Water, the power behind water jet cutting systems, serves two primary purposes: processing and cooling.
Process Water
Process water is the water that is supplied to the high-pressure pump and used by the cutting head to cut the material. This inlet water comes directly from the tap or from a water treatment system such as a reverse osmosis system.
Cooling Water
Cooling water is introduced into the hydraulic loop via a heat exchanger and is used to cool the hydraulic fluid in the pump system.
This blog will focus on Process Water and how to minimize waste.
In some regions, water supply is taken for granted. In others, not so much. Additionally, to keep your CNC water jet cutter and ultra-high pressure pump performing at its peak, the water needs to be maintained at a core temperature.
Reliable, as we use it in this context, means having confidence that you will have enough water from your supply source to run your water jet system without interruption. Water use restrictions directly affect the "reliability" of your water supply by imposing usage limits and/or high utility costs from your municipal water utility.
Water use restrictions are an increasingly common issue in parts of the United States, hit by severe and prolonged droughts. The following graphic from the National Oceanic and Atmospheric Agency (NOAA) U.S. Drought Monitor System illustrates the extent of drought areas as of November 8, 2022. Locations with the darkest red already have restrictions, and other regions are actively considering the need.
Let's face it, your water jet cutting system requires a large amount of water. Most systems rely on a continuous incoming water stream flowing through the cutting head to make cuts. The added Process Water flows into the catcher tank and is drained off via an overflow drain, hence, an “Open Loop System”. Many companies, if not most, just discharge the excess water directly into the city sewage or drainage system. These Open-Loop Systems incur higher utility costs but avoid the capital cost of water recycling.
Conversely, closed-loop systems, often referred to as Closed Loop Filtration Systems or Closed Loop Water jet Recycling Systems, reduce total water consumption by recirculating the Process Water rather than continually discharging it to a drain. If abrasive cutting is performed, an abrasive removal system is added to the system, collecting the spent garnet and filtering the process water before returning it to the high pressure pump. Recycling water is both an environmental decision and a compliance decision in areas with water use restrictions. See our blog on disposing of spent garnet to learn more about managing spent abrasive.
The catch tank incorporates a sweeper package, which pulls the heavier, suspended garnet and small material drops in the tank to an abrasive collector via an abrasive separator pump. The used abrasive is captured in a sack for removal and the filtered water is returned to the catcher tank.
Additionally, water is pulled from the top of the catcher tank into a settling weir for further filtering, prior to delivering it to the closed loop filtration system. The Closed Loop Filtration system will again filter the water and deliver it to an inline chiller that will to bring it back to 70o F. The chilled water will be returned to the high pressure pump, beginning the the cycle again.
Open-loop water jet systems benefit from their simplicity and usually the incoming Process Water remains at temperatures within recommendations and does not require additional cooling. Closed loop systems will be preferred when:
As mentioned, environmental agencies are regulating water use more strictly, especially in drought-impacted areas. Restrictions on the amount of water used represent the most common approach to managing the water resource. Environmental agencies also regulate water discharge by volume and the content of the discharged water. In both cases, closed-loop systems offer a superior solution by managing input and discharge water volumes.
The benefits of closed-loop water jet systems are substantial and represent the best practice for water jet cutting. However, they can increase the upfront system costs and complexity of your water jet cutting system.
Talk with a Jet Edge expert who can help you engineer the closed-loop system that matches your unique needs and read these excellent blog topics on related subjects:
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