What is a vapor recovery unit (VRU)?
A VRU system is primarily composed of a scrubber, reciprocating compressor, motor, and switchgear. Its main purpose is to recover vapors that normally would be discarded by releasing to the atmosphere or flaring off. The pressure switch detects pressure variations inside the tanks and turns the compressor on and off. The vapors are sucked through a scrubber, where the liquid trapped is returned to the liquid pipeline system or to the tanks, and the vapor recovered is pumped into gas lines.
Corken reciprocating compressors mounted on engineered skid packages are used to boost pressure on pipeline applications as well as to scavenge vapors from well sites and tank farms (see Vapor Recovery illustration for more details).
Typical Reciprocating compressor applications include…
Candidates for vapor recovery units includes propane bottle filling stations, petroleum tank farms, pipelines, well sites where fugitive emissions are an issue, refineries, chemical processing plants, recycling plants, and gas utilities.
The through the use of a four-way valve, a vapor recovery unit can also be used for a liquefied gas transfer application. A common example of liquefied gas transfer is tank car unloading. The principles of the liquefied gas transfer are fairly simple. Through the use of a vapor return line, a reciprocating compressor reduces the pressure in the stationary tank and increases the pressure in the tank car. The increased pressure in the tank car forces the liquid through liquid return line at the top of tank car and through the liquid line at the bottom of the stationary storage tank (see the Liquid Transfer illustration below for details).
Recommended Reciprocating Compressors…
Corken single-stage reciprocating compressors work well in low pressure recovery, our two stage compressors are for the high pressure applications up to 600 psig max working pressure. For the high flow area like scavenging from several well sites or a large storage tank, Corken’s horizontal reciprocating compressors are a great choice.
Materials of construction…
The compressor’s materials of construction vary as to what the gas being recovered is.Natural gas would primarily use Buna-N o-rings and aluminum gaskets. Process gases may need more exotic O-rings like Kalrez® (Kalrez is a registered trademark of DuPont) or PTFE, and Iron-lead gaskets. Corken can also add a corrosion resistant nickel and PTFE coating to the gas wetted components when compressing a corrosive gas. If there is no electrical power on site to run an electric motor for the compressor, the units can be driven by a diesel fired engine.
Corken offers several standard mounting configurations for all of its reciprocating compressors, sliding vane pumps, turbine pumps, and side channel pumps. A standard mounting primarily consists of a compressor or pump, baseplate or skid, belt or coupling guard, adjustable driver slide base and an optional driver. When one of Corken’s standard mountings does not fit into your application, we will customize a compressor package or pump skid for you. Most custom compressor packaging and pump skids are a modification of our standard mountings.
All of Corken’s regenerative turbine pumps are known as a Coro-Flo®. The DL-/DLD-/DLF-model regenerative turbine pump is a direct mount made for a standard, two pole C-Face motor with a 8.5″ rabett diameter. A 8.5″ rabett diameter fits 182TC, 184TC, 213TC and 215TC motor frames. 
If you are limited to single phase electric power and your pumping application requires high differential pressures, then the optional HDP turbine pump package is for you. With the optional HDP package you get a variable frequency drive (VFD) that allows you to convert a single phase electrical power to three phase power. Three phase electrical power is necessary to operate the larger horsepower motors required for building 125 to 250 psi (8.6 to 17.2 bar) of differential pressure.