Frequently Asked Questions


“Why are hydrocarbons detrimental to the environment?”
When hydrocarbons enter the atmosphere anywhere in the world they react, in the presence of sunlight, with products of combustion forming low level ozone, or “smog”. This air pollutant is a serious health hazard; a threat to us all. This realization became the key motivating factor in a global move nearly 50 years ago to reduce the release of hydrocarbons into the atmosphere. The largest emitters were identified. Truck, rail, and marine (ship and barge) petroleum liquids terminals, handling huge volumes of hydrocarbons every day, were among the first, since they move the most hydrocarbon liquids. They were also among the first to install hydrocarbon vapor emission control systems. The earliest of those systems lacked any monitoring systems and we simply “assumed” to function properly. In the following decades it became apparent that most were failing to eliminate hydrocarbon emissions due to neglect and their obsolete control systems, while during this same time instrumentation, computerization, and process technology advanced in quantum leaps.

“What was the first VRU system and why did it change?”
The earliest vapor recovery units (VRUs) were pressure swing adsorption-absorption systems regenerated using liquid ring vacuum pumps with no monitoring controls. These “wet” vacuum pumps were the weak link. Some VRU providers chose to boost vacuum pump efficiency by adding Roots blowers to draw a deeper vacuum. This proved to be overly complex, and created another problem, noise pollution. By the later 1990s comprehensive emissions testing proved the fallacy of operating unmonitored, as most units tested failed emission the test. In 2002 an independent group, led by Tim Hammond, owner of a vapor control system service company in Indianapolis, Indiana, USA decided to resolve the wet pump, monitoring, and other problem area lessons learned by his team over decades of hands-on experience, and to apply 21st century instrumentation and software technologies to a new class of VRUs to bring vapor control systems up to date.

“What was done to modernize the VRU technology?”
First, the wet liquid ring vacuum pump and its controls were exchanged for a dry screw vacuum pump developed specifically for this application by Busch, a German manufacturer of worldwide vacuum pump renown. Next, to eliminate disastrous carbon temperature excursions, common when highly reactive carbon was used, a more ideal carbon was selected based on safety to avoid the frequent overheating events caused by the overly reactive carbon used by others in the past. Then the obsolete and horribly limited control system was re-engineered to use the most modern monitoring and measuring systems available, feeding operating data to a PLC and newly developed software package that self-manages the entire system through a qualified process logic controller (industrial computer system).

“Was all of this change acceptable to the industry?”
Tim’s efforts, through SYMEX Technologies, completely modernized the vapor control system and changed the entire world of vapor emission control for the better. Tim called it “DRYVac™” … though most of his clients simply called it marvelous. Each new DRYVac™ System was smaller, simpler, smarter, and far more efficient than anything else available!

“We’ve heard about a transition at SYMEX Americas. What’s that all about?”
Sadly, Tim passed away unexpectedly early in 2019, but DRYVac™ lives on through the efforts of Tim’s friend and business associate William Lin! And while Tim is gone now, the world knows that he perfected this technology. He proudly left it in the very capable hands of Mr. Lin. The technical team Tim surrounded himself with is still here to assure each client that the application expertise needed is applied to each new system. The carefully selected SYMEX Technologies technical team remains intact, and is considered second to none in this field. As SYMEX Technologies grew to international acclaim William Lin has helped manage the business internationally. SYMEX Technologies is now well positioned to promote DRYVac™ worldwide; to minimize the greenhouse effects caused by emissions from petroleum liquids terminal everywhere.

“Who is SYMEX Technologies?”
SYMEX Americas is 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 lube oil or 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. This increases both CAPEX and OPEX.

“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 compressor manufacturer Busch designed a dry screw compressor specifically for hydrocarbon vapor recovery applications. Since then, many older systems have been retrofit with the DRYVac™ vacuum pump, and the majority of new vapor recovery systems use this marvelous pump too.

“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 250 DRYVac™ systems are now in service worldwide. Many of these use multiple DRYVac™ compressors, so the total number of dry screw compressors operating in this service now exceeds 500.

“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 compressors like the Hori used occasionally by others has proven inferior to be a maintenance headache 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 are extremely safe.

“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, our automation shuts down the entire system, still several hundred degrees short of auto-ignition. This safety system has proven effective for over fifteen years. 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 hardware and 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 through the use of the most modern of all instruments, valves, and controls. 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. Our clients agree that our new software and controls package is well worth its cost.

“Is the DRYVac™ process the same as any other vapor recovery system?”
It may appear similar, but DRYVac™ is not exactly the same as systems offered by others. The carbon we use is specific to the DRYVac™ technology, selected to avoid heat-ups and to provide many years of satisfactory service. It is a formed (compressed and pelletized) carbon so the pressure drop through it is minimized. Furthermore, formed carbon is nearly twice as hard as random shaped carbon, so it is far less prone to powder into fine carbon dust like too many other carbon types used by others. The pore space in formed DRYVac™ carbon is also greater which means that loading rates won’t ever have to be reduced because of carbon saturation. DRYVac™ carbon cuts replacement costs by at least 4:1 over the life of a system, just one more saving as a result of superior DRYVac™ engineering.