Seal flush purpose

BSD of gas oil will be recycled back through the coke drums or visbreaker soaker coils. At 15 (U.S.) a barrel downgrading cost, that s 6000 (U.S.) a day. All to no purpose. Just remember to turn the seal flush back on before restarting the pump. 

If the seal flush can be water (i.e., sour water or amine), the dry seal design serves no purpose. 

Modern pump designs also include a means for flushing the piston with solvent behind the pump seal (not shown in Figure 13.4). The solvent for this is drawn in from a separate reservoir and pumped back into this same reservoir. The purpose is to continuously rinse the piston free of mobile phase residue such that abrasive solute crystals resulting from a mobile phase that has dried out on the piston will not deposit there. These solutes, such as the salts dissolved in the buffered mobile phases used in ion exchange chromatography, may otherwise crystallize on the piston and then damage the piston or the pump seal when the piston moves back and forth. Mobile phases that contain such solutes must be flushed from the system after use so that there is also no crystallization on the front side of the seal. 

Note 1. A mixture of 100 ml of hydriodic acid and lg of purified red phosphorous is refluxed gently for 2h under a carbon dioxide atmosphere and then distilled. Distillate, having a constant boiling point of 126-127°C, is collected. It is convenient to divide the distillate into 5-ml portions and transfer each portion to a 10-ml brown, general-purpose ampule. The ampules are flushed with nitrogen and sealed with a flamesealing torch. One ampule of hydriodic acid is used for each methoxyl... 

Charging the lube oil, seal oil, and oil cooling systems with flushing oil and circulating for cleaning purposes. 

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