Alkali Hydrolysis – A failure mechanism that can occur in lightweight castables due to the reaction of carbon dioxide in the atmosphere with lime in the cement. Typically, surface layers of the refractory become friable and delaminate. The failure occurs when the refractory is exposed to certain environmental conditions after placement and when some time passes before dryout. One of the most effective preventative measures is to conduct a timely refractory dryout.
Bake Out – This term is sometimes used to refer to a refractory dryout.
Bulk Density – A quality measure used for refractory. It is the weight of an object divided by the volume that it occupies. In refractory, bulk density can be reduced by excess porosity.
Burnout Fibers – Refractory manufacturers often create intentional porosity and permeability in their materials by including fibers in the mix that will burn out (and leave voids) at low temperatures.
Burner Turndown Capability – This is the ratio of the maximum firing rate of a burner divided by its minimum firing rate. Many pre-mix process burners have a turndown capability of 3 to 1.
Castable Refractories – A mixture of heat-resistant aggregate materials and heat-resistant hydraulic cement. It is typically mixed with water in order to be placed by casting, ramming or gunning. Castable refractories can be installed in the field to conform to the shape of the furnace, vessel, trough, cyclone or duct.
Ceramic Bond – The mechanical strength in refractory that is developed during heat treatment and is the result of cohesion between adjacent aggregate particles.
Circulating Fluidized Bed Boiler (CFB) – This technology suspends particles of fuel and limestone in a stream of air in order to create efficient low temperature burning and to limit the generation of pollutants such as NOX and SO2. This technology has environmental advantages and flexibility on the quality of the fuel.
Checker Burnout – A term used by some to refer to the sulfate burnout process for opening clogged regenerators on a glass furnace.
Chemical Cleaning – A commissioning process used in the start up of new boilers. Various cleaning and passivating fluids are temperature controlled and circulated thru the boiler tubes in order to clean and condition them before being placed into service.
Coating Cure – Various coatings are used in industrial processes to reduce corrosion attack and/or to change the emissivity of a surface. Frequently these coatings are applied wet and need to be dried and cured before being placed into service.
Cold Crushing Strength (CCS) – This is a quality measure of a refractory that measures its resistance to compressive forces.
Cold Water Glass Furnace Drain (CWD) – At the end of a glass furnace campaign, the liquid glass in the furnace must be removed in order to enable repairs to the refractory. One method for removing the liquid glass is to drill a hole in the furnace and drain the hot glass into a water stream that will quench it and transport it to a storage area. In a cold water drain, the water is used in a “once thru” manner.
Crown Rise Monitor (CRM) – When heating up a glass furnace, the refractory expands and the steel restraining structure must be adjusted to accommodate the expansion. In order to monitor and control this process, it is beneficial to measure the position of the refractory crown on the furnace. Traditionally this has been done by manually measuring “tell-tales” that compare the crown position to its original elevation. Crown Rise Monitor (CRM) uses linear position transducers and a data recorder to continuously monitor the position of the crown.
Cullet – Broken fragments of glass collected either as a byproduct of glass manufacture or as a result of post consumer recycling. This material is frequently used as a raw material in glass manufacturing.
Cullet Filling – When a glass furnace is first put into production, it is heated and must have an initial charge of glass to begin the production process. Cullet filling is often used to provide this initial charge. Cullet is frequently charged into the hot furnace either by blowing or vibrating it into the melter.
Excess Air Burner – This style of burner does not try to maintain a fixed ratio of fuel to combustion air. It has the advantage of providing a high volume and low temperature stream of gas at the burner discharge nozzle when turned down to low firing rates. This functionality is particularly well suited to refractory dryout.
Expansion Control Supervision (ECS) – During the heatup of a glass furnace, the refractory is contained by a steel structure and large adjustment bolts. As the furnace heats up and expands, the steel structure must be adjusted to accommodate the growth of the refractory. Expansion Control Supervision is a service provided to manage these adjustments.
Freeze Protection – On occasion, critical assets must be protected from freezing due to environmental conditions. Usually these issues arise either during construction or during an extended outage. Freeze protection is a service that can be used to protect critical assets during cold weather.
Furnace Heatup – Many industrial furnaces recycle waste heat and they rely on that recycled heat to sustain the process. Stoves, regenerators, checkers, and recuperators are all examples of technologies used to recycle process heat. When one of these process is completely cold (either due to an outage or new construction), it is often necessary to “kick-start” the process with an external heat source. Furnace heatup is a service to bring these industrial furnaces from ambient temperature up to a sustainable operating condition.
Furnace Hold Hot – When an industrial furnace interrupts the generation of the process heat but it isn’t desirable to allow the process to cool down, a furnace hold hot service is often used. Emergency hold hot service is sometimes used due to utility interruptions or natural disasters. Planned hold hot services may be used when a portion of the process needs to undergo repairs and it is undesirable to cool down the entire process.
Furnace Outage – Many large industrial furnaces operate 24 hours per day and 7 days per week. The processes are continuous and are rarely interrupted. On occasion, a furnace outage is scheduled in order to conduct maintenance and repairs that can only occur during a process stop. In some industries, the outages are referred to as a turnaround.
Gunned Refractories – Refractory material may be installed via a method known as gunning. Refractory material is transported in a compressed air stream and is projected onto the refractory surface. The material may have water added at the nozzle or may be pre-moistened. The objective is to have the material stick to the target surface and to avoid rebound.
