Precious Metal Granulator

— Precious Metal Granulator: Melt Protection, Orifice Selection and a Declared Granule Specification

A precious metal granulator works in four stages — melting, protection, granulation, collection — set by three choices: protection method, pour size and granule cut. Metal is melted in a graphite crucible by medium-frequency induction, held to ±1 °C and protected by an inert-gas atmosphere of nitrogen or argon, or by a vacuum chamber. The melt leaves through a bottom nozzle or a multi-hole orifice plate and freezes in the circulating quench water; the granules are drained, dried, screened to the declared cut and weighed, with out-of-cut material returning to the melt. The output serves refining and sampling, alloy preparation for jewellery and bullion, and fast remelting, where free-flowing granules replace bars and offcuts in a casting charge. An inert-gas atmosphere is standard for high-purity gold and silver including Au99.99 and Ag99.99; vacuum suits complex K-gold alloys such as 14K and 18K. Units run from 2 kg to 10 kg per batch to refinery platforms at 50 kg to 300 kg, quoted by volume rather than by mass.

Product Overview

The granulator defined on this page is an induction melting and water-quench granulation unit. Metal or alloy is charged into a graphite crucible inside the machine, heated by a medium-frequency induction field to a controlled pour temperature that can reach 1,600 °C, held under an inert-gas atmosphere or under vacuum so that the surface does not oxidise, stirred electromagnetically so that the melt is homogeneous, and then released through a multi-hole orifice plate or breaker plate directly into a circulating water tank. The melt breaks into droplets at the plate, the droplets freeze within a fraction of a second in the water, and the result is a bed of solid granules that is lifted out, dewatered, dried, graded on a sieve set and weighed.

Everything about that sequence is a controlled variable, and the machine exists to control it. The melt temperature and the time at temperature decide whether the alloy is homogeneous. The atmosphere or the vacuum decides whether the granule surface is bright or blackened. The orifice geometry, the metal head above the plate and the pour temperature together decide the droplet mass. The water temperature, the water depth and the circulation decide whether the droplet freezes as a discrete granule or lands on the one before it and fuses into a clump. The sieve set decides what the customer receives. When a plant reports that granules stick together, that granules come out as tails or teardrops, that the batch colour varies from the previous batch, or that the size drifted after a plate change, the report is always about one of those five variables, and a machine bought with a declared specification for each of them is a machine whose defects are diagnosable.

Two positions in the flowsheet, one machine. A granulator earns its place in two different parts of a precious-metal plant, and both of them are legitimate. On the input side it prepares metal for dissolution: an alloy or doré block granulated into a high-surface-area form dissolves markedly faster in acid parting than the same metal presented as a solid block or a thick plate, which shortens the leach cycle and improves the fineness of the resulting gold because the silver has been able to leave the metal. On the output side it produces the finished saleable form: purified metal granulated into graded granules, dried, weighed and packed, either sold as granules or transferred to a vacuum ingot caster as a pre-weighed charge. The brief for this page fixes both positions, because the same machine serves both, and the difference between them is the feed form and the sieve cut, not the machine.

What decides the purchase. Four variables decide the configuration, and three of them are decided by the buyer’s own material rather than by the machine. The first is the largest actual pour. This is a volume question, and it is the single most common specification error in the category, because a crucible rated at a mass of one metal gives a different mass of another: at 19.3 g/cm³ for gold, 10.49 g/cm³ for silver and 8.96 g/cm³ for copper, one litre of crucible volume holds about 19.3 kg of gold, about 10.5 kg of silver or about 9.0 kg of copper. A machine sized on a silver pour will be undersized the first time the same crucible is loaded with gold. The second is the alloy list, because formulation work needs electromagnetic stirring and because oxidation-sensitive K-gold alloys need vacuum protection. The third is the protection method, which follows from the surface specification rather than from the price list. The fourth is what the granules feed: a remelt and sampling duty tolerates a two-tier sieve set and a lift-out basket, while a continuous production duty justifies a platform configuration with a larger quench system and an in-line discharge.

Capacity bands. The machine family runs from a compact laboratory and small-workshop class at the low single-figure kilogram scale, through a production class in the tens of kilograms per pour, to a platform class that reaches the tens to hundreds of kilograms per pour for continuous granule production. The band that matters is the one your largest real pour falls into, verified per metal and by volume, because the capacity that has to be engineered is the capacity of the quench loop at that pour. Exceeding the quench capability rather than the melting capability is what produces clumped batches, and it is the failure that a nominal capacity figure always hides.

Protection: atmosphere or vacuum. The rule is stated plainly because it is a specification line with a real cost attached. A protective inert-gas atmosphere, nitrogen or argon, is the standard duty for high-purity gold and silver, including Au99.99 material, because those metals are oxidatively stable at pour temperature and the gas blanket is sufficient to keep the granule surface bright. A vacuum chamber is specified where complex K-gold and formulated jewellery alloys have to be held under strict oxidation control, because those alloys contain elements whose oxides are not acceptable in the finished granule and because the vacuum also removes dissolved gas from the melt before it is released. The decision is made from the surface acceptance criterion in the buyer’s own specification, not from a preference for the more impressive configuration.

What the machine is not. This is the granulation unit, and it does not own the melting-furnace selection, the refining chemistry, the electrolysis step or the ingot-casting line. Those are separate engineered items in the same plant. The furnace chosen upstream decides the melt rate and the maximum charge; the granulator described here takes the melt from the point where protection begins and owns everything from the protected release to the dried, graded, weighed granule. Where a plant already has a melting furnace, the granulation unit is bought on its own; where the plant is starting from metal powder, sponge or crystal, the two are bought as a pair and the interface is the pour temperature and the pour size.

Records, not just output. Every batch is logged. The set-point and the actual temperature trace, the time at temperature, the pour temperature at release, the protection state, the quench-water temperature at the start and at the end of the pour, the plate or nozzle fitted, the sieve result and the dried weight are recorded against a batch number, and the batch ticket travels with the sealed drum. That record is what makes a granule specification verifiable later, and it is the reason a buyer can reconcile a customer complaint about size or surface with the run that produced the material.

