API 936 flashcards

35 cards. Read the term and the definition here. The deck at the top of this page is optional.

Low-cement castable CaO range

Low-cement castables contain 1.0 to 2.5 percent calcium oxide by weight, while ultra-low-cement castables contain 0.2 to 1.0 percent calcium oxide.

Conventional castable CaO threshold

Conventional castables contain more than 2.5 percent calcium oxide by weight, which lowers refractoriness and increases porosity compared with low-cement castables.

No-cement castable definition

No-cement castables contain less than 0.2 percent calcium oxide and rely on other bonding systems such as hydratable alumina or colloidal silica.

Abrasion resistance in FCC

Abrasion resistance of monolithic refractory increases with higher bulk density, lower apparent porosity, harder aggregate, and a stronger aggregate-matrix bond.

Silica attack by vanadium

Vanadium and sodium in FCC feed flux silica-containing refractories, so high-alumina or spinel refractories are selected for erosive and chemical service.

Thermal conductivity versus density

For dense monolithic refractories, thermal conductivity generally increases with bulk density and decreases with rising service temperature.

Spinel refractory benefit

Alumina-spinel castables resist thermal shock and slag attack because spinel has low thermal expansion and resists alkali and iron oxide penetration.

Hexmesh anchor typical spacing

Hexagonal mesh anchors are commonly on 2-inch centers, 3/4 to 1 inch deep, and 12 to 14 gauge stainless steel for dense monolithic linings.

Anchor alloy temperature limit

Type 304 stainless anchors suit oxidizing service to about 1500°F, type 310 to about 1900°F, and nickel alloys for higher or reducing service.

Anchor hot-face clearance

Anchor tips should terminate roughly 1/2 to 1 inch below the hot face so the refractory covers and protects the metal from overheating.

Expansion joint purpose

Expansion joints relieve thermal growth in castable linings; they are placed at regular intervals and at shell discontinuities to prevent random cracking.

Lining thickness tolerance

Installed monolithic lining thickness is typically checked against specification tolerance, commonly plus or minus 1/4 inch unless the project specifies tighter limits.

Shell temperature design limit

Refractory and insulation thickness are chosen to keep the steel shell below its design temperature, often about 500 to 650°F in FCC service.

Mixing water temperature

Clean mixing water should be about 50 to 80°F; hot water accelerates setting and cold water slows it, both altering working time and strength.

Castable working time

Working time is the period after mixing during which the castable can be placed and vibrated; it shortens as ambient and mix temperature rise.

Vibration of castable

Castable is consolidated with internal vibrators until air bubbles stop and the surface turns glossy; over-vibration causes segregation.

Gunning rebound rule

Rebound material that bounces off the target must never be reused or worked back into the lining because it lacks fines and bond.

Curing low-cement castable

Low-cement castables are typically moist-cured for about 24 hours at 65 to 85°F before dryout to allow hydraulic bond development.

Test panel requirement

Test panels are cast from the same mix and at the same time as field placement, then cured and dried with the lining for quality testing.

Cold weather installation limit

Refractory installation should not proceed when the shell or ambient temperature is below 50°F unless heating and enclosures maintain proper curing conditions.

Cold crushing strength test

Cold crushing strength is measured on cured and dried cube specimens, usually 2-inch cubes, per ASTM C133 to verify material strength.

Bulk density acceptance

Bulk density of field samples is commonly required to be within about 5 percent of the manufacturer's published value for the same product.

Hammer tap inspection

Hammer tapping detects voids, delamination, and unbonded refractory by a change from a sharp ring to a dull thud.

Permanent linear change test

Permanent linear change measures irreversible dimensional change after reheating a specimen to a specified temperature and cooling it.

Abrasion resistance test

Abrasion resistance is evaluated by ASTM C704, which blasts a specified abrasive at a refractory surface and measures volume loss.

Anchor weld inspection sampling

Anchor welds are inspected visually and by bend testing samples; failed welds require repair and re-inspection before lining placement.

Moisture before dryout

Residual moisture in a new lining should be checked and documented before dryout; excessive water can cause steam spalling during heat-up.

Material storage requirement

Cement-bonded castables are stored dry, off the ground, and within shelf life; bagged material that has caked or hardened is rejected.

Dryout hold at 250°F

A typical dryout holds at about 250 to 300°F to remove free water slowly before raising temperature further, preventing steam spalling.

Dryout heating rate

Dense castable linings are commonly heated at 25 to 50°F per hour during initial dryout, with slower rates for thick or low-permeability sections.

Chemical water release

Chemically bound water in cement-bonded refractories is driven off roughly between 500 and 900°F, requiring a controlled hold in that range.

Repair area preparation

Repairs require removal of all cracked, spalled, or unbonded material to sound refractory, with square edges and clean exposed anchors.

Anchor replacement criterion

Anchors that are severely oxidized, deformed, or have failed welds are replaced rather than embedded in new refractory.

Crack repair threshold

Cracks wider than about 1/8 inch or deep cracks that reach anchors are typically cut out and repaired during turnaround maintenance.

Dryout vent purpose

Vents or weep holes in a lining allow steam and water vapor to escape during dryout, reducing pressure buildup and spalling risk.