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Overview Molecular sieve dehydration (MSD) is used to remove water from natural gas. The dehydration is

necessary to mitigate problems caused by hydrate formation and corrosion. MSD is common to many

processes that use natural gas as a feedstock, including pipelines, natural gas processing plants, LNG

regasification, and power plants. These dehydrating systems typically consist of multiple adsorptioncolumns filled with solid desiccant. The columns are cycled between adsorption, regeneration (where

the desiccant bed is heated to drive off water), and cooling.

Catalyst particles, temperature,and frequent cycling requirespecialized isolation switchingvalve performance.

Isolation switching valves controlthe flow of gas through the MSDprocess, including input andoutflow to the system, and eachof the desiccant columns.

Zero-leakage is critical to theprocess. Water that remains inthe gas reduces processeffectiveness, can lead tocorrosion and increaseddehydrator maintenance.

Valves in MSD applications face multiple challenges to zero leakage and service life. A key aspect of enhancinsystem performance is addressing all of them.

Perhaps the most critical valve challenge comes from the catalyst. Molecular sieve beds generate catalyst

carryover. The granular material can abrade the seat and sealing surfaces on conventional valves.Temperature is also an issue. The valve must withstand high regeneration temperatures that typically rangeup to 800F [427C].

MSD Isolation switching valves must also endure frequent cycling during the regeneration process. Theconstant use can accelerate wear and reduce valve life. Catalyst, temperature, and cycling demands like theseplace high demands on valves that can result in premature failure and leakage.

Vanessa triple offset valves (TOV) ensure zero leakage and longer valve life in MSD applications. Acam-actuated sealing design avoids the scuffing that occurs with conventional valves when catalystparticles are ground into the seal face.

Instead, the TOV design applies torque to radially charge a seal ring fitted to the valve disc. The ring uniformlydistributes torque to the seat to create the seal. This sealing process avoids the wear inherent in draggingcatalyst particles across the sealing surface during frequent cycling.

A leak-proof closing is ensured even if particles are caught in the seal. These particles lodge betweenthe resilient metal seal ring and a body seat featuring a weld overlay of Stellite grade 21. This maintains azero-leak seal to API 598 and API 6 D standards, and enhances wear resistance to maintain the efficiencyof the drying system.

Temperature cycles during regeneration are easily handled by the TOV design. The valve disc is made ofthe same metal as the valve body. As a result, there is no temperature limitation due to thermal expansionand contraction up to the limit imposed by ASTM to WCB.

MSD applications create tremendous demands on valves. Failure compromises the process and causes costlyproblems. Vanessa metal-to-metal, non-rubbing valves provide all the key characteristics to ensure performancin difficult MSD applications.

ADSORBING

COLUMN

REGENERATING

COLUMN

COOLING

COLUMN

DRIED G

WET GAS

HEATER

REGENERATION

GAS COOLER

WATER KNOCK OUT

OPEN VALVE

CV = CONTROL VALVE

ISV = ISOLATION SWITCHING VALVE

ISV ISV ISV

ISV ISV ISV

ISV

CV

Application: Molecular sieve dehydration of natural gas

Objective: Zero-leakage, longer life for isolation switching valves

Solution: Vanessa triple offset metal-to-metal, non-rubbing valves

VANMC-0646-US-1205

Copyright 2012 by Tyco Flow Control, Inc. All Rights Reserved.

Critical dehydrator performance

Valve challenges

The Vanessa advantage

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Vanessa Feature Benefit for molecular sieve dryer operators

The Vanessa Triple Offset Valve offers the following benefits:

Standard Stellite hardface seat Further enhances durability at higher temperatures and resistsabrasion.

The design rigidly fixes a super-hardened thrust washer to theshaft while maintaining an intermediate sliding thrust washer,further extending service life.

Compliant with API 609 and requirements from EPA and TA Luft,fugitive emissions are minimized.

Bearing protectors keep catalytic solids from the bearing journal,extending service life.

A duplex stainless steel seal ring is installed in the disc assemblyto provide true zero leakage (as per API 598 and or API 6D)maintaining the efficiency of the drying system.

Imparts a camming effect resulting in no metal-to-metal rubbingbetween the seat and the seal. This prevents abrasion fromcatalyst carryover.

Quarter turn valves are easier to actuate and more reliable thanlinear valves. Packing wear is greatly reduced.

High-cycle thrust bearing

Two-piece packing gland

assembly with externally

retained anti-blowout stem

Upper and lower graphite

bearing protectors

Resilient metal seal

Triple offset seat design

www.tycoflowcontrol.com

VANMC-0646-US-1205

Copyright 2012 by Tyco Flow Control, Inc. All Rights Reserved.

Quarter turn operation