2 replies to this topic

[prav]

Hi,
The FCC slide valve is not functioning properly in our unit. When given a signal from DCS, it opens or closes in strokes (not smoothly). The slide valve actuator is powered by air. In the last shut down, we checked the interior of the valve and could not find any mechanical problems. We decided to put a oil box from which the air passes by to regulate the actuator. This was a move to lubricate the actuator so that it can function smoothly (Not mentioned in the Operators Manual). Now the valve is responding very slowly. When given an opening of 50% manually from DCS, it goes till 90% and then starts to close. I've some doubts regarding the operation of this slide valve:

1. The catalyst is circulating at nearly 400°C and 1 barg pressure. Is it possible that if the catalyst is wet, it can cause the slide valve to function irregularly (I doubt that the catalyst can be wet at this temperature, the water is produced in the reaction)

2. Is putting the oil box has actually caused the actuator to function more discontinuously ?

3. What was causing the problem before ? (No mechanical difficulties, actuator power sufficient)

Also, the delta P across the valve is significantly low causing poor catalyst circulation.

Any suggestions ?

Thank You

[Root]

Hi,
The FCC slide valve is not functioning properly in our unit. When given a signal from DCS, it opens or closes in strokes (not smoothly). The slide valve actuator is powered by air. In the last shut down, we checked the interior of the valve and could not find any mechanical problems. We decided to put a oil box from which the air passes by to regulate the actuator. This was a move to lubricate the actuator so that it can function smoothly (Not mentioned in the Operators Manual). Now the valve is responding very slowly. When given an opening of 50% manually from DCS, it goes till 90% and then starts to close. I've some doubts regarding the operation of this slide valve:

1. The catalyst is circulating at nearly 400°C and 1 barg pressure. Is it possible that if the catalyst is wet, it can cause the slide valve to function irregularly (I doubt that the catalyst can be wet at this temperature, the water is produced in the reaction)

2. Is putting the oil box has actually caused the actuator to function more discontinuously ?

3. What was causing the problem before ? (No mechanical difficulties, actuator power sufficient)

Also, the delta P across the valve is significantly low causing poor catalyst circulation.

Any suggestions ?

Thank You

Hi,
Your temp is not enough ( Reactor temp at-least 530⁰C and re-generator 700⁰C). More over check your servo valve. your problem looks more with servo valve.
check it and coming back again for further discussion.
Toor

[prav]

Its a bit different process than FCC. The structure is the same but the reaction is different. According to you, what can cause the low Delta P across slide valve?