Product Core Selling Points

It is a melting machine with a protection decision built in, not a tank that catches metal. Medium-frequency induction in a graphite crucible, up to 1,600 °C, with the melt held under an inert-gas atmosphere or a vacuum before release, so the granule surface is bright and the inside is pore-free instead of oxidised and gassy.
The granule size is a specification, not a guess. Orifice plates are supplied as a per-metal kit, and the delivered size is declared as a sieve cut with a size distribution, an oversize limit and an undersize limit attached, so a refinery can plan batching and weighing instead of sorting after the fact.
Batch capacity is quoted as a pour volume, which is the only honest way to quote it. The same crucible holds about 1.84 times more gold than silver and about 2.15 times more gold than copper, so the machine is sized from the largest real pour rather than from a marketing maximum.
The quench loop is engineered from the metal’s heat content. Roughly 0.21 MJ of heat enters the water per kilogram of gold poured, 0.34 MJ per kilogram of silver and 0.66 MJ per kilogram of copper, and the tank, pump, weir and chiller are sized to hold the water window for the whole pour rather than for the first thirty seconds.
Pour control can be free-flowing or plug-released. A self-flowing orifice suits single metals and straightforward alloys; a stopper-rod release suits alloy work where the pour has to start and stop under control and the melt has to be stirred immediately before it is released.
Temperature is closed-loop with a stated accuracy. The PID loop holds the set point to ±1 °C and runs a ramp-and-soak programme, which is what makes alloy colour repeatable from batch to batch instead of negotiable.
The power supply is built for campaign duty. All-solid-state IGBT with an ultra-low-voltage induction coil and a machine self-protection layer, rated for full-load operation across a working day rather than for a demonstration.
It closes the loop on undersize instead of writing it off. Granules below the declared cut are returned to the next melt as a recorded recycle fraction, so the material balance is closed on paper as well as in the tank.
Acceptance is witnessed, sampled and retained. A test pour on the buyer’s own alloys, a sieve sample, a sealed retained sample and a quench-loop hold check are part of delivery, and the warranty clock starts at site acceptance.
The granular form is a legitimate finished product, not an intermediate compromise. Granules are an accepted feed form for bar casting and an accepted saleable form in their own right, and they dissolve faster than a solid block when the same metal goes to acid parting.

Application Scenarios

Precious metal refinery finishing line. Granulation is placed after the purification step and before bar casting, so that the purified metal leaves the wet side in a form that can be weighed, sampled and remelted without a second handling step. The granule becomes the refinery’s own buffer stock, held as weighed, assayed, sealed drums rather than as bars that have to be re-cut for a part order. Output: graded granules with a batch ticket.
Jewellery alloy and K-gold workshop. Formulated gold alloys are melted, stirred to uniform colour and granulated, which converts a variable melt into a uniform, repeatable feedstock for the casting bench. The colour of a K-gold granule batch is decided by the homogeneity of the melt before release, so electromagnetic stirring is a specification item rather than a convenience. Output: uniform-colour alloy granules.
Sampling and assay office. Granules are the easiest precious-metal form to sample representatively. A granulated batch can be split, quartered and subsampled without cutting, drilling or milling, and the retained sample is a sealed granule aliquot that is chemically identical to the delivered material. Output: sealed reference sample per batch.
Feed preparation before acid parting. Alloy, doré and bullion that will be dissolved in aqua regia or parted with nitric acid is granulated first so that the acid reaches the whole mass quickly instead of working inwards from a block face. The gain is a shorter leach cycle and better silver removal from gold-rich metal. Output: high-surface-area dissolution feed.
Pre-weighed charge for a vacuum ingot caster. The ingot caster takes a pre-weighed charge of granules or raw material, so the granulator is the weighing and batching station upstream of the bar line. Granules meter into a mould more accurately than offcuts or powder and they carry no flux into the caster. Output: weighed, mould-ready charge lots.
Silver refinery after reduction or electrolysis. Silver recovered by chemical reduction or drawn from the electrolytic cell is melted and granulated to convert an irregular powder or crystal product into a dense, dust-free, saleable granule form. Dense granules do not dust the way dried powder does, which changes the housekeeping and the metal account. Output: dense silver granules, dust-free handling.
Copper and copper-alloy granulation. Copper and copper-rich alloys are granulated for downstream melting, alloying and sampling duty, including anode and alloy preparation where a uniform feed particle size improves the melt-down behaviour in the furnace that follows. Output: sized copper and alloy granules.
Laboratory and pilot plant. Small pours of experimental alloys and small lots of high-value metal are granulated so that each trial is held as a discrete, weighable, sealed lot with a recorded composition, which keeps development work auditable. Output: discrete trial lots with records.
Plant metal account and security. Granules can be weighed to a finer resolution and reconciled more tightly than bars, so plants that handle high-value metal use granulation as part of their metal-accounting routine: the inventory is counted in weighed and sealed drums, and the batch ticket closes the mass balance between the charge and the delivered product. Output: reconciled inventory by weight.

Applicable Raw Materials

The machine is specified for gold, K-gold and formulated gold alloys, silver and its alloys, and copper and copper alloys. Feed form matters much less than feed chemistry, because the machine melts whatever is charged and the granule inherits the composition of the melt; what the feed form changes is the charging practice, the melt-down time and the amount of dross that has to be skimmed before the pour.

Purified gold powder and sponge. Reduced gold powder and sponge from a wet purification route is charged directly once it has been washed neutral and dried. The fineness of the granule is the fineness of the sponge; granulation adds nothing and removes nothing. Charging dried sponge in a single compacted charge rather than in successive scoops keeps the melt-down time repeatable and reduces the amount of powder that reaches the extraction system. Output: gold granules at the charged fineness.
Cemented and precipitated silver. Silver produced by chemical reduction or by cementation arrives as a fine, reactive, easily dusted product. It is charged as a compacted load, melted under protection, and granulated into a dense granule that cannot dust. The change from powder to granule is where the metal-account loss in this part of the plant normally disappears. Output: dense silver granules.
Electrolytic crystal and cathode product. Silver crystal drawn from an electrolytic cell is a high-purity, coarse, free-flowing feed that charges cleanly and melts quickly. Because the crystal is already at high fineness, the granule is a direct repackaging of the cell product into a weighed, sealed, customer-ready form. Output: high-fineness granule from cell crystal.
Doré and alloy bullion. Doré bars and alloy buttons are granulated so that they can be sampled and dissolved efficiently. Where the metal is an alloy of gold with a substantial silver content, granulation is the step that lets the acid parting solution reach the silver, and it is the reason the parting can be completed in a shorter cycle with better resulting gold fineness. Output: dissolution-ready alloy granules.
High-purity gold and silver bullion. Metal already at Au99.99 or Ag999 fineness is melted and granulated when the customer wants a granule product rather than a bar, or when the plant wants a pre-weighed charge for the caster. No alloying element and no flux is introduced during granulation, so the granule carries the fineness of the metal charged and nothing else. Output: Au99.99 and Ag999 granules.
K-gold and formulated jewellery alloys. Karat gold and formulated alloys are the material that most often justifies vacuum protection, because the oxides of the base-metal additions are not acceptable in the finished colour and because the alloy has to be homogeneous before it is released. The alloy list is supplied at enquiry, and the orifice kit and the recipe are set per alloy family. Output: homogeneous, correctly coloured alloy granules.
Copper and copper-rich alloys. Copper is granulated for alloy preparation and for sampling duty, and its higher heat content per kilogram is what sets the quench-water requirement for any configuration that has to run copper as well as gold and silver. Output: sized copper granules.
Anode offcuts, sprues and process returns. Runners, sprues, blanking offcuts from anode preparation and consolidated process returns are re-melted and granulated so that they re-enter production as a sized, weighed, recorded feedstock rather than as an unmeasured scrap pile. Output: recycled granules with a batch record.
NOT the right feed. Granulation is not a comminution step. It does not crush, shred, mill or sort metal, and it is not a wire or cable granulator. It handles metal that can be melted in a crucible, and material that cannot be melted in a crucible belongs to a different process upstream.

