Some components of the standard timer boards can be added to meet the demand for cleaning, are either a Photohelic type device that a print ad (as our standard Magnehelic gauge) with a series of pressure switches, or (1 ) to (2) pressure switch with a separate differential pressure combined.
The display switches as the Photohelic are very easy to use. They have some disadvantages and limitations when it comes to installation and wiring.
The current version ofDwyer Photohelic must be shared brand and mounted with the face on the outside, and the relays on the inside of an approved facility that must be drilled for the meter. A lot of work is required to obtain only a NEMA 4 electrical rating. This is less than convenient, and still relies on the installer into a ball of silicone-rubber supply in order to make the seal.
Wiring for our use requires the installation of two reset jumper on the terminal board of the unit and Photohelicrequires prior knowledge or the manual to read (this must be), because the jumper locations are not clearly marked on the back of the Photohelic.
Photohelic theory of operation is that the Photohelic gauge two-point-set has needles. One thing is for the high-value, and one is for the low pressure setpoint. Wiring is received from our standard timer that requires the Photohelic, the use of dry contacts on the Photohelic. The reason for this is that one sets the timer boardControl voltage to one of the two terminals, called "pressure switch". If the jumper is installed on the timer board (no pressure switch) is used, then the board will always run and clean the bags every time is turned on. If the jumper is not installed (in the case of a pressure switch or Photohelic), the timer only runs when the contacts are closed to the pressure switch or Photohelic.
The term "dry contact" refers to the use of the device as a switch only that gives no electricity(since the timer board supplies the power to the pressure switch terminals). The way we use the Photohelic is to lock (with the jumpers on the Photohelic) in the "high" relay when the pressure exceeds that of the high needle set point. This is effectively like pressing the start button. The jumpers use a set of contacts on the high relay to lock in the relay (like a motor starter does with it's AUX contact to "latch" the start button) until the low relay is activated which is effectively like Press the STOP button.
Photohelic simplifies operations:
The filter cleaning timer is running, when the differential pressure needle (black filled) or exceeds the high-pressure needle (red needle on the right side).
The active filter cleaning will cause the differential pressure to fall.
Once the difference in needle (black)) drops to or below the low-pressure needle (red needle on the left side is the Photohelic unlock and the filter for cleaningstop.
Photohelic simplifies operations:
The filter cleaning timer is running, when the differential pressure needle (black filled) or exceeds the high-pressure needle (red needle on the right side).
The active filter cleaning will cause the differential pressure to fall.
Once the difference in needle (black)) drops to or below the low-pressure needle (red needle on the left side is the Photohelic unlock and stop the filter cleaning.
There are other devices're doing out there that do not work the Photohelic, and some do a better job than others. Consider devices with LED displays (LED bar-graph can be easier to read, read from a distance as a numeric LED) for the ability to remotely. Some devices do not need a jumper and have only a set of terminals to the timer. Most of these devices are in a number of tensions and with options for 4-20mA analog output.
With pressure switches in conjunction with a differentialManometers
It must be taken to achieve the selection of a single pressure switch to the desired result. Dwyer Model 1626, for example, with a dead band with a very small adjustment to the starting line to reach and stop function of the timer board. The dead-band settings, and the maximum difference between the fixed points should be taken into consideration when making a selection. Others can work single switch, but some will require an external relay, perform the latch function, which we desire.
Two separatepressure switches and a relay are another (very good) method to use when a differential pressure indicator is already in place. The Dwyer Series 1800 are a good low cost alternative. The -5 and -10 models suit most of our needs. There are miniature pressure switches that cost even less.
Pressure switches have the advantage of being very user repairable, and removes the more costly Photohelic from the stores room shelves.
Pressure switches are easily mounted and enclosed, but beware Pressure connections in the cabin that can store electrical rating.
A pressure switch disadvantage is the difficulty of set-up and calibration. It has been obtained using a hand held vacuum pump (in most auto parts stores for under $ 30.00) to simulate the differential pressure, a gauge of Magnehelic to the current vacuum, a screwdriver to adjust the switch, and a test light or continuity meter to view or listen to see if the adjusted contact trips, all at the same time.
Is"The demand cleaning" the right thing for your application?
This question can not be on gut feelings or opinions to be answered. This question can not be answered on the previous experience with an identical request, unless that same application is in the same plant with the same materials and conditions, and this in itself is very rare.
Only experience and testing to determine whether a particular application can benefit from "on-demand cleaning". These can be determined within a few hours in generalof run time.
Applications that must clean continuously to keep the differential pressure in check, will rarely benefit from this technology.
Component Selection Considerations
1) Ensure components are selected with the proper range, and voltage.
2) What electrical enclosure is required for the location?
3) Will the location be inside or outside? (affects enclosure type, and should be a consideration on any electronic displays. LED for in and outside. Non- backlit LCD for well-lit interiors. Backlit LCD respectively. LED for poorly lit locations)
4) If the system includes a transmitter? (useful when the device is not easy to achieve, when continuous monitoring is required, and if needs dictate registers)
5) If a data logging system required?
6) If the acquisition is necessary, broken bag detector outputs will also be logged?
7) If the acquisition is a requirement, what other elements need to be logged?
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