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EnglishWhat is the Zeal Draft Survey (Load Line) Hydrometer used for?
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The Zeal D4040 Draft Survey (Load Line) Hydrometer is a glass hydrometer used to measure the density of liquids in draft surveys — the process of determining how much cargo a vessel is carrying by measuring its displacement. Zeal lists it at £39.50 ex. VAT. It suits marine surveyors, cargo inspectors and shipping professionals who need a portable density reading as part of load-line or draft survey calculations, rather than laboratory-grade density measurement.
What a draft survey hydrometer does
A draft survey works out cargo weight from the difference between a ship's loaded and empty displacement. That calculation depends on knowing the density of the water the vessel floats in, because displacement tables are referenced to a standard density. A draft survey hydrometer gives that density reading directly from a sample of sea or dock water.
The instrument is a weighted glass float that sits at a depth determined by the liquid's density. You read the value at the liquid surface against the scale. The "load line" label refers to its use alongside load-line and freeboard checks, where accurate water density matters for compliance and cargo documentation.
Where it fits in the survey
- Taking a water sample at the survey location (harbour, berth or open water)
- Reading density with the hydrometer at the sample temperature
- Applying the reading to displacement and cargo calculations
- Recording the result for the survey report
The Zeal D4040 model
Zeal's product listing shows the D4040 Draft Survey (Load Line) Hydrometer at £39.50 ex. VAT, with a "view product" link for full details. The site groups it under its hydrometer range, which also includes Zeal Quality Hydrometers (listed as 90 items) — so the D4040 is one specific instrument within a broader catalogue rather than the only option.
The listing does not state the measurement range, scale divisions, calibration temperature or materials on the category page. Those are the specifications that matter most for this instrument, so check the individual product page before ordering.
Who typically needs one
| User | Typical need |
|---|---|
| Marine surveyors | Water density for draft survey and cargo quantity calculations |
| Cargo inspectors | Verifying cargo weight against documentation |
| Ship's officers | Load-line and stability checks requiring local water density |
| Port and terminal staff | Checking density at berth for loading calculations |
If your work is laboratory density measurement, a general hydrometer from Zeal's wider range may fit better. The draft survey model is aimed at field use in marine conditions.
Specifications to check before buying
Because the category page is thin on detail, confirm these on the product page or with Zeal directly:
- Measurement range — must cover the density of the water you sample (fresh, brackish or salt).
- Scale divisions — finer divisions give better resolution for cargo calculations.
- Calibration temperature — readings are only valid at the stated reference temperature; you may need a temperature correction.
- Length and sample volume — a hydrometer needs enough liquid depth to float freely.
- Material and durability — glass hydrometers are fragile; consider a protective case for field work.
Practical notes
- Read at eye level at the liquid surface, and let the instrument settle before reading.
- Record the sample temperature alongside the density value; corrections depend on it.
- The listed price excludes VAT, so confirm the total cost including delivery and any case.
- For NHS, clinical and home-use medical products, Zeal's separate medical thermometer categories are the relevant section — this hydrometer is a marine instrument, not a clinical one.
For the exact scale and range of the D4040, use the product link on the Zeal site or contact Zeal directly, since the category listing alone does not give enough to confirm suitability for a specific survey.