API 571

pro ben

What crude unit hydrocarbon streams will probably contain the most sulfur?

Gas oil

A Fluidized Catalytic Cracking Unit (FCCU) will do what?

Produce significant amounts of gasoline

A neutralizer injected into the Crude Unit Atmospheric Overhead Condenser system, is injected for the purpose of neutralizing what type of acid?

Hydrochloric (HCL)

A crude unit is processing a high sulfur material crude slate. Which of the following streams is most likely to contain the most sulfur?

Atmospheric Tower Bottoms

When testing the water chemistry, which of the following most closely represents the desired pH range of the condensate (water) that condenses in the Main Fractionator at the Delayed Coking Unit (DCU)?

6.0 to 7.0

In many refinery units, water and H2S combine to form what corrosive agent?

Wet H2S

A Delayed Coking Unit (DCU) does what?

Thermally crack large hydrocarbon chains into smaller chains.

What stream from the Crude Unit are potentially going to contain the most nitrogen compounds?

Heavy Gas Oil

A desalter is going to remove what corrosive components?

Salt and Solids

What is the typical length of time for a coke drum cycle on a Delayed Coking Unit (DCU)?

1 Day

Is the Chloride ion (Cl) corrosive?

Yes, but only when combined with water.

In what part of the hydrotreating process do most of the ammonium salts form corrosive liquid salts?

Reactor Effluent Air Condenser (REAC’s)

Which of the following is a catalyst used in an Alkylation (Alky) Unit?

Sulfuric Acid

Which process stream will produce the most sulfur after going through a hydrotreater unit?

Vacuum Gas Oil

Which of the following statements is true concerning the catalyst on an Alkylation Unit?

The more concentrated the catalyst, the lower the corrosion rate.

Does the rich amine enter at the top of the Stripper (Regenerator) Tower or at the bottom?

Always at the top.

What is the purpose of the caustic wash on the outlet of the Alkylation (Alky) Unit?

To neutralize acid.

In the process flow, will the amine unit be located upstream or downsteam of the Crude Unit desalter?

Downstream

Hydrotreater feed contains Sulfur (S) & Nitrogen (N2). When processed in the Hydrotreater under high temperature and pressure, this sulfur is converted into what compound?

H2S

Is amine water soluble, or hydrocarbon soluble?

Water

How do raw crude Tank Farm Operators help mitigate refinery corrosion?

Blend crude.

Is amine an acid or a base?

Base

An Alkylation unit can be designed to operate with one of two catalysts. What are these two catalysts?

Hydrofluoric Acid and Sulfuric Acid

What upstream units provide the cracked gas feed for an Alkylation Unit?

Delayed Coker and the FCCU

Besides its primary product, what beneficial byproduct is produced in a Catalytic Reforming Unit?

Hydrogen

Will every refinery operate with an Amine Unit? Why?

No.

Sweet crude does not have sulfur to process from dedicated unit

In an amine treating system, what vessel operates at the highest temperature?

Amine Regenerator

An Alkylation Unit is primarily constructed of what metallurgy?

Carbon Steel

What is the purpose of the CRU?

Produce high octane gasoline.

What is the purpose of the Sour Water Stripper (SWS)?

Strip H2S from water.

Where will the hydrogen from the CRU go when it leaves the unit?

The hydroprocessing units.

Which of the following types of hydrotreater operates at the highest pressures?

Gas Oil

What are the reasons to hydrotreat?

Remove sulfur and nitrogen.

Independent of the type of catalyst used in an Alkylation unit, what is one of the key parameters to controlling the corrosion rate in such a unit?

Operating Temperature

For most corrosion mechanisms, the corrosion rate of bare metal decreases with time. This is because?

The passive layer protects the metal from further corrosion.

Most carbon steels used in a refinery contain how much of the alloying element carbon (C)?

0.15 – 1.0 %

What is a metallurgical treatment that works to prevent cracking of carbon and low alloy steel?

PWHT

The carbon equivalent (CE) formula is comprised of 7 elements. What single element has the greatest contribution to the results of the overall formula?

Carbon - C

What is a common deoxidizing agent used in Killed Steel?

Silicon

What cooling method will result in a material with the smallest grain size?

Quenching

What alloying element in Cast Iron makes it difficult to weld?

Carbon (C)

Which of the following is a Duplex grade of SS?

2205

316

4909

304L

2205

As the carbon content in a steel alloy increases, does the alloy become more brittle or more ductile?

The alloy becomes more brittle.

What is the recommended water to use in the desalter?

Deoxygenated water

Which of the following is not a control parameter for a desalter?

Amount of sulfur injected

Amount of mixing required

Temperature of operation

Amount of wash water added

Amount of sulfur injected

Which of the following would be a "typical" weld hydrogen bake-out temperature?

600°F

In general, what statement is true concerning the presence of oxygen and corrosion reactions?

Oxygen will typically speed up the corrosion rates.

In general, if a metal has a large grain size, has it had a rapid or slow cool down?

