I85PREP
⌘ K
API 936 study materials
API 936 study resources

API 936 practice questions

One question at a time. Build your API 936 understanding.

First 50 of 200 questions. Each one lists the choices, the correct answer, and an explanation. The checker at the top of this page saves progress in this browser when it is available.

Continue in the practice tool above to load more questions, 50 at a time.

Question 1Refractory Materials, Properties, and Selection

Which monolithic refractory product is formulated to be placed by pouring or pumping into a form and then cured and dried?

  1. Castable Correct answer.
  2. Ramming mix
  3. Gunning mix
  4. Plastic refractory

Explanation

Castables are granular refractory mixes with a binder and enough water or carrier liquid to flow into a form, where they set and are then dried. Plastic refractories are moldable, ramming mixes are compacted by impact, and gunning mixes are sprayed.

Question 2Refractory Materials, Properties, and Selection

What is the principal function of an insulating castable in a refractory lining?

  1. Reduce heat loss through the lining Correct answer.
  2. Resist high-velocity abrasive particle impact
  3. Carry structural loads from the vessel shell
  4. Provide maximum resistance to molten slag attack

Explanation

Insulating castables are formulated with high porosity and low density to lower thermal conductivity. They are used as backing insulation or low-load linings, not as the primary slag- or abrasion-resistant layer.

Question 3Refractory Materials, Properties, and Selection

Which test measures the compressive strength of a cured refractory castable specimen at room temperature?

  1. Pyrometric cone equivalent
  2. Hot modulus of rupture
  3. Permanent linear change
  4. Cold crushing strength Correct answer.

Explanation

Cold crushing strength is determined by compressing a cured or fired specimen at room temperature until failure. It reflects the integrity of the bond and matrix at ambient conditions.

Question 4Refractory Materials, Properties, and Selection

A refractory castable must resist molten iron slag at 1500°C. Which aggregate chemistry is most suitable?

  1. Tabular alumina Correct answer.
  2. Silica
  3. Andalusite
  4. Fireclay

Explanation

Tabular alumina is a high-purity, high-alumina aggregate with good resistance to basic ironmaking slags and high refractoriness. Silica and fireclay are more acidic and lower in alumina, while andalusite offers only moderate slag resistance.

Question 5Refractory Materials, Properties, and Selection

Compared with a conventional cement-bonded castable, a low-cement castable typically contains what?

  1. A single coarse aggregate size and no fines
  2. Less calcium aluminate cement with optimized particle packing Correct answer.
  3. Organic fiber as the primary bond
  4. More Portland cement and higher water demand

Explanation

Low-cement castables use a small amount of calcium aluminate cement together with a well-distributed particle-size curve and dispersants. This reduces lime content and water demand while improving density and hot properties.

Question 6Refractory Materials, Properties, and Selection

What is a key advantage of a colloidal silica-bonded castable compared with a calcium aluminate cement-bonded castable of similar alumina content?

  1. It cannot be installed by casting
  2. It requires a longer water cure to set
  3. Lower CaO content and higher hot strength Correct answer.
  4. It develops strength only after firing above 1000°C

Explanation

Colloidal silica provides a binder that leaves essentially no lime, reducing low-melting phase formation and often improving hot strength. It sets by gelation and drying rather than by hydraulic cement hydration.

Question 7Refractory Materials, Properties, and Selection

Why must a dense castable lining be dried slowly on first heat-up?

  1. To increase the CaO content of the bond
  2. To let steam escape without explosive spalling Correct answer.
  3. To convert cement phases to mullite
  4. To prevent aggregate from expanding too little

Explanation

Water in the castable turns to steam during heat-up, and if vapor cannot escape it builds pressure and causes explosive spalling. A slow, staged heat-up with holding periods allows water vapor to migrate out.

Question 8Refractory Materials, Properties, and Selection

Which property combination best indicates good thermal shock resistance for a refractory?

  1. High thermal expansion and low thermal conductivity
  2. High strength and high elastic modulus
  3. High density and low porosity
  4. Low modulus and low thermal expansion Correct answer.

Explanation

Thermal shock resistance is favored by low thermal expansion, low elastic modulus, and some ability to accommodate strain without storing large elastic energy. High strength and high modulus can make a material more brittle under rapid temperature change.

Question 9Refractory Materials, Properties, and Selection

In a cyclone with fine catalyst particles at 700°C, which refractory property is most directly relevant to lining life?

