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The advantages and disadvantages of the liquid level switch and its technical index

The advantages and disadvantages of the liquid level switch and its technical index


Float level switch

1. Advantages: float switch does not contain components such as make failure parts, bellows, springs, seals, etc. Instead, it uses the straight float to drive the internal magnet, the simple lever of the float to make the switch instantly move. Float cantilever angle limit design, prevent float vertical. Float liquid level switch is a simple structure, easy to use, safe and reliable liquid level controller. It is faster than general mechanical switch and long working life; Compared with electronic switch, it has the characteristics of strong load resistance, and a product can achieve multi-point control, easy to maintain. It is widely used in shipbuilding, papermaking, printing, generator equipment, petrochemical industry, food industry, water treatment, electrician, dye industry, oil pressure machinery and so on.

2. Faults: float switch is a simple passive device and has no self-checking function, so it is recommended to check and maintain regularly. Float or buoy is an active part, so it gets dirty when used in a thicker or viscous liquid. Measurement accuracy is poor.

3, Technical indicators: maximum cable length: 30 m; working temperature: standard: 0 ~ 80℃medium temperature type: 0 ~ 120℃; ambient temperature: - 40 ~ 70℃; Working pressure: atmospheric pressure; medium density:≥0.6 g/cm; contact capacity: 220 vac 10a; electrical interface: M20 * 1.5; protection grade: IP65; process connections: HG20592 ~ 20635-97, above DN100, other flange standards (GB, JB/T, HGJ, ANSI, DIN, etc.); Contact liquid material: stainless steel.

Tuning fork liquid level switch

1. Advantages: vibration tuning fork switch can truly protect from flow, bubbles, turbulence, foam, vibration, solid content, dip, liquid characteristics and product changes. And don't need to calibrate, just have to go through the minimal setup to complete the installation. No active parts or cracks are actually implemented to avoid maintenance. Strong self-check and diagnosis function to ensure high reliability of high and low level measurements, certain types of material level meter can even performance curve and send fault trend signal before a failure.

2. Disadvantages: the tuning fork switch is not suitable for very viscous medium which would induce folk connected by material accumulation, which will interfere with the object detection.

3, Technical indicators: power supply: DC12V ~ 24 v, AC220; power consumption: 1 w; vibration frequency: 200Hz; output: NPN, transistor output, maximum 30 v, 100 ma (overvoltage and overcurrent could burn out); material: stainless steel 316; protection: IP68; maximum pressure: 1 mpa; density: liquid≥0.8 g/cm3 powder≥0.2 g/cm3 liquid viscosity: up to 1000㎡/ s detection time: the output motion vibration (stop) 0.5 seconds outputs close (initial) for 3 seconds;  working temperature:‐10℃~ + 85℃

Capacitor liquid level switch

1. Advantages: anti-hanging material, corrosion resistance. Applicable to various environments, such as plastic, cement and other non-metal cans, acid and alkali resistance.

2. Disadvantages: calibration difficulty, poor accuracy, the dielectric constant need > 2, the pressure, density and dielectric constant are required in the container, the installation needs to halt production, clear can, open hole and fire.

External liquid level switch

1. Advantages:

A, security: when measuring poison, explosion, corrosion, stress, easy to bums, easy to volatile, easy to leak, do not use valves, pipe, joint, no funneled, not contact liquid and gas in tank, very safe. Even if the instrument is damaged or repaired, there is no possibility of leakage, poisoning or explosion.

B, installation and maintenance are convenient: the installation and maintenance do not use fire, not clear the tank, and not affect the production.

C. reliable and durable: non-mechanical moving parts in sensors and gauges, strictly sealed, isolated from the outside world, not worn or corroded.

D, widely applicable: it has nothing to do with the pressure, temperature, density, dielectric constant, viscosity and corrosion of the measured medium. It is widely used in petrochemical, chemical, tank farm, oil, electricity, liquid storage and transportation, medicine and other industries.

2. Disadvantages: the material of the tank cannot be non-rigid. The installation requirement is high, the measuring probe installation spacing is about 1 meter, and the two probes cannot have the seam (i.e. on the same piece of steel plate).

Rf (radio frequency) admittance liquid level switch

1. Advantages:

A. versatility: it can be used to measure the position of liquid level and material, which can meet the measurement requirements of different temperature, pressure and medium, and can be applied to such bad situations as corrosion and impact.

B. anti-hanging materials: unique circuit design and sensor structure, so that the measurement can be not affected by hanging material, which need not be cleaned regularly, avoid mismeasurement.

