API-936 Practice Questions

The purpose of a mock-up for vibration cast installations, as defined by API 936, is to qualify the installation procedure. This test specifically demonstrates that the proposed equipment (e.g., mixers, vibrators), the method of attaching the vibrators to the forms, and the overall vibration technique (e.g., frequency, duration, pattern) are adequate to achieve a properly consolidated refractory lining. This qualification ensures the chosen procedure can produce a dense, void-free lining consistent with the material manufacturer's requirements and project specifications before full-scale installation begins.

A. craftsman's ability to construct the forms.

This is incorrect because the mock-up primarily qualifies the vibration procedure, not the individual craftsman's skill in formwork, which is covered under general applicator qualification.

1. American Petroleum Institute (API). (2014). API Standard 936: Refractory Installation Quality Control—Inspection and Testing Monolithic Refractory Linings and Materials (4th ed.).

Section 6.3.3.1: This section explicitly states

"A mock-up shall be installed to demonstrate the adequacy of the equipment

means of vibrator attachment

and vibration method." This directly supports options B

C

and D as the correct answers.

Section 6.2: This section

"Applicator/Installer Qualification

" covers the qualification of the individual craftsman's skills

which is a separate requirement from the procedure qualification mock-up discussed in Section 6.3. This supports why option A is incorrect.

A pigment, or fugitive dye, is added to the curing compound to provide a distinct color that contrasts with the refractory lining. This color serves as a crucial visual aid for both the installer and the quality control inspector. It allows for immediate and easy verification that the compound has been applied uniformly across the entire surface, ensuring there are no missed spots. Complete coverage is essential for the curing compound to effectively perform its primary function of retaining moisture for proper cement hydration and strength development.

A. prevent ultraviolet light damage.

While some pigments offer UV resistance, this is not the specified purpose for their use in refractory curing compounds according to industry standards.

B. help the lining retain moisture.

The curing compound's film-forming resin is what retains moisture; the pigment is an inert colorant and does not contribute to this function.

C. help the lining retain heat.

The pigment's role is not related to thermal management. Curing is primarily concerned with controlling moisture loss, not heat retention.

1. American Petroleum Institute. (2014). API Recommended Practice 936: Refractory Installation Quality Control—Inspection and Testing Monolithic Refractory Linings and Materials (4th ed.).

Section 6.4.3.2: "Membrane curing compounds shall be applied by spray to the refractory surface immediately after finishing... The curing compound shall contain a fugitive dye to aid in obtaining complete

uniform coverage." This clause explicitly states the purpose of the dye (pigment) is to ensure full coverage.

2. Schacht

C. A. (2004). Refractories Handbook. Marcel Dekker

Inc.

Chapter 5

Section 5.4.2

Curing: In the discussion on curing monolithic refractories

the text notes that pigmented curing compounds are used "so that the applicator can see where the compound has been applied to ensure complete coverage." This corroborates the visual aid function.

3. Missouri University of Science and Technology

Materials Science and Engineering Department. CER 4310: Refractory Materials Courseware

Module on Installation of Monolithic Refractories.

Section: Curing of Castables: "To ensure proper application

curing compounds are specified to contain a fugitive dye. This allows for visual inspection to confirm that all surfaces have been adequately coated

preventing localized rapid drying which can lead to cracking and reduced strength."

The statement is false. According to API Standard 936, Table 1, "Qualification Test Requirements for Monolithic Refractories," the test for Cold Crushing Strength (CCS) requires two 2 in. (50 mm) cubes. The dimensions provided in the option, 4-1/2 in. × 4-1/2 in. × 4-1/2 in., are incorrect for this specific test. Furthermore, the metric conversion provided in the option is inconsistent, listing both 144 mm and 114 mm for the same 4-1/2 in. dimension, which is an additional error.

B. This is a true statement. API 936, Section 4.3.2.2, allows density to be determined using specimens prepared for permanent linear change (bars), abrasion resistance (plates), or from cubes.

C. This is a true statement. API 936, Section 4.3.2.5, explicitly specifies that abrasion resistance shall be determined using two 4-1/2 in. × 4-1/2 in. × 1 in. (114 mm × 114 mm × 25 mm) specimens.

D. This is a true statement. API 936, Section 4.3.2.4, requires that permanent linear change be determined using one 2 in. × 2 in. × 9 in. (50 mm × 50 mm × 230 mm) specimen.

1. American Petroleum Institute (API). (2014). API Standard 936: Refractory Installation Quality Control—Inspection and Testing Monolithic Refractory Linings and Materials (4th ed.).

For Correct Answer (A): Table 1

"Qualification Test Requirements for Monolithic Refractories

" page 8

specifies "Two 2 in. (50 mm) cubes" for the Cold Crushing Strength test.

For Incorrect Option (B): Section 4.3.2.2

page 7

states

"Density shall be determined...using the same specimens as used for permanent linear change (see 4.3.2.4) or abrasion resistance (see 4.3.2.5)." Table 1 also lists "Two 2 in. (50 mm) cubes" for density.

