ok, i see.. i guess now i get which by pass did you mean.
so the PHE is offline. then it mean that your PHE is used as a spare for your heater treater. your PHE will only usable during the shutdown/maintenance of your heater treater.
by the way, how about the temperature of the emulsion before entering the heater treater? is it freezing your emulsion so you have an ice particle (solid) within the emulsion.? if it was the case. if you think you are okay with those conditions then you can remove your PHE, i mean if there was a shutdown to your heater treater and you have to route your emulsion through bypass without PHE.of course all of your equipments on downstream will have to handle those ice particle (solid). i think you should make sure of it. cause i think those solid particle will give more damage to your equipments downstream.

cheers

adi cahyanto