  1. Abrasion resistance Correct answer.
  2. Thermal conductivity
  3. Permanent linear change
  4. Refractoriness under load

Explanation

Fine particles moving at high velocity cause erosion of the refractory surface. Abrasion resistance, supported by hard aggregates and a strong matrix, is therefore the most direct property for this wear mechanism.

Question 10Refractory Materials, Properties, and Selection

What is the primary purpose of metallic anchors in a monolithic refractory lining?

  1. To react with slag and form a protective glaze
  2. To increase the thermal conductivity of the refractory
  3. To anchor the lining and control cracking Correct answer.
  4. To replace the need for drying

Explanation

Anchors support the monolithic lining, transfer loads to the shell, and help distribute shrinkage or thermal cracks. They are not intended to conduct heat, replace dryout, or react with slag.

Question 11Refractory Materials, Properties, and Selection

The pyrometric cone equivalent test is used to determine what?

  1. Thermal conductivity
  2. Refractoriness Correct answer.
  3. Gas permeability
  4. Cold crushing strength

Explanation

The pyrometric cone equivalent compares the deformation of a test cone with standard cones under a prescribed heating schedule. It is an indicator of the material's refractoriness, not of mechanical strength or transport properties.

Question 12Refractory Materials, Properties, and Selection

A refractory lining carries load at 1400°C for long periods. Which test best evaluates time-dependent deformation?

  1. Cold crushing strength
  2. Creep in compression Correct answer.
  3. Abrasion resistance
  4. Modulus of rupture at room temperature

Explanation

Creep in compression measures deformation under a constant load at elevated temperature over time. This directly addresses time-dependent sag or deformation in a hot, loaded lining.

Question 13Refractory Materials, Properties, and Selection

What does a permanent linear change test measure?

  1. Volume of open pores
  2. Reversible thermal expansion during heating
  3. Irreversible dimensional change Correct answer.
  4. Strength loss after thermal cycling

Explanation

Permanent linear change measures the irreversible change in length of a fired specimen after a specified heat treatment. It indicates whether the refractory expands or shrinks permanently in service.

Question 14Refractory Materials, Properties, and Selection

Which refractory characteristic most directly governs the ease with which gases pass through a lining?

  1. Permeability Correct answer.
  2. Thermal expansion
  3. Refractoriness
  4. Cold crushing strength

Explanation

Permeability quantifies the flow of gas through a porous refractory under a pressure gradient. It is therefore the direct property for judging gas migration through a lining.

Question 15Refractory Materials, Properties, and Selection

A slag with high lime and iron oxide attacks a silica-containing castable. Which selection change is most appropriate?

  1. Increase porosity to absorb slag
  2. Use a higher-alumina, lower-silica refractory Correct answer.
  3. Reduce anchor spacing
  4. Increase silica content to form a glass

Explanation

High-lime, iron-rich slags are basic and attack silica-rich phases aggressively. Reducing silica and increasing alumina content generally improves chemical resistance by forming more refractory phases and reducing slag fluxing.

Question 16Refractory Materials, Properties, and Selection

What installation method sprays a refractory mix with water onto a surface?

  1. Ramming
  2. Troweling
  3. Gunning Correct answer.
  4. Casting

Explanation

Gunning uses pneumatic equipment to convey a refractory mix and add water at the nozzle before it is sprayed onto the surface. Ramming, casting, and troweling use different placement methods.

Question 17Refractory Materials, Properties, and Selection

What is a characteristic of phosphate-bonded refractories?

  1. They are limited to temperatures below 400°C
  2. They bond chemically without hydraulic cement Correct answer.
  3. They contain Portland cement as the main bond
  4. They require steam curing to set

Explanation

Phosphate-bonded refractories rely on chemical reactions between phosphate binders and refractory oxides, developing strength during drying and heating. They do not depend on hydraulic cement hydration and are used at high temperature.

Question 18Refractory Materials, Properties, and Selection

In a reducing atmosphere containing carbon monoxide, which condition makes a refractory lining most vulnerable to CO disintegration?

  1. High-alumina lining above 1600°C
  2. Dense, low-porosity lining with no iron
  3. Iron-bearing, porous lining at intermediate temperature Correct answer.
  4. Silica lining with low permeability

Explanation

CO disintegration occurs when carbon monoxide decomposes and deposits carbon inside pores, a reaction catalyzed by iron or iron compounds. Porous, iron-bearing refractories at intermediate temperatures are therefore most susceptible.