Finished Products

The product of the machine is a declared granule specification and a sealed drum with a batch ticket. Every item below is part of what is delivered, and each one is a statement a purchaser can inspect rather than an adjective.

Gold granules. Solid, bright, pore-free gold granules, at the fineness of the metal charged, in the sieve cut declared for the order. The form is an accepted feed for bar casting and an accepted saleable form in its own right; a granule batch is also the easiest form in which to hold a refinery’s working inventory, because it can be weighed to a fine resolution and reconciled against the batch record. Output: gold granules at the charged fineness.
Silver granules. Dense silver granules in the declared cut, produced from reduced silver, cell crystal or bullion. Granulation converts a material that is notorious for dusting into one that can be handled, weighed and shipped without a housekeeping penalty, and the density and the dust-free handling are the reason silver granulation is often justified on the metal account alone. Output: dense, dust-free silver granules.
K-gold and alloy granules. Alloy granules with a uniform colour across the batch, produced under the protection method the alloy requires. Colour uniformity is a release criterion, not a marketing claim, which is why the melt is stirred electromagnetically before the pour is released. Output: colour-uniform alloy granules.
Copper and alloy granules. Sized copper-bearing granules for remelting and alloying duty, supplied in the declared cut. Output: sized copper granules.
The declared sieve cut. The primary size specification: the cut that the delivered material falls in, stated as a range with the sieve set that defines it. The cut is set by the orifice plate fitted and the quench conditions held, and it is agreed before the order rather than discovered on delivery. Output: material inside a declared cut.
The size distribution. A granule batch is not one size. The distribution of the delivered material across the sieve set, with the percentage passing and the percentage retained on each cut, is issued with the batch, because batching, metering and customer acceptance all follow the distribution rather than the nominal size. Output: a distribution statement per batch.
A declared oversize and undersize fraction. The percentage of granule material above the top cut and below the bottom cut is a quantity, not a defect, and it is stated. The oversize fraction is returned for remelt; the undersize fraction is returned to the next melt as a recorded recycle quantity, so nothing leaves the metal account. Output: stated oversize and undersize fractions.
A retained reference sample. A sealed, labelled aliquot taken from the delivered batch, held by both parties, which is the sample that settles a dispute about fineness or size later. The sample is chemically identical to the delivered material rather than representative of a different part of the melt. Output: sealed retained reference sample.
A dried, weighed and sealed product. Granules are dewatered, dried, weighed to a recorded figure and packed into sealed drums, so the receiving plant takes delivery of a mass rather than an estimate. Moisture content after drying is stated, because entrained moisture becomes a weighing dispute in a metal that is bought by mass. Output: dried, weighed, sealed drums.
The batch ticket and record. A complete batch record: charge weight, feed identity, alloy, set-point and actual temperature trace, time at temperature, protection state, pour temperature, plate fitted, quench-water temperatures at the start and the end of the pour, sieve result, dried weight and the reconciliation between the charge and the product. Output: batch record issued to both parties.
Fineness verification on request. A granule batch can be assayed by the buyer’s own method, and the granule form makes that straightforward because a granule sample can be dissolved completely and quickly. The usual release route is a combination of the supplier’s assay, the buyer’s independent assay and the retained sample, so that the delivered fineness is supported by two measurements rather than one. Output: assayed and double-checked fineness.
Dry, flux-free granules suitable for bar casting. No flux and no cover salt is introduced by the process, so the granule is a clean charge for a vacuum ingot caster or for a remelt furnace. Where the granules will become bars, the bar is delivered against its own grade specification — for example the London Good Delivery minimum fineness of 995.0 parts per thousand for gold, or the Shanghai Gold Exchange one-kilogram grade at a minimum of 99.99 % gold — and the granule is the weighed intermediate that the caster charges to reach it. Output: charge-ready granules for the bar line.
NOT a delivered product. The machine does not deliver ingots, bars, anode plates or finished jewellery. Bar casting and mould filling belong to the ingot-casting line, and the granule is the charge those lines consume.

Precious Metal Smelting Machine Process Flow

The nine stages below are the machine’s own working cycle, from the point where the feed is characterised to the point where the crucible has been changed and the machine is ready for the next campaign. Each stage has a failure mode attached to it, and each failure mode is a specification item rather than an operator’s discretion.

Precious metal granulator process flow — nine stages from the assay that fixes the pour volume to a machine reloaded and ready for the next campaign, with the protection state, the quench loop and the sieve result carried through the batch record.

Steps 1 — Feed Assay and Pour-Volume Sizing. The feed is identified and assayed, and the proposed pour is converted into a volume rather than a mass. Gold at 19.3 g/cm³, silver at 10.49 g/cm³ and copper at 8.96 g/cm³ give three different masses in the same crucible, so one litre of crucible volume holds about 19.3 kg of gold, 10.5 kg of silver or 9.0 kg of copper, and the crucible, the orifice kit, the quench volume and the chiller duty are all fixed from that volume. The alloy list and the surface requirement are confirmed at the same time, because they decide the protection method. Output: fixed pour volume, alloy list and protection method.

Steps 2 — Crucible Charging and Melt-Down. A graphite crucible is seated and the charge is loaded in the pattern that suits the feed form: compacted powder and sponge are charged as a single load to keep the melt-down repeatable and to keep powder out of the extraction system, while crystal, granules, offcuts and bullion are charged in stages as they sink. Minimum load and maximum fill are both respected, because a part-loaded crucible changes the melt geometry and a crucible filled above the safe line risks metal over the rim when the first gas is released. Output: a correctly loaded crucible at the start of the melt.

Steps 3 — Atmosphere or Vacuum Protection Build-Up. The working headspace is closed and the protection is established before the metal reaches the temperature at which it would oxidise. On the atmosphere configuration, nitrogen or argon displaces air and the flow is held through the pour; on the vacuum configuration, the chamber is pumped down so that the melt is also degassed before release. This is the stage that decides whether the granule surface comes out bright or blackened, and it is recorded as a state rather than assumed. Output: a melt under a verified protective state.

