Level gauges and level switches
Sight glass level gauges with or without thermometer, float level switches and electronic level switches: components that show and monitor the fluid level in the tank.
In a tank that is running low on oil the pump draws in air, becomes noisy and wears out quickly. On the hydraulic tanks we build we make the level readable from outside and, where required, add a switch that stops the unit at low level.
Types
Level gauges
Sight glass gauges mounted on the side wall of the tank; the level is read at a glance. Types with a thermometer also show the temperature in the same body.
Float level switches
The float rises and falls with the level and gives a contact at the set point; used for low level alarm and pump protection.
Electronic level sensors
Measure the level continuously and convert it into a signal; used when several level points or uninterrupted monitoring are required.
How to select
The length of the level gauge has to cover the working range of the tank: the lowest level should be well above the pump suction port, and the highest level should allow for the oil that returns when the cylinders retract.
In switch selection, what the contact will do is decided first: give a warning only, or stop the unit. A low level switch protects the pump from running dry; it should not be left out where the unit runs automatically and unattended.
Hydraulic tank volume by pump flow rate
| Pump flow rate | Recommended tank volume |
|---|---|
| 10 L/min | 30-50 L |
| 20 L/min | 60-100 L |
| 40 L/min | 120-200 L |
| 60 L/min | 180-300 L |
| 100 L/min | 300-500 L |
Common design rule: the tank volume should be 3-5 times the oil the pump delivers in one minute; this is a starting value, not a standard. The smaller the tank, the faster the oil heats up and the more the level fluctuates; the level gauge has to cover this fluctuation as well.
Frequently asked questions
How long should a level gauge be?
Long enough to show both the lowest and the highest working level in the tank; the oil level in the tank changes between cylinders extended and cylinders retracted.
Why is a low level switch needed?
When the level drops, it prevents the pump from drawing in air and running dry; it stops the unit or gives an alarm.
Can a level switch be fitted to an existing tank?
It can be fitted to most tanks; we select the side mounted or top mounted type according to the tank construction.
Why does a level gauge have a thermometer?
A level gauge with thermometer shows two quantities on the tank in a single body; no separate hole or separate component is needed. It is common on small and medium power units.
What causes the hydraulic oil level to keep dropping?
There is an external leak somewhere in the circuit: a hose connection, a cylinder seal or the pump shaft seal. As the level drops, the risk of the pump drawing in air increases.
Why does the level gauge sight glass turn dark?
Overheating and oxidation of the oil darken the gauge over time. This is also a sign that the oil and the temperature need to be checked.
Stock, sizes and part numbers
We select and supply the products in this group according to the application. Send us your requirement, the size and the operating conditions on WhatsApp and we will recommend the right product.