Heat Recovery Steam Generator (HRSG) – This is a type of boiler that captures excess process heat. They may be installed before the exhaust stack on an industrial furnace or they can be used in conjunction with a combined cycle power generator. A combined cycle turbine has one stage driven by the products of combustion and a second stage driven by steam from the HRSG that captures some of the heat left over after the first stage.
Hydrocarbon Processing Industries (HPI) – This industry category refers to oil refining, gas processing, LNG, and petrochemical industries.
Meltouts – On occasion, liquid materials solidify in the wrong place and need to be removed. One method of removing these materials is to melt them back into a liquid and allow the liquid to flow to the desired location.
Modulus of Rupture (MOR) – A quality measure of a refractory that measures its strength in resisting flexural (bending) forces.
Monolithic Refractory – A refractory that is applied on-site in the unfired state and forms a continuous mass. Examples of monolithic refractory include castable, shotcrete, gunning mixes, plastic and ramming materials. Once placed, a refractory dryout is required to create the refractory properties.
Permeability – The ability of a gas to pass thru a refractory structure. Permeability is enhanced when porosity interconnects and provides a gas path. Porosity does not necessarily create permeability. During refractory dryout, steam uses permeability to escape from the refractory structure.
Porosity – Voids in the refractory structure create porosity. Porosity can occur as large individual voids or as micro voids dispersed throughout the structure.
Plastic Refractory – A refractory mixture utilizing bonding agents such as clays, phosphates or resins. The material is typically delivered for installation as wet blocks. During installation, plastics do not require as much compaction/deformation as ramming material. The blocks are typically tamped together to form a continuous lining. Once placed, a dryout is required to create the refractory properties.
Post Weld Heat Treating (PWHT) – When metal structures are welded, the heat affected zone has modified metallurgical properties compared to the parent metal. In order to restore metallurgical properties, a thermal cycle is often required. Most post weld heat treating is conducted locally on the weld with electrical resistance heating. In some cases, it is beneficial to heat an entire tank or weldament and, in these cases, combustion post weld heat treating is often deployed.
Ramming Refractory – A refractory mixture utilizing bonding agents such as clay, organics, phosphates, silica or tar. The material may be delivered for installation either in wet or dry form. The material is typically compacted with a pneumatic hammer or other compacting tool. Shear created during ramming contributes to the materials density and final properties. Once placed, a dryout is required to create the refractory properties.
Ratio Burner – Ratio burners attempt to maintain an optimal mixture of air and fuel. This ratio is usually slightly greater than the stoichiometric ratio in order to ensure complete combustion of all fuel. This type of burner is typically selected for process burner applications since it has good energy efficiency, environmental advantages, and is well suited to maintaining high temperature processes.
Recycled Hot Water Glass Furnace Drain (RHWD) – This service is similar to the cold water glass furnace drain except that the water is collected after separation from the cullet and it is recycled back to be used again in a continuous closed loop.
Refractory Cure – This is the initial period after placement of a castable refractory before the start of the dryout. During this period, reactions are occurring that result in the hard set of the refractory. Typically the refractory manufacturer specifies the duration of the cure period and it may be a function of the ambient temperature.
Refractory Dryout – For monolithic refractory, following installation and the cure period, heat is applied per the manufacturer’s schedule in order to drive off both free and chemically combined water. This thermal treatment is the last step in achieving the desired properties in the installed refractory. This process is sometimes referred to as bake-out, heat cure, dry out, dry-out, or preheat.
Refractory Spall – A mechanical failure of a refractory lining resulting in cracks, fractures, delamination, crumbling and/or explosive failure. Refractory spalling can occur due to many different root causes but, if it occurs, it typically happens during the refractory dryout. During dryout the refractory lining is exposed to high forces as water is converted to steam and it tries to escape the lining. If the refractory properties have been compromised due to any prior activities, then failure is likely to occur during the dryout. Refractory spalling typically occurs because the material does not have the strength to withstand the forces caused by the evolving steam during dryout. The two main issues are the material properties and the rate of steam generation. This condition is also referred to as explosive spalling or refractory blowout. Quality control procedures and adherence to the manufacturer’s mixing, placing, curing and drying instructions are the best preventative measures to avoid this condition.
Regenerator Decongestion – This is another term for the sulfate burnout process.
Shotcrete – A refractory material that is mixed (like a castable) and then applied by pumping the mixture to a nozzle where it is mixed with air and an activator to begin the curing. The mixture is pneumatically “shot” on to the installation surface. Once placed, a dryout is required to create the refractory properties.
Sulfate Burnouts (SBO) – In glass furnaces with regenerators, sulfates tend to condense in the checker-pack over time. The accumulation of sulfates restricts air passage and eventually furnace operation is impacted. One method of removing sulfates from the checkers involves installing a burner in the bottom of the regenerator and heating the checker pack to above the melting point of the sulfates. This allows the sulfates to run out of the checkers to the bottom of the regenerator and air flow is restored to the furnace. This process is also referred to as regenerator decongestion or checker burnouts.
Turnaround – In oil refineries and other process industries, periodic maintenance outages are planned where the process is completely stopped. Extensive planning and preparation is done to optimize the work accomplished and to minimize the downtime. These outages are frequently called turnarounds.