Steps 4 — Alloy Homogenization by Electromagnetic Stirring. Once the charge is fully molten the melt is stirred electromagnetically for a controlled period. Stirring is what makes a K-gold or formulated alloy the same colour at the top of the pour as at the bottom, and it is what prevents the segregation that otherwise only shows up as an inconsistent batch days later. On single-metal duty the same loop shortens the time needed to equalise the melt temperature. Output: a homogeneous melt at a uniform temperature.

Steps 5 — Pour-Temperature Verification and Stopper Release. The pour is released only when the melt has reached the pour temperature and held there through the soak. The PID loop holds the set point to ±1 °C, which is what makes the pour temperature a repeatable number rather than a judgement. Release is either free-flowing through the orifice or controlled by a stopper rod; where the alloy needs it, the head above the plate is stabilised before the release opens, because the metal head is one of the variables that decides droplet mass. Output: release at a verified pour temperature and head.

Steps 6 — Orifice-Plate Granulation into the Quench Tank. The melt passes through the multi-hole orifice plate or breaker plate and breaks into droplets that fall directly into the circulating water tank, where they freeze into discrete granules. Droplet mass is set by the orifice diameter, the metal head, the pour temperature and the melt’s own surface tension and density; whether the droplet ends up as a discrete granule or as a tail or a clump is decided in the same instant by the water temperature, the water depth at the impact point and the circulation under the plate. The plate or nozzle fitted is recorded against the batch. Output: solidified granules in the quench bed.

Steps 7 — Granule Dewatering, Drying and Sieve Grading. The granule bed is lifted clear of the tank, dewatered on a screen, dried and graded on the sieve set that defines the declared cut. The grading produces three streams: the delivered cut, the oversize fraction that returns for remelt, and the undersize fraction that returns to the next melt as a recorded recycle quantity. Drying is a specification step rather than a housekeeping step, because residual moisture becomes a mass dispute in a metal sold by weight. Output: graded, dried granule fractions.

Steps 8 — Granule Quality Verification and Retained Sample. The batch is verified against the declared specification: the sieve result against the agreed cut and distribution, the surface condition against the brightness requirement, the colour uniformity on alloy duty, the moisture content after drying, and the dried weight against the charge. A sealed, labelled retained sample is taken from the delivered fraction and held by both parties. Any batch that fails the size or surface criteria is returned to the next melt rather than downgraded quietly. Output: verified batch and sealed retained sample.

Steps 9 — Quench-Loop Recovery, Crucible Change and Reset. The quench water is recovered, filtered and returned to the loop, with the make-up volume recorded, and any granule fines carried in the water are recovered from the filter rather than left in the circuit. The crucible is inspected and changed on its own wear record, the orifice plate is inspected and replaced when its bore has worn, the headspace, seals and protection lines are checked, and the machine is reset with the next recipe loaded. The batch record is closed and issued. Output: closed batch record and a machine ready for the next campaign.

Product Structure (Main Equipment)

The granulation unit is supplied as a set of assemblies, each of which is specified against the pour rather than against a catalogue frame. The list below is the equipment set; the capacity, connected load and installed footprint are engineered per configuration and issued in the general arrangement drawings.

Melting and containment

Graphite crucible and crucible seat. The crucible is graphite, sized by the pour volume fixed in Steps 1, and it sits in a seated, replaceable arrangement so that a crucible change is a planned maintenance activity rather than a rebuild. The crucible’s load line and minimum load are marked, because under-filling and over-filling are both granulation defects, not just melting defects.
Induction coil and refractory surround. The coil is wound around the crucible with an insulation layer between coil and crucible, energised by the medium-frequency power supply and cooled by the same water loop as the power electronics.
Furnace chamber and sealed headspace. The chamber closes over the crucible to contain the protection atmosphere or to hold the vacuum, and it carries the seal, the observation or inspection provision, and the extraction connection. The headspace seal is the component that decides whether an atmosphere configuration actually keeps its atmosphere over a pour.

Heating and protection

Medium-frequency induction power supply. An all-solid-state IGBT power supply, rated for full-load duty across a working day, with an ultra-low-voltage induction coil arrangement and a machine self-protection layer that covers over-current, over-voltage, over-temperature, coolant fault and earth fault.
Protection-gas train. Regulator, flow measurement, purge sequence and the line into the headspace, sized for nitrogen or argon and set per alloy. Gas consumption per batch is declared for the chosen configuration.
Vacuum package on the vacuum configuration. Chamber, pump set, sealing arrangement, vacuum measurement and pump-down sequence, with the vacuum state interlocked to the heating programme so that the melt cannot be released before the specified pressure is reached.
Electromagnetic stirring. A stirring coil or the main coil driven in a stirring mode, with a defined stirring period in the recipe, so that homogenisation is a programmed step rather than an operator’s habit.

Release and granulation

Free-flow orifice head. The self-flowing release: the melt leaves through the orifice plate under its own head, which suits single metals and straightforward alloys and gives the simplest repeatable pour.
Stopper-rod release on the plug-released configuration. A stopper rod opens and closes the outlet under control, which suits alloy work where the pour has to start and stop, and where the melt is stirred immediately before the release is opened. Stopper rods are a consumable with a declared service life.
Multi-hole orifice plate and breaker plate, with the per-metal orifice kit. The plates are supplied as a kit covering the metals and the cuts in the order, because the bore that suits gold does not suit silver and does not suit copper. Bore wear is a named inspection point on the maintenance schedule, because a worn bore is the most common cause of a size drift that nobody can explain.
Pour tundish and droplet path. The short, heated path between the plate and the water surface, arranged so that the droplet leaves the plate cleanly, the metal head stays stable, and there is no place for a cold slug of metal to hang and later break off as a tail.

Quench and recovery

Circulating quench-water tank. The tank holds the water bed, the settled granule, and the circulation pattern that governs whether droplets freeze discretely or fuse. Tank volume is sized from the heat-load calculation for the largest pour, not from the nominal machine size, and the water depth at the impact point is a controlled dimension.
Quench-loop pump, weir and heat-exchange interface. The pump and the weir hold the circulation pattern, and the chiller or heat-exchanger interface holds the water window across the whole pour. Flow, level and temperature are interlocked with the pour so that a cooling fault stops the release rather than ruining the batch.
Granule lift-out or drag discharge. The tank discharge lifts the granule bed clear of the water so that the bed is not left standing wet, which is both a handling matter and a corrosion matter on water that has been through a hot metal pour.
Quench-water filtration and fines recovery. A filter or settling arrangement downstream of the tank recovers the granule fines that the quench inevitably produces, so that fines return to the metal account instead of leaving in the bleed stream.

