PRECIOUS METAL ASSAY LABORATORY

Introduction to Assaying

The assaying process is a necessary step to determine the quantity of precious metals present in an alloy.
Cupellation is one operation of the assay process in which a sample of gold, wrapped in lead foil, is melted in a special crucible known as a cupel: this cupel has the capacity of absorbing the non-precious metals contained in the gold alloy. The weight of the gold alloy sample is usually about 250/1000.
Although this is the most ancient method to determine the purity of an alloy, assaying by means of cupellation gives greater precision than more modern methods (fluorescent or x-ray spectrophotometry) and is considerably less expensive.

Laboratory lay-out

THE ASSAY LABORATORY

WEIGHING THE SAMPLE

ELECTRONIC ANALYTIC BALANCE TYPE ABT220

• Weight range : from 0 to 82 gr ( indicates up to five decimal figures )

• Weight range : from 0 to 220 gr ( indicates up to 4 decimal figures )

DRILLING OPERATION

BENCH DRILL TYPE TRB/A

• Max. capacity to drill : 10 mm

• Speeds : n°4

• Spindle speeds : 450/rpm

• Ground base dimensions : 230x270 mm

ANTI-VIBRATING TABLE TYPE TAV/A.

• Overall dimensions : 890x710x800 mm

• Weight : 76 Kg

CUPELLATION

CUPELLATION FURNACE TYPE FCOPP/A

• Max. working temperature : 1350°C

• Silicon carbide muffle : 155x205x80 mm

• Number of cupels : n°12 diam 25 mm

• Resistances : ceramic

• Power : 8.5 Kw

• Dimensions : 830x950x1850 mm

Consumables/spare parts for cupellation furnace

ANNEALING

MACHINE FOR THE TREATMENT OF CUPEL BALLS TYPE MSLR/B

• Power supply : three phase

• Total power : 1.5 Kw

• Water consumption : 1-2 lt/1’

• Dimensions : 750x450x1300 Kg

• Weight : 120 Kg

ACID ATTACK

SEPARATION HOOD TYPE CS/B

• Number of 6 place ovens : n°2

• Power : 4 Kw

• Dimensions : 1150x650x1820 mm

• Weight : 90 Kg

SCRUBBING OPERATION

NEUTRALIZATION TOWER FOR ACID FUMES TYPE TLF/500

• Power : 0.25 Kw

• Overall dimensions : 653x700x2165

• Weight : 65 Kg

Consumables for assay laboratory

Melting Dept

MEDIUM FREQUENCY INDUCTION MELTING FURNACE TYPE FIM/20TCPU

The furnace is ideal to melt precious metals. All ITALIMPIANTI ORAFI induction melting furnaces are fitted with static frequency converters.
A high efficiency of the electrical output that drastically reduces electricity consumption, maintaining the production rate, is obtained by the frequency conversion system used.
The modular construction of the electric circuit board greatly simplifies maintenance operations and guarantees high reliability even in the most demanding working conditions.
The highest technical standards used to design the inductors along with the modular construction and the use of only high quality materials guarantee maximum production even in the worst conditions.

Technical Data of the furnace

• Capacity of the crucible : 25 Kg of silver or 40 Kg of Gold
• Melting time : 20 minutes
• Interchangeability of the crucible to melt different precious metal alloys
• Mechanical tilting of the crucible using a reduction gear and handwheel
• Dimensions : 800x1300x1700 mm (LxWxH)

Technical data of the converter

• Power output : 20 kW
• Working frequency : 5 Khz
• Power-supply tension : threephase
• Power factor (cosF-i) : 0.9
• Required cooling power (generator/furnace) : 9000 Kcal/h
• Minimum water cooling capacity : 15 lt/min
• Min pressure for the cooling water pump : 3 Bars
• Cooling water inlet temperature : 30° + 35°C
⇒ The converter is fitted with a centrifugal pump to recycle the cooling water, fitted with a pressostat, thermals, fuses and a timer to automatically stop the pump. You require only a storage tank for demineralised water or a water cooling plant.
⇒ Display monitoring of the working parameters of converter as tension and absorbed power.
⇒ Computerised alarm diagnostics for as many as 12 alarms or warnings which the worker must take note of for the system to work properly. Instructions and advice are shown on the display.

⇒ Closed ring power regulation which allows the system to absorb the set power regardless of the quantity
and type of metal to melt.
⇒ The internal environment of the convertor is conditioned by an air-water exchanger
⇒ Threephase power-supply transformer :
• Nominal power: 20 KVA
• Nominal tension : depends on where the machines
• Allowed fluctuation of the electrical mains : +/- 10%

Spare parts & Accessories

Water chilling unit model FRIGO/51

These chilling units are ideal for all cases where it is important to keep the temperature of the cooling water within certain limits. Suggested uses are with :
• Water cooled induction melting furnaces
• Trichloroethylene degreasing machines
• Brazing belt furnaces
• Deoxidation furnaces
• Fumes condensors for hollowing and refining plants.

Technical characteristics

GRAIN PRODUCTION TANK TYPE RPG/E

The container is used both for the production of metal balls and of fine sand (dimensions : 1-2 mm3) used for refining.
It is made entirely out of stainless steel and is cylindrical in shape. It can be easily tilted to recover the grains. It is also fitted with a centrifugal pump to circulate the water as well as to empty the tank.

