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The Severe Service Journal is published quarterly by the Emerson severe service team and is distributed by email. To subscribe, go towww.FisherSevereService.com . The Emerson severe service team provides global customers with Fisher severe service control

valve solutions. Whether it is severe service applications for the power, hydrocarbon, chemical or pulp and paper industry, thesetechnical experts deliver sound solutions to address critical applications for aerodynamic noise, cavitation and out-gassing issues,as well as particulate erosion. Please visit our website or contact your local Emerson sales ofce for more information.

July 2011 Volume 11, Issue 3

Look to Emerson for Control Valve Corrosion Solutions

Corrosion is the deterioration of a material, usually ametal, which results from a chemical or electrochemicalreaction with its environment. In this sense, the wordenvironment is not only limited to the external

environment, but also to the environment in contactwith the component in question, such as the processuid in contact with a valve trim component.

There are many chemicals that can be corrosive topipelines and valves. Some of the process uids resultingin severe corrosion are often found in the hydrocarbonindustry. These are due to the naturally corrosive natureof the chemicals that are separated out of crude oil andthe chemicals needed to further process oil and gas. Forexample, the most common problematic componentencountered in oil and gas production is hydrogensulde (H

2S), which can cause corrosion and sulde

stress cracking (SSC) in piping, vessels, and control valvesif proper material selection and material processing arenot employed.

Type 316 stainless steel plugshowing severe corrosion

There are many different forms of corrosion, rangingfrom general corrosion (which basically affects theentire exposed surface in a primarily uniform manner)to localized corrosion mechanisms such as pitting

(formation of small, deep pits) and stress corrosioncracking (SCC).

Some materials are inherently more resistant tocorrosion than other materials. Alloys containingchromium get their corrosion resistance from a passiveoxide layer on their surface, which acts as a barrier tofurther oxidation or corrosion. Most stainless steeland nickel alloys rely on this layer for their corrosionresistance.

Type 316 stainless steel exhibits this type of protectivelm and is commonly used as a trim/body material in

Fisher valves. Corrosion resistance can also be enhancedby increasing the amount of nickel. For example nickelalloy C, commonly known by the Haynes Internationaltrademark Hastelloy C, exhibits excellent resistanceto sulfuric, hydrochloric, and organic acids as well asammonia, dry chlorine, and hydrogen sulde. Nickel alloy625, commonly known by the Special Metals trademarkInconel 625, also has high corrosion resistance in a widerange of environments, and is commonly specied inthe oil and gas industry for resistance to pitting, crevicecorrosion, and SCC caused by high chloride levels, as wellas resistance to sulde stress cracking.

Emerson Process Management offers a vast range ofcorrosion resistant options for a range of severe servicecontrol valve applications. Your local Emerson Sales orLocal Business Partner ofce can help obtain the bestsolution to your corrosion problems.

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Cladding is dened as the act or process of bonding onemetal to another, usually to protect the inner metalfrom corrosion. Traditionally this has been a processutilized in the hydrocarbon industry for piping. Recently,

it has begun to gain favor in other components such ascontrol valves.

The main driver for utilizing this process on valves andpiping is to allow for a less expensive base material, suchas carbon steel, to have the corrosion properties of amuch more expensive material such as Inconel 625 atthe surface. The benets are that the wetted surfaceshave the corrosion resistance of the clad material with anoverall cost closer to that of the base material.

Emerson Process Management is able to offer thisoption on our Fisher NPS 824 globe style valves and

NPS 3 and larger angle valves. All sizes can be offered inboth high pressure and low pressure valves. A variety ofmaterials are available including Inconel 625, Incoloy825, Hastelloy C, Duplex Stainless Steels, AusteniticStainless Steels, and Alloy 400 with other materialsavailable upon request.

Fisher Cladding Technologies

Thus, if you feel that this technology may be a good tfor your process, contact your local Emerson ProcessManagement sales ofce today for an application andtechnology review.

standardized on material offerings and suppliers. To

provide the optimum properties at the best value, thespecic material grades shown below have becomethe standard offering for higher grade alloy materials.Standardizing on a group of experienced global suppliershas provided shorter lead times due to the ability toforecast these materials.

Using these materials is suggested when selecting highergrade alloy steels for use in corrosive service.

Alloy Solutions

For many years, the 300 series stainless steels (SST) have

been the workhorse alloys for corrosive applications.For severe applications, the nickel-base alloys were thenext step in corrosion resistance. The cost differential,however, was great (four to ten times, or more). In recentyears, Duplex and Super Austenitic SSTs have started toll this void as cost-effective alternatives.

In an effort to provide customers with a more costeffective solution, Emerson Process Management has

Common Name Typical Composition Castings Forgings Bar

Duplex 22% chromium,5% nickel, 3% molybdenum

ASME SA995Grade CD3MN or 4A

ASME SA182Grade F51

S31803

Super Duplex 25% chromium, 7% nickel,3.5% molybdenum, and traces of tungsten and copper

ASME SA351Grade CD3MWCuN or 6A

ASME SA182Grade 55

S32760

Super Austenitic 20% chromium, 18% nickel,6% molybdenum, 1% copper

ASME SA351Grade CK3MCuN

ASME SA182Grade F44

S31254

Alloy 625 22% chromium, 9% molybdenum,2% iron, balance nickel

ASTM A494Grade CW6MC

ASME SB564Grade N06625

N06625

Alloy 825 21% chromium, 42% nickel,3% molybdenum, 2% copper, balance iron

ASME SA494Grade CU5MCuC

ASME SB564Grade N08825

N08825

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and stepwise cracking, stress-oriented hydrogen-induced cracking, soft zone cracking, and galvanically-induced hydrogen stress cracking.