Dewatering, grading and control

Dewatering screen and drying provision. Screen dewatering followed by a drying step, which exists because the delivered product is sold by mass and residual moisture is a weighing dispute.
Sieve set for the declared cut. The sieve set defines the cut and produces the distribution statement, the oversize return stream and the undersize recycle stream.
Control cabinet and recipe system. PID temperature control to ±1 °C with a ramp-and-soak programme, protection-state sequencing, stirring period, quench-loop supervision, the alarm and interlock layer, and per-alloy recipes so that a repeat batch needs a recipe selection rather than a re-derivation.
Batch record and data log. The record template that captures charge weight, temperature trace, time at temperature, protection state, pour temperature, plate fitted, quench-water temperatures, sieve result, dried weight and the reconciliation, issued as a batch ticket with the sealed drum.

Product Features

Protection is established before it is needed. The atmosphere or the vacuum is built up and verified before the melt reaches oxidising temperature, so the protection window covers the whole of the hot period rather than the pour alone.
The pour temperature is a number with an accuracy attached. Closed-loop PID control to ±1 °C on a ramp-and-soak programme, which is what makes alloy colour and droplet behaviour repeatable between batches.
Two pour-control philosophies, chosen by duty. Free-flowing release for single metals and simple alloys, stopper-rod release for alloy work that needs a controlled start and stop and a stir immediately before release.
Granule size as a delivered specification. A per-metal orifice kit and a declared sieve cut with a distribution, an oversize limit and an undersize limit, so the size is a purchase term rather than an outcome.
The quench loop is sized from the metal, with the heat load stated. About 0.21 MJ per kilogram of gold, 0.34 MJ per kilogram of silver and 0.66 MJ per kilogram of copper reach the water, and the tank, pump, weir and chiller are sized at the largest pour on that basis.
Undersize is a recycle stream, not a write-off. Granules below the cut return to the next melt as a recorded quantity, and fines recovered from the quench water return to the metal account.
Campaign-rated power electronics. An all-solid-state IGBT supply with an ultra-low-voltage coil and a self-protection layer, built for full-load operation across a working day.
Homogenisation before release. Programmed electromagnetic stirring, which is the mechanism behind uniform alloy colour and the reason a batch is not judged by its top surface.
Dry, weighed, sealed delivery. Dewatered, dried and weighed granules in sealed drums with a batch ticket, so the receiving plant takes a mass and a record rather than an estimate.
Documented as built, not as catalogued. Crucible size, plate kit, chamber arrangement, tank volume, circulation duty, chiller interface, electrical supply, extraction connection and utility interfaces are engineered to your alloy list, pour volume and cut, and are issued with the drawings.
Verification built into delivery. A witnessed test pour on the buyer’s own alloys, a sieve sample, a sealed retained sample and a quench-loop hold check are part of acceptance, and the warranty clock starts at site acceptance.

Technical Parameters And Specifications

The engineering parameters below are the standard design basis for a machine in this family and are the numbers that decide granule quality. They are published as fixed values. Where a figure depends on the buyer’s own material — batch capacity, connected electrical load, installed footprint, gas consumption, chiller duty and installed utility flows — the machine is engineered per configuration, the calculation behind the figure is issued with the design package, and the resulting value appears on the general arrangement drawings rather than in this table.

Precious metal granulator — technical parameters and specifications.

Parameter	Specification
Product class	Precious metal granulator: an induction melting and water-quench granulation unit that converts molten gold, silver and copper-bearing metal into uniform, high-density granules
Working principle	Medium-frequency induction melting in a graphite crucible, with the melt held under protection and released through a multi-hole orifice plate or breaker plate into a circulating water quench
Applicable metals	Gold, K-gold and formulated gold alloys, silver and silver alloys, copper and copper alloys
Metal fineness handled	Up to Au99.99 and Ag999 feed in powder, sponge, crystal, granule, offcut and bullion form
Heating method	Medium-frequency induction heating of a graphite crucible, with an insulation layer between coil and crucible
Power electronics	All-solid-state IGBT power supply with an ultra-low-voltage induction coil arrangement and a machine self-protection layer
Duty cycle	Rated for full-load operation across a working day
Maximum working temperature	1,600 °C
Temperature control	Closed-loop PID with a ramp-and-soak programme
Temperature control accuracy	±1 °C at the set point
Pour temperature	Set per metal and per alloy from the recipe; recorded at release for every batch
Melt homogenization	Programmed electromagnetic stirring with a defined stirring period per recipe
Melt protection — standard duty	Inert-gas atmosphere, nitrogen or argon, contained by a sealed headspace and held through the pour
Melt protection — oxidation-sensitive duty	Vacuum chamber with a pump-down sequence and an interlock that prevents release before the specified pressure is reached
Protection selection rule	Protective atmosphere is the standard duty for high-purity gold and silver including Au99.99 material; vacuum is specified where complex K-gold and formulated alloys require strict oxidation control
Melt release control	Free-flowing release through an orifice plate, or stopper-rod controlled release on the plug-released configuration
Granulation element	Multi-hole bottom orifice plate or breaker plate, supplied as a per-metal orifice kit; bore wear is a scheduled inspection point
Granule size determination	Set by the orifice bore, the metal head above the plate, the pour temperature and superheat, and the quench water conditions, all held within the recipe
Granule size specification	Declared as a sieve cut, issued with a size distribution across the sieve set and with stated oversize and undersize limits
Granule form	Solid, discrete, pore-free granules with a bright surface when the protection state and the quench conditions are held
Quench medium	Circulating water in a tank, with the water depth at the impact point held as a controlled dimension
Quench water control	Water temperature, depth and circulation held within the declared window for the whole pour, with flow, level and temperature interlocked to the release
Quench heat load	About 0.21 MJ per kilogram of gold, 0.34 MJ per kilogram of silver and 0.66 MJ per kilogram of copper, from pour temperature to a cooled granule
Quench water demand basis	About 2.5 litres of water per kilogram of gold at a permitted 20 K rise in the loop, about 4.1 litres per kilogram of silver and about 7.9 litres per kilogram of copper; tank, pump and chiller are sized at the largest pour on this basis
Pour-volume reference	One litre of crucible volume holds about 19.3 kg of gold, about 10.5 kg of silver or about 9.0 kg of copper, so the same crucible holds about 1.84 times more gold than silver
Granule removal	Lift-out basket or drag discharge from the quench tank, so the bed is not left standing in the water
Dewatering and drying	Screen dewatering followed by drying, with moisture content after drying included in the release criteria
Grading	Sieve set producing the delivered cut, an oversize return stream for remelt and an undersize recycle stream for the next melt
Fines recovery	Quench-water filtration recovering granule fines back into the metal account rather than into the bleed stream
Capacity	Engineered per configuration: the crucible, orifice kit, quench volume, circulation and chiller duty are sized to your largest actual pour, verified per metal by volume and issued with the calculation
Capacity classes	Compact laboratory and small-workshop class at the low single-figure kilogram scale, production class in the tens of kilograms per pour, and platform class in the tens to hundreds of kilograms per pour, all quoted as pour volume per metal
Connected electrical load	Engineered per configuration; the load figure is issued with the electrical drawing at order confirmation
Electrical supply	380 V, three-phase, 50/60 Hz as standard; other supplies quoted on request
Cooling	Water-cooled induction coil and power supply, on a closed-loop quench and cooling circuit with a chiller or heat-exchanger interface
Installed footprint	Engineered per configuration, including the crucible change envelope, the granule handling area and the operator access required for a pour
Protection gas consumption	Declared per batch for the selected configuration; consumption is part of the configuration proposal rather than a standard figure
Compressed air	Required for actuation and purge where the configuration uses it; consumption declared per configuration
Fume and dust control	Sealed headspace with an extraction connection to the plant fume system, so charging dust and pour fumes are captured at source
Effluent	Quench water is circulated and made up rather than discharged; the bleed stream and the filter residue are routed to plant water treatment and to the metal account respectively
Control system	PID temperature control, protection-state sequencing, stirring period, quench-loop supervision, alarm and interlock layer, and per-alloy recipe storage
Safety interlock layer	Over-current, over-voltage, over-temperature, coolant flow and level, protection-gas or vacuum loss, quench-loop fault and emergency stop
Batch record	Charge weight, feed identity, alloy, temperature trace, time at temperature, protection state, pour temperature, plate fitted, quench-water temperatures at the start and end of the pour, sieve result, dried weight and mass reconciliation
Consumables	Graphite crucible, orifice plates or nozzles, stopper rods and gaskets; service life and unit price are declared per configuration because both follow the alloy and the superheat
Output verification on delivery	Witnessed test pour on the buyer’s alloys, sieve sample against the declared cut, sealed retained sample, protection-state check and quench-loop hold check
Output fineness	Carries the fineness of the metal charged; granulation introduces no alloying element and no flux
Delivered product form	Dried, weighed granules in the declared cut, packed in sealed drums with a batch ticket
Documentation issued	General arrangement drawings, orifice kit schedule, material certificates, electrical documentation, operating and maintenance manual, consumable schedule and the batch record template
Warranty basis	24 months from site acceptance, with consumables excluded and the spares list released before the warranty clock starts

