Reason analysis of zero drift on the differential pressure transmitter
Special statement: This article is about the zero drift of the smart differential pressure transmitter in Shanghai alone, but it is not malicious slander. Please make clear this point, we only do our own. The following is a consultation case provided by a new customer.
The refinery branch of a petrochemical plant in Zhejiang used to use the intelligent differential pressure transmitter of the self-instrument in the past two years, and purchased a total of 30 units. Half of them often have zero drift, and because their engineers and our technology know each other under the chance of a forum, they communicated.
According to the years of practical experience of the refinery, the root cause of the zero drift in use is the dirt between the space in which the positive pressure chamber is installed and the lever. Since many users use Teflon gasket as sealing material in the positive pressure chamber plug, the gasket is crushed by the elastic force and falls to the contact between the lever and the positive pressure chamber; of course, there is also a medium in the measured medium. The slag or rust rubs against the lever, causing the output to return to its original position.
Secondly, because the instrument is too strong in the special nut under the upper lever, the thread is twisted, so that the installation position of the bellows and the lever is not suitable, and it may cause zero drift.
From the above, we suggest that the lever should be removed when overhauling such instruments (this point, we are not very advocating, we are generally good at all factory calibration, and rarely appear. If there are a lot of such Phenomenon, it means that the factory did not do well, there are individual phenomena, but also to return to the factory for repair, after all, not all users are very experienced, do not necessarily have the relevant equipment), remove the dirt between the positive pressure chamber and the lever, check Whether the thread under the lever is twisted or not, users with such instruments may wish to try. Of course, the assembly must be correct, so I won't go into details here.