flow = 1/100th max DPĮnsure that there are sufficient straight pipe runs up and down stream of the orifice plates.Ĭorrectly installed impulse lines from the pressure tappings to the DP transmitters.Ĭorrectly sized gas control valve and actuator with good quality positioner (pneumatic are generally quicker and more accurate).Ĭonsider speed of response and lead/lag (gas or air lead?) which will cause the burner to go rich or lean during changes to burner throughput. Good quality, accurate DP transmitters (preferably with square root extraction built in as said by others) properly calibrated.ĭon't expect turndown to be fantastic, remember 1/10th max.
Off the top of my head here are a few things to watch out for:Ĭorrectly sized, manufactured and installed orifice plates. These systems are not very forgiving if not done properly. I've been involved in numerous burner applications with electronic fuel/air flow ratio control using O plates and DP transmitters and can say that there are plenty of pitfalls. The calculation could then be done to find the orifice size, determine a suitable differential pressure (dp) and the applicable flowfactor. Ratio of Specific Heats if fluid is a gas.
Operating temperature upstream of orifice plate.ĭensity at reference conditions (P and T). Operating pressure upstream of orifice plate. Required flow rate at 100% ouitput of dp transmitters. The first question is do you require to measure the mass flow rates, volumetric flow rates at operating conditions, or else volumetric flow rates at standard conditions, and are you using imperial units or metric units? The answers to this question will determine what process conditions will be required to do sizing calculations for the orifice plates.ĭata required to do the orifice sizing calculation is as follows: You need to input your dp signals from your transmitters to the PLC, take the square roots and multiply the results by the flow factors obtained from the orifice plate calculations which gives you the flow rates. This sizing of an orifice plate is a straightforward calculation.
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