Urgent help: The differential pressure of the throttle device is too low; how can it be measured accurately?
Thread Content
There is currently a boiler for which the flow measurement points for the primary, secondary, and tertiary air streams, as well as the throttling devices, all use cross-sectional flow meters supplied by Yokogawa Automation Asia Pte. Ltd. (Singapore). The installation meets the requirements specified in the 3D guidelines. However, due to the very small pressure difference range of these throttling devices – typically between 0 and 100 Pa – the EJA120A differential pressure flow meters used on-site result in significant measurement errors; it is suspected that the actual air flow rate is significantly underestimated. My question is: 1. Are there any good solutions for these conditions? Would Rosemount’s 3051CD perform better in similar differential pressure scenarios? 2. If the throttling device is replaced under the same operating conditions, can the pressure difference range be increased?
For conventional differential pressure transmitters, it is recommended to shorten the length of the pressure tap pipes, as long as there are no leaks at the connection points of these pipes.
The differential pressure is too low; eliminate pipeline leaks.
If the pressure difference is small, the pressure tap pipe is subject to significant turbulence effects, resulting in continuous fluctuations in the measurements. If the pipe is too long, the linearity becomes poor and the time required for pressure transmission increases. In my opinion, flow meters that rely on throttling pressure differences should not be used; turbine flow meters are a better choice, as they offer high precision and essentially provide direct measurement without any interference from intermediate variables
This post was last edited by rocketbull on 2011-8-24 19:44. Reply to 3# nmgsbl: How to check for air leaks? Is it just by relying on human sensation? Soap water?
This post was last edited by nmgsbl on 2011-8-25 07:03. Reply to 5# rocketbull: Use a small brush dipped in soapy water to check for leaks at the joints; the pressure difference is too low. Alternatively, you can change the measurement range. Give me the current data and I’ll do the calculations for you.
If the differential pressure is too low, the 3051 series micro-differential pressure transmitters, such as the 3051CD or 3051S, can be chosen; they offer acceptable accuracy. The pressure tap tube should preferably not be too long, and leakage must be prevented
For the measurement of the primary air, secondary air, and tertiary air in boilers, if the calculated pressure difference is too small, it is recommended not to use differential pressure type flow meters; instead, thermal mass flow meters can be employed.