Technical Advantages

The pour is sized by volume, and the calculation is stated. The most expensive specification error in this category is a machine sized on a mass figure printed for one metal. Gold at 19.3 g/cm³, silver at 10.49 g/cm³ and copper at 8.96 g/cm³ mean that one litre of crucible volume holds about 19.3 kg of gold, about 10.5 kg of silver or about 9.0 kg of copper, so the same crucible carries about 1.84 times more gold than silver. This machine is quoted from the largest actual pour, converted to volume and verified per metal, and the conversion is issued with the proposal so that the buyer can check it.

The quench loop is engineered from the metal’s heat content, not from the frame. Every kilogram of pour carries a calculable quantity of heat into the water: about 0.21 MJ for gold, 0.34 MJ for silver and 0.66 MJ for copper between the pour temperature and a cooled granule. At a permitted 20 K rise in the loop that is roughly 2.5, 4.1 and 7.9 litres of water per kilogram respectively. The tank volume, the circulation, the weir and the chiller interface are sized at the largest pour on that basis, which is why the machine holds its water window for the whole pour and why clumping is a specification question rather than an operator’s bad luck.

Granule size is delivered as a specification with a distribution behind it. Most published figures in this category are a bare size range. A granule batch is not one size, so the delivered specification states the cut, the distribution across the sieve set, the oversize limit and the undersize limit. That is what allows a plant to weigh, meter, batch and sell the material, and it is why the sieve set is part of the machine rather than a laboratory afterthought.

The protection decision is stated as a rule. The atmosphere configuration is the standard duty for high-purity gold and silver, including Au99.99 material, because those metals are oxidatively stable at pour temperature. The vacuum configuration is specified where complex K-gold and formulated alloys need strict oxidation control and where dissolved gas has to be removed before release. Stating the rule allows the buyer to decide from the surface acceptance criterion rather than from the equipment list, and it prevents the two most common waste cases: paying for a vacuum package on bullion duty that does not need it, and buying an atmosphere machine for an alloy that will blacken in it.

The pour control matches the duty. A free-flowing orifice gives the simplest repeatable release for single metals and simple alloys. A stopper-rod release gives a controlled start and stop and allows the melt to be stirred immediately before release, which is what alloy work needs. Neither is presented as the better option, because the correct choice follows from whether the shop is running bullion or formulation.

Undersize and fines are returned to the metal account. The machine produces three size streams and a filtered water stream. The delivered cut ships, the oversize returns for remelt, the undersize returns to the next melt as a recorded recycle quantity, and the fines captured from the quench water return to the account. In a metal that is bought by mass, closing those loops on paper is the difference between a granulation line that reports its yield and one that reports a mystery.

Acceptance is witnessed and the sample is retained. A test pour on the buyer’s own alloys, a sieve sample against the declared cut, a sealed retained sample held by both parties and a quench-loop hold check are part of delivery rather than an optional extra. The warranty period starts at site acceptance, which means the clock starts when the machine has been shown to work on your metal rather than when it left the works.

Documentation is issued as built. Crucible size, orifice kit schedule, chamber arrangement, tank volume, circulation and thermal duty, chiller interface, electrical supply, extraction connection and utility interfaces are engineered to the buyer’s alloy list, pour volume and declared cut, and are issued with the drawings. There is no catalogue model number to hide behind, and no marketing capacity figure that expands and contracts between pages.

The machine is built for campaign duty, and it is maintained as an asset. All-solid-state IGBT power electronics, an ultra-low-voltage coil arrangement and a self-protection layer support full-load operation across a working day. The consumable items that follow from that duty — graphite crucible, orifice plates, stopper rods and gaskets — have declared inspection points and declared service lives, so the running cost of the machine is a schedule rather than a surprise.

The granular form is a legitimate output, not a compromise. Granules are an accepted feed form for bar casting and an accepted saleable form in their own right. They weigh more accurately than offcuts, they meter better than powder, they dust far less than dried powder, and they dissolve faster than a solid block when the same metal goes forward to acid parting. For a refinery that holds working inventory between the wet side and the bar line, that combination is the reason the machine pays for itself outside the casting schedule.

Service Process

Step 1 — Requirement Review and Feed Assay. The alloy list, the feed forms, the target granule cut, the largest actual pour, the site services available and any downstream constraint are reviewed together, and the feed is assayed or the buyer’s assay is reviewed so that the configuration is designed against real material rather than a generic duty.

