Switches Indicators & Gauges

Level Transmitters

A level transmitter is an electronic device that converts level measurements from a sensor to a display for a user. They can measure the level of both liquids or solids within a defined space or container (water tank, oil drum, etc), sending the data via a signal to a receiver. The receiver can be either a computer-controlled device or to a display for a user to read.

The term ‘hydrostatic’ refers to the pressure that fluids exert or transmit. So a hydrostatic sensor will measure the increase in hydrostatic pressure resulting from the increasing height of the liquid. A displaced electrical charge will accumulate, generating an output signal. Applications include measuring levels in groundwater, deep wells, water towers, rivers, sewage treatment plants and so on.

Hydrostatic Level Transmitter

Semrad Pty Ltd, distributor of high quality industrial level sensors, gauges, switches and transmitters, is dedicated to providing cost effective and technically advanced solutions for measuring and controlling liquid and bulksolid levels. Their products are specifically designed to perform accurately and reliably in a range of environments, including caustic, hazardous, non-contact and invasive configurations. Their years of experience have included thousands of installations worldwide in a range of industries from chemical to wastewater, mining, beverage, electronic, material handling, agriculture, textile, pharmaceutical, medical and environmental.

Semrad’s NivoPress NT-100 is a two-wire hydrostatic level transmitter that can be used in applications from liquids and masses in tanks and vessels to chemicals with dense vapour or gas layers above the surface, foaming liquids, and viscous or corrosive materials. It is controlled by a microprocessor to measure the pressure difference between the hydrostatic pressure of the liquid head above the sensor and the actual atmospheric pressure. The changes in pressure are converted into a 4-20 mA output signal. It features a ceramic diaphragm, scalable analogue output, programmable damping, secondary lightning protection, high overload capability, high accuracy (<0.2%), and a process temperature range of -30° to +100°C. The probe material is made of stainless steel, takes a power supply between 12 - 30V DC, and 8 ranges starting at 0.1 bar.

Hydrostatic Pressure

Hydrostatic pressure is the pressure at any given point in a static fluid. Pressure in open conditions (e.g. the ocean, the atmosphere, a pond) can be approximated as the pressure in static conditions, since the motion of currents or waves create only negligible changes in pressure. It is the same at any given point because otherwise the fluid would move in the direction of the resulting force.

According to the principles of equilibrium, the pressure of a liquid at rest is isotropic, meaning it acts with equal magnitude in all directions. If a point in the fluid is thought of as an infinitesimally small cube, the pressure of every side of this unit of fluid must be equal. This characteristic allows fluid to transmit force through the length of pipes (a closed condition).

Hydrostatic pressure is useful for determining the levels of liquid in a tank, among other things, using devices such as a hydrostatic tank gauge.

Hydrostatic Bubbler

Semrad Pty Ltd offers a range of industrial level gauges, sensors, switches and transmitters. Their WaterLOG® H-3531 FlashLite™ is a NIST traceable pressure sensor. It combines low cost with high accuracy, as it can directly measure dry gas with accuracy better than 0.02% FSO. It comes with built-in temperature compensation, with an operating range between -40° and +60°C.

This non-submersible pressure sensor has an easy to use Simple RS-232 Menu Interface, and a non-conductive and corrosion proof enclosure. Its SDI-12 output provides measurement data in engineering units (e.g. feet or meters), it is easy to use with the H-355 Gas Purge System and is compatible with the RS-232 Data Logger. It also features extended SDI-12 command for setting the stage to the correct water elevation or pressure. It operates on low currents and deviates less than 0.02% from a staight line referenced to end points.

Oil Separators

An oil separator is a large drum designed to separate production fluids into oil, gas and water. These three components have different densities, meaning they stratify when moving slowly. Gas works it way to the top, water falls to the bottom and oil stays in the middle. The oil and water are separated by a baffle set at the height of the oil-water contact. This allows the oil to spill over the side, trapping the water on the other.

Valves on the oil and water outlets are controlled to ensure the interfaces are kept at optimum levels for separation to occur. Oil separators are used for bulk separation as droplets of water will not settle by gravity and will remain in the oil stream. To remove the last of the water the oil is routed to a coalescer. Any solids will drift to the bottom and this sludge is removed with a mechanical scraper or a sludge pump.

Water and oil separators are used throughout industry, with the oil either being further refined to develop petroleum or the water purified and pumped back into a reservoir or the sea.

Alarm Sensors

Oil separator alarm sensors indicate when the sludge deposit or layer of oil or grease needs to be emptied. The alarm is the only way to be sure when it is economically sound and environmentally safe to collect the hazardous waste.

Semrad’s Oilset 1000 and 2000 are interface level detectors for oil, water, sand, sludge and grease. They feature reset and test functions, no moving parts, high accuracy, a large display, no calibration needed, and explosion proof models. The alarm is audible, can operate in temperatures between -30° and +55°C, and the cabling between controller and sensor can reach up to 3m. They are wall mounted sensors whose internal buzzer and external alarm can be muted. The direction of the alarm can also be changed.