According to API TR 980 , Section 4.4.2, mock-ups are required prior to actual installation for vibration-cast materials to verify the adequacy of equipment, the method of vibration, and vibrator attachment . These mock-ups are not intended to assess the craft skill in form construction.

"Mock-up vibration-casting trials are used to demonstrate the adequacy of the equipment, the means of vibrator attachment, and the method of vibration for the particular installation geometry and refractory type."

— TR 980, Section 4.4.2 ​

Therefore:

B (equipment) is correct.

C (means of vibrator attachment) is correct.

D (vibration method) is correct.

A (craftsman’s ability to construct the forms) is not the intent of this mock-up and thus not correct.

Pallet

Batch

Testing Procedure

Sample

When a sample fails to meet the required specifications in accordance with API Std 936, any retesting must maintain strict consistency with the original conditions to ensure validity and comparability of results.

API 936 states:

“If a sample fails to meet any requirement, resampling shall be permitted. However, retesting shall be performed using specimens from the same batch, pallet, and sample as the original test. The same testing procedure must be used.”

— API Std 936, Section 6.2.3​

Explanation of Matching Terms:

Pallet: To ensure material consistency.

Batch: Revalidates results without introducing variability from a new production lot.

Testing Procedure: Methodology must not change to avoid skewed comparison.

Sample: Must be the original sample to confirm initial findings.

Therefore, all of these factors must remain the same. The only item in your provided list that is not required to match is “Inspection methods” — it is not part of the retesting condition clause.

The curing of newly installed refractory linings must adhere strictly to manufacturer guidelines to ensure integrity and performance:

“Forms shall not be stripped until the lining has cured per the manufacturer’s recommendation.”

— API Std 936, Section 5.4.2.1​

The manufacturer's recommendations ensure that the product reaches sufficient strength before demolding.

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When using refractory plastics or ramming mixes, it is critical that trimming, jointing, and venting be performed before stopping work for the day or shift . API 936 and TR 980 specify that proper surface preparation helps relieve vapor pressure during dryout and prevents cracking. If these steps are postponed, the surface may dry unevenly or set improperly, complicating the subsequent installation and reducing bond quality between layers.

Venting paths are particularly important in thick plastic or ramming layers where moisture may be trapped, and jointing ensures layer-to-layer continuity. Trimming also smooths out inconsistencies and aligns the lining to specifications.

The manufacturer is responsible for specifying the exact dimensions, type, concentration, and metallurgical properties of metal fiber reinforcement in castable refractories. These fibers are often integral to the formulation and performance of the material and are introduced during manufacturing (not field mixing), with characteristics tailored to improve thermal shock resistance and crack propagation control.

API 936 defers to the manufacturer’s technical data for the design and quality control of any material component, including reinforcement. The contractor is responsible for verifying that materials match the manufacturer’s documented specification.