through pipes from the furnace to the cooling tower. But unlike open systems, when the water reaches the cool- ing tower, it continues to travel under pressure through pipes in a heat transfer coil, where the cooling takes place. Te cooled water is then pumped directly from the heat transfer coil to the furnace. Te heat transfer coil can be part of an evaporative cooling tower where it is cooled by water from a sump. Or, it can be housed in a dry air cooler where it is cooled directly by air flow. It also can be part of a hybrid cooling system. Closed water systems keep water clean and free of
debris and require minimal maintenance. However, closed water systems cost more to build. Tis is because as closed- loop systems they require heat exchange coils, expansion tanks, air vents and air scoops—all items not needed in open systems. Whether a metalcasting facility uses an open or closed
system to cool its furnaces, the water that recirculates through an induction power supply must be a closed system. Its electronic components require the water to be clean and deionized to ensure it is not electrically conduc- tive. Typically, a heat exchanger provides cooling for the water in the power supply without intermingling with the water used to cool the furnace. Te new cooling system at Chassix is open, like its
former equipment. Te decision to continue to use an open system reflects the metalcaster’s desire to incorporate exist- ing plant piping, controls and electrical network into the new cooling installation. “Being able to reduce our costs by using our existing cooling system infrastructure within the foundry was a key requirement,” Burton said. “It probably saved about $100,000 and allowed us to stay within our capital budget. It also greatly shortened the downtime that would be needed to install the new system.” Although Chassix’s new cooling system operates as an
open system, Brian James, maintenance superintendent, reported the water remains cleaner because the strainers at the pumps are easy to clean. “With the old system, dirty water was a problem because there were no strainers at the pump. What got into the sump got into the pump,” he said. “Te old system relied only on strainers downstream to catch the dirt and debris, and coils were constantly being clogged.”
Pump Selection and System Design Pumps are the heart of the foundry cooling system and
their power, flow rate and pressure must be balanced with the cooling requirements of the furnaces and other con- nected equipment and with the design specifications of the cooling tower. Of equal importance is the overall design of the pumping installation to provide for backup pump- ing capacity in the event of a pump failure or for routine system maintenance. Te ability to replace a pump quickly and ease of access for maintenance also are important. In the case of the new Chassix installation, water flow is provided by three 100-HP pumps, together able to move
塔，继续在压力下进入管道中的换热盘管，通过换热 盘管冷却。冷却后的水，通过管道和水泵直接从换热 盘管回到炉体。换热盘管可以作为蒸发式冷却塔的一 部分，通过储水槽的水喷淋蒸发冷却。或者，它可以 被安置在干式空气冷却系统中，直接通过空气对流冷 却。它也可以是混合式冷却系统的一部分。 封闭式冷却系统需要保持水质清洁，没有杂物，只 需要最低限度的维护。然而，封闭式冷却系统的成本 比较高。这是因为，作为闭环系统需要热交换盘管、 膨胀水箱、排气阀和通气口- 所有这些部件在开放式 系统中是不需要的。
无论铸造厂采用开放或封闭式冷却系统来冷却炉 体，通过感应炉电源的循环水必须使用封闭式的冷却 系统。因为冷却电子元件的水要求是纯净水和去离子 水，以确保它不导电。通常，电源的水冷却系统与炉 体的水冷却系统是分开的。
与以前的设备一样，Chassix公司新的冷却系统是 开放式的。继续使用开放式系统是考虑到把工厂现有 的管道、控制和电气网络利用到新的冷却系统中。 “能够利用铸造厂现有冷却系统的基础设施以降低 我们的成本是重要的条件，” Burton说，“这可能 省了大约10万美元，并符合我们的资金预算，并大大 缩短了安装新系统的停机时间。”
虽然Chassix公司新的冷却系统是开放式的系统， 但是维护主管Brian James报告称水仍然是清洁的， 因为水泵处的过滤器易于清洁。“在旧系统中，水中 的杂物是个问题，因为水泵处没有过滤器。能进入储 水槽的东西都能流入泵里，”他说，“旧系统只能依 靠集水槽上的过滤网拦挡污垢和碎屑，线圈经常被堵 塞。”
泵的选型和系统设计
泵是铸造厂冷却系统的心脏和动力，流量和压力必 须稳定，与炉体和其它辅助设备的冷却需求相匹配， 符合冷却塔设计规范。泵站系统的整体设计需要考虑 在主泵发生故障或常规的系统维护时备用泵的流量， 以及快速更换备用泵和维修保养的便捷性也很重要。 Chassix公司新系统安装了3台100 HP的泵，同时 启动时水流量能达到3600 GPM。这些专门选配的泵 效率高且功率适合现场的工况。
3台新泵每一台都以独立模块的形式接入系统，有 66 |
FOUNDRY-PLANET.COM | MODERN CASTING | CHINA FOUNDRY ASSOCIATION September 2014
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