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Headworks Calculator — Bar Screens & Grit Chamber

Screen-channel width with velocity checks · Kirschmer head loss · horizontal grit chamber with 0.2 mm sand capture

iWhat this tool does

Two headworks units that protect everything downstream. The screen is sized by what happens through the bars; the grit chamber by keeping the horizontal velocity constant so sand falls out but organics don't. Both are checked at peak flow.

1Bar screens

Screenings assumptions

2Horizontal grit chamber

Results — bar screensPEAK FLOW

Channel width
—m
Head loss — clean
—cm
Head loss — 50 % clogged
—cm
ItemValueUnit

Results — grit chamberPEAK FLOW

Length
—m
Width × depth
—m
Sand capture
—OK
ItemValueUnit

Headworks instrumentationMAPPED TO OUR RANGE

Rakes / grit conveyors are mechanical equipment, not our line — the instruments we carry and quote at factory-direct price are below.
DutyInstrumentModel / specQty

Quote this headworks' instruments at factory price

Open-channel flow, level control for rake actuation, and pump-station instruments at the manufacturer's ex-works price — our margin comes solely from the export tax rebate.

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Sources & parameter basis

[1]Bar-screen design factors (Clay et al.) & rectangular grit-chamber worked design — velocities (through-bar 0.6–1.0 mech / 0.3–0.6 manual; V_h 0.3 m/s), v_s 0.016–0.022 m/s for 0.2 mm sand, detention 45–90 s.
[2]Ten States Standards / US headworks practice — approach velocity 0.3–0.9 m/s, redundant channels.
[3]Metcalf & Eddy, Wastewater Engineering, 5th ed. — screenings 0.0035–0.0375 m³/10³ m³, Kirschmer shape factors, bar spacings, head-loss allowances.
Velocity control is the design. A grit chamber only removes grit if V_h stays ≈ constant as flow varies — specify a proportional weir or flume. Rake actuation for mechanical screens is set on measured head loss, so keep the differential level transmitter in the budget.
Method. Screen channel sized at peak flow through the bars; head loss by Kirschmer h_L = β(w/b)^(4/3)·(v²/2g)·sin θ, shown clean and at 50 % clogging. Grit chamber by constant velocity V_h = 0.3 m/s; length = V_h × t with a 0.2 mm-sand capture check (v_s,req = H/t ≤ 0.02 m/s). Results are preliminary design only — verify with local screenings/grit data and equipment suppliers.
⚠ Screening values only. Outputs from this tool are engineering screening estimates. Final equipment sizing, and any construction or permit submission, must be confirmed against the manufacturer’s verified performance curves and the applicable local regulation (e.g., Vietnam QCVN 14 / Indonesia PERMENLHK 68).
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