Cattanach, Kyle (Baker Hughes Incorporated) | Jovancicevic, Vladimir (Baker Hughes Incorporated) | Ramachandran, Sunder (Baker Hughes Incorporated) | Sherik, Abdelmounam (Research & Development Center)
Paramesh, Meenakshi H.N. (Avinashilingam University for Women) | Anand, Anisha (Avinashilingam University for Women) | Krishnamurthy, Shyamala R. (Avinashilingam University for Women) | Mani, Saratha R. (Avinashilingam University for Women) | Krausher, Jennifer (CANMET Materials Technology Laboratory) | Papavinasam, Sankara (CANMET Materials Technology Laboratory)
Jauhari, Smita (Applied Chemistry Department Sardar Vallabhbhai National Institute of Technology) | Parekh, Kinnari (Department of Physics Indian Institute of Technology) | Upadhyay, R.V. (Institute of Applied Sciences)
The effect of chloride on the pitting and cracking propagation of UNS S30403 and UNS S31603 exposed to sour service was studied. Laboratory testing to simulate the extreme ends of process conditions found in our acid gases removal plant were conducted. The typical Gas process conditions vary from 110oF (43oC) to 300oF (149oC) with high and low loads of H2S and CO2 in equilibrium with a solution of an acid gas selective solvent and water. This study covered a range of chlorides from 0 to 500 ppm. Cyclic polarization and potentiostatic electrochemical techniques were used to determine the limits of chlorides required to cause stable pitting leading to cracking. Cracking was confirmed by means of 30-days exposure testing of stressed coupon. Conducting cracking testing at several applied stress levels to better resembling applied stresses at the plant piping and vessels are planned
INTRODUCTION Two of the wells feeding the Lost Cabin Gas Plant, are causing an incremental increase in chloride (Cl-) levels in the gathering system and plant due to increased formation water. Limitations on the water handling systems at the front end of the plant caused operational upsets with carry over of chlorides to the acid gases removal unit which was originally not designed to handle this type of environment. In this plant unit Poly ethylene dimethyl ether (referred to as solvent in the rest of the paper) dissolves the acid gases from the feed gas by physical absorption at relatively high pressure. The rich solvent containing the acid gases is then let down in pressure and steam stripped to release and recover the acid gases. The current guideline provided by the licensor limits the chloride levels to a maximum of 40 ppm. However there was not data available to support these guidelines. Due to the potential risk for pitting and cracking of Stainless Steel equipment and the economic implications, a multidisciplinary team was identified and assembled by LCGP to manage this issue. As part of the overall program electrochemical tests and immersion testing on UNS S30403 and UNS S31603 stainless steel were conducted to assess the impact of chlorides on pitting and cracking resistance of these alloys in laboratory environments intended to screen the acid gases removal plant conditions
EXPERIMENTAL MATRIX AND TEST PROCEDURES
Testing conditions were selected to cover the more aggressive conditions through out the unit. Initial selected conditions were as follows:
• Maximum temperature for low pressure service, 300oF (149oC) as observed at outlet reboiler at bottom of the stripper column
• Maximum temperature for high pressure service, 110oF (43oC), as observed at H2S absorber bottom.
• Range of four chloride concentrations added as NaCl
o 40 ppm (process licensor's recommended limit)
o 100 ppm (slightly above present chloride concentration in the plant)
o 250 ppm (expected concentration in 2012)
o 500 ppm (expected concentration in 2014) As the laboratory work was conducted and results analyzed the scope of work was modified and new conditions were tested.
Shoemaker, Lewis (Huntington Alloys / Special Metals Corporation) | Crum, Jim (Huntington Alloys / Special Metals Corporation) | Maitra, Debajyoti (Huntington Alloys / Special Metals Corporation) | Muro, Ruben (Corrosion Materials, Inc) | Neighbor, Marlena (Corrosion Materials, Inc)