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I find it much easier to break down a complex process into its various parts, that way I find it much easier to understand. Take a piping system, it doesn’t matter how many tanks, pumps, components, control valves, or pipelines a pumped system can be broken down into three basic components. By working together these three basic components make it so the system can meet its design objective.
The three basic components of a piping system are the 1) Pump, 2) Process equipment and 3) Control equipment. I will use the drawing to help categorize the items in the system.
Item 1 is the pump, which is the easiest element in the system because they are usually grouped together. In this case, we have a single centrifugal pump; it provides the energy needed to overcome the resistance to flow. What makes the pump simple to understand is that it can only operate on its pump curve.
Item 2, is the process equipment. It’s easy to identify the process equipment because this is why the system is built. The purpose of this system is to supply 1,200 gpm of treated water to the product tank to meet the plant’s needs. Here’s how the various items are used
Each of the items in the process group consumes the energy supplied by the pump.
Item 3 is the energy needed to control the system. For a given flow rate the pump produces a given head value, and at that same flow rate the system requires a given head valve. The difference between what the pump produces and what the system requires, is consumed by the control valve. Once again the energy drop across the control valve is supplied by the pump.
Some people call the energy drop across the control valve as wasted energy. I find this totally incorrect; I like to refer to it as the price that must be paid to control the system. During normal system operation the levels and the pressure in the tanks vary, changing the amount of energy that the system needs for a flow rate. To meet the changes the control valve needs to open and close to control the product tank level. As the treated water flow rates vary to meet the plant’s requirements, changes both the head the pump produces and the losses in the pipelines and components, once again the control valve opens or closes to control the flow rate to the required value.
We can put this into the following formula:
Pump Head = Component Losses + Control Valve Losses
See it as simple as 1, 2, 3.
For simple systems like the one displayed above the pumps curve can be overlaid with the systems curve to create a pump / system curve. The difference between what the pump produces and what the system requires for a given flow rate equals to the pressure drop across the control valve.
If you would like to see how to develop pump / system curve, and see how to evaluate more complex systems please refer to a three part article on the Engineered Software Knowledge Base entitled: Value of a System Resistance Curve.
Remember it as simple as 1, 2, 3.
Leave your questions or comments below or send an email to blogger@eng-software dot com. We really do read every one!
I find it much easier to break down a complex process into its various parts, that way I find it much easier to understand. Take a piping system, it doesn’t matter how many tanks, pumps, components, control valves, or pipelines a pumped system can be broken down into three basic components. By working together these three basic components make it so the system can meet its design objective.
The three basic components of a piping system are the 1) Pump, 2) Process equipment and 3) Control equipment. I will use the drawing to help categorize the items in the system.
Item 1 is the pump, which is the easiest element in the system because they are usually grouped together. In this case, we have a single centrifugal pump; it provides the energy needed to overcome the resistance to flow. What makes the pump simple to understand is that it can only operate on its pump curve.
Item 2, is the process equipment. It’s easy to identify the process equipment because this is why the system is built. The purpose of this system is to supply 1,200 gpm of treated water to the product tank to meet the plant’s needs. Here’s how the various items are used
- The raw water tank provides transient storage to allow for fluctuations in raw water flow.
- The pipeline provides a conduit to deliver the raw water from the tank to the water treatment plant.
- The water treatment plant treats the water to its meet the systems water quality requirements.
- The pipeline delivers the treated water from the water treatment plant to the product tank.
- The product tank provides a transient storage to allow for fluctuations in the treated water flow.
- The various valves and fittings are added to redirect the flow in the pipelines as well as isolate system equipment for maintenance
Each of the items in the process group consumes the energy supplied by the pump.
Item 3 is the energy needed to control the system. For a given flow rate the pump produces a given head value, and at that same flow rate the system requires a given head valve. The difference between what the pump produces and what the system requires, is consumed by the control valve. Once again the energy drop across the control valve is supplied by the pump.
Some people call the energy drop across the control valve as wasted energy. I find this totally incorrect; I like to refer to it as the price that must be paid to control the system. During normal system operation the levels and the pressure in the tanks vary, changing the amount of energy that the system needs for a flow rate. To meet the changes the control valve needs to open and close to control the product tank level. As the treated water flow rates vary to meet the plant’s requirements, changes both the head the pump produces and the losses in the pipelines and components, once again the control valve opens or closes to control the flow rate to the required value.
We can put this into the following formula:
Pump Head = Component Losses + Control Valve Losses
See it as simple as 1, 2, 3.
For simple systems like the one displayed above the pumps curve can be overlaid with the systems curve to create a pump / system curve. The difference between what the pump produces and what the system requires for a given flow rate equals to the pressure drop across the control valve.
If you would like to see how to develop pump / system curve, and see how to evaluate more complex systems please refer to a three part article on the Engineered Software Knowledge Base entitled: Value of a System Resistance Curve.
Remember it as simple as 1, 2, 3.
Leave your questions or comments below or send an email to blogger@eng-software dot com. We really do read every one!
