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Plant Engineering Calculator

Updated Sep 17, 2026

Steam Drum Hold-Up Time Calculator — Usable Water Inventory & Ride-Through

Calculate usable drum water inventory and hold-up time from vessel geometry, usable level fraction, density and net drawdown rate.

Live calculationWorking shownPrivate in browser

Inputs

Results

Cylinder volume 10.60 m³
Usable water volume 2.12 m³
Usable inventory 1802 kg
Hold-up time 10.8 min
More actions

Shared links reopen these inputs. Recent and saved calculations stay in this browser unless you clear site data.

Formula

V=πD²L/4×usable fraction; t=ρV/net draw.

Your calculation, step by step

These steps use the values currently entered above so the result can be checked independently.

  1. 1.Gross cylinder volume = π × 1.50² ÷ 4 × 6.00 = 10.60 m³.
  2. 2.Usable level-band volume = 10.60 × 0.200 = 2.12 m³.
  3. 3.Usable mass = 2.12 × 850 = 1802 kg; hold-up = inventory ÷ net drawdown = 10.8 min.

How to use this calculator

  1. Enter measured or design values using the units shown beside each field.
  2. Review the live results and the substituted calculation steps before using the estimate.
  3. Check the assumptions below, then continue to a related calculator when the next engineering decision needs another model.

Worked example

A 1.5 m diameter, 6 m drum with 20% usable level band contains about 2.12 m³ usable volume before density correction.

Assumptions and limits

  • Simplified cylindrical inventory model; real drum internals reduce usable volume.
  • Do not use this screening result to override boiler protection or low-water trip requirements.

How to interpret the result

Treat the primary result as an engineering screening value, then use the secondary outputs to understand scale, energy or operating impact. Confirm site measurements, equipment limits and applicable standards before making a design or control change.

Questions engineers ask

What does steam-drum hold-up time represent?

It estimates how long the usable water inventory can cover a specified net drawdown rate. It is an inventory screening metric, not a replacement for boiler protection logic.

Why is usable level fraction different from total drum volume?

Normal operation only permits a limited level band, and internals occupy volume. Treating the entire geometric drum as usable water would overstate ride-through inventory.

Can hold-up time be used to change low-water trips?

No. Trip settings and protection requirements must follow the boiler manufacturer, applicable code and site safety analysis.

Continue the calculation

Use the next calculator in the same engineering workflow instead of restarting from search.

deaerator level bandboiler steam outputboiler turndown
Methodology. MAXScanner shows the governing formula, entered values and calculation outputs so the estimate is auditable. The calculator is a screening aid; assumptions and equipment-specific limits remain part of the engineering review.