For Incorrect Option (C): Section 4.3.2.5

page 7

states

"Abrasion resistance shall be determined...using two 4 1/2 in. × 4 1/2 in. × 1 in. (114 mm × 114 mm × 25 mm) specimens..."

For Incorrect Option (D): Section 4.3.2.4

page 7

states

"Permanent linear change shall be determined...using one 2 in. × 2 in. × 9 in. (50 mm × 50 mm × 230 mm) specimen..."

According to API Standard 936, the contractor holds the primary responsibility for the quality of the refractory installation work. This scope of responsibility explicitly includes performing and fully documenting the results of both material qualification tests and applicator qualification tests. The contractor must maintain these records as part of the overall installation documentation, which is then subject to review and verification by the inspector and approval by the owner. This ensures a clear chain of accountability for the quality control process during the installation.

A. Inspector: The inspector's role is to witness, verify, and review the contractor's documentation and procedures to ensure compliance with the standard, not to create the primary documentation.

B. Manufacturer: The manufacturer is responsible for providing material data sheets and batch test results for their product but is not responsible for documenting the contractor's on-site applicator qualification tests.

D. Owner: The owner specifies the project requirements, designates the inspector, and provides final acceptance, but they do not generate the detailed test documentation for the contractor's activities.

References:

1. American Petroleum Institute (API). (2014). API Standard 936: Refractory Installation Quality Control—Inspection and Testing Monolithic Refractory Linings and Materials (4th ed.).

Section 9.1: "The contractor shall maintain a record of the installation, which shall be available to the inspector."

Section 9.2 (c) and (d): This section lists the specific items that must be documented by the contractor, which include "material qualification test results" and "applicator qualification test results."

Section 4.3.1: "The contractor shall be responsible for the quality of the installation work, which shall meet the requirements of this standard and the owner’s specification."

Section 6.1: "The contractor shall qualify each application crew (see 3.1.2) for each refractory material and installation method used." This implies the contractor is responsible for the associated documentation.

According to API Standard 936, the primary purpose of pre-installation testing (which includes casting sample mock-ups) is to qualify the installation procedures (the method) and the personnel (the installation crew or "fabricator") before actual work begins. The testing demonstrates that the specific combination of materials, equipment, procedures, and personnel can produce a refractory lining that meets the project specifications.

Other options like "mixing time" and "mix water levels" are variables that are established, optimized, and recorded during the testing to define the procedure, but they are not the entity being "qualified" in the certification sense. The "quality of the inspection equipment" is verified through calibration, not by the mock-up itself.

API Standard 936, Refractory Installation Quality Control—Inspection and Testing Monolithic Refractory Materials. Section: Pre-Installation Testing (Qualification of Installation Procedure and Crew).

Quote: "Pre-installation testing shall be performed to qualify the material, installation equipment, installation procedures, and personnel (installation crew)."

API 936 Body of Knowledge, Quality Control - Qualification, American Petroleum Institute.

According to API Standard 936, the quality control requirements for manufactured refractory shapes, such as bricks, mandate specific testing protocols before installation. For physical attributes testing conducted on a lot basis, the standard explicitly defines the acceptable quality limit (AQL). This limit is set to ensure a high probability that the percentage of nonconforming items in a given lot does not exceed a specified value. The standard requires that the AQL for this type of testing shall be 4.0%.

A. 1%: This AQL is more stringent than the value specified by API 936 for the physical attribute testing of bricks.

C. 5%: This value is incorrect. The standard explicitly mandates an AQL of 4.0%, not 5.0%.

D. 10%: This AQL is too lenient and would permit a higher defect rate than what is allowable under the API 936 standard for these materials.

1. API Standard 936

Refractory Installation Quality Control—Inspection and Testing Monolithic Refractory Linings and Materials

4th Edition

May 2014.

Section 4.3.2.2: "Physical attributes testing of manufactured shapes shall be performed on a lot basis. The sample size shall be in accordance with Table 1. The acceptable quality limit (AQL) shall be 4.0 %."

According to API Standard 936, the installation contractor holds the primary responsibility for the satisfactory installation of the refractory lining. This responsibility is defined by the owner's specifications and drawings. To ensure alignment and prevent disputes, the standard explicitly mandates that the contractor must obtain an "advance agreement" from the owner that covers all details of the installation process. This agreement forms the contractual basis for the work and the benchmark against which the inspector will verify compliance. The owner is the ultimate client and authority for the project.

A. Engineering company: The engineering company typically provides the design and specifications, but the contractual agreement for execution is between the contractor and the owner.

B. Inspector: The inspector's role is to verify that the installation conforms to the pre-agreed details, not to establish or approve those details.

D. Manufacturer: The manufacturer provides the refractory materials and application procedures, but they are not the party with whom the contractor finalizes the overall installation agreement.

