Vapour Recovery Unit Sizing: Every Oil & Gas Site Needs a Different Solution

Vapour recovery unit sizing is one of the most important parts of any recovery project. A system that is too small may not keep up with vapour generation, while a system that is too large can add unnecessary cost without improving performance. The right size is the one that fits the site’s actual operating conditions, not just a general assumption about flow.

Every oil and gas site produces a different vapour profile. Tank size, fluid composition, operating pressure, temperature changes, and production rate all influence how much vapour can be recovered. That is why a custom VRU is usually a better solution than a standard package. When sizing is based on real data, the system is more likely to perform reliably over time.

Vapour Flow Rates are Rarely Steady

Vapour flow rates can change significantly throughout the day. A site may see short bursts of vapour during tank filling, unloading, or pressure changes, followed by longer periods of lower activity. Those fluctuations matter because a compressor must be able to operate across the full range of expected conditions.

If the unit cannot handle peak vapour flow rates, pressure may build and the site may lose recovery opportunity. If the system is oversized, the compressor may short cycle or run inefficiently. A properly engineered VRU is designed to manage both the average load and the spikes that happen during normal operation.

Storage Tank Vapours Need Site-Specific Analysis

Storage tank vapours are not the same from one site to another. Some tanks release vapours that are rich in light hydrocarbons, while others produce heavier streams or more condensate. That changes how the vapour behaves, how it enters the system, and what type of recovery equipment is needed.

A site with multiple tanks can also create different vapour events depending on which tanks are active. In those cases, the recovery system has to handle more than one operating scenario. This is why proper engineering depends on field data, not just nameplate assumptions. Better input data usually leads to a better and more reliable result.

Compressor Sizing Affects the Whole System

Compressor sizing is not just about matching flow. It also depends on suction pressure, discharge pressure, gas composition, and how the site actually operates. A compressor that is not matched properly to the application can create reliability issues, maintenance problems, and lower recovery rates.

A good sizing study looks at the full process, not just one number. It should account for tank conditions, liquid carryover risk, downstream pressure requirements, and whether the site may expand in the future. When those variables are considered early, the resulting system is far more likely to work as intended.

Custom VRU Packages with Eagle Pump & Compressor

A custom VRU is built around the site instead of forcing the site to fit the equipment. That means the design should reflect the real vapour load, the expected operating envelope, and the practical realities of the location. It should also allow enough flexibility to deal with changes in production or vapour characteristics.

At a minimum, a good design should account for peak and average vapour flow rates, gas composition, temperature and pressure variations, liquid handling, and maintenance access. If those factors are ignored, the system may still function, but it is less likely to operate efficiently or consistently. In many cases, the difference between a standard unit and an engineered solution shows up later in uptime, service cost, and emissions performance.

Proper VRU Sizing Pays Off

The value of proper vapour recovery unit sizing goes beyond getting the equipment to run. A well-sized system can recover more product, reduce venting, and help the operator maintain compliance without constant troubleshooting. It also tends to be easier to maintain because it is not being forced to operate outside its intended range.

For the right VRU system, contact Eagle Pump & Compressor:

Telephone: 403-253-0100