Automatic Self-Cleaning Strainer Takes the Heat
Self-cleaning filter reduces production and maintenance costs at an iron and steel manufacturing plant.
No matter where you look, you will see that industries worldwide rely on iron and steel as an integral component within projects such as shipbuilding, bridge construction and railway infrastructure. The global appetite for these materials is huge, and for most manufacturers of iron and steel, production is an around-the-clock process.
China is a major supplier to the global iron and steel market. The manufacturer Xinxing Ductile Iron Pipes, based in He Bei Province, employs more than 23,000 people in order to produce more than 13 million tons of iron and steel annually. It is therefore imperative that the manufacturer’s processes are optimized to reduce the amount of production downtime to satisfy the global demand.
The manufacturing environment is typical of the production of iron and steel and can be considered somewhat hostile. High levels of water consumption can lead to contamination issues. High temperature equipment and a high temperature ambient environment are common factors in iron and steel manufacturing facilities, with furnaces and associated equipment utilized throughout their processes. Cooling this manufacturing equipment with water is required to keep it running at optimum levels.
Contamination Affects System Performance
Once applied to cool the iron-making furnace equipment, the water is gravity-fed upstream to a collection sink basin. Then, it is pumped at a flow rate of 13,210 gal/min to a heat exchange recycle system. The water that is collected for reuse has a very high level of contamination, however, with iron fragments, sand and mineral particles present. The water must be filtered in order to remove these contaminants before it can be pumped onward.
The iron and steel manufacturer was faced with a sink basin with cooling water that is contaminated with iron fragments, sand and mineral particles. After being filtered with the automatic self-cleaning strainer, the cooling water is ready for reuse.
The filtration system that was being utilized could not keep up with the process of removing those particles. Any contamination greater than 0.15748” (4 mm) in size was causing problems within the heat exchanger — essential process equipment containing sensitive components such as flow rate valves. When these valves were fed with “dirty” water, they degraded rapidly in terms of performance and even failed. Maintenance was an ongoing issue, and biweekly cleaning was required to remove the contamination. Typically, these maintenance periods lasted around one week and entailed a full system shutdown, incurring significant production losses. The situation simply could not be sustained by Xinxing, and the manufacturer realized that the current installation setup had to be replaced.
The recycled water has a number of different uses around the factory. One of the non-process uses was within a district heating system for local residents, who had come to rely on the source for warmth in winters where temperatures can drop below -22°F (-30°C). Also, wastewater drainage represented an environmental risk due to strict policies. It was harmful to maintenance employees and increased the total cost of production.
Automatic Self-Cleaning Strainer Reduces Plant Maintenance
Following a period of consultation with a filtration equipment manufacturer, it was determined that an automatic self-cleaning strainer with a 0.15625” (3.9 mm) perforated convoluted element would resolve the concerns with the recycling water intake-piping system.
The recommended solution is a motorized unit designed for the continuous removal of entrained solids from liquids in pipeline systems. It is intended to prevent damage to pipeline system components and eliminate the previously required shutdown periods. The filter has a shaft seal that positively prevents leakage from the backwash shaft at the top of the strainer. With the shaft seal, the exterior of the strainer stays dry and clean in service. According to the manufacturer, there is rarely any external leakage or weeping of the process media down the sides of the strainer.
With an automatic control system monitoring the strainer operation, cleaning is accomplished by an integral backwash system. A small portion of the screen element is isolated and cleaned by reverse flow. The remaining screen area continues to strain, providing uninterrupted flow. With this design, only a small amount of the liquid being strained is used to carry away the debris from the strainer.
This strainer is designed for continuous, uninterrupted removal of entrained solids from liquids in pipeline systems. It is offered with flow rates of up to 35,000 gal/min, multiple screen options, automatic backwashing and design for leak-free service.
At the Xinxing plant, one 30” (76.2 cm) automatic self-cleaning strainer is used within the process. It replaced three sets of filters, saving a significant amount of space on the factory floor. In addition, 98 percent of the particles greater than 0.15748” are removed from the water, reducing the potential for damage to upstream components.
Once installed, the filtration system with 30” automatic self-cleaning strainer reduced water consumption in the plant by 20 percent. It also cut down on unplanned interruptions to the local heating system. Perhaps most importantly, plant maintenance shutdown was minimized to ensure that production could continue uninterrupted. Xinxing now only conducts maintenance once a year, saving on both labor and spare parts costs for components that had needed to be replaced using the previous solution.
“The issue of contamination within the recycled water supply presented a major challenge for us in terms of breakdowns and maintenance,” says Wang Qi, production manager at Xinxing Ductile Iron Pipes. “The performance of the new solution exceeded our expectations.”