Steam trap loss calculator
A trap that has failed open vents steam around the clock and gives no outward sign: no noise, no puddle on the floor. This calculator shows what that costs per year at your own tariff, and gives you a figure you can attach to a procurement request.
Inputs
Defaults are typical for a mid-sized plant in Kazakhstan. Replace them with your own values; the result recalculates immediately.
How many are installed across the plant.
Typically 15-25 % without a testing programme.
Operating gauge pressure in the line.
Diameter of the trap seat. 4.8 mm equals 3/16 inch.
Continuous production is about 8000 h.
Your own cost or the supplier's tariff.
Set to 100 if the steam is purchased.
Result
Cost of losses
32,806,363 KZT/year
Per month: 2,733,864 KZT/month
- Traps failed open
- 20
- Steam loss
- 1,027 kg/h
- Steam loss per year
- 8,213 t/year
- Thermal power lost
- 579 kW
- Heat lost per year
- 4,687 Gcal/year
- Per failed trap
- 1,640,318 KZT/year
- Your calculation, written up as a document for an internal memo
- A ready technical specification for the instrument, for the procurement plan
- A one-day survey programme for your site
How it is calculated
The core is Napier's formula for steam discharge through an orifice. It is the same method used in SDT's reference calculator for the SDT 270 and SDT 340 series, so the result is comparable with the report you receive after an instrumented survey.
Steam flow is converted into thermal energy through the latent heat of vaporisation from saturated steam tables (interpolated by absolute pressure), then into gigacalories and into tenge at your tariff, accounting for boiler efficiency.
Steam loss, lb/h = 24.24 x P abs.(psia) x D²(inch) -> kg/h -> kW -> Gcal/year -> KZT/year
The calculation is deliberately conservative: it excludes make-up water, water treatment and deaeration, so the plant's actual cost is usually higher. Napier's formula describes full discharge through the seat — for a partially blowing trap, lower the failed share or the seat diameter.
Frequently asked questions
Where do I get the share of traps failed open if no survey has been done?
At plants without regular testing, 15-25 % of traps are failed, and roughly two thirds of those have failed open. With no data at all, start at 20 %, the industry average. A one-day ultrasound survey gives the exact figure.
Why are losses shown in Gcal rather than tonnes of steam?
Because heat is tariffed in gigacalories in Kazakhstan, and the finance department budgets in KZT per Gcal. Tonnes of steam are shown separately, for the process engineers.
Can this calculation be used as a procurement justification?
Yes, that is its purpose. It states annual losses in tenge — the figure the instrument's price is weighed against when a request goes into the annual procurement plan. On request we will write the calculation up as a document and attach a technical specification for the equipment.
What instrument is used to test steam traps?
An ultrasonic leak detector and analyser. A trap that has failed open emits a characteristic continuous ultrasonic signal, which the instrument picks up without contact, without stopping the line and without opening the insulation. In our practice that is the SDT 270 and SDT 340.