Step 2 — Configuration Proposal and Pour-Size Verification. The pour is converted from mass to volume per metal, and the crucible size, orifice kit, chamber arrangement, protection method, quench volume, circulation duty, chiller interface and extraction connection are proposed on that basis. The calculation behind the capacity, connected load and footprint figures is issued with the proposal so that it can be checked.

Step 3 — Orifice Kit and Alloy Trial Definition. The orifice kit and the cut to be delivered are fixed, and the trial pours to be run at acceptance are defined: which metals, which alloys, which cut, and which acceptance criteria the batch has to meet. This is the stage where the granule specification becomes a contractual term rather than an expectation.

Step 4 — Manufacture, Factory Test and Witnessed Test Pour. The machine is built to the issued drawings and factory-tested, including the witnessed test pour on the buyer’s alloys or on agreed reference metals, a sieve result against the declared cut, a quench-loop hold check and a protection-state check. The factory result becomes the reference against which the site acceptance test is compared.

Step 5 — Shipment, Installation and Commissioning. The machine ships with the documentation package, is installed to the general arrangement drawing, and is commissioned against the site services — electrical supply, cooling circuit, protection gas, compressed air where applicable, extraction and the quench-loop water. The commissioning record states the as-installed utilities and the as-commissioned set points.

Step 6 — Operator Training and Site Acceptance Test. Operators are trained on the pour sequence, the protection sequence, the recipe system, the sieve procedure, the batch record and the alarm response, and the site acceptance test is run on the buyer’s own alloys against the criteria fixed in Step 3.

Step 7 — Spares Release and Warranty Registration. The spares list — graphite crucible, orifice plates, stopper rods and gaskets — is released with unit prices and service lives before the warranty clock starts, and the warranty is registered from the site acceptance date rather than from the shipment date.

Step 8 — Preventive Maintenance and Consumable Supply. A preventive maintenance schedule covering crucible wear, orifice bore wear, headspace seals, protection lines, quench-loop condition, filter condition, temperature-loop calibration and interlock testing is issued, and consumables are supplied against the declared service lives and the recorded duty.

Warranty And After-Sales Service

The machine carries a twenty-four month warranty from site acceptance. The start date matters, and it is stated deliberately: a warranty that runs from shipment begins expiring while the machine is on a ship and in a warehouse, and the interval between shipment and commissioning is precisely where the disputes in this equipment category are born. On this machine the clock starts when the site acceptance test has been passed on the buyer’s own alloys, which is also the date on which the spares list, the as-commissioned set points and the batch record template have been handed over.

What the warranty covers. Manufacturing defects in the machine structure, the induction coil and its insulation, the power supply, the chamber and its sealing arrangement, the release mechanism, the quench tank and its circulation system, the control cabinet and the interlock layer, and the sieve set. Also covered are the engineering parameters the machine was sold on: the maximum working temperature of 1,600 °C, the temperature control accuracy of ±1 °C at the set point, and the ability of the quench loop to hold its water window across the declared pour, each verified against the acceptance test record.

What the warranty does not cover. Consumables, which wear by design and are supplied against their declared service lives: the graphite crucible, the orifice plates and nozzles, the stopper rods and the gaskets. Nor does it cover damage from feed outside the agreed alloy list, from operation above the declared pour volume or maximum temperature, from protection gas or vacuum not being available, from cooling water outside the specified condition, from unauthorised modification, or from the site failing to carry out the preventive maintenance schedule.

Consumables, honestly specified. Crucible and orifice-plate life both follow the alloy, the superheat and the duty cycle, so a single life number would be misleading. The service life and the unit price for each consumable in the buyer’s configuration are declared at order stage, and the machine is supplied with a starting spares set — crucible, orifice kit covering the ordered metals, stopper rods and gaskets — so that the first months of operation do not depend on an air freight.

Spares, drawings and documentation. A general arrangement drawing, the orifice kit schedule, the material certificates, the electrical documentation, the operating and maintenance manual, the consumable schedule and the batch record template are issued with the machine. The as-built documentation is what allows a second unit to be ordered, the machine to be duplicated, or a line to be extended in a later phase without re-deriving the design.

Technical support and remote assistance. Commissioning support, operator training and process advice on the pour recipe, the protection sequence, the quench window and the sieve procedure are available from the works. Remote support over the machine’s control and inspection provisions is used for the first production campaigns, which is where the recipe usually needs its final tuning to the plant’s own water and alloy.

Process support on the granule specification. Where a batch does not meet its declared cut or its surface criterion, the support route is diagnostic rather than persuasive: the batch record is read for pour temperature, protection state, plate fitted and quench-water temperatures, and the deviation is located in the machine’s variables. The declared acceptance criteria are what makes that diagnosis possible rather than an argument.

Change of alloy or cut over the life of the machine. The recipe system and the per-metal orifice kit allow a subsequent change of alloy or granule cut to be handled by a recipe and a plate change with a re-verification run, rather than by a replacement machine. Additional orifice plates and support on the re-verification are supplied on request.

Frequently Asked Questions

What is a precious metal granulator?

A precious metal granulator is an induction melting machine that converts molten gold, silver or copper-bearing metal into uniform, high-density granules. Metal is melted in a graphite crucible by medium-frequency induction at temperatures up to 1,600 °C, held under an inert-gas atmosphere or under vacuum so that the surface does not oxidise, stirred electromagnetically so that the melt is homogeneous, and released through a multi-hole orifice plate or breaker plate directly into a circulating water tank. The droplets freeze into discrete granules, which are lifted out, dewatered, dried, graded on a sieve set and weighed.

How do I size a precious metal granulator for my pour?

Size it on your largest actual pour, converted to volume and verified per metal, plus your alloy list, the protection method your surface specification demands and what the granules feed next. The family runs from a compact laboratory and small-workshop class at the low single-figure kilogram scale, through a production class in the tens of kilograms per pour, to a platform class in the tens to hundreds of kilograms per pour, and the number that must be engineered is the capacity of the quench loop at your largest pour. A machine sized on a nominal mass figure rather than on a verified pour volume is the most common specification error in this category.

Why does the same crucible hold less gold than the figure on the plate?

Because a crucible is a volume, and the mass it holds depends on the density of what is poured into it. Gold is 19.3 g/cm3, silver is 10.49 g/cm3 and copper is 8.96 g/cm3, so one litre of crucible volume holds about 19.3 kg of gold, about 10.5 kg of silver or about 9.0 kg of copper, and the same crucible carries about 1.84 times more gold than silver. A machine rated on its silver pour will be undersized the first time the same crucible is loaded with gold, and that is why this machine is quoted as a pour volume per metal.