C. maintenance: no moving parts of the measurement process, no damage to mechanical parts, no maintenance.

D. Anti-interference: contact measurement, strong anti-interference ability, can overcome the influence of steam, foam and stirring on measurement.

E. accurate and reliable: the measurement quantity is varied, makes the measurement more accurate, is not affected by the environmental change, high stability, and long service life.

F. applicable scope: chemical, oilfield, water and sewage treatment, paper making, pharmaceutical, power plant, metallurgy, cement, grain and other industries.

Paddle Switch Level indicator

1. Advantages:

A. small bucket professional technology, three bearing support, run more reliable;

B. original seal design can prevent dust infiltration (patent reality);

C. the torque is stable and reliable, and adjustable.

D. the blade is overloading, the clutch is automatically skidded and the protection motor is not damaged.

E. electro-mechanical separation structure, the whole body needn’t disassemble is easy to maintain;

F. junction box IP65

2. Technical indicators:

A. the material is dry powder and granular, allowing the maximum size of material size to be 20mm

B. material bulk density is≥0.5g/cm3

C. the material temperature: normal temperature, high temperature≤185℃

D. Control mode: bit style

E. power supply: 220V.AC,50Hz

F. output contact capacity: 250v.ac, 5A

G. life: mechanical 5 x 107 times electric 5 x 105 times

H. rotation speed: 6 RPM

I. power consumption: 4W

J. using the environment temperature: - 10 ~ + 55℃

K. relative humidity: no more than 85%

Electromagnetic liquid level switch

Advantages: electronic pressure protection function; the electromagnetic leakage current protection can reach 300MA, divided into a multi-level and a large amount.

Electronic liquid level switch

1. Advantages: resistance to fouling, pour shake resistance, turbulence, strong drop resistance, salt fog resistance, acid and alkali resistance, not magnetic fields impact, not the metal body impact, not afraid of water pressure change, not afraid of the light, no blind area and outside have no moving parts, are not afraid of the influence of solid floater.

2. Scope of application: water, all kinds of sewage, acid base, sea water, water treatment disinfectant, stream, textile and dyeing water, industrial waste water, and also suitable for ship water level switch, etc.

Photoelectric liquid level switch

1. Advantages: no mechanical moving parts, high reliability; Small volume, high cost performance; High precision of liquid level control, good repeatability.

2. Disadvantages: not suitable for freezing liquid and crystalline liquid.

Ultrasonic liquid level switch

1. Advantages: ultrasonic liquid level meter is non-contact measurement,±0.2% accuracy, 1-25m range, excellent focusing: 5 degree acoustic beam Angle, multiple sensor materials, built-in full range temperature compensation. The ultrasonic liquid level meter measures the corrosive (acid and alkali) medium, the contaminated situation, or the material that produces adhesion. Suitable for liquids that cannot be physically approached.

2. Disadvantages:

A. It is related to the viscosity of the measured medium, which is not measured when the medium viscosity is larger.

B. Affected by temperature, when the temperature is high, the transmission speed will change, the instrument will be slow response, and the alarm will be delayed.


Classic cases

1. Float liquid level switch

Common faults and treatment methods:

Float ball not action:

The proportion of liquid is less than that of float

Water leakage

The foreign matter stuck float

Processing methods:

Reconfirm the float weight

Contact the company to replace float

Remove the foreign matter

Float movement, but no signal output:

The float position deviation

The magnetic spring switch is damaged

Processing methods:

Adjust the float position

Replace the magnetic reed switch

Signal output is unusual, there is magnetic disturbance nearby:

Treatment: remove the magnetic field

The signal remains, cannot be restored, the ball cannot be regrouped, there is a foreign matter stuck.

Treatment: remove foreign objects

At one point there will be two signal outputs, and the loop will move:

Processing method: adjusting the position of the ring

Tuning fork liquid level switch

Tuning fork level switch, impact resistant ability is poor, cannot by extrusion, because no resonance after deformation, high level can also be installed, low level can't be used, when installation should avoid feeding port and discharging port, if not, need to install baffles. Measurement medium cannot be adhesive, if material adhere on the tuning fork, will change the inherent vibration frequency, a tuning fork is also easy to cause resonance fault.

External liquid level switch

Common failure analysis and processing:

1. Loss of parameters causing false alarm;

2. Loss of coupling agent leads to false alarm;

3. It is easy to misreport if the liquid is not double calibrated (single calibrated only).

Treatment:

1. Contact the manufacturer for instrumentation upgrade;

2. Reapply the coupling agent and recalibration;

3. It is best to do double calibration.