairn India Limited (CIL)- Barmer / Mangala Well Pads(MPT Oil field) At project stage, we have supplied more than 400 Nos. of NRV to CIL for Crude oil lines & water injection lines. Valve Locations: 1. Well Pads 2. Water injection lines 3. Processing terminal. Population of our NRV s at MPT well pad area: Details of L&T AUDCO NRV's installed at MANGALA WELL PADS Valve Type S.No. Valve Size Rating Qty 1 2 " " " " " AUDCO NRV's 6 4 " " " " " " TOTAL 464 * More than 400 valves are installed on well pad area. Major failures are observed in sizes marked in red above: 6 #1500 & 12 #600 valves.

2 Application: Valves are installed on crude oil lines well pad area. Application is crude oil mixed with gas with fluctuating pressure levels. Failure Detail NRV flappers are failing on crude oil lines installed at well pad location. Experiencing the major failures at crude oil lines for the valves installed at well head locations. NRV flapper is found dropped inside the valve & the threaded portion of the disc gets sheared off. Material of construction

3 #1: Detail failure report Size and class: # 1. Threaded portion in the Disc found sheared off. 2. Hinge found broken into two pieces. Threaded area gets sheared off & Disc found lying inside the valve.

4 #2: Detail failure report #3: Detail failure report Size & Class: # 1. Disc found sheared off from the Hinge and blocking the Passage of the fluid. 2. Disc Nuts, Disc pin and Disc washers dislocated after shearing. Size & Class: # 1. Disc found sheared off from the Hinge. 2. Disc Nuts, Disc pin and Disc washers dislocated after shearing.

5 #3: Detail failure report Size and class: # 1. Stud in the boss of disc got sheared and dislocated. 2. Disc Nuts, Disc pin and Disc washers also dislocated after shearing. 3. Stopper was also found in unhealthy condition. FAILURE ROOT CAUSE: Continuous slamming action which is occurring at site due to fluctuating fluid flow. NRV s are not recommended for fluctuating fluid flow as the design is not suitable to take shear occurred due to continuous pressure fluctuation. Due to continues slamming action, chattering is occurred in the valve & the Disc nut slams over the stopper area. Due to shearing & slamming of nut over the stopper continuously, threaded portion of disc nut get sheared off & that causes the flapper to loosen up. SPARES- FLAPPER ASSEMBLY SUPPLIES: Action Taken Result Conclusion MOC of the flapper assembly changed to SS for more durability Changing MOC from WCB to SS has increased the life of the valve but failure issue still persists MOC change is not a permanent solution for these failures. This is temporarily increasing the working span of the valve thereby delaying the failure. Welding over the disc nut & nut pin. Disc Nut being the most sheared part which is getting sheared off sue to slamming action over the stopper, the Welding is provided over the disc nut & nut pin is keeping the assembly in place for a longer time. Failure still exists.

6 CONCLUSION/SOLUTION (As suggested by various discussions happened with R&D Chennai) As the root cause of failure of these flappers is the continuous slamming action which is occurring at site due to fluctuating fluid flow, for going to any modified design, the slamming action of the valve needs to be controlled. Incorporating Hydraulic damper arrangement for higher size NRV s shall eliminate the closing slams and water hammer for entire closing stroke. Tilting disc check valve where slamming action can be avoided as per the design features. The valve is closed quickly because its pivot (hinge pins) is shut by a very small arc. Moreover, line fluid flows both over and under the disc, so that valve closing is cushioned by the line fluid itself. Thus providing a Non Slam process.

7 ACTION REQUIRED: As suggested by our R&D Team Chennai that swing type NRV is not suitable for fluctuating flow. R&D has suggested the modified designs as above. The same we have proposed to CIL for which they have accepted for tilting disc check valve & asked us for a sample valve size 6 CL1500 or either 12 CL600 as the major failures are happening in these two sizes. CIL shall review its performance for at least 2 months on site. On successful working of this modified valve CIL has assured for procuring the same design for all the failure cases. We need to supply a sample valve size either6 CL1500 or 12 CL600 in modified design( Tilting Disc check valve) for confirming its suitability to this application. Thanks Dheeraj Sikri