37 Building, namely, building construction services; construction of industrial facilities; demolition of industrial facilities; customer service, namely, installation, cleaning, retrofitting and repair, replacement in the nature of repair and maintenance of machines for drying, heating, calcining and cooling of industrial materials in chemical processing plants, industrial processing plants for minerals and in power plants namely, gypsum, limestone, coal and ore; customer service, namely, installation, cleaning, retrofitting and repair, replacement in the nature of repair and maintenance of process gas coolers for machines and motors for the petrochemical or chemical industry including for gasification processes; customer service, namely, installation, cleaning, retrofitting and repair, replacement in the nature of repair and maintenance of heat exchangers as part of machines and plants for heat recovery from manufacturing processes in the chemical, petrochemical, metallurgical or glass industry or for heat recovery in power stations; customer service, namely, installation, cleaning, retrofitting and repair, replacement in the nature of repair and maintenance of recuperators as part of machines or plant for use in the metallurgical industry, on melting furnaces of mineral wool production, chemical or petrochemical manufacturing processes, or on fluidized bed furnaces for sludge combustion; customer service, namely, installation, cleaning, retrofitting and repair, replacement in the nature of repair and maintenance of heat exchangers as part of machines for air or fuel preheating; customer service, namely, installation, cleaning, retrofitting and repair, replacement in the nature of repair and maintenance of heat exchangers as parts of machines for recovery of gas turbine waste heat; customer service, namely, installation, cleaning, retrofitting and repair, replacement in the nature of repair and maintenance of industrial grinding machines being grinding mills, rolling mills, impact mills, bowl mills and pulverizers for chemical processing, minerals processing, foodstuffs processing and power generation plants consisting of electric grinding devices; customer service, namely, installation, cleaning, retrofitting and repair, replacement in the nature of repair and maintenance of air classifiers and associated system components for mills for power generation and industrial applications including for mineral processing industries, namely, dynamic or static filtration system consisting of mesh filter and cyclonic filtration apparatus; customer service, namely, installation, cleaning, retrofitting and repair, replacement in the nature of repair and maintenance of chimney flues and installations for conveying exhaust gases, namely, away from industrial furnaces and boilers; customer service, namely, installation, cleaning, retrofitting and repair, replacement in the nature of repair and maintenance of air preheaters and gas-gas heaters for gas processing including use in thermal power generation facilities and industrial plants, including rotary regenerative heat exchangers not being parts of machines and heat exchangers not being parts of machines for chemical plants; customer service, namely, installation, cleaning, retrofitting and repair, replacement in the nature of repair and maintenance of flat and profiled heat exchanger panels; customer service, namely, installation, cleaning, retrofitting and repair, replacement in the nature of repair and maintenance of coolers, namely, those used in industrial chemical or materials processing applications; customer service, namely, installation, cleaning, retrofitting and repair, replacement in the nature of repair and maintenance of heat exchangers not being parts of machines; customer service, namely, installation, cleaning, retrofitting and repair, replacement in the nature of repair and maintenance of convection recuperators for chemical processing and other industrial processing applications; customer service, namely, installation, cleaning, retrofitting and repair, replacement in the nature of repair and maintenance of thermal oxidizers for use in industrial plant; customer service, namely, installation, cleaning, retrofitting and repair, replacement in the nature of repair and maintenance of systems consisting of heat exchangers and process gas coolers for the heat transfer for petrochemical chemical am metallurgical production processes, namely, process gas coolers not being part of machines in the nature of transfer line exchangers and steam generating heat exchangers not being part of machines used in gasification processes; customer service, namely, installation, cleaning, retrofitting and repair, replacement in the nature of repair and maintenance of waste heat steam generators and high temperature heat exchangers not being parts of machines; customer service, namely, installation, cleaning, retrofitting and repair, replacement in the nature of repair and maintenance of steam generator system consisting primarily of steam generators for processing gas and heat recovery in steam reforming manufacturing processes, heat recovery in chemical and metallurgical manufacturing processes, heat recovery processes after partial oxidation; customer service, namely, installation, cleaning, retrofitting and repair, replacement in the nature of repair and maintenance of heat recovery downstream system comprised primarily of heat exchangers not being part of machines used to assist ammonia combustion in nitric acid and caprolactam manufacturing processes; customer service, namely, installation, cleaning, retrofitting and repair, replacement in the nature of repair and maintenance of heat recovery steam generators in fire tube, water tube and double tube design for chemical metallurgical and glass technological manufacturing processes; customer service, namely, installation, cleaning, retrofitting and repair, replacement in the nature of repair and maintenance of heat recovery steam generators for the utilization of gas turbine heat; customer service, namely, installation, cleaning, retrofitting and repair, replacement in the nature of repair and maintenance of industrial flash dryers for dehydrating solid particles; customer service, namely, installation, cleaning, retrofitting and repair, replacement in the nature of repair and maintenance of mechanical separators for removing solid particles from air; customer service, namely, installation, cleaning, retrofitting and repair, replacement in the nature of repair and maintenance of industrial dryers for materials and food processing plants not being parts of machines; customer service, namely, installation, cleaning, retrofitting and repair, replacement in the nature of repair and maintenance of industrial coolers for materials and food processing plants not being parts of machines; customer service, namely, installation, cleaning, retrofitting and repair, replacement in the nature of repair and maintenance of industrial calciners, namely, limestone calcination machines; customer service, namely, installation, cleaning, retrofitting and repair, replacement in the nature of repair and maintenance of kilns for industrial purposes; customer service, namely, installation, cleaning, retrofitting and repair, replacement in the nature of repair and maintenance of heat exchangers as parts of a steam generator system for heat recovery from manufacturing processes in the chemical petrochemical metallurgical or glass industry or for heat recovery in power stations; customer service, namely, installation, cleaning, retrofitting and repair, replacement in the nature of repair and maintenance of high temperature preheaters as parts of a steam generator system for air, gaseous or liquid substances for chemical am metallurgical manufacturing processes or glass manufacture; customer service, namely, installation, cleaning, retrofitting and repair, replacement in the nature of repair and maintenance of recuperators as parts of a steam generator system for use in the metallurgical industry, on melting furnaces or mineral wool production, chemical or petrochemical manufacturing processes, or on fluidized bed furnaces for sludge combustion; customer service, namely, installation, cleaning, retrofitting and repair, replacement in the nature of repair and maintenance of thermal post-combustion furnaces for dust-laden gases, blast furnaces gas containing C02 or exhaust air containing solvents downstream of various manufacturing processes, and heat exchangers as parts of a steam generator system for air or fuel preheating; customer service, namely, installation, cleaning, retrofitting and repair, replacement in the nature of repair and maintenance of heat exchangers as parts of a steam generator system for the recovery of gas turbine waste heat