A large grain size indicates a slow cooling rate

What material is added to the mix to make killed steel?

Silicon

What is a common deoxidizing agent used in killed steel?

Aluminum

Name a grade of Austenitic grade of SS?

304L

What is the relationship between temperature and corrosion rates?

Higher temperature will increase the corrosion rate by increasing the rate of reaction

What does the "L" mean in material grades such as 304L and 316L?

Low Carbon Content

A killed steel made from what deoxidizing agent will provide a larger grain size?

Silicon

In reference to CE, what element will have more impact on weldability?

Carbon

What is one advantage of using killed steel?

It’s more corrosion resistant.

Pros and cons of quenching include?

Higher hardness but more brittle

Is “outgassing” required prior to all welding procedures?

No, outgassing is not always needed to remove hydrogen gas.

Functions of a refinery tank farm include __________.

Blend the crude oil for the desalter

Remove solids from the crude oil

Dewater the crude oil

Will corrosion occur in pure water with no dissolved oxygen or ionic species in the solution?

No.

What is the main reason for Post Weld Heat Treatment?

To relieve residual stresses.

Amine corrosion in a refinery system is caused by ?

Dissolved acid gases (CO2 and H2S)

Amine degradation products

Contaminants

A bulk caustic tank is heated. Which of the following is most susceptible to caustic stress cracking?

Internally around the manway repad.

Tank floor under the heating coils.

Around the small external repads.

Around the tank chime.

Tank floor under the heating coils.

What is the greatest contributor to lean amine corrosion?

Impurities (or Contaminants)

Carbonate SCC is generally going to manifest itself in what manner?

Parallel to the weld in the adjacent base metal, but can also occur in the weld deposit of HAZ .

In general, the possible damage mechanism(s) associated with steam out of non-PWHT’d carbon steel piping and equipment in caustic service should be mitigated in what manner ?

Steam out should be avoided.

Wet H2S cracking of carbon steel in amine service is most often associated with

Rich Amine

What material is normally used to handle ambient temp dilute caustic solutions?

Carbon Steel

The appearance of carbonate SCC has the appearance that is easily mistaken for that of another SCC mechanism. The difference can be distinguished by?

Carbonate cracks are further from the toe of the weld and have multiple parallel cracks.

What is the threshold for amine concentration above which there is a propensity for cracking?

Any

What internal NDE methods are best used to determine amine corrosion?

Visual & UT

What material is the least resistant to carbonate cracking?

Carbon Steel

_______ (or higher alloy) is required for amine piping operating in a flashing environment.

300 Series SS

300 Series SS that has been exposed to caustic and has cracked is very difficult to distinguish from what other damage mechanism ?

Chloride SCC

While the amine does remove other contaminants, the targeted material for removal is what?

Mercaptans, CO2 and H2S

Crack detection due to amine SCC is best performed with?

ACFM and WFMT

What external NDE methods are best to determine amine corrosion?

UT and RT

Amine Cracking in Carbon steel is most often associated with ?

Lean amine

When comparing Carbonate SCC to SSC or SOHIC, the carbonate cracks are usually ________ the toe of the weld and have multiple parallel cracks.

Further from

Cracking is most likely to occur with what amines that are commonly used?

MEA & DEA

Caustic gouging in boiler tubes is typically characterized by ______.

grooves

If the desalter is malfunctioning, where will the majority of the corrosion show up?

Crude Unit

On the FCCU, where is Carbonate SCC most prevalent?

Fractionator Overhead Condenser

When caustic stress corrosion cracking is a concern, steam out of _________ carbon steel piping and equipment should be avoided.

Non-PWHT

Application of a post-fabrication stress relieving heat treatment of about ______ is a proven method of preventing carbonate cracking.

1200º F (648°C)

The regenerator reboiler and the regenerator are areas where the temperature and __________ of the amine stream are the highest.

Turbulence

What is the major critical factor for caustic corrosion?

The presence of (KOH or NaOH)

Lean amine is generally not corrosive because of what reason?

Low Conductivity and / or High pH

Caustic corrosion is related to what other damage mechanism.

Caustic SCC

Carbonate cracking typically propagates _________ to the weld; the pattern of cracking observed on the surface is sometimes described as ________.

Parallel, Spider web

What materials is the most resistant to caustic embrittlement?

Nickel Based Alloys

What is the lower limit of caustic known to cause Caustic SCC?

50 ppm to 100 ppm

What are the critical factors for Carbonate SCC

Residual stress level and water chemistry.

In high-strength caustic, temperatures above what will cause general corrosion of carbon steel

170ºF

What material is most susceptible to amine cracking?

Carbon Steel

Amine corrosion depends on the design, operating practices, the type of amine, amine concentration, temperature and _________.

Velocity

Amine units remove CO2 and H2S. It will also remove what?

Mercaptans

Cyanide is a result of the presence of ________.

Nitrogen

What unit thermally cracks its feed?

Delayed Coker Unit