Fatma87
Chemical
- May 12, 2013
- 2
Hello everyone;
In our Plant we are using a Screw Compressor to compress Hydrogen (Recycle & make-up) to get the desired discharge pressure for Hydrotreating Reactors. At 09:11:07 am, the compressor got alarm for Low Suction Pressure from three pressure indicators (Part of ESD system) as shown in the attached picture. After 4 seconds only ( at 09:11:11) the compressor tripped due to low pressure of suction (16.04 barg). The normal suction pressure of compressor has to be ( 17.6 barg).
Actually the compressor tripped in just seconds after alarm was showing and suction pressure dropped by around 2 bargs in four seconds only. Nothing was reported abnormal before tripping except the alarm from suction Drum pressure followed by alarm from ESD indicators of suction pressure, other indicators were reading normally. No upset reported before tripping from other parameters in the Area.
We expected that the Pressure Relief valve opened for instant causing Low pressure in Suction Drum and re-set itself automatically because it is (Modulating Relief Valve). But How it comes that Flow indicator (46272.1 Nm3/hr ) didn’t capture any reduction in flow while the pressure indicators in its upstream and downstream were reading low pressure four a few seconds??!!!
Does the RV capable to reduce the pressure by 2 barg in just 4 seconds ?
(RV Data attached in the pictures) . Flare Header Pressure is 0.013 barg.
Before the accident, the Controller valve of Recycle Hydrogen wasnt matching the reading in DCS by +30% and one of the operator saw this valve was fluctuting between the set point by +-20% in the field. Plus the unmatching of reading in DCS and in the Field wasnt the matter for a long time and we are processing normally by this unmatching in readings.
I was suggesting that the Recycle Hydrogen valve closed for instant causing the Low pressure in Sucrion Drum!!! How can I know my idea or their ideas are right !!! Is there any other assumptions?
Why we didnt say the RV of Separator vessel pop-up and re-set itself directly (Modulating type) ??
(RV Data attached in the pictures)
Thank You
In our Plant we are using a Screw Compressor to compress Hydrogen (Recycle & make-up) to get the desired discharge pressure for Hydrotreating Reactors. At 09:11:07 am, the compressor got alarm for Low Suction Pressure from three pressure indicators (Part of ESD system) as shown in the attached picture. After 4 seconds only ( at 09:11:11) the compressor tripped due to low pressure of suction (16.04 barg). The normal suction pressure of compressor has to be ( 17.6 barg).
Actually the compressor tripped in just seconds after alarm was showing and suction pressure dropped by around 2 bargs in four seconds only. Nothing was reported abnormal before tripping except the alarm from suction Drum pressure followed by alarm from ESD indicators of suction pressure, other indicators were reading normally. No upset reported before tripping from other parameters in the Area.
We expected that the Pressure Relief valve opened for instant causing Low pressure in Suction Drum and re-set itself automatically because it is (Modulating Relief Valve). But How it comes that Flow indicator (46272.1 Nm3/hr ) didn’t capture any reduction in flow while the pressure indicators in its upstream and downstream were reading low pressure four a few seconds??!!!
Does the RV capable to reduce the pressure by 2 barg in just 4 seconds ?
(RV Data attached in the pictures) . Flare Header Pressure is 0.013 barg.
Before the accident, the Controller valve of Recycle Hydrogen wasnt matching the reading in DCS by +30% and one of the operator saw this valve was fluctuting between the set point by +-20% in the field. Plus the unmatching of reading in DCS and in the Field wasnt the matter for a long time and we are processing normally by this unmatching in readings.
I was suggesting that the Recycle Hydrogen valve closed for instant causing the Low pressure in Sucrion Drum!!! How can I know my idea or their ideas are right !!! Is there any other assumptions?
Why we didnt say the RV of Separator vessel pop-up and re-set itself directly (Modulating type) ??
(RV Data attached in the pictures)
Thank You
