In a fuel terminal, vapor recovery can live in two places: at the loading rack, where the vapor is generated in bursts, or on the storage tanks, where it accumulates steadily. The choice shapes piping, equipment size and how the terminal behaves at peak. Getting it right is less about technology preference and more about where the terminal’s vapor actually comes from.
Two vapor sources with different characters
Loading generates vapor in waves: every truck connection displaces tank headspace and sends a slug of hydrocarbon-rich vapor back to be handled. Storage tanks breathe more gently, with filling operations and daily temperature cycles producing a steadier, smaller stream. Rack-focused recovery handles big bursts and idles between them; tank-focused recovery handles continuous load and lets the rack push vapor into tank headspace as a buffer.
What the rack arrangement implies
Placing the unit at the rack means sizing for the burst: the largest simultaneous loading case decides the duty. The vapor piping is short and the response time is tight, because the vapor arrives exactly where the equipment sits. The trade is in peaking: a unit sized for three trucks loading at once spends much of its life waiting, and control strategy matters as much as capacity.
The tank arrangement inverts the picture. The unit runs against a smoother load, which suits certain technologies and simplifies sizing, but the rack bursts must be absorbed somewhere first. That somewhere is tank headspace and the vapor piping between rack and tanks, and its capacity becomes a design variable the terminal must respect in operating procedures: how many trucks can load simultaneously before the buffer is spent.
The split arrangement
Many terminals land between the poles: rack recovery for the loading bursts, with tank venting tied into the same vapor network so breathing losses are handled too. The split adds interconnection piping and coordination requirements, and buys in return a system where neither part needs to be sized for the worst case alone. It is the arrangement most often met in modern terminal work.
Deciding the arrangement for a terminal
- Quantify the vapor sources: rack loading patterns and tank breathing together;
- Check the existing vapor network between racks and tanks for capacity and condition;
- Decide where bursts are absorbed: at the unit, in tank headspace, or both;
- Size equipment against the chosen arrangement, including the peak case;
- Write the operating rules the arrangement depends on, especially simultaneous loading limits;
- Review the choice when throughput or product slate changes materially.
Arrangements compared
| Arrangement | Strength | Depends on |
|---|---|---|
| Recovery at the rack | Handles bursts at the source | Unit sized for peak simultaneous loading |
| Recovery at the tanks | Smooth duty, simpler sizing | Enough headspace to absorb rack bursts |
| Split arrangement | Neither part sized for worst case alone | Vapor network capacity and coordination |
| Rack unit, tank venting separate | Simple, independent systems | Accepting duplicated equipment |
Why the question returns
Terminals grow, product slates shift, and a loading pattern that once fit the buffer quietly outgrows it. The arrangement decision is therefore not made once but revisited: throughput reviews are the natural moment to check whether the vapor still behaves the way the design assumed. Terminals that keep that check on the calendar avoid the loud rediscovery of the answer.
Frequently asked questions
Which arrangement costs less overall?
It depends on the terminal’s own numbers. Rack recovery spends on peak capacity; tank recovery spends on network and headspace; the split spends on interconnection. The cheapest arrangement is the one that matches the actual vapor profile rather than the generic one.
Can existing equipment be kept when the arrangement changes?
Often yes, at least partially. Units relocate, vapor networks extend, and operating rules adjust. The review should establish what genuinely fits the new arrangement rather than assuming the current equipment was the reason for the old one.
What is the most common arrangement mistake?
Ignoring the buffer. Arrangements that rely on tank headspace to absorb loading bursts work only while operating procedures respect the limit; the mistake is designing for a discipline nobody wrote down.
Luoyang Wohong Petrochemical Equipment Co., Ltd. designs and manufactures vapor recovery units, membrane separation skids and condensers for fuel depots, terminals and retail sites. Contact us for duty assessment and equipment selection support.