DELOACH BLOG

In water treatment systems it is often important to measure the rate at which water is flowing through the system. Data from flow measurement devices can be used to control chemical dosing, set pump speeds, control filter loading rates, inform maintenance programs, and other tasks necessary for the operation of a water treatment facility or on key components such as Degasification and Decarbonation systems or Biological Odor Control Systems. As with most types of instrumentation, there is an array of technologies that can be used for the task, each one with various strengths and optimal applications. For modern electronically controlled systems, the most common types of flow sensors used are axial turbine flowmeters, paddlewheel flowmeters, differential pressure/orifice plate flow transducers, and magnetic flowmeters. This article will briefly discuss the technology and features of each of these types.

A turbine flow meter,

consists of a tube that contains supports to hold a multi-bladed metal turbine in the center. The turbine is designed to have close clearance to the walls of the tubing such that nearly all of the water is made to flow through the turbine blades as it travels through the pipe. The turbine is supported on finely finished bearings so that the turbine will spin freely even under very low flows. As the turbine spins, a magnetic pickup located outside of the flowmeter housing is used to sense the tips of the turbine blade spinning past the pickup. An amplifier/transmitter is then used to amplify the pulses and either transmit them directly or convert the pulse frequency into an analog signal that is then sent to a programmable controller for further use elsewhere in the system. One advantage of a turbine flowmeter is that the electronics are separated from the fluid path. The magnetic pickup is the only electronic component, and it is installed outside of the turbine housing, reading the presence of the turbine blade tips through the wall of the sensor body. In clean water applications, this can be advantageous because the magnetic pickup can be replaced if needed without removing the turbine from service. However, the turbine itself covers most of the pipe area and creates back pressure in the system, requiring increased pumping energy to move a given amount of water. In Industrial Water Treatment or Filtration Treatment,  turbines can also easily become fouled or jammed if they are used to measure water or other fluids with entrained solids, algae or bacteria cultures which cause significant accumulation, or corrosive chemical components that can degrade the turbine bearings.

In an industrial environment, electric motors are used for a variety of applications.

These often include pumping water or other fluids, transporting material on conveyors or lifts, or providing motive force to moving parts of a mechanical device. The electric motor dominates the field whenever something needs to move. Regardless of the end user, all these motors will have one thing in common, a motor controller.

A motor controller is a device with the means to turn the motor on and off, provide circuit protection, and serve as a disconnecting means to render the circuit safe during maintenance. Traditionally, this is done with a direct-on-line (DOL) motor starter. A DOL starter installation consists of a branch breaker combined with a DOL motor starter and overload module. In a typical DOL motor starter installation, the branch breaker will serve as short circuit protection, as well as a means of electrical disconnect. The motor starter unit is essentially a large relay with a magnetic coil and high-power contacts held apart by springs. When the motor is called to run, the magnetic coil is energized, pulling in the contacts and bridging the line side to the load side terminals, allowing power to flow. Once the motor starter has contact, electrical power flows out through an overload disconnect module, and then to the electric motor. The DOL motor starter is a well-proven design that is familiar to almost anyone in the industrial space and is still what is found in a majority of applications.

Different types of electric pumps, blowers, compressors,

and even material conveying equipment utilized to operate a water treatment process facility whether it is municipal, industrial, aquaculture, or a pisciculture facility.  All of these applications share a common requirement which is the need to have an electric motor provide the torque and energy necessary to operate the equipment and perform the required function. 

One of the most common questions asked or considered during the design phase of the water treatment process is what type of motor enclosure should be selected.  There are 7 

types of motor enclosures that are available and defined by NEMA standards MG1-1.25 through MG 1.27.  The final decision should be driven by the all of demands that the application will have placed upon it.

The selection of the type of motor enclosure can be a difficult choice. 

If the application is for a process like Reverse Osmosis, Degasification, or Decarbonation, it is important to consider the efficiency of the motor and what the motor will be exposed to during its operating life cycle.    We will briefly review each of the 7 different types that NEMA defines for motor enclosure types. 

The ODP (open drip proof) is one of the most common types of enclosures. 

The enclosure is open and vented at the back end of the motor and allows air to circulate in and around the motor windings carrying off heat.  The ODP motor is designed to prevent liquid from entering the motor at a 15-degree angle based on the vertical alignment.  ODP motors are normally utilized at water treatment facilities or aquaculture facilities where they will not be exposed to corrosive conditions such as HVAC systems.