High duct-static pressure creates problems during a building fire when fire dampers close. Closed fire dampers cause downstream duct sensors to detect a drop in pressure. The duct pressure sensors in turn send signals to crank the air handler even faster to get back up to normal operation. Because the fire dampers are closed, when the air handler ramps up, the duct pressure upstream of the fire dampers will increase to a point where a high static pressure switch will cut power to the VFD (variable frequency drive) and send a signal to the DDC (direct digital control). Switches in this application — by specification — are all manual reset and require two outputs: one for cutting power to the VFD and one for sending the signal to the DDC.
Traditionally, there have been three tactics to address this issue, each with its own problems. Continue reading “Solve High Duct-Static Cutout Problems with the Series 1831”
Stability is defined as a change (or lack of change) in accuracy over a period of time.
Drift is commonly used as a specification to illustrate the stability, or change in accuracy over a period of time, commonly shown as X%/year where X = a number; i.e. 0.25%/year. In this scenario, a device with a ±1% accuracy, would be expected to have an accuracy of ±1.25% (1%+0.25%) after a period of one year. Depending on the design, brand, and range of the sensing instrument, the stability can vary widely. Continue reading “What is Stability and Why is it Important?”
Are you having problems with your current lift station level controls? Dwyer Instruments may just have the cost effective solution you need. In this article we will review several level sensing strategies, the advantages and disadvantages of each, as well as an option you may want to consider for your next project.
Lift Station Basics
In an ideal gravity fed wastewater collection system, sewage would flow downhill from its point of origin in residential or commercial areas to its final treatment plant destination. Due to a number of factors including total distance, topography, geology, economics, etc., the ideal piping design is not always feasible. Therefore, in most cases, sewage flows downhill to a lift station where it collects and then is pumped to a higher elevation in order to begin its downhill journey again. Continue reading “Lift Station Level Sensing”
As the year comes to a close and we celebrate this time with our families and friends, all of us at Dwyer want to give a big thank you to the customers and teammates that we’ve depended on throughout the year. We certainly couldn’t have done it without you.
This year has been unlike any other, to say the least. The COVID-19 pandemic shook the world as hospitals and emergency personnel struggled to keep up with demand for ventilators and isolation rooms. Worldwide manufacturing slowed, as non-essential businesses shut down and companies shifted to CDC guidelines and recommendations. Continue reading “Happy Holidays | Year in Retrospect”
Maintaining efficiency in wet chemical scrubbers has become one of the most important missions of current APC facilities due to urban growth and plant expansion/modernization projects as good stewards of the community. Systems often run above the 90% efficiency mark with the help of accurate make-up water control instruments. Continue reading “Sump Level Make-Up Water Controls in Wet Chemical Scrubbers”