The two current standards that are applicable to controlvalves are NACE MR0175/ISO 15156 - Petroleumand Natural Gas Industries - Materials for use in H

2S

Containing Environments in Oil and Gas Productionand NACE MR0103 - Materials Resistant to SuldeStress Cracking in Corrosive Petroleum RefiningEnvironment.

NACE MR0175-2003, the short-lived precursor to NACEMR0175/ISO 15156, is still referenced occasionally andNACE MR0175-2002, which was the last revision of NACEMR0175 prior to the scope expansion, is still speciedquite frequently for upstream applications.

NACE MR0175/ISO 15156 includes added environmentalrestrictions (such as maximum temperature limits) toaddress chloride stress corrosion cracking, an issueusually associated only with upstream applications. NACEMR0103 places extra emphasis on welding controls inseveral material groups, as welding is more prevalentin renery piping and equipment. NACE MR0103 listscertain materials and/or material conditions that are notlisted in NACE MR0175/ISO 15156, and vice versa.

It is important to note that it is always the end usersresponsibility to request NACE-compliant materials. Endusers are also responsible for specifying which of thetwo standards is applicable to their process, and whatrevision applies. As a manufacturer, Emerson ProcessManagement is responsible for meeting the speciedmetallurgical requirements.

NACE Standards - A Fundamental Overview

The consequences of sudden failures of metallic oil andgas eld components, associated with their exposureto production uids containing hydrogen sulde (H

2S),

led to the preparation of the rst edition of NACE

MR0175, which was published in 1975 by the NationalAssociation of Corrosion Engineers, now known as NACEInternational.

Sulde stress cracking (SSC) is actually a form ofhydrogen stress cracking (otherwise known as hydrogenembrittlement). The following factors are required forSSC to occur:

1. Presence of H2S and water (even a trace amount of

moisture is sufcient)2. Susceptible material composition, strength/hardness,

heat treatment, and microstructure

3. Tensile stress (residual and/or applied)

From a valve manufacturer standpoint, sulde stresscracking can be controlled through the use of propermaterials in the proper conditions.

The NACE standards establish H2S limits above which

precautions against sulde stress cracking (SSC) may benecessary. They also provided guidance for the selectionand specication of SSC-resistant materials when theseH

2S limits are exceeded. The standards do not specify

any type of NACE Test to certify a valve assembly.

Although the initial revisions of NACE MR0175 were onlyconcerned with sulde stress cracking, revisions since2003 address several mechanisms of cracking that canbe caused by H

2S and/or chlorides, including chloride

stress corrosion cracking, hydrogen-induced cracking

Scanning electron microscope image ofintegranular fracture surface caused by

sulfide stress cracking

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Fisher Controls International LLC 2011 All Rights Reserved.

Fisher is are mark owned by one of the companies in the Emerson Process Management business division ofEmerson Electric Co. Emerson Process Management, Emerson, and the Emerson logo are trademarks andservice marks of Emerson Electric Co. All other marks are the property of their respective owners.

The contents of this publication are presented for informational purposes only, and while every effort hasbeen made to ensure their accuracy they are not to be construed as warranties or guarantees, expressor implied, regarding the products or services described herein or their use or applicability. All sales are

governed by our terms and conditions, which are available upon request. We reserve the right to modifyor improve the designs or specifications of such products at any time without notice. Neither Emerson,Emerson Process Management, nor any of their affiliated entities assumes responsibility for the selection,use, or maintenance of any product. Responsibility for proper selection, use, and maintenance of anyproduct remains solely with the purchaser and end-user.

The Severe Service Journal is published quarterly by the Emerson severe service team and is distributed by email.To subscribe, go to www.FisherSevereService.com .

Valve Plug Seizure and Corrosion Eliminated in HydrogenRecycle Application Using Fisher Severe Service Control Valve

A hydrogen recycle valve, controlling hydrogen ow tothe hydrocracker, was causing frequent disruption to the

renerys operation and impacting plant efciency dueto valve plug seizure and stress corrosion problems.

The hydrocracking process produces lighter hydrocarbonproducts from heavy feedstocks through reaction withhydrogen in multiple heated catalyst beds. Controllinghydrogen feed into the catalyst bed directly impacts thecracking conversion process and the quality of the lighthydrocarbon products. At the same time, piping andvalves in this application experience corrosion due topolythionic acid, caustics, and napthenic acid.

The renery approached Emerson Process Management

for a control valve solution to address the problems.

Emerson Process Management engineers evaluated theapplication and recommended an NPS 6 Fisher EHZsevere service control valve with a 347 SST body withproper trim material to address the stress corrosionproblem that was occurring under the severe operatingconditions.

The post-guided Fisher EHZvalve design was selected to

minimize the seizure effect ofsolid particle buildup in thevalve. Sufcient actuation forceto overcome excessive valvefriction, which could result frompotential particle deposits, wasalso incorporated in the design.

Since startup, the Fisher severeservice control valve hasoperated smoothly withoutany of the valve plug seizure orcorrosion problems experienced

by the original valve.

For more information on severeservice solutions, visitwww.FisherSevereService.com.

Emerson Process ManagementMarshalltown, Iowa 50158 USA

Sorocaba, 18087 BrazilChatham, Kent ME4 4QZ UKDubai, United Arab EmiratesSingapore 128461 Singaporewww.EmersonProcess.com/Fisher

MX69 (H:) / Jul11