September 8, 2008 at 4:42 pm #3441
Has anyone ever considered or put in a minimum flow line for their coker charge pumps? We have had multiple heater trips on low flow when we’ve attempted to switch pumps (light product in the spare pump flashes when put online and causes a low flow scenario in the heater). We’re considering putting in minimum flow lines so we can ensure the offline pump is hot and free of lighter product before attempting to bring it online. We’re thinking about routing the minimum flow to the upstream side of our unit feed drum. Thanks.
September 11, 2008 at 5:18 pm #6597
The cokers I have seen do not have a minimum flow line. We did experience that problem at the coker I worked, but it was corrected by changing operating procedures.
The problem I see with a minimum flow line in this service is keeping it hot enough so that the resid won’t solidify in it.
Did you read the post from Ken Osment from Suncor on pump swap ?
Please e-mail me if I can be of any help.
September 14, 2008 at 6:03 am #6590
antonio saura CebrianParticipant
As Mr Claus said, is not normal found DCU units, that have recirculation line for heater pumps, I have been in two units, that have that line; one of them worked through a Restriction orifice and the other have a control valve (Flowmeter with minimum flow set point ), that unit additionally to the control valve had a switch (low pressure discharge) that starts the spare pump (automatically), also the recirculation line had a steam injection downstream and up to the control valve to ensure that the line was available (in order to avoid plugging)
These systems had to be designed in this way, motivate the high capacity of the unit and low turndown and where the customer is NOT allowed INSTALLATION OF 3 pumps (two in operation and one in spare, only allowed the installation of two pumps)
Points to keep in mind are: the type of control valve, vibration of the line due to differential pressure that is generated between the discharge pressure of the pump and the point of return (bottom of the fraction), and plugging for bad warming of the line
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