Question 19Refractory Materials, Properties, and Selection

As the bulk density of a refractory increases, what generally happens to its porosity?

  1. Porosity remains unchanged
  2. Porosity increases
  3. Porosity becomes negative
  4. Porosity decreases Correct answer.

Explanation

Bulk density and porosity are generally inversely related for a given refractory type: a denser body contains less pore volume. Chemistry and aggregate type still influence the exact relationship.

Question 20Refractory Materials, Properties, and Selection

What does hot modulus of rupture evaluate?

  1. Abrasion loss at room temperature
  2. Gas permeability at elevated temperature
  3. Flexural strength at elevated temperature Correct answer.
  4. Strength after freezing and thawing

Explanation

Hot modulus of rupture is a bending-strength test performed at elevated temperature. It indicates how the refractory bond and matrix behave under flexural stress when hot.

Question 21Refractory Materials, Properties, and Selection

Which measure reduces the risk of explosive spalling during dryout of a thick castable lining?

  1. Increase the heating rate to drive water out quickly
  2. Add more mixing water to increase fluidity
  3. Install vent holes and use a slow, staged heat-up Correct answer.
  4. Seal the surface with an impermeable coating

Explanation

Vent holes provide escape paths for steam, and a slow, staged heat-up keeps vapor pressure below the level that causes explosive spalling. Faster heating, sealing, or extra water all increase the risk.

Question 22Refractory Materials, Properties, and Selection

A refractory is described as basic. Which material is consistent with that classification?

  1. High-alumina
  2. Silica
  3. Magnesia Correct answer.
  4. Fireclay

Explanation

Basic refractories are composed mainly of alkaline-earth or similar basic oxides, with magnesia being a common example. Silica is acidic, while fireclay and high-alumina materials are acidic to neutral in slag reactions.

Question 23Refractory Materials, Properties, and Selection

In a cement kiln, alkali vapors attack an alumina-silica refractory. What is a typical consequence?

  1. Low-melting phases form and cause spalling Correct answer.
  2. Complete conversion of alumina to silicon carbide
  3. Reduction of thermal expansion to zero
  4. Increase in refractoriness of the affected zone

Explanation

Alkali vapors react with alumina-silica refractories to form low-melting alkali aluminosilicate phases. These phases can densify the affected zone, cause volume changes, and lead to cracking or spalling.

Question 24Refractory Materials, Properties, and Selection

For a ladle lining contacting basic slag, which refractory type is generally preferred?

  1. Silica
  2. Basic brick Correct answer.
  3. Fireclay
  4. Acidic ramming mix

Explanation

Basic slags react strongly with acidic refractories, so basic refractories such as magnesia-based brick are generally selected for basic slag contact. The chemical compatibility reduces slag fluxing and erosion.

Question 25Refractory Materials, Properties, and Selection

A refractory has thermal conductivity that increases sharply with temperature. What is the most likely consequence for a furnace lining design?

  1. The lining becomes immune to thermal shock
  2. Heat flow through the lining increases Correct answer.
  3. The cold face temperature falls to ambient
  4. The refractory's refractoriness increases

Explanation

Higher thermal conductivity at operating temperature increases heat flow through the lining and raises the cold-face temperature unless insulation or thickness is adjusted. Thermal conductivity is separate from refractoriness and thermal shock resistance.

Question 26Refractory Materials, Properties, and Selection

What does the cold crushing strength test primarily measure in a refractory product?

  1. Its compressive strength at room temperature Correct answer.
  2. Its resistance to slag penetration at service temperature
  3. Its ability to deform without cracking under thermal cycling
  4. Its permeability to gases at elevated temperature

Explanation

Cold crushing strength is a room-temperature mechanical test that gives a comparative measure of a refractory's structural strength after manufacturing. It is used mainly for quality control and does not by itself predict high-temperature behavior such as slag resistance, thermal shock resistance, or creep.

Question 27Refractory Materials, Properties, and Selection

Why are expansion joints incorporated into a refractory brick lining?

  1. To improve bonding to the steel shell
  2. To provide a path for slag drainage
  3. To increase the thermal conductivity of the lining
  4. To accommodate thermal expansion and prevent buckling Correct answer.

