2 replies to this topic

[deltaChe]

I wonder how the process engineer get precise High High, High, Low Low ,and Low Alarm value.
For example, I have a condensed pump with pressure tranismiter on the discharge side.
There is a High High, High pressure alarm for this pressure tranismiter on the datasheet need to be
checked. And there connected an interlock to hand switch on the pump motor, as High High preesure
alarm be sensed, the singal will activated alarm, and the hand swith stop the pump motor.

I wonder that the process engineer can apply the 90% rule of thumb to check the high high pressure alarm
for I&C designer or any other good rule suggest?

Thank you very much.

[fallah]

I wonder how the process engineer get precise High High, High, Low Low ,and Low Alarm value.
For example, I have a condensed pump with pressure tranismiter on the discharge side.
There is a High High, High pressure alarm for this pressure tranismiter on the datasheet need to be
checked. And there connected an interlock to hand switch on the pump motor, as High High preesure
alarm be sensed, the singal will activated alarm, and the hand swith stop the pump motor.

I wonder that the process engineer can apply the 90% rule of thumb to check the high high pressure alarm
for I&C designer or any other good rule suggest?

Thank you very much.

In your case pump shut-off pressure would dictate HH alarm set point leading to pump stop.

[Himanshu Sharma]

i am not very experienced in this field but i have never seen an interlock generated trip for centrifugal pump because of High High Pressure (nearing Shutoff pressure).

Mostly what i have noticed is start permissive interlocks for Pumps and a trip on Low Low flow value.

High High or Low Low means an interlock action with an alarm buzzing in control panel,they are always preceeded by a High or low alarm for operator to take action.

What alarm values to be taken is a debatable topic since primary motive is to have human intervention and answer to 'how much time is required for that' is a politically correct 'depends' !