Tuesday, January 3, 2012
Friday, May 29, 2009
Water Meter
A water meter is a device used to measure the volume of water usage.
In many developed countries water meters are used at each residential and commercial building in a public water supply system. Water meters can also be used at the water source, well, or throughout a water system to determine flow through that portion of the system. Water meters typically measure and display total usage in cubic feet, cubic meters or US gallons on a mechanical or electronic register.
There are several types of water meter in common use. Selection is based on different flow measurement methods, the type of end user, the required flow rates, and accuracy requirements.
There are three common methods of flow measurement in use:
Water meters are generally owned, read, and maintained by a public water provider such as a city, rural water association, or private water company. In some cases an owner of a mobile home park, apartment complex or commercial building may be billed by a utility on one meter, and want to share the cost of the bill among the tenants. In this case, private meters may be purchased to separately track usage of each unit in what is called submetering.
In many developed countries water meters are used at each residential and commercial building in a public water supply system. Water meters can also be used at the water source, well, or throughout a water system to determine flow through that portion of the system. Water meters typically measure and display total usage in cubic feet, cubic meters or US gallons on a mechanical or electronic register.
There are several types of water meter in common use. Selection is based on different flow measurement methods, the type of end user, the required flow rates, and accuracy requirements.
There are three common methods of flow measurement in use:
- Displacement
- Velocity
- Electromagnetic
- Multi-jet Meter
- Single-jet Meter
- Positive Displacement Meter
- Turbine Meter
- Compound Meter
- Fire Meter
- Fire Hydrant Meter
- Mag Meter
Water meters are generally owned, read, and maintained by a public water provider such as a city, rural water association, or private water company. In some cases an owner of a mobile home park, apartment complex or commercial building may be billed by a utility on one meter, and want to share the cost of the bill among the tenants. In this case, private meters may be purchased to separately track usage of each unit in what is called submetering.
Rotameter
A Rotameter is a device that measures the flow rate of liquid or gas in a closed tube. It is occasionally misspelled as "rotometer."
It belongs to a class of meters called variable area meters, which measure flow rate by allowing the cross-sectional area the fluid travels through to vary, causing some measurable effect.
A rotameter consists of a tapered tube, typically made of glass, with a float inside that is pushed up by flow and pulled down by gravity. At a higher flow rate more area (between the float and the tube) is needed to accommodate the flow, so the float rises.
Floats are made in many different shapes, with spheres and spherical ellipses being the most common. The float is shaped so that it rotates axially as the fluid passes. This allows you to tell if the float is stuck since it will only rotate if it is free. Readings are usually taken from the top of the float. Some manufacturers may use a different standard, so it is always best to check the documentation provided with the device.
Note that the "float" does not actually float in the fluid: it has to have a higher density than the fluid, otherwise it will float to the top even if there is no flow.
A rotameter requires no external power or fuel, it uses only the inherent properties of the fluid, along with gravity, to measure flow rate.
A rotameter is also a relatively simple device that can be mass manufactured out of cheap materials, allowing for its widespread use.
Due to its use of gravity, a rotameter must always be vertically oriented and right way up, with the fluid flowing upward.
Due to its reliance on the ability of the fluid or gas to displace the float, graduations on a given rotameter will only be accurate for a given substance. The main property of importance is the density of the fluid; however, viscosity may also be significant. Floats are ideally designed to be insensitive to viscosity; however, this is seldom verifiable from manufacturers specs. Either separate rotameters for different densities and viscosities may be used, or multiple scales on the same rotameter can be used.
Rotameters normally require the use of glass (or other transparent material), otherwise the user cannot see the float. This limits their use in many industries to benign fluids, such as water.
Rotameters are not easily adapted for reading by machine; although magnetic floats that drive a follower outside the tube are available.
History
The first variable area meter with rotating float was invented by Karl Kueppers in Aachen in 1908. This is described in the German patent 215225. Felix Meyer found the first industrial company "Deutsche Rotawerke GmbH" in Aachen recognizing the fundamental importance of this invention. They improved this invention with new shapes of the float and of the glass tube. Kueppers invented the special shape for the inside of the glass tube that realized a symmetrical flow scale. The brand name Rotameter was registered by the British company GEC Rotameter Co, in Crawley, and still exists, having been passed down through the acquisition chain: KDG Instruments, Solartron Mobrey, and Emerson Process Management. Rota with their "Rotamesser" are now owned by Yokogawa Electric Corp.
What is Water Flow Meter
A flow meter, in contrast to an ordinary water meter, measures rate of flow rather than volume of flow.
Large Pipe Lines:
In large pipelines, flow meters operate on various differential pressure principles. Flow meters for small flows are usually based on the lifting of a spherical or cylindrical float by the hydraulic action of fluid flowing through a vertical tube.
In a water plant where the water output is variable, such as in cases where more than one pump is used, a flow meter on the main line serves two purposes:
Small Pipe Lines:
The type of flow meter used in small pipelines, often known as rotameter, can be located in the water supply line leading to the dissolving chamber of a dry feeder.
Large Pipe Lines:
In large pipelines, flow meters operate on various differential pressure principles. Flow meters for small flows are usually based on the lifting of a spherical or cylindrical float by the hydraulic action of fluid flowing through a vertical tube.
In a water plant where the water output is variable, such as in cases where more than one pump is used, a flow meter on the main line serves two purposes:
- The flow meter indicate the flow rates for which the fluoride feeder or feeders must operate.
- If so designed, flow meters provide an electrical, pneumatic, or hydraulic signal that adjusts the feeder output to correspond to changes in water flow rate.
Small Pipe Lines:
The type of flow meter used in small pipelines, often known as rotameter, can be located in the water supply line leading to the dissolving chamber of a dry feeder.
Because detention time is a function of water flow rate, the flow must be regulated and maintained at the prescribed value.
In general, a flow meter must be selected on the basis of pipe size and, in particular, the range of flows expected. For greatest accuracy, the range of flow meter should coincide with the range of flows that will be encountered in each particular installation.
In general, a flow meter must be selected on the basis of pipe size and, in particular, the range of flows expected. For greatest accuracy, the range of flow meter should coincide with the range of flows that will be encountered in each particular installation.
Pacing Meter - Variable Speed Motor Control
Pacing Meter - Electronic Metering Pump
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