Should I choose inert gas or vacuum protection?

Choose from the surface acceptance criterion in your own specification. A protective inert-gas atmosphere of nitrogen or argon is the standard duty for high-purity gold and silver, including Au99.99 material, because those metals are oxidatively stable at pour temperature and the gas blanket is enough to keep the granule surface bright. A vacuum chamber is specified where complex K-gold and formulated jewellery alloys need strict oxidation control, because the base-metal oxides are not acceptable in the finished colour and because the vacuum also removes dissolved gas from the melt before release.

How is the granule size decided?

Granule size is decided before the pour, by the orifice bore, the metal head above the plate, the pour temperature and its superheat, and the melt’s own surface tension and density, and then held by the quench conditions. Because the size follows from the machine settings rather than from the frame, the delivered size is issued as a declared sieve cut with a size distribution across the sieve set and with stated oversize and undersize limits. Bore wear on the plate is a scheduled inspection point, because a worn bore is the usual cause of a size drift that appears for no obvious reason.

What does the granule specification include?

The cut, the size distribution across the sieve set as percentages passing and retained on each cut, a declared oversize fraction and a declared undersize fraction, the surface condition against the brightness requirement, colour uniformity on alloy duty, the moisture content after drying, and the dried weight reconciled against the charge. Every one of those items is recorded on the batch ticket that travels with the sealed drum, so that the specification can be checked after delivery rather than only at the machine.

Why do granules stick together or come out as tails?

Granules stick together when the quench cannot take the heat it is being given: the water is too warm, the bed is too shallow at the impact point, the circulation under the plate is too weak, or the release rate is too high for the water volume. They come out as tails or teardrops when the droplet leaves the plate badly: the pour temperature is too low, the metal head is unstable, the bore is worn or partly blocked, or the droplet path is too long. Both are diagnosed in the same order, from pour temperature to protection to plate to quench, and the batch record carries the readings needed to do it.

How is the quench loop sized?

From the heat the metal brings with it. Every kilogram of pour carries a calculable quantity of heat into the water: about 0.21 MJ for gold, 0.34 MJ for silver and 0.66 MJ for copper between the pour temperature and a cooled granule. At a permitted 20 K rise in the circulating loop that is roughly 2.5 litres of water per kilogram of gold, about 4.1 litres per kilogram of silver and about 7.9 litres per kilogram of copper. Tank volume, circulation, the weir and the chiller interface are sized at the largest pour on that basis, because clumping is a water-system failure at maximum batch rather than a melting failure.

What is the difference between a granulator and a melting furnace?

The furnace produces the melt and owns the melt rate, the maximum charge and the alloy chemistry; the granulator owns everything from the protected release onwards — melt protection, pour control, granulation, quench, dewatering, grading and the batch record. Where a plant already has a melting furnace the granulation unit is bought on its own, and where a plant is starting from powder, sponge or crystal the two are bought as a pair. The interface between them is the pour temperature and the pour size, which is why both are fixed at enquiry.

Can one granulator run gold, silver and K-gold?

Yes, with a per-metal orifice kit and a recipe per alloy, because the bore that suits gold does not suit silver and does not suit copper, and because the alloy determines whether the protection has to be a vacuum. The machine is rated by pour volume so that each metal is charged at the volume, not at the mass, and the quench loop is sized on the largest heat load in the metal list, which is usually copper rather than gold or silver.

What happens to the undersize granules?

They return to the next melt as a recorded recycle quantity rather than being written off or quietly blended. Undersize is one of three size streams the machine produces, alongside the delivered cut and the oversize fraction that goes back for remelt, and the granule fines carried in the quench water are recovered on a filter and returned to the metal account as well. In a metal bought by mass, closing those streams on paper is what lets the plant report a yield instead of an estimate.

How much metal is lost during granulation?

Granulation itself introduces no alloying element and no flux, so the granule carries the fineness of the metal charged. The losses that do occur are oxidative loss, which is what the inert-gas or vacuum protection exists to prevent, and handling dust, which is why the headspace is sealed and connected to extraction and why the quench loop is filtered. The loss for a batch is measured rather than asserted: the charge weight is reconciled against the dried, graded granules and the recovered fractions, and the reconciliation is part of the batch record.

How do I verify granule quality on delivery?

By a witnessed test pour on your own alloys or on agreed reference metals, followed by a sieve sample checked against the declared cut and distribution, the surface condition checked against the brightness requirement, the moisture content after drying, the dried weight, a sealed retained sample held by both parties, and a quench-loop hold check at the maximum pour. The machine parameters the unit was sold on are verified in the same session: the maximum working temperature, the temperature control accuracy at the set point, and the quench loop’s ability to hold its water window across the pour.

What consumables does it use and how often are they changed?

The graphite crucible, the orifice plates or nozzles, the stopper rods on the plug-released configuration, and the gaskets. Both crucible and plate life follow the alloy, the superheat and the duty cycle, so a single life figure would be misleading and is not published as one: the service life and the unit price for each consumable in the buyer’s configuration are declared at order stage, the machine is supplied with a starting spares set, and crucible and plate condition are scheduled inspection points on the maintenance plan.

Does the granulator replace ingot casting?

No, the two are complementary and they produce different things. Granules are a legitimate finished form, easier to weigh, meter, sample and dissolve than offcuts or powder, and they are the accepted pre-weighed charge for a vacuum ingot caster. Bars are the delivery form for the grades that require it, such as the London Good Delivery minimum fineness of 995.0 parts per thousand for gold or the Shanghai Gold Exchange one-kilogram grade at a minimum of 99.99 % gold. A plant usually owns both: granulate to produce a weighed, assayed, sealed stock, then either sell the granules or feed the caster.

What power supply and utilities does it need?

A 380 V three-phase supply at 50 or 60 Hz as standard, with other supplies quoted on request. The machine needs a closed-loop cooling circuit for the induction coil and the power supply with a chiller or heat-exchanger interface, a circulating quench-water loop with make-up, a connection for nitrogen or argon on the atmosphere configuration or a vacuum package on the vacuum configuration, compressed air for actuation and purge where the configuration uses it, and an extraction connection to the plant fume system. The connected electrical load, installed footprint, gas consumption and utility flows are engineered per configuration and issued with the drawings.

What is the warranty and when does it start?

Twenty-four months from site acceptance. The start date is deliberately tied to site acceptance rather than to shipment, because the interval between a machine being shipped and being commissioned is exactly where warranty disputes begin. Consumables are excluded because they wear by design, and the spares list with unit prices and service lives is released before the warranty clock starts. The machine parameters the unit was sold on — the 1,600 °C maximum working temperature, the temperature control accuracy of ±1 °C at set point, and the quench loop holding its window across the declared pour — are verified against the acceptance test record at the start of the period.