Hindustan Scale Company · Est. 1955Wireless crane scales — safe-distance readout

A pull test without a record is an opinion.

The crane held the test load. The winch pulled. Everyone who was there agrees. But when an inspector asks, two years later, what force was reached and for how long, an agreement is not a number. A wireless dynamometer — a load link in the line that sends the tension to a hand-held unit or a remote display — gives you the number while the line is loaded and keeps it afterwards. This article covers what the rules ask a test to prove, why the reading must come from a distance, and how to start.

CRHRD3K – Electronic Crane Scale With Remote Display - the HSCo product this paper is about.
The load link hangs in the line; the number comes to the hand-held. Nobody walks up to a loaded line to read it.

The rules fix the test load, so the instrument has to show it

A proof-load test checks that the gear carries a set margin above its safe working load (SWL) without damage — and the margin is narrow.

India’s crane code, IS 3177:2020, requires a new overhead crane to “lift and sustain” a minimum test load of 125 % of the working load. The US rule, 29 CFR 1910.179, comes from the other side: test loads “not more than 125 percent” of rated load unless the maker says otherwise. The UK’s Code of Safe Working Practices for Merchant Seafarers (2026 edition) sets the ladder for ships’ gear — 1.25 × SWL up to 20 t, SWL + 5 t from 21 t to 50 t, 1.1 × SWL above — and adds that a static retest may be done “by dynamometer where appropriate”.

Together they put the test window at 125 %, and never far above it: a floor in one code, a ceiling in another, tapered for heavy gear in the third. So the instrument in the line has to show the force actually reached — not a block’s nominal weight, and not the winch operator’s feel for the lever.

Safe working load Test load by rule (COSWP Table 19.2 / IS 3177)
10 t 1.25 × SWL = 12.5 t
20 t 1.25 × SWL = 25 t
30 t SWL + 5 t = 35 t
50 t SWL + 5 t = 55 t
100 t 1.1 × SWL = 110 t
Bar chart: test load against safe working load for 10, 20, 30, 50 and 100 t gear — the margin narrows from 25 % to 10 % as gear gets heavier
Five pieces of gear, five test loads by rule: a 25 % margin at 10 t, 10 % at 100 t. The instrument has to show the force actually reached.

Why is a pull test without a record an opinion?

Because every rule that asks for the test also asks for the paper, and treats the test as not done until the paper exists.

India’s Factories Act 1948, section 29, requires every lifting machine, chain, rope and tackle to be thoroughly examined by a competent person at least once in twelve months, “and a register shall be kept” of every examination. At the ports, the Dock Workers (Safety, Health and Welfare) Regulations 1990 go further: the Form II register, with the test certificate attached, is kept for at least five years, and regulation 51(4) says no lifting appliance “shall be used for dock work unless and until” the entry has been made. The UK’s LOLER code and the US crane rule ask the same — LOLER for “particulars of any test”, the US rule for a report kept on file.

What the record must contain is not “passed”. It is the force reached and held, on a date, against a named piece of gear. That is a measurement, and measurements have one weak point: the moment a person reads a number off one thing and writes it on another.

A 2019 study in the Journal of the American Medical Informatics Association compared 6,930 instrument results typed by hand with the same results sent by the instrument. 260 — 3.7 % — did not match, and about 5 in every 1,000 were wrong by a clinically dangerous margin. A hospital is not a crane yard, but the copying step is the same step. A hand-held unit that stores the reading and produces the report from it removes the step entirely.

Diagram: where a wireless dynamometer sits in the line — between the hook or winch and the fixed point — and how the tension reaches the hand-held, the remote display and the register
The link sits inside the cleared area; the reader, the record and the register sit outside it.

Where does a wireless dynamometer fit, and what is it not?

A dynamometer is a load link: a steel body with a shackle at each end, a load cell inside and, in a wireless unit, a small radio that sends the force to a hand-held or a remote display instead of showing it on the body. Shackled between hook and test load, or between a winch line and a fixed point, it measures the tension in the line whatever direction the line runs.

That is the difference from a crane scale. A crane scale weighs a load hanging from a hook — vertical lifting and, in trade use, a stamped weight. Hindustan Scale Company’s CRH electronic crane scale does that job from 1 t to 10 t, with a jumbo display and a remote display up to 200 m. A dynamometer measures force in a line — vertical under a crane, horizontal on a winch pull, angled on a mooring check. HSCo’s HSC-Dynamometer series runs from 2 t to 100 t in ten capacities.

Three things a wireless dynamometer is not:

  • Not a trade-weighing instrument. Proof and pull tests are force measurement, not buying and selling, so a test dynamometer is judged by its calibration certificate, not a trade stamp.
  • Not the winch brake-render kit. That test uses a hydraulic jack on the drum. The dynamometer’s job on the mooring deck is the line-pull test, the bollard and fitting pull check, and the tension in a line that is actually holding.
  • Not the competent person. The decision to load-test, and the judgement on the result, stay with a competent person; the instrument gives that person a number to sign.

