Checking high level switch safety cut float operation

[RANGER1]

Recently experienced faulty LLC float on liquid overfeed vessel.
Has anyone access to procedure for correct testing procedure?
Thanks

[Brian_UK]

Parkers 61-10 document has some details that should help.

https://www.google.com/url?sa=t&sour...vqae9BgXiO1DA6

[RANGER1]

Brian,
Thanks.
Was really referring to the mechanical float itself, not necessarily switch, although it has to be tested as well.
Can get a bit messy to actually test float itself for it’s operation without having to make a real high level.
Come to conclusion that you add ammonia to control column with ammonia bottle or source, which means hoses full of liquid etc. Not saying it can’t be done, but messy.
Best way, close top control column isolating valve & if installed purge off gas at top of column to draw ammonia level up column to check float operation.
A lot of places these days is difficult to check due to possible smells & production never seems to stop.

[cricri]

Hi Ranger,
we had an accident many many years ago.
Liquid solenoid valve to intermediate vessel passing and high level failling.
Float worn by vibrations. Then high stage cylinder gaskets blown off and important ammonia leak (firemenn, police, authorities, etc...).
We had to write a procedure for the authorities to test the mechanical and electrical operation.
It consisted in the addition of a valve and 1/2 inch connection between bottom isolating valve and float.
We used the a manual oil pump (Sabroe) to lift the ball with refrigeration oil used in the plant.

It works. we don't use parker floats at this time, so procedure and valve are fogotten.

[Grizzly]

What a Clever answer to the Problem cricri.
Sad thing I suppose, is that I assume.
The system charge had to be removed to enable the necessary pipework modifications to take place?
Grizzly

[cricri]

all levels were fitted with isolating valves, service valve was added at the Arrow point.LLC.JPG
about the accident, unfortunatly I have seen worse.
Have been involved in death investigations for accidents: ammonia x 7 / R22 x 2

[RANGER1]

Thanks cricri,
Oil is a good one.

See page 2, level control column.
In future thinking about adding purge valve to atmosphere at very top of column as well.
Found a procedure, close top valve, open purge valve to atmosphere, liquid is drawn up column.
Obviously if plant in vacuum, raise to positive pressure.

https://www.parker.com/Literature/Re...ins/313209.pdf

Other ways oil, or refrigerant from another source, like ammonia bottle, or from the system.

[Tycho]

Ranger, is this on the LP drum?

I would have ran a hose from the HP receiver, liquid side, with a T-connection to the HP gas side.
connect it to the service valve on the bottom of the level control column.

Closed the bottom valve on the level control column and slowly introduced liquid from the HP receiver.

Once done, close the valve on HP receiver liquid, open the bottom valve on the level control column, purge the liquid out of the hose with hotgas.

Ideally, I would have purged the level control column, removed the LLC, and got it on a work bench to test it properly with oil.

[RANGER1]

Ranger, is this on the LP drum?

I would have ran a hose from the HP receiver, liquid side, with a T-connection to the HP gas side.
connect it to the service valve on the bottom of the level control column.

Closed the bottom valve on the level control column and slowly introduced liquid from the HP receiver.

Once done, close the valve on HP receiver liquid, open the bottom valve on the level control column, purge the liquid out of the hose with hotgas.

Ideally, I would have purged the level control column, removed the LLC, and got it on a work bench to test it properly with oil.

Tycho,
Thanks, yes LP accumulator.
Nearly all cases float valve welded in & cannot be removed.
Also insulation on them, so not practical, say for an annual test.
Some plants also not very compact, so not easy.

Is it something that you would do very often, or at all?

[Tycho]

Tycho,
Thanks, yes LP accumulator.
Nearly all cases float valve welded in & cannot be removed.
Also insulation on them, so not practical, say for an annual test.
Some plants also not very compact, so not easy.

Is it something that you would do very often, or at all?

We have a few on intermediate pressure vessels around that we check once a year, and on those I usually check with a magnet 1 year and then by forcing the level the next year.

The ones we use are danfoss, flanged in, and the insert can be replaced.
https://assets.danfoss.com/images/pr...51_preview.jpg
they are a bit easier than the hermetic ones