Heater level Turbine Trip 3

[flinana]

Hi,

I have a problem with the levels in the LP and HP hetaers of our solar plant. When there is a high level on the LP heaters the turbine closes its extraction and it trips the turbine. The heaters have 3 wave guided level transmitters from VEGA. These High levels are usually sudden peaks and never remain as high.
I was thinking to configure the transmitters with a damping so that theses peaks are not detected, I am not sure and cant really prove that they are real condensate peaks. If they are and I ignore these with a damping I might be putting water in the Turbine, but If they are not, I am tripping the turbine for the sake of it.

1. How can I determine if these peaks are real, having someone by the local level indicator to contrast this is hard since these are not frequent or slow).

2. Could It be to risky to damp the signals?

 

[rmw]

If you don't damp them for long periods, there should be no problem. On my first job ever, many years ago, I had to have a 5 second delay put on a boiler drum level transmitter to keep spike signals (caused by people walking on the grating near the transmitter) from tripping the boiler. Logic was that if the high/low signal made and stayed there for 5 seconds, then it was a true high/low level.

Is it the level transmitters or the level control valves that are causing the level swings, and as asked in the other thread, is the source of the condensate that is dancing your DA all over the map?

rmw

 

[tickle]

Are the level transmitters in stilling wells? A stilling well would minimise waves forming on teh liquid surface

 

[sshep]

I worked on a project that involved a guided wave radar level that gave all sort of intermitent false signal problems. I am not an electrical engineer, but one of those smart guys (like you) observed that a long cable that allowed the rod to be removed was coiled in a loop around the mounting flange, causing the problem.

If the trips seem spurious and unrelated to anything, you might investigate to rule out whether there is a problem with the grounding of this instrument, or some other installation problem.

 

[flinana]

thank you all, you are all very helpful!


I think its a combination of LTs and evacuation valves from one heater to another. And yes I believe that the mother of all begins at controlling the level in condenser and flow from this to the DA with the same valve.

it is a coaxial level sensor. High frequency microwave pulses are coupled onto the internal rod of the coax system and guided along the probe. The pulses are reflected by the product surface. The time from emission to reception of the signal is proportional to the level in the vessel.

So being a rod i don't think the need for stilling well tickle.

I will check that what you mention sshep. It could be the rod and flange problem, although generally they work fine and its 3 in each heater so I find it hard to believe that the 3 are wrong, but hey all is possible!!!

 

[flinana]

I am beginning to think that either we maintain a too high level on the heaters so that the inner tubes are flooded and the heat exchange is not done properly.
The heaters end up de-stabilizing the system, not only tripping the turbine but flooding the condenser and affecting the DA etc...