Why the number must come from a distance

When gear is loaded beyond its SWL for a test, the UK’s LOLER code lists the precautions: clear the area, keep only essential workers, and do the test “in an area where the consequences of failure are minimised”. India’s crane-safety code, IS 13367 (Part 1), gives the reason: under overload “the structure might buckle or collapse without warning”.

Lines are worse. The 2026 seafarers’ code tells a mooring party to “consider the entire area dangerous in the event of snap-back” and warns that a snatched rope “may be projected with lethal force”. On 02/03/2015 a deck officer on an LNG carrier was struck by a parted mooring line and suffered severe head injuries; the UK Marine Accident Investigation Branch found he had stood in an area assumed safe but within the snap-back zone.

Reading a display on the link means walking up to a loaded line. A wireless readout puts the reader where the rules already want him: outside the cleared area, with the number in his hand.

Competent person at the edge of a port test area attaching a printed test report to the lifting-gear register while the tested crane stands behind the barrier
The test is not done until the entry is made. At an Indian port the gear may not be used until the register carries it.

Winch and mooring checks are numbers, not judgements

Mooring is the clearest case. OCIMF’s Mooring Equipment Guidelines (fourth edition, 2018) set a winch brake to render — slip — at 60 % of the ship design minimum breaking load, so the brake, not the line, is the weak link. The vetting body RightShip repeats the setting, caps the brake at 80 % of the same base, wants the test repeated preferably every year and after any brake work, with the date, the tested force in tonnes or kN and the percentage marked on the winch.

The brake test uses a jack kit. But the pulls around it — a winch’s rated line pull, a bollard or fairlead check, what a line is really carrying — are dynamometer jobs, and they produce the figures the rules want kept: force, date, percentage.

One thing the rules do not say: no standard we could find requires a peak-hold function. IS 3177 requires the load to be lifted and sustained; the register needs the force held. Ask any supplier, HSCo included, how their unit stores a reading during a held load.

A force reading is only as good as its calibration

Force instruments are graded. India’s calibration method for force-proving instruments, IS 4169 (aligned with ISO 376), puts a class 1 instrument at 0.20 % repeatability and 0.10 % zero and interpolation error; class 2 at double those. Three rules from the same standard matter on site:

  1. The certificate expires — its validity “shall not exceed 26 months”. A link used on five-yearly tests may be running on a certificate that lapsed two tests ago.
  2. An overload voids it. An instrument that “sustains an overload higher than the test overload” must be recalibrated, so the highest force the unit has seen matters to the unit itself.
  3. Use it as it was calibrated — loaded in line, not sideways; the standard calibrates at 18–28 °C and asks for a correction elsewhere.

EURAMET’s calibration guide on force measurement (2022) adds the field’s own errors: temperature, end fittings, side loads from misalignment, jerking loads. Rig the link straight, load it smoothly, hold it steady, then read.

What changes on Monday morning

  1. The test load is a measured number, not a nominal one. 12.5 t on a 10 t hoist is 12.5 t on the record — inside the window the rules set, provably.
  2. Nobody stands at the line to read it. The hand-held is with the tester outside the cleared area.
  3. The record writes itself. Force, date and time go into the hand-held’s memory — up to 30,000 records with downloadable reports on HSCo’s unit — and from there to the certificate, with no copying step.
  4. The instrument’s own history is known — calibration date and highest load on file, so the reading can be defended five years later.

How to start: one test, thirty days

  1. Pick the next scheduled test — the crane due its twelve-month examination, the winch due its annual pull, the port sling set due its five-year test.
  2. Size the link for the test load, not the SWL. A 20 t crane is tested at about 25 t, so a 30 t dynamometer is the tool; HSCo’s range steps 2, 3, 5, 10, 15, 20, 30, 50, 75 and 100 t.
  3. Check the calibration certificate — date, class, capacity — before the gear is rigged.
  4. Clear the area, rig the link straight, read from outside the line. Hold the load; store the reading with the time.
  5. Download the report, attach it to the register — Form II at a port, the section 29 register in a factory — and compare with the last paper test: readings copied, hours of paperwork, people near the line.

Hindustan Scale Company has made weighing instruments in Mumbai since 1955 and builds the HSC-Dynamometer wireless series itself: 2 t to 100 t, read on a hand-held unit, a remote display up to 200 m or a jumbo display, about 40 hours on a charge — company figures. Indicative prices before GST run from ₹21,950 to ₹3,99,500 across the range. For weighing a lifted load rather than measuring a pull, see the crane scale range and the crane scale buying guide.

Frequently asked questions

What is a wireless dynamometer used for?

It measures the tension in a line — the force carried by a crane hook, a winch rope, a sling or a mooring line — and sends the reading to a hand-held unit or a remote display instead of showing it on the body. It is used for proof-load tests of cranes and lifting gear, winch line-pull tests, bollard and fitting pull checks, and any job where the force in a line has to be known and recorded.

