Centrifugal Fan / Blower - Changeover procedure for Incinerator application
Centrifugal Fan / Blower - Changeover procedure for Incinerator application
(OP)
Dear Members,
We are planning to install a spare blower ( centrifugal fan - API610) for our SRU Tail Gas incinerator. The control system obviously needs modification. We are trying to work out a scheme that will permit changeover from operating blower to standby blower with no interruption or flow rate change to the incinerator. If any of you have experience with these systems, can you advise a sequence? I would like to believe this is being routinely done with pumps in many process plants and someone will be able to suggest a scheme.
For information, the blowers have inlet flow measurement, inlet and outlet dampers, and discharge to a common header. please oblige.
We are planning to install a spare blower ( centrifugal fan - API610) for our SRU Tail Gas incinerator. The control system obviously needs modification. We are trying to work out a scheme that will permit changeover from operating blower to standby blower with no interruption or flow rate change to the incinerator. If any of you have experience with these systems, can you advise a sequence? I would like to believe this is being routinely done with pumps in many process plants and someone will be able to suggest a scheme.
For information, the blowers have inlet flow measurement, inlet and outlet dampers, and discharge to a common header. please oblige.





RE: Centrifugal Fan / Blower - Changeover procedure for Incinerator application
Johnny Pellin
RE: Centrifugal Fan / Blower - Changeover procedure for Incinerator application
RE: Centrifugal Fan / Blower - Changeover procedure for Incinerator application
If you are trying to maintain constant conditions after a trip event then that will be virtually impossible because the standby motor is reacting to the event and not running in anticipation of the event, unless you have the standby motor running so it is idling just below the speed where forward flow would occur - but that will almost certainly cause other problems.
RE: Centrifugal Fan / Blower - Changeover procedure for Incinerator application
RE: Centrifugal Fan / Blower - Changeover procedure for Incinerator application
As noted above there are two scenarios and I don't know which one you refer to.
1) Switch over from duty to standby as part of a planned operation / regular occurrence
2) Trip of the duty unit followed by standby unit coming to life.
Makes a big difference.
It all depends on the susceptibility of the system to small variances in flow. True "bumpless" transfer takes a lot of time and effort and requires some sort of flow control on the two units to swap duty over a certain time period ( say 30 seconds) and react to changes to maintain a fixed outlet flow. Not sure VFD would do the trick as the reduction in speed would affect the outlet pressure and hence overall flow rate. Might need control valves / dampers.
A lot of pump systems you just turn on the second pump, wait a few seconds as it gets to speed then turn off the first one. Bigger pipeline units you would probably simply start second pump against a closed valve, wait until it had got to full pressure and then simply open one valve as you close the other on the first pump. All depends on your downstream system.
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: Centrifugal Fan / Blower - Changeover procedure for Incinerator application
If I was switching two general purpose pumps, I might consider two options. One, as suggested above, would be to simply start the back-up pump and shut down the main pump as soon as the back-up is developing pressure. If this was too much upset to the process, I would start the second pump blocked in and gradually work the valve open while gradually pinching down on the discharge of the main pump. This requires running both pumps dead-headed for at least a few seconds. I could not do that with our high speed, overhung process blower.
Depending on the configuration of your blowers and drivers, it might be possible to do some automation of the switching procedure for a planned switch. But, for a trip and auto-start scenario, it may be impractical. In any case, you need to provide more details about the service, the blowers and the drivers.
Johnny Pellin
RE: Centrifugal Fan / Blower - Changeover procedure for Incinerator application
My apologies for the late response & Sincere thanks for your inputs..
The Fan is to API 673. It was a mistake in my original post.
it is direct drive. No VFDs. No gear boxes.
It is Switch over from duty to standby as part of a planned operation / regular occurrence.
There is inlet and outlet damper on both fans.
I recognize there will be bumps during switchover.
My question is:
1. I propose to start the standby blower, with minimum flow and progressively increase. While doing the reverse with operating blower.
2. But, at lesser loads, can the standby blower develop sufficient head to discharge into the common header? The operating blower is already at full head.
3. I am told the inlet damper flow control will mean outlet pressure will fall with reduced flow.
4. There is indeed a fan curve that shows the effect of varying damper openings. But it will help if someone could explain.
Please oblige.
RE: Centrifugal Fan / Blower - Changeover procedure for Incinerator application