Explanation

Refractory bricks expand when heated, and a lining built too tightly can develop high compressive stresses that lead to buckling or spalling. Expansion joints absorb this movement while remaining narrow enough to limit slag penetration.

Question 28Refractory Materials, Properties, and Selection

Which of the following is classified as a neutral refractory?

  1. Silica
  2. Magnesia
  3. Alumina Correct answer.
  4. Dolomite

Explanation

Neutral refractories such as alumina and chromite resist attack by both acidic and basic slags. Silica is acidic, while magnesia and dolomite are basic.

Question 29Refractory Materials, Properties, and Selection

What is the main effect of adding excess water to a refractory castable mix?

  1. Longer working time with no change in final properties
  2. Improved slag resistance and lower permeability
  3. Increased porosity and reduced strength Correct answer.
  4. Higher density and lower porosity

Explanation

Water beyond the amount needed for flow leaves voids after drying and hydration, raising porosity and lowering strength and abrasion resistance. Excess water can also increase shrinkage and permeability.

Question 30Refractory Materials, Properties, and Selection

The refractoriness-under-load test evaluates which behavior?

  1. Time-dependent deformation at a fixed temperature
  2. Volume change after firing at a specified temperature
  3. Strength loss after repeated thermal cycling
  4. Deformation under constant load as temperature rises Correct answer.

Explanation

Refractoriness under load measures the temperature at which a standard specimen begins to deform or fail under a defined load while being heated at a controlled rate. It reflects the combined effect of load and rising temperature, unlike a creep test, which holds temperature constant.

Question 31Refractory Materials, Properties, and Selection

What is the main reason graphite is added to magnesia-carbon refractory bricks?

  1. To increase the cold crushing strength
  2. To improve thermal shock resistance and slag resistance Correct answer.
  3. To raise the bulk density and reduce porosity
  4. To promote bonding with calcium aluminate cement

Explanation

Graphite has low wettability by molten slag and high thermal conductivity, which helps the brick tolerate rapid temperature changes and limits slag adhesion. It does, however, require antioxidants because carbon can oxidize at service temperatures.

Question 32Refractory Materials, Properties, and Selection

What is the purpose of a deflocculant in a low-cement refractory castable?

  1. To prevent oxidation of metallic fibers
  2. To accelerate the set of calcium aluminate cement
  3. To increase the porosity of the dried lining
  4. To reduce the water needed for flow Correct answer.

Explanation

Deflocculants disperse fine particles and break up agglomerates so that the required flow can be achieved with less water. Lower water demand reduces porosity and improves strength and density after installation.

Question 33Refractory Materials, Properties, and Selection

Why are thin joints preferred in high-duty refractory brick linings?

  1. Thin joints increase the overall thermal expansion
  2. Thin joints remove the need for expansion gaps
  3. Mortar joints are a weak corrosion path Correct answer.
  4. Thin joints simplify brick replacement

Explanation

Mortar is often more porous and less slag-resistant than the brick, so a thick joint becomes a preferential path for corrosive penetration. Keeping joints thin reduces this weak zone and improves lining life.

Question 34Refractory Materials, Properties, and Selection

What is the main advantage of using insulating firebrick in a backup lining?

  1. It provides higher hot strength than dense brick
  2. It eliminates the need for a working lining
  3. It lowers heat loss and lining weight Correct answer.
  4. It has better slag resistance than dense brick

Explanation

Insulating firebrick has high porosity and low thermal conductivity, so it reduces heat flow to the shell and lowers structural load. It is not intended to replace the working lining or to resist slag directly.

Question 35Refractory Materials, Properties, and Selection

Why must magnesia-based refractories be protected from moisture during storage?

  1. Magnesia hydrates and expands, leading to cracking Correct answer.
  2. Moisture leaches graphite and lowers conductivity
  3. Hydration forms a low-melting glass in the brick
  4. Water dissolves magnesia grains and washes them away

Explanation

Magnesium oxide reacts with water or water vapor to form magnesium hydroxide, which occupies a larger volume and disrupts the brick structure. This can cause cracking, strength loss, and eventual disintegration.

Question 36Refractory Materials, Properties, and Selection

What is the function of metallic antioxidants such as aluminum or silicon in carbon-containing refractories?

