Cylinder supply or on-site generation: how to decide honestly

The question behind the question

Nobody actually wants a gas plant. They want gas, reliably, at the lowest total cost — and at some volume, making it yourself becomes the cheaper way to get it.

Where that point sits is a real calculation, worth doing properly rather than being talked into or out of.

What each side is good at

	Cylinder supply	On-site generation
Capital	None	Substantial
Unit cost of gas	Higher	Lower at volume
Operators	None needed	Trained operators required
Maintenance	Supplier’s problem	Yours
Licensing and inspection	Supplier’s burden	Yours
Delivery dependency	Real	None
Flexes with demand	Easily	Poorly — it idles or is short
High purity, small volume	Often cheaper	Expensive

The four variables that decide it

1. Steady consumption — not peak. This is the one people get wrong. A plant sized to your busiest hour idles most of the week and never repays its capital. Compare average continuous demand against the plant that would meet it, and cover peaks from cylinders or storage.

2. Required purity. This matters more than flow, and it surprises people. Raising the purity requirement can multiply a plant’s size, energy use and cost, while the same step in a cylinder supply may be nothing more than a different fill.

3. How continuous the demand is. A plant running two shifts a day pays back. A plant running four hours on Tuesdays does not.

4. Whether you can actually run it. A generating plant needs trained operators, a maintenance regime, and someone who will answer to an inspector. If that capability does not exist and will not be built, the rest is academic — operating an acetylene plant sets out what is genuinely involved.

The costs that get left out

Comparing gas price against gas price is how year two goes wrong. Include:

• Electricity — on PSA plants this dominates running cost
• Sieve or media replacement — not small, not optional
• Compressor maintenance — the largest mechanical item
• Operator time and training
• Licence, inspection and compliance burden
• Floor space, and what else it could be doing
• Backup supply, because most critical installations keep cylinders anyway

Start with cylinders. Let them do the sizing study.

If you are unsure, this is almost always the right sequence:

1. Take cylinder supply and run it for a year
2. Use the invoices as a measured consumption record — real demand, real pattern, real peaks
3. Size the plant against that record, not against an estimate

Buying a plant on an estimate is exactly how plants end up oversized, and an oversized plant is worse than none: it carries the capital, the maintenance and the licence burden while running at a fraction of the efficiency it was costed at. There is a working method for acetylene specifically on sizing an acetylene plant.

Ask someone with an interest on both sides

KIGL fills cylinder gas and builds acetylene plants. That does not make us disinterested, but it does mean the answer is not settled in advance by what we happen to sell. Tell us what you use, how steadily, and at what purity, and we will tell you which side of the line you are on — including when the answer is to keep buying cylinders.

Sources

• IS 8471 — Acetylene generators