Overview
HM-90(30) Series is a Displacer Type Level Switch installing on the top of tank, operated with the usage of buoyancy to the displacer and spring tension. It is generally used to control liquid level for high temperature and pressure process with On/Off contact signal.
Characteristics
- Strong structure and long life cycle
- Easy installation
- Applicable to explosion area (Ex-Proof version)
- Widely used to detect various liquid levels
- Available to use for high temperature and pressure process
Operation Principle
Displacer Type Level Switch is operated based on Archimedes principle that the weight of objects in liquid becomes lighter as much as the weight of liquid flowing over. That object is called by displacer instead of float because it is impossible to float for itself. When a displacer is immersed in a liquid, displacer becomes lighter due to a buoyancy force and this force is transferred to spring. While the loosened spring is constructed due to the gained buoyancy force, rising core moves a magnet by magnetism and finally switch is operated. As described in below [Fig 1] and [Fig 2], the buoyancy force F can be expressed by the following equation.
F = r X s X I
[r=Specific gravity of liquid, s=Cross section area of displacer, l=Buoyancy of submerged displacer]
As the displacer is immersed in a liquid [Fig 2], displacer becomes lighter due to a buoyancy force and this force is transferred to spring. After that, the compressed spring [Fig 1] by the weight of displacer is loosened [Fig 2] due to the gained buoyancy force and then the core rises. The rising core moves the magnet and it activates the switch.
Specification
Dimension of Housing as per Temperature
Dimension
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Standard Version (HM-90)
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High Temp. Version (HM-90H)
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Ex-Proof Version (HM-90-Ex) |
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Standard Version (HM-90B)
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High Temp. Version (HM-90BH)
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Ex-Proof Version (HM-90B-Ex)
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* Actual product may have a tolerance slightly
Dimension
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Standard Version (HM-90A)
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High Temperature Version (HM-90AH)
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Ex-Proof Version (HM-90A-Ex)
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Standard Version (HM-30)
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* Actual Product may have a tolerance slightly
Installation
Below recommendation should be considered when installation.
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Product should be installed at the place far from inlet in order to avoid the malfunction. |
Protection tube or external chamber should be applied if there is a flow or slopping of the medium in the tank. |
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Bracket should be installed with the product when the installation on the concrete as per above figure. |
Inner diameter ("d") of tank nozzle should be larger than the outer diameter of float as per above figure. |
※ The standard specific gravity for setting of product is 0.8 and 1, so that the tolerance might be occurred depend on the usage environment. If user want to measure in an accurate measurement, user have to do the setting at the site based on site condition.