  1. They lower the thermal shock resistance of the brick
  2. They increase the carbon content of the brick
  3. They react with oxygen and protect the carbon Correct answer.
  4. They act as a lubricant during brick pressing

Explanation

Antioxidants preferentially react with oxygen or carbon monoxide that enters the brick, forming protective oxides and preserving the carbon bond. This helps maintain thermal shock resistance and slag non-wetting during service.

Question 37Refractory Materials, Properties, and Selection

How does increasing the alumina content of an alumina-silica refractory generally affect its performance?

  1. It lowers the refractoriness and increases glassy phase
  2. It increases porosity and permeability
  3. It makes the refractory more acidic and slag-prone
  4. It improves refractoriness and creep resistance Correct answer.

Explanation

Higher alumina content promotes mullite formation and reduces the amount of silica-rich glass, raising refractoriness and resistance to deformation under load. These improvements are limited by the overall phase assemblage and service environment.

Question 38Refractory Materials, Properties, and Selection

What happens when calcium aluminate cement-bonded castables are heated through the hydrate conversion range?

  1. Carbon dioxide is released and forms closed pores
  2. The bond becomes ceramic with no volume change
  3. The cement rehydrates and fills pores, raising density
  4. Hydrates convert and porosity rises, lowering strength Correct answer.

Explanation

During heating, metastable hexagonal calcium aluminate hydrates convert to the stable cubic hydrate C3AH6, which has a lower solid volume. The result is increased porosity and reduced strength, especially in high-cement castables.

Question 39Refractory Materials, Properties, and Selection

In an alumina-magnesia castable, what is the main consequence of in-situ spinel formation during firing?

  1. Complete loss of alumina from the matrix
  2. Formation of a low-melting liquid phase
  3. Expansion that can offset sintering shrinkage Correct answer.
  4. Shrinkage that opens wide cracks

Explanation

The reaction between alumina and magnesia to form magnesium aluminate spinel is accompanied by a volume expansion. This can be beneficial by compensating firing shrinkage, but too much expansion can cause cracking.

Question 40Refractory Materials, Properties, and Selection

Why is fused silica refractory suitable for applications involving rapid thermal cycling?

  1. Its low thermal expansion resists thermal shock Correct answer.
  2. Its high thermal expansion relieves stress
  3. It remains completely stable above 1400°C
  4. It has the highest slag resistance of silica types

Explanation

Fused silica has a very low coefficient of thermal expansion, so it develops small thermal stresses during rapid heating or cooling. Its use is limited, however, by devitrification to cristobalite and by reduced stability at sustained high temperature.

Question 41Refractory Design and Specification

What is the primary structural function of metallic anchors in a monolithic refractory lining?

  1. Transfer lining loads to the equipment shell Correct answer.
  2. Act as expansion joints between adjacent lining panels
  3. Increase the density of the castable at the shell interface
  4. Provide a conductive path that keeps the shell at a uniform temperature

Explanation

Anchors mechanically tie the lining to the shell, carrying the weight of vertical and overhead sections and limiting the width of shrinkage and thermal cracks. They are structural attachments, not thermal devices or expansion features, and they do not change the density of the surrounding castable.

Question 42Refractory Design and Specification

Under the conventional classification of monolithic castables by lime content, a low-cement castable contains what CaO level?

  1. Less than 0.2 wt%
  2. 1.0 to 2.5 wt% Correct answer.
  3. Greater than 2.5 wt%
  4. 0.2 to 1.0 wt%

Explanation

The standard classification divides castables into conventional (above 2.5 wt% CaO), low cement (1.0 to 2.5 wt%), ultra-low cement (0.2 to 1.0 wt%) and no-cement (below 0.2 wt%). Lower lime content generally brings higher density, higher hot strength and lower permeability, but also greater sensitivity to water addition and to dryout.

Question 43Refractory Design and Specification

A vessel's hot-face lining operates continuously near 1800 deg F (980 deg C) in a reducing atmosphere. Which anchor material is most appropriate?

  1. 310 stainless steel Correct answer.
  2. Galvanized carbon steel
  3. 304 stainless steel
  4. Carbon steel

Explanation

Type 310 stainless, with roughly 25% chromium and 20% nickel, retains useful strength and oxidation and sulfidation resistance at the upper end of refractory service temperatures. Carbon steel scales rapidly above about 1000 deg F and 304 stainless is generally limited to cooler linings, so neither is suitable for continuous duty near 1800 deg F.

