Hot tub boilers include electric hot tub boilers, oil-fired hot tub boilers, and gas-fired hot tub boilers, among others. Hot tub boilers are also known as bath boilers or shower boilers, referring to specialized boiler equipment for producing hot water for bathing purposes. These boilers require a thermal insulation water tank for showers. Generally, the boiler heats the heat medium water to 40-45°C. Using a hot water circulation pump, it forces the water in the boiler and the thermal insulation water tank to circulate, ensuring consistent temperatures, thereby achieving the bathing objective.
One. Condenser Feedwater System Cleaning
1. Rinse
Condenser - The water supply system should be manually cleaned with 2% sodium hydrogen phosphate (Na3PO4). 12H2O) prior to rinsing, then rinse the system with clean water.
Better use softened water for formal system flushing. The circulating power for flushing is provided by the condensate pump, and the condenser hot well serves as the water storage container. To prevent damage to the condensate pump caused by suspended particles, a filter should be installed at the pump's inlet. Flushing should start from the condenser well and gradually proceed through the condensate and feedwater systems until the boiler. Flush each component until the wastewater is cleared. Typically, water samples are collected at some discharge points to confirm the end of flushing. For all circuits with branches (such as drain outlets, ventilation openings, instrument joints, etc.) or circuits with parallel channels (such as bypass pipelines), consider these branches and branches during operation to ensure the system is completely clean. It is recommended to prepare a checklist before starting the cleaning operation, indicating the operational sequence of each branch and bypass pipe as well as the corresponding valve status.
2. Alkaline Wash
Condenser - Water supply system for alkaline cleaning, containing 2,000 ppm trisodium phosphate (2,000 ppm Na3PO4 or 4,600 ppm)
Na3PO4.12H2O and 1000ppm disodium phosphate (Na2PO4) with a compatible wetting agent solution. Alkaline chemicals are typically dry and powdered, so they must be mixed into a concentrated solution prior to use and then injected into the circulating system. After alkaline washing, the cleaning solution should be replaced with condensate or demineralized water to flush the system.
Condenser --- The water supply system typically requires only one alkaline cleaning during its service life. For water heater feed, usually only the tube side of the base needs to be cleaned. If a petroleum-based anti-corrosion agent has been used on the outer shell and tube side of the water heater feed and cannot be removed with hot condensate water, the system should be cleaned alkalinely in two stages.
At the start of alkali washing, the condensate feed system should be filled with demineralized water. The alkali washing cycle typically consists of a chemical cleaning pump. The alkali washing solution is injected into the chemical cleaning header, and is circulated continuously at a temperature of 200°F for at least 24 hours. Alkali washing generally employs a higher flow rate as it provides better removal of non-soluble particles in the bends of the pipes. The degasser is usually cleaned within the system or bypassed. During alkali washing, pumps and other equipment that may be worn or damaged by the alkali solution or suspended solids should have their internal components bypassed or removed.
After cleaning is complete, replace the fluid in the system with deionized water to expel waste base solution. The water side and shell edges of the water heater should also be separately cleaned.
3. Pickling
At the start of the pickling operation, the condenser---water supply system should be kept full of softened water. Then, use a chemical pump to establish a circulation corresponding to the equipment's full-load flow, including the low-pressure heater, deaerator, and high-pressure heater, and bypass the feed pump. Once the pickling circulation is established and the fluid in the system reaches 200°F, inject a mixture of ethanoic acid, formic acid, and ammonium dichloride inhibitors into the system. To ensure uniform concentration, the acid solution should be injected at a constant rate, i.e., the injection time equals the time required for a complete cycle to pass through the system. After pickling is complete, the desalinated filling system can be used to drain the spent pickling solution and flush the system. After pickling, the system should be filled with condensate water containing 40 ppm ammonia and 500 ppm helium to钝ize the system. During the passivation operation, the pH should be maintained at 9.0 or higher, with cerium concentration above 200ppm. Note that if some components of the feedwater heater are made of stainless steel, the solution prepared by the aforementioned method cannot be used for pickling.
During alkali washing, pumps and other equipment that may be damaged by acidic solutions or suspended solids abrasion should have their internal components bypassed or removed. Valves and pipelines should be inspected to prevent accidental acid discharge or equipment contamination.
After the acidic cleaning solution returns from the high-pressure heater, it should be cycled for 4-6 hours, taking water samples every half-hour to analyze iron content. During the cleaning process, the fluid flow path should be altered to clean the bypass of the make-up water heater.
