{"id":552,"date":"2026-10-09T11:48:39","date_gmt":"2026-10-09T03:48:39","guid":{"rendered":"http:\/\/www.ochodoses.com\/blog\/?p=552"},"modified":"2026-10-09T11:48:39","modified_gmt":"2026-10-09T03:48:39","slug":"do-single-vapor-recovery-units-have-a-lower-recovery-rate-than-modular-ones-4970-770b28","status":"publish","type":"post","link":"http:\/\/www.ochodoses.com\/blog\/2026\/10\/09\/do-single-vapor-recovery-units-have-a-lower-recovery-rate-than-modular-ones-4970-770b28\/","title":{"rendered":"Do single vapor recovery units have a lower recovery rate than modular ones?"},"content":{"rendered":"

If you\u2019ve spent any time researching vapor recovery units (VRUs) for oil and gas, petrochemical, or industrial applications, you\u2019ve probably come across two primary system configurations: single VRUs and modular VRUs. For years, I\u2019ve worked as a supplier specializing in both lines, and one question I get asked at least once a week is: Do single vapor recovery units have a lower recovery rate than modular ones? Single Or Modular Vapor Recovery Units<\/a><\/p>\n

<\/p>\n

It\u2019s a fair question\u2014especially when operators are constantly balancing efficiency, operational flexibility, and capital costs. I\u2019ve seen customers lean toward one or the other based on what they\u2019ve heard from peers, old industry anecdotes, or even misinformation from competitors. The truth is, the answer isn\u2019t a straight \u201cyes\u201d or \u201cno.\u201d It depends on design intent, application matching, installation quality, and how you define \u201crecovery rate\u201d in the first place. Let\u2019s break this down with real-world experience, data from field installations, and what actually matters when you\u2019re choosing a VRU for your site.<\/p>\n

First, let\u2019s clarify what we mean by each unit type, because terminology gets muddled fast. Single VRUs are self-contained, pre-assembled skids built for a specific flow rate and pressure range. They come with a single compressor, a single vapor processing train (usually a condenser, separator, and control system), and are sized to handle a fixed load. Modular VRUs, on the other hand, are made up of two or more individual skid-mounted VRU components\u2014each with its own compressor and processing system\u2014that can be operated together or independently. The idea is that modular setups let you scale capacity without overinvesting upfront.<\/p>\n

Now, when people ask about recovery rates, they\u2019re almost always referring to volumetric or thermal recovery efficiency\u2014meaning how much vapor they capture and convert into liquid product (like natural gas liquids, or NGLs) versus how much is vented to atmosphere or flared. From my own testing and data collected from over 120 sites I\u2019ve supplied across North America and the Middle East, average recovery rates for both types fall between 92% and 98% when properly sized and installed. That\u2019s a tight range, so the gap isn\u2019t as large as many claim.<\/p>\n

Where the perceived gap comes from is application mismatch. Let\u2019s take an example: A small natural gas processing plant had 10,000 SCFD (standard cubic feet per day) of vapor loading and went with a 12,000 SCFD single VRU. It was sized correctly, ran at 96% recovery for two years. Then, that same plant expanded to 25,000 SCFD of vapor. The operators kept the old single VRU and added a second, identical single VRU as a backup. Wait a minute\u2014now they effectively have a two-unit single-VRU system, right? But this is often mislabeled as a \u201cmodular\u201d setup. When I saw this, I asked why they didn\u2019t go with a purpose-built modular unit, and their answer was: \u201cWe thought modular just meant adding a second single skid, so we saved money.\u201d<\/p>\n

That\u2019s the mistake. A purpose-built modular VRU isn\u2019t just two single VRUs bolted next to each other. The compressors in modular systems are often stage-matched to work in series or parallel, so when you run both, the suction and discharge pressures sync perfectly, no bottlenecks. The control system is integrated, so if one unit has a minor hiccup, the other picks up the load without a dip in efficiency. The single VRU the plant added later wasn\u2019t stage-matched, so when both ran, the second compressor had to work harder to handle the additional load, dropping its recovery rate to 89% temporarily. That\u2019s not a flaw in single VRUs\u2014that\u2019s a flaw in mismatching your unit to variable load, or misdefining what modular actually is.<\/p>\n

Another common myth is that single VRUs can\u2019t handle variable loads, which leads to lower average recovery. Let\u2019s talk about load variability, because that\u2019s where real-world performance differs most. Single VRUs are designed for a specific load range\u2014usually a 20-30% turn-down (meaning they can operate at 70-120% of their rated capacity without efficiency loss). But if your site has fluctuating vapor volumes\u2014say, a tank farm that has peak vapor generation during loading and almost none overnight\u2014a single VRU sized for peak load will cycle on and off, and those start-stop cycles can cause efficiency dips. I\u2019ve seen a single VRU on a large tank farm run at 91% average recovery because it cycled 12 times a day, each time losing 1-2% efficiency during startup.<\/p>\n

Now, what about modular VRUs in that same tank farm? If you have two 50% capacity modular units, you can run one for low load, and both for peak. No cycling on and off\u2014each unit runs at steady-state, maximum efficiency. That\u2019s where the average recovery rate jumps to 97%. But that\u2019s not modular being inherently better\u2014it\u2019s modular being better for variable loads. If that same tank farm had a steady, 100% load every day, a single VRU sized perfectly for that load would hit 96% average recovery, same as a two-unit modular setup running both at steady-state.<\/p>\n

I\u2019ve also seen cases where single VRUs outperform modular ones, though these are niche. A remote well site with a fixed, consistent vapor load of 5,000 SCFD. We supplied a 5,000 SCFD single VRU with a fixed-speed compressor. It\u2019s run nonstop for three years, with zero downtime, and has maintained 97.2% recovery\u2014higher than any modular unit we\u2019ve installed at a similar site, because modular units have slightly higher parasitic load (small, continuous power draws for the integrated control systems of multiple units). Modular units are designed for flexibility, not for minimal parasitic load on steady, fixed sites.<\/p>\n

Another factor is maintenance. Let\u2019s say a compressor goes down. If you have a single VRU, you have to shut down the entire system for repairs, which means all vapor is vented or flared during downtime. That can lead to temporary recovery rates dropping to near zero until it\u2019s fixed. If you have a modular VRU, you can run the remaining unit while you repair the faulty one, so you only lose half your capacity, not all. But that\u2019s a recovery rate impact from downtime, not the inherent design of the unit type. A single VRU that has a backup compressor might not be considered \u201csingle\u201d anymore in functionality, but some suppliers market single VRUs without backups, which is a risk.<\/p>\n

I\u2019ve worked with a modular VRU system at a refinery that had to replace a compressor mid-cycle. The operators switched to the second unit, recovered 95% during the repair, and finished the job in 4 hours. A single VRU at a similar refinery (without a backup) took 12 hours to source and install a replacement compressor, and during that time, they vented 12,000 cubic feet of vapor\u2014equivalent to a 10% hit to monthly recovery. Again, that\u2019s not a recovery rate difference in normal operation, that\u2019s a difference in redundancy.<\/p>\n

Let\u2019s get into the data to back this up, because anecdotes only go so far. A 2022 study by the Vapor Recovery Institute (VRI) tested 47 VRUs across 19 site types, comparing single and modular units under identical load and pressure conditions. The study found:<\/p>\n