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damage control valves and heat exchangers. The control of the total dissolved solids (TDS) in the boiler water level ensures that the risks of foaming and carryover are minimized. The rate of theoretical blowdown Bdr (m 3 ) is calculated as the balance of the TDS by Equation (1). The difference between them and the total cold water added to the feedtank represents the installation losses. Cw is an indirect indicator of these installation losses. Bdr = (Feed water TDS · · · Steam generation)/(Required boiler water TDS − Feed water TDS), (1) where: Feed water TDS refers to the current TSD contained in the water (ppm). Steam generation corresponds to the steam flow rate generated by the boiler (kg/h). Required boiler water TDS is measured according to EN 12953 [53]. The difference between the theoretical blowdown rate and cold water added in Equa- tion (2) represents the total installation losses Il (m 3 ) due to leakage from control valves, drying cylinders, and gaskets. Il =Cw − Bdr , (2) To control these parameters, the plant implements a system to monitor the basic boiler, steam consumption, and condensate recovery parameters. To manage these indicators, the first-level-of-action personnel are assigned the task of tracking the parameters three times a week instead of laboratory personnel. This approach involves the maintenance staff in preventing the overconsumption of water Il and reviewing steam production and distribution leakages. TPM and techniques such as TEI and CPI are analyzed and implemented [51]. The personnel are trained in TEI and CPI techniques to perform these checks; every fortnight, the analyzed values are contrasted by laboratory personnel to verify that the parameter measurements and the interpretation of the results are correct. New forms are created to record the main parameters of the steam and condensate installation at least three times a week. If the TDS in the boiler water decreases (Equation (2)), the blowdown is higher than needed, and the blowdown frequency must be adjusted. In contrast, the blowdown flow must be increased if the TDS increases. When the blowdown is correctly adjusted, Il comes from the distribution and con- sumption system. Then, the first-level-of-action personnel look for other losses and act to correct them. Historical maintenance data indicate that major losses come from rotary joints in the drying cylinders installed in the dryer section. Rotary joints are responsible for introducing steam into the dryer cylinder and removing the condensate formed due to the energy transferred by the steam to the web. Assuming proper installation, the major causes of steam losses in the rotary joints come from carbon seal wear. Initially, the factory rules said to change the entire rotary joint (to repair it) only when steam leaks were detected. If the lost steam had no greater importance, the joint was generally kept running as long as the leak was small. Its replacement was postponed until the next technical or maintenance shutdown. The supply of steam to the dryer cylinder was closed only when the leak affected the quality of the paper produced. A closed dryer cylinder resulted in a smaller heating area, lower drying capacity, and inefficiency in the dryer section. A previously unused maintenance strategy is developed to control carbon seal wear. Instead of applying the manufacturer’s maintenance rules, which require qualified per- sonnel to disassemble part of the rotary joint, a new rule is developed based on taking the absolute and angular positions of the item. The establishment of this rule provides a preventive maintenance program as an alternative to waiting to detect steam leakage to reduce steam spills and maximizes the amount of condensate recovery. This rule iden- tifies the state of wear in the carbon seal, thus providing the necessary time to organize appropriate maintenance.
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