Dear Member,

Has anyone here had experience with out of range 3051 sensor? We bought 3051 transmitter range 2 (-625 mbar to 625 mbar) with remote capillary seal. it was installed on stripper column with transmitter mounted in the middle between two tapping points. distance between two tapping points is 18 meter, which cause static pressure on the sensor around -1.6 bar. If refer to 1199 capillary calculation manual, 4mA point should be set at this pressure. but since transmitter range only -625 mbar, we could not change the URV down to -1.6 kPa. Is there any solution beside change the sensor to higher range?

appreciate if any of you have solution for this kind of issue.

thanks.

 

> Is there any solution beside change the sensor to higher range?

No. The capillary fill fluid presses on the low side (upper) sensor diaphragm applying a 'static' positive pressure and the fill fluid pulls away from the high side (lower) sensor diaphragm applying a static negative pressure.

So with zero applied process pressure, the transmitter sees<pre>
High side minus low side
= High side (H) negative pressure minus low side (L) positive pressure
= -(H) minus (L)
= a large negative value for the LRV, outside the sensing range of the transmitter cell/sensor.</pre>

 

I would consider a 3051 ERS (Electronic Remote Sensor) system. It would eliminate the capillaries and all their potential problems such as temperature differential etc. There is a restriction of Operating Pressure/DP Span of 100:1 max. Capillaries are replaced by wiring.

 

You say remote seal, Do you only have one?

If this is the case, lower the transmitter closer to the seal to lower the static DP and extend the other side with no seal. Provided the (no seal) side is dry it will have no effect on the DP.

You can also ensure no liquid enters the dry leg by running vertical up for a couple of feet before running back down to the transmitter. Sometimes we add a small nitrogen purge to the dry leg just to ensure there is no ingress.

 

The 3051 ERS system consists of two transmitters a Primary and Secondary. One transmitter is mounted at the elevation of the upper vessel tap and one at the lower tap. The Primary transmitter has the 4-20mA connections. A four conductor cable is connected between the Primary and Secondary transmitters. This cable communicates the Secondary pressure to the Primary which calculates the differential between them. Each transmitter can have a regular process connection or a diaphragm seal which ever is required. A capillary would not be required if each transmitter is mounted at the appropriate tap centerline. The distance between the taps is only limited by the four conductor cable resistance. Google 3051 ERS to find information and Youtube.