Question 44Refractory Design and Specification

A lining is redesigned from 4 in. to 6 in. of the same castable. Which anchor change preserves the original design intent?

  1. Lengthen anchors to hold the tip setback Correct answer.
  2. Shorten the anchors to keep the same welded length
  3. Keep the existing anchors because tip position is not critical
  4. Increase anchor spacing to reduce the number of anchors

Explanation

The tip setback, meaning the distance from the anchor tip to the hot face, governs how hot the anchor runs and how well it is embedded in the lining. Increasing lining thickness therefore requires longer anchors so that the same setback is maintained. Leaving anchors short pushes them too close to the hot face, and lengthening the spacing reduces support.

Question 45Refractory Design and Specification

What is the typical minimum distance between the tip of a castable anchor and the hot face?

  1. At least 4 in. (100 mm)
  2. The tip is installed flush with the hot face
  3. At least 1 in. (25 mm) Correct answer.
  4. At least 6 in. (150 mm)

Explanation

Common design practice keeps anchor tips at least 1 in. (25 mm) behind the hot face so that the metal stays cooler and remains covered by sound refractory. Larger setbacks are used at higher temperatures, but 4 in. and 6 in. would leave too little of the anchor engaged in a typical lining.

Question 46Refractory Design and Specification

Why are expansion joints specified in a monolithic refractory lining?

  1. To allow inspection of the shell beneath the lining
  2. To provide a path for moisture to enter the lining
  3. To reduce the required anchor density near joints
  4. To accommodate thermal expansion and shrinkage without buckling or spalling Correct answer.

Explanation

Monolithic linings expand on heat-up and shrink on cool-down, and restrained movement produces compressive stress, buckling and spalling. Properly placed joints give the lining room to move so that stresses are relieved at planned locations rather than at random cracks. Joints are not access features and must not become paths for moisture or hot gas penetration.

Question 47Refractory Design and Specification

A 6 in. castable lining must pass through a shell nozzle. Which detailing is most appropriate?

  1. Cast the nozzle and the shell lining as one continuous piece with anchors on the bore
  2. Terminate the lining at the shell and leave the nozzle bare
  3. Continue the lining across the nozzle with no interruption to maximize coverage
  4. Provide a separate, isolated lining in the nozzle with a joint at the interface Correct answer.

Explanation

Nozzles and other penetrations have different geometry, restraint and movement than the main shell lining, so they are normally lined as separate elements with an expansion or isolation joint at the interface. This lets each lining move independently and confines cracking to a planned location. Continuous monolithic casting across the transition concentrates shrinkage and thermal stress and typically cracks.

Question 48Refractory Design and Specification

What is the purpose of moist curing a hydraulically bonded castable?

  1. To accelerate removal of free water before heat-up
  2. To let cementitious bonds hydrate and develop strength Correct answer.
  3. To leach excess calcium oxide out of the castable
  4. To prevent the anchors from oxidizing during installation

Explanation

Hydraulic bonds form by reaction of cement with water, and that reaction needs time and retained moisture to develop design strength. Cutting curing short leaves a weak, dusty surface and a lining that is more prone to spalling during dryout. Curing does not remove water; water removal is the job of the dryout schedule.

Question 49Refractory Design and Specification

Which condition most often causes explosive spalling of a newly installed dense castable during initial heat-up?

  1. Heating the lining more slowly than the schedule allows
  2. Installing the lining at too high an ambient temperature
  3. Steam pressure from water that cannot escape the lining Correct answer.
  4. Anchors expanding more than the refractory

Explanation

Water in the lining turns to steam during heat-up, and if vapor cannot migrate out through the porosity as fast as it is generated, internal pressure builds until the surface bursts off. That is why dryout schedules hold at intermediate temperature plateaus to let water escape gradually. Ambient placement temperature and anchor expansion affect quality but are not the classic spalling mechanism.

Question 50Refractory Design and Specification

Why is a test panel cast alongside the field installation?

  1. To measure the thermal conductivity of the steel shell under operating conditions
  2. To calibrate the mixer output during the pour
  3. To provide specimens representative of the installed material for testing Correct answer.
  4. To provide a wear plate later installed in the vessel

Explanation

A test panel is produced from the same material, water addition and placement method as the lining, then cored or cut into specimens for density, strength and other property tests. It demonstrates what was actually installed rather than what the data sheet claims. Panels are not wear parts and do not measure shell behavior.