Microwave Solids Flow Monitors Model SFD-2 & SFI

BULLETIN 813

Monitor's line of microwave solids flow monitors are high quality, industrial grade instruments capable of providing a signal indicating the flow/no-flow condition of solids and powders in gravity chutes, feeders and pneumatic pipelines. The Model SFD-2 Solids Flow Detector provides relay outputs that can be setup to indicate changes in the target flow stream (on/off). The Model SFI Solids Flow Indicator provides an analog output which varies with changing conditions of the material flow stream. These non-contact monitors contain no moving parts or probes that can wear out or break off in the material flow, thus ensuring process integrity.

The SFD-2 and SFI use low power microwaves to sense motion within the chute or pipeline being monitored. Microwaves are virtually unaffected by ambient noise and light, heat, humidity, pressure, vacuum, high or low temperatures or dust. This provides maximum effectiveness in typical industrial application environments. These advantages over sonic or mechanical flow monitors make microwave technology the best choice for solids flow monitoring.

Principle of Operation

Both the SFD-2 and SFI utilize a microwave transceiver (combination transmitter/receiver) enclosed within a watertight, dust-ignition proof powder coated aluminum housing with a screw-on/off cover. A process seal (Teflon® or Ryton®) acts as a transparent window through which the microwave energy is transmitted and the reflected return signal is received. The transceiver module generates and transmits a microwave signal into the area where material flow is to be monitored. The reflected microwave signal shifts in accordance with the Doppler Effect phenomena. The Doppler-shifted energy is analyzed to determine the appropriate output from the unit.

The SFD-2 has a split-architecture design consisting of the transceiver and a separate power supply/conditioning circuit board. The relays are incorporated on the power supply/conditioning circuit board, which is optionally available with a fiberglass enclosure and indicating lights. With the SFD-2, the Doppler-shifted energy signal from the transceiver is carried back to the power supply/conditioning circuit board through the user-supplied signal and power supply cable. At the power supply/conditioning circuit board the signal intensity is indicated with an LED and converted into a relay output based upon the sensitivity adjustment. The power supply/conditioning circuit board provides the power to drive the transceiver and contains the controls for setting sensitivity, hold-off time delay, hold-on time delay and fail-safe selection.

The SFI Solids Flow Indicator, unlike the SFD-2, consists solely of a transceiver. In this case the transceiver will receive its DC power through the user supplied signal cable and power supply. The three-wire design allows the user to monitor the analog output while providing the supply power to the unit. The Doppler-shifted energy is relative to the magnitude of the flow/no-flow condition that exists, when material velocity is constant, and this is reflected in the varying analog output signal.

Applications

Monitor's Solids Flow Detector and Indicator can be used in a variety of applications to detect flow/no-flow conditions of powders and solid materials. The selection of either SFD-2 Solids Flow Detector or the SFI Solids Flow Indicator is based upon the type of output required (relay or analog).

	Detection of a partial or full plug in a conveying line
	Detecting the bridging of material in a storage vessel upstream
	Sensing inadequate or a lack of flow due to upstream equipment failure (conveyor, blower, diverter valve, feeder)
	Verifying flow conditions
	Turning on/off equipment or processes downstream

Use of SFI Analog Outputt

The Model SFI Solids Flow Indicator can be used to infer the relative amount of flowing material within the target conduit (by monitoring the available analog signal). However, it should be noted that this device provides an output that should be considered, at best, a very rough estimate of the flow of material. The analog signal corresponds to the magnitude of the Doppler-shifted energy created by the flow of material through the microwave energy field.

Note: Monitor Technologies LLC accepts no responsibility for the accuracy of the analog output signal. This signal can be influenced by several varying factors including, but not limited to, particle size distribution, dielectric constant variation, moisture content variation, dispersion of material flow, variation in velocity of material flow, movement of auxiliary equipment, temperature variations and type of conveying system. Please consult the factory to discuss applications where the accuracy of the analog output is of importance.

Pictured at the right is a SFI installed in a plant that manufactures ink for desktop printers and copy machines. 100-pound batches of carbon black come out of a feeder and are pneumatically conveyed through a four-inch vertical line. The SFI is used to indicate when a batch of carbon black has cleared the line.

Features

Options

RYTON® PROCESS SEAL
Both the SFD-2 and SFI come standard with a Teflon® process seal window through which the transmit/receive signal passes. While this material is compatible with most applications, a Ryton® seal is available for use in applications where the seal is subjected to high pressure or abrasive materials.

ENCLOSURE FOR CIRCUIT BOARD (SFD-2 only)
The standard SFD-2 does not provide an enclosure for the power supply/conditioning circuit board. This allows the user to install the board wherever is appropriate. A NEMA 4X enclosure is available. When selected, the power supply/conditioning circuit board is supplied installed within a fiberglass enclosure furnished with long-lasting LED indicators flush with the enclosure face.

Left: Power Supply/Conditioning Circuit Board Right: Optional Enclosure

Accessories

GALVANIZED HALF-COUPLING
Monitor provides a galvanized half-coupling which can be welded to the chute or pipe for mounting the transceiver. Half Coupling: P/N 17-3111

LOCKNUT
The optional locknut provides flexibility in the depth of the mounting of the transceiver to ensure that the process seal is flush with the inside of the conduit in which the target material flows. Lock Nut: P/N 17-3000-7C

SADDLE COUPLING
The saddle coupling provides a means of mounting the transceiver without welding a mounting coupling. The saddle coupling, which includes a gasket, is suitable for round chutes 4-10" (102-254mm) in diameter and can be easily clamped to the chute or pipeline. Saddle Coupling: P/N 17-3102-1

STAINLESS STEEL ADAPTERS
Four different mounting adapters can be used to provide a stainless steel process contacting surface. The adapter can be of either 1-1/2" NPT or Tri-Clamp® food grade construction.
1-1/2" NPT: P/N 17-3303-1 (Teflon® seal) P/N 17-3303-3 (Ryton® seal)
Tri-Clamp: P/N 17-3305-1 (Teflon® seal) P/N 17-3305-3 (Ryton® seal)

Specifications

Ryton® - Trademark of Phillips Chemical Co.
Teflon® - Trademark of Dupont Chemical Co.
Tri-Clamp® - Trademark of Tri-Clover, Inc.

Warranty

Monitor Technologies LLC warrants each SFD-2/SFI it manufactures to be free from defects in material and workmanship under normal use and service within two (2) years from the date of purchase. The purchaser must give notice of any defect to Monitor within the warranty period, return the product intact and prepay transportation charges. The obligation of Monitor Technologies LLC under this warranty is limited to repair or replacement at its factory. This warranty shall not apply to any product which is repaired or altered outside of the Monitor Technologies LLC factory, or which has been subject to misuse, negligence, accident, incorrect wiring by others or improper installation. Monitor Technologies LLC reserves the right to change the design and/or specifications without prior notice.

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