How much test load does a proof-load test need?

The test window sits at 125 % of the safe working load, and never far above it. IS 3177:2020 asks for a minimum of 125 % for a new overhead crane; the US rule caps the test at 125 % unless the maker says otherwise; the UK seafarers’ code tapers it for heavy gear — 1.25 × SWL up to 20 t, SWL + 5 t up to 50 t, 1.1 × SWL above. The competent person in charge of the test sets the exact figure.

Do I need a crane scale or a dynamometer?

A crane scale weighs a load hanging from a hook and, in trade use, gives a stamped weight — HSCo’s CRH crane scales cover 1 t to 10 t. A dynamometer measures force in a line in any direction — vertical, horizontal or angled — and is the tool for proof-load, pull and tension tests. If the question is “how much does this weigh?”, buy the crane scale; if it is “how much force is this gear carrying?”, buy the dynamometer.

How long must a load-test record be kept in India?

At the ports, the Dock Workers Regulations 1990 keep the Form II register and its test certificates for at least five years after the last entry, and the gear may not be used until the entry and certificate are in place. In a factory, section 29 of the Factories Act requires a register of every twelve-monthly examination by a competent person. For comparison, the UK keeps the report for two years or until the next one.

Does a test dynamometer need Legal Metrology stamping?

Not for proof-load or pull tests — those are force measurement, not buying and selling, and the instrument is judged by its calibration certificate and accuracy class. Stamping becomes relevant only if the same unit is also used to weigh goods for sale.

How often should a dynamometer be calibrated?

Under IS 4169 (aligned with ISO 376) a force instrument’s calibration certificate is valid for at most 26 months, and the instrument must be recalibrated sooner if it takes an overload beyond its test overload. Check the certificate date and the unit’s highest recorded load before every test.

Next step

Tell us the next test on your calendar — crane, winch or sling set — and its safe working load, and we will propose the dynamometer capacity and a thirty-day recorded-test trial.

Hindustan Scale Company (HSCo) · Mumbai · est. 1955 · www.hindustanscale.com · hsc@hindustanscale.com

Sources

  1. Bureau of Indian Standards — IS 3177:2020 Electric Overhead Travelling Crane and Gantry Crane for all Applications — Code of Practice (third revision), clauses 64.2, 64.3.18 and 66.5.1.
  2. US OSHA — 29 CFR 1910.179 Overhead and gantry cranes, paragraph (k)(2) Rated load test.
  3. UK Maritime and Coastguard Agency — Code of Safe Working Practices for Merchant Seafarers, 2026 edition (published 20/03/2026), paras 18.28.9, 19.4.1–19.4.4, 26.3.2–26.3.3 and Table 19.2; MGN 332 (M+F) Amendment 4 (January 2026).
  4. The Factories Act, 1948 (India), section 29 — Lifting machines, chains, ropes and lifting tackles.
  5. Government of India — Dock Workers (Safety, Health and Welfare) Regulations, 1990, regulations 41, 47 and 51.
  6. UK Health and Safety Executive — L113 Safe use of lifting equipment: LOLER 1998 Approved Code of Practice and guidance (2nd ed., 2014), regulations 9(3), 10 and 11, Schedule 1 item 8(e), paras 282, 285 and 310.
  7. Bureau of Indian Standards — IS 13367 (Part 1):1992 Safe use of cranes — Code of practice, clauses 13.3, 14.2.2 and 14.4.
  8. UK Marine Accident Investigation Branch — Report 13/2017, failure of a mooring line on board an LNG carrier with one person injured (accident 02/03/2015; published 15/06/2017).
  9. Oil Companies International Marine Forum — Mooring Equipment Guidelines, 4th edition (MEG4), 2018; RightShip — What is render testing (vetting guidance, accessed 14/09/2026).
  10. Bureau of Indian Standards — IS 4169:1988 Method for calibration of force-proving instruments used for the verification of uniaxial testing machines (aligned with ISO 376), Table 2 and clauses 5.4.3.1, 6.3.2, 6.3.2.1, 7.1 and 7.4.
  11. EURAMET — Calibration Guide No. 4: Guidelines on the Uncertainty of Force Measurements, version 3.0 (February 2022), section 7.1.
  12. Mays J. A., Mathias P. C. — “Measuring the rate of manual transcription error in outpatient point-of-care testing”, Journal of the American Medical Informatics Association 26(3): 269–272 (2019); Paulsen A., Overgaard S., Lauritsen J. M. — “Quality of data entry using single entry, double entry and automated forms processing”, PLoS ONE 7(4): e35087 (2012).
  13. Hindustan Scale Company — HSC-Dynamometer Series and CRH Electronic Crane Scale product pages (read 14/09/2026); indicative prices, September 2026, before GST.