FAQ's -
Frequently Asked Questions

The following is a random listing of
Frequently Asked Questions
about the DRYVac™ dry vapor recovery technology.

"Who is SYMEX Americas?"

SYMEX Americas is a woman-owned and controlled business engaged in the business of designing, manufacturing, and supplying high-tech complete and retrofit hydrocarbon vapor recovery systems used by the petroleum liquids loading industry worldwide.

"Why is it called dry?"

Earlier vapor recovery designs used liquid ring vacuum pumps. These pumps are sealed with a mixture of ethylene glycol, a hazardous waste, and water (wet). The DRYVac™ System uses close tolerance screw-type vacuum compressors that do not use any seal fluid, thus the term "dry".

"What is the significance of dry versus wet in vapor recovery systems?"

In the wet system design, the vacuum pump must be sized to move both the full vapor stream and the recirculating seal fluid stream. Since liquid is a significant portion of the stream being moved by the vacuum pump, the energy required in this design is significantly higher.

"How much more energy does the wet system use compared to the dry system?"

Typically, the wet system uses about 30-35% more energy to do the same job.

"If the DRYVac™ System saves 30-35% energy why aren't all vapor recovery systems dry?"

The wet system was the standard of the industry for over 25 years. It was not considered possible to use dry compressors until the early 1990s when a compressor manufacturer designed a dry screw compressor specifically for hydrocarbon vapor recovery applications. Since then, more and more new vapor recovery systems have been dry.

"Can you convert the energy reduction into bottom line dollars?"

Yes. In a typical terminal, the old vapor recovery system consumes about 150 HP of power worth about $78,500 per year. The equivalent DRYVac™ System will consume about 100 HP. This is a savings of $26,000 per year, or $780,000 over the 30 year depreciation schedule and life expectancy of the total system.

"How many dry systems are installed?"

Well over 100 dry systems are now in service worldwide. Many of these use multiple DRYVac™ compressors. The number of dry screw compressors operating in this service now exceeds 300.

"Do other manufacturers offer dry systems too?"

Yes. However, their dry screw compressors were designed for other, simpler service applications, not specifically for gasoline vapor recovery applications. Further, the compression efficiency and life expectancy of the dry screw compressors used by others is unproven or has proven inferior compared to the DRYVac™ compressor

"Is the dry screw compressor cost effective?"

It can be if the life expectancy exceeds that of liquid ring pumps previously used. Properly maintained liquid ring pumps in vapor recovery service have a much shorter life than that quoted by manufacturers, averaging 3-5 years. Dry compressors used by others have proven life cycles equal to or less than liquid ring compressors. The life expectancy of the DRYVac™ system is 10 or more years when properly maintained, making it very cost effective.

"Are dry compressors safe to use in vapor control applications?"

The safe application of dry compressors depends on the system design. Concerns for heat of compression and auto-ignition of vapors must be addressed. When these conditions are addressed during the engineering phase of design, dry screw compressors can be safely applied.

"How does SYMEX Americas address the safety issues mentioned in the question above?"

We go to great pains to monitor and control safe operating conditions. The DRYVac™ compressor has a jacketed housing. We circulate a slipstream of the absorption gasoline through this cooling jacket to keep the compression temperature hundreds of degrees below auto-ignition conditions. We continuously monitor the flow of this coolant stream, and its temperature. In the event of a 50°F rise in coolant discharge temperature, we shut down the entire system, still several hundred degrees short of auto-ignition. This safety system has proven effective. SYMEX Americas has never had a safety issue with this design.

"Can we retrofit our existing wet systems with the DRYVac™ System?"

Yes. This is where DRYVac™ Systems have their greatest advantage. The wet system is large and bulky by comparison, so by replacing it with the DRYVac™ system, not only does the system use 30-35% less energy, the retrofit usually fits on the same foundations since it is much smaller. This means far less cost, and a speedier retrofit. In the terminal operations business, time is money. At SYMEX Americas we understand that minimizing downtime is critical to you.

"Can we use our existing controls if we replace or retrofit our existing system?"

While this is certainly possible, doing so sacrifices the 21st century software that is standard with all DRYVac™ systems. DRYVac™ software was developed specifically to operate this more efficient system with a focus on conserving as much energy as possible. The dry vacuum compressors are operated using variable frequency drives to minimize energy (eliminating start-up power loads) and to maximize compressor life (slow starts and stops). In addition, our ESP™ software package determines the actual hydrocarbon loading on the carbon and sets the intervals between regeneration cycles accordingly, saving even more energy. Most clients agree that the new software and controls package is worth the extra cost.

"Is the DRYVac™ process the same as any other vapor recovery system?"

It is quite similar, but not exactly the same. The carbon we use is specific to the DRYVac™ technology. It is a formed carbon so we can minimize the pressure drop through the carbon beds. Formed carbon is nearly twice as hard as random shaped carbon, so it is far less prone to break down into fine dust. The pore space in formed carbon is also greater. This means your loading rates won't ever have to be reduced because of the carbon.