Naphtha Flushing System

SCOPE

An oil and gas customer was planning on using crude oil to cool their vacuum pump on a vapor recovery unit.  They approached Furey to design a system to flush the cooling lines when the vacuum pump was shut down preventing the crude oil from crystallizing in the cooling lines.  Naphtha is a common solvent for crude oil and was available on site to use for the flushing.

 

CHALLENGES

  • Naphtha is flammable and the skid was located in a classified hazardous area, requiring it to be explosion proof
  • Naphtha was available near the skid, but it was not a continuous reliable source
  • The system is in a remote area where it wouldn’t be visually monitored and needed to be fail safe
  • The system would feed multiple cooling loops that would require a range of 0-20 GPM dependent on which loops were being used
  • The system needed to maintain a constant pressure at the discharge regardless of the flow rate

 

SOLUTION

Furey’s engineers brainstormed to determine the best way to handle the wide flow ranges while maintaining a constant pressure at the cooling line connections.  Our engineers utilized a positive displacement gear pump to maintain a flow rate greater than required, recirculating any excess flow with an actuated control valve.  This valve would be controlled via a pressure transmitter at the skid discharge to maintain a constant pressure at any flow rate.  To make the system fail safe, Furey supplied spring return pneumatically actuated valves that would automatically close on loss of power, control signal, or air pressure.  In addition, Furey provided a skid mounted storage tank to ensure a reliable source of naphtha.  To prevent overfilling, the actuated valve on tank fill connection was directly wired to a normally closed ultrasonic high level switch that would immediately close the valve on high level.  The electrical components were prewired back to explosion proof junction boxes to allow for a faster integration with the vapor recovery unit PLC on site.  The skid has been in operation since 2016 and has been providing reliable naphtha flushing without issue.