LOT vs VOT Systems: Which Fits Your Industrial Gas Application?
When an industrial plant's LPG demand outgrows a standard bulk-tank-plus-regulator setup, two engineering approaches emerge: Liquid Off Take (LOT) and Vapor Off Take (VOT). These are often confused but solve very different problems. This post compares them so you can make an informed choice.
What is VOT (Vapor Off Take)?
VOT is the standard industrial setup: LPG is stored as liquid in a bulk tank; gas is drawn from the vapour space at the top of the tank. A pressure regulator drops the vapour pressure to the required working pressure, and the vapour is piped to consumption points.
It is simple — the tank itself acts as a passive vaporiser. But it has capacity limits: the liquid's natural vaporisation rate depends on ambient temperature and tank surface area. In winter, or at high sustained demand, the pressure drops and the supply stutters.
Read more about VOT system installation.
What is LOT (Liquid Off Take)?
LOT draws liquid from the bottom of the tank using a pump (or gravity where head is available), passes it through an external vaporiser, and then feeds the vapour to the distribution network. The external vaporiser decouples gas supply from the tank's natural vaporisation rate.
LOT is more complex — more equipment, more safety systems — but supports much higher and more consistent gas supply.
Read more about LOT system installation.
Side-by-side comparison
| Factor | VOT | LOT |
|---|---|---|
| Capex | Lower (₹3-8 lakh add-on to tank) | Higher (₹10-30 lakh for pump + vaporiser + safety) |
| Max sustainable demand | ~80 kg/hr (tank-size dependent) | 500+ kg/hr (vaporiser-size limited) |
| Temperature sensitivity | High — winter supply may drop | None — external vaporiser compensates |
| Pressure stability | Variable with demand & ambient | Rock-solid |
| Complexity | Low | Moderate |
| Safety equipment required | Basic (regulator, safety relief) | Extended (ESDV, pump protection, vaporiser trips) |
| Installation time | 1-2 days (on existing tank) | 5-8 days (new pump house + electrical) |
| Maintenance | Annual regulator check | Semi-annual pump service, vaporiser AMC |
| Failure modes | Pressure drops, supply stutters | Pump trip — bypass needed to continue |
When to choose VOT
- Total demand below 80 kg/hr sustained
- Operations in mild-ambient cities (Mumbai, Chennai, Bengaluru)
- Budget-constrained projects
- Low-complexity operational environments
- Tank is already sized with enough vapour space for current demand
When to choose LOT
- Demand above 100 kg/hr sustained
- Cold-ambient plant locations (Chandigarh, Jaipur, Delhi in winter, hill stations)
- Pressure-sensitive processes (ceramics, metals — where pressure variation affects burner output)
- Plants planning to scale demand 50%+ in next 3 years
- Tiered refill schedules where tank level varies significantly between refills
Hybrid approach: dual-mode tanks
Some industrial installations combine both — VOT for low-demand hours/standby, LOT for peak production. This gives you the energy efficiency of VOT when possible (no pump / no vaporiser element running) with the capacity of LOT when needed. The extra complexity is justified above ~10 MT tank size.
Frequently asked questions
Can VOT be upgraded to LOT later?
Yes — we design VOT tanks with LOT-ready provisions (bottom nozzles, spare flanges) so you can bolt on a pump skid and vaporiser when demand grows.
What's the failure mode of LOT?
Typically pump trip (electrical or mechanical). A bypass line allows low-rate VOT-mode supply to continue while the pump is serviced — usually 2-8 hours.
Do you manufacture LOT skids in-house?
Yes — we fabricate skids to a tested design, and we also integrate OEM skids per specification.
Schedule a system sizing consultation or call +91-9891-282-705.