1. API Standard 936

Refractory Installation Quality Control—Inspection and Testing Monolithic Refractory Linings and Materials

4th Edition

December 2014.

Section 6.1.1: "The contractor shall secure advance agreement from the owner concerning all installation details."

Section 4.2.1: "The contractor shall be responsible for the satisfactory installation of the refractory in accordance with the requirements of the owner’s specification and drawings."

According to API Standard 936, when a sample fails to meet the required specifications, retesting is permitted to validate the result. To ensure the retest is scientifically valid and comparable to the original failed test, variables must be minimized. The standard explicitly states that retesting shall be performed using specimens drawn from the same batch, same pallet, and the same sample (the original quantity of material extracted) as the original test. Furthermore, the same testing procedure (methodology) must be utilized to ensure the results are correlated. Inspection methods (which typically refer to visual field monitoring or installation oversight) are distinct from the specific laboratory testing protocols and are not a variable that applies to the retesting of a specific material sample.

API Standard 936, Refractory Installation Quality Control—Inspection and Testing Monolithic Refractory Materials, Section: Testing and Quality Control (specifically subsections on Sampling and Retesting/Resampling).

Note: The standard dictates that to confirm compliance or failure, the re-evaluation must rule out material variation; thus, the original source material (Batch/Pallet/Sample) and the yardstick (Testing Procedure) must remain constant.

API 936 Body of Knowledge, Quality Control - Testing Variables, American Petroleum Institute.

Phosphate-bonded plastic refractories develop their permanent strength through a chemical reaction that occurs during the initial heating or dryout process. This reaction forms strong aluminum phosphate bonds. According to the American Petroleum Institute (API) Standard 936, this critical chemical bonding phase, which imparts permanent strength to the refractory before it reaches full operating temperature, occurs specifically within the temperature range of 300°F to 500°F (150°C to 260°C). Heating through this range at a controlled rate is essential to properly form the bond and drive off chemically combined water without damaging the refractory structure.

A. 100°F to 300°F (38°C and 150°C): This temperature range is primarily associated with the removal of free, uncombined water from the refractory. Significant permanent chemical bonding has not yet initiated.

B. 50°F to 100°F (10°C and 38°C): This represents ambient installation and air-drying temperatures. No significant chemical reaction or permanent bond formation occurs in this range.

D. 500°F to 700°F (260°C and 370°C): While the bond may continue to strengthen and transform at these temperatures, the primary formation of the strong chemical bond is completed below this range, as specified by API 936.

1. API Standard 936

Refractory Installation Quality Control—Inspection and Testing Monolithic Refractory Linings and Materials

4th Edition

November 2014.

Annex B

Section B.3.3: "Phosphate-bonded materials develop a strong chemical bond between 300 °F and 500 °F (150 °C and 260 °C)."

2. Schacht

C. A. (2004). Refractories Handbook. CRC Press.

Chapter 3

Section 3.2.2

"Plastics and Ramming Mixes": The text describes the bonding mechanism of phosphate-bonded plastics

noting that the chemical reactions that form the aluminum phosphate bond begin around 120°C (250°F) and are well-established by 260°C (500°F)

aligning with the range specified in API 936.

3. Gitzen

W. H.

& Hart

L. D. (1965). Phosphate Bonding of Alumina Refractories. The American Ceramic Society Bulletin

44(9)

699-703.

This foundational paper discusses the chemistry of phosphate bonding

explaining that the key dehydration and polymerization reactions that create a strong bond occur in stages

with significant reactions initiating above 150°C (302°F).

As-installed testing is the correct term for the evaluation of refractory samples taken from the actual installation. This testing is performed to verify that the physical properties of the refractory material, after being mixed and applied on-site, meet the project's specified requirements. It confirms the quality of both the material and the installation workmanship, accounting for variables like water content, mixing procedure, and application technique. This is distinct from pre-qualification testing, which is done on the material before it is shipped to the site.

A. Hammer testing: This is a qualitative, non-destructive inspection method used after curing to check for voids or delamination, not a quantitative test of physical properties on a sample.

B. Pre-qualification testing: This testing is performed on refractory materials before installation to qualify the manufacturer's product, not on samples taken from the actual on-site installation.

D. Visual testing: This is a form of inspection to identify surface defects, improper application, or other visible flaws. It does not involve taking samples to measure physical properties.

1. American Petroleum Institute (API) Standard 936

4th Edition

December 2014. Refractory Installation Quality Control—Inspection and Testing Monolithic Refractory Linings and Materials.

Section 3.1.4: Defines "as-installed testing" as "Testing to determine physical properties of refractory materials taken from the installation." This directly supports the correct answer.

Section 3.1.31: Defines "pre-installation testing (qualification testing)" as "Testing to determine physical properties of refractory materials before installation..." This clarifies why option B is incorrect.

Annex A

Section A.4.3.1: Lists "Hammer testing" as a post-installation inspection activity to check for voids

confirming it is an inspection technique

not the term for sample testing.