TECHNICAL DATA

• Power supply : three-phase
• Power : 0.4 Kw

• Capacity :150 lt

• Overall dimensions : 900x900x1200mm (length-width- height)

• Weight : 50 Kg

Aqua Regia Refining Dept

TUMBLER REFINING UNIT MODEL IAO/BR250

More Information On The Aqua Regia Process Click Here

Description

The aqua regia gold refining tumbler is a new technology compared to static refining plants.
This refining unit consists of one PPL tumbler with a total volume of about 400 litres, inclined to 30° and rotated by a motor, with the possibility to adjust the rotation speed. The rotation forces the gold grains to continuously rub against each other reducing the overall dissolution time.
External to the tumbler there is a Pyrex glass condenser to condense the acid fumes reducing their overall volume, thus resulting in a easier fume neutralization operation.
Another advantage is that it can work during the night without supervision.
The maximum daily quantity you can refine every day is 50 kgs of gold grains with a final gold purity of
999,5/1000 (minimum).
These rotating refining systems can refine gold grains as well as casting scraps and some types of precious ashes.
The plant is made up of :

• N.1 PPL tumbler with a total volume of about 400 litres

• N. 2 Graduated tanks for HCl and HNO3. Acid transfer from the reactors by vacuum.

• N. 2 Filter units on wheels with a compressed air diaphragm pump to transfer the solutions.

• N. 1 500 litre cementation uit.

• N. 1 Electrical board

Consumables

Accessories

NEUTRALIZATION TOWER FOR FUMES MODEL TLF/850

The tower is used to neutralize fumes and remove organic substances. It is built out of polypropylene sheets. A sprayer is installed inside the tower to spray a 1300 mm thick layer of raschig rings.
In order to avoid drop dragging, a second 310 mm thick layer of raschig rings has been placed upstream to the sprayer.
A neutralization solution container is placed beneath the tower. The solution circulation pump has a capacity of 55 Lts/1' with a head of 6 m. The suction fan has a max capacity of 2000 m3/hour.

Technical data:

• Power supply : three-phase.
• Power : 3 kW
• Overall dimensions : 1500x1200x3500 mm (length-width-height).
• Working weight : 350 kg

Water treatment Dept.

RESIN RECOVERY SYSTEM TO RECOVER TRACE PRECIOUS METALS

Pretreatment storage tank

This is tank where the waste waters are initially sent before the resin treatment process is started. It has a 2000 lt capacity and is connected to the resin unit. Fitted with :

• n.1 Pneumatic valve, PVC/EPDM, NC DN32-028

• n.2 Ball valves, PVC/EPDM, 546- DN32

• n.1 Pneumatic level regulator, PVC/EPDM, with flange DN100

• n.1 Centrifugal pump, threephase, 1.1 kW, PVDF, with PP base

• n.1 Valve 546-DN40

• n.1 PVC flowmeter, 1000 lt/hour

• n.1 Pressure gauge, 2.5 Bar, with trap

• n.1 Non-return valve, PVC/EPDM, DN15

• n.1 Pneumatic valve, PVC/EPDM, NC DN15-028

• n.1 Valve 546-DN15

Resin unit

The unit contains a series of selective resins to recover precious PGM and Au metals from the incoming solution.
Non precious metals ( Cu, Zn etc) pass through to the pre-treatment storage tank with the waste solution before proceeding to the neutralisation tank.
This unit can filter up to 400 lt per hour. Fitted with :

• n.3 Columns, 2 round bottoms DN300, 3 DN25 flanges, 1 DN100 handrail, PP nozzles

• n.1 Column resting base

• n.4 Pressure gauges with traps

• n.22 Valves 546-DN15

• n.1 Pneumatic valve 028 DN15

Storage tank

Post treatment PE storage tank, 2000 Lt capacity, with containment tank. Fitted with :

• n.1 Pneumatic pump, PP body with flow rate regulator

• n.1 Valve 546-DN25

• n.1 Non-return valve 303 DN25

• n.1 Pneumatic level control

ACID WATERS NEUTRALISATION PLANT MODEL IN/B

DESCRIPTION OF THE IN/B UNIT

This plant can be used to treat all types of acid water but in particular the solutions coming from the refining process as well as precipitating all non-precious metals in the form of hydroxides.
This plant consists of :

A) No. 1 1500 lts. capacity tank complete with agitator to stir the incoming solution.

B) n°1 Filter press type 440/50.

ƒ The filter press is used to filter water and slime in order to recover precious metals. The press is fitted with a 700 liters pneumatic pump. The components of the filter press, from the smallest to the largest, are single-block structures that are electrically welded, machined and carefully inspected; the design has allowed very low stress levels, even under maximum operating pressure.

ƒ The heads and longitudinal bars are plated with stainless steel or other metals depending on the
chemical properties of the solutions to be filtered.
ƒ The cloths, the shape and the dimensions of the plates, as well as the materials used inside the filter
elements, constitute the most important part of a filter press. The choice of these elements is the result of years of experience on the part of those who are familiar with these problems.
ƒ The pump is provided with an electronic level control probe for the automatic starting and
stopping of the plant.

ƒ The solutions exiting the filter press contain chlorides, nitrates and sodium sulphates that can be

concentrated or diluted with other waste waters.

Technical Data of the Filtering Press Unit :

ƒ Overall dimensions of the Filtering Press : Length= 4050 x Depth= 850 mm. x Height= 1300 mm.

FUMES NEUTRALIZATION PLANT TYPE TLF/960SC

Description

It consists of :
ƒ n. 1 scrubber diameter 960 mm Height 6000 mm complete with automatic Ph-meter; Level control;
density control
ƒ As these are diluted alkaline solutions, no safety tank is required for the liquid soda.
ƒ The 960 x 6000 scrubber has one 250 lt/min pumps with a head of 10 m and a 5000 m3/hr suction fan
ƒ H2N2 dosing device
The scrubbers are used to neutralise the acid fumes. They enter the scrubber from the bottom, filter through the raschig rings and exit. The neutralising solution of soda and water is sprayed onto the fumes from the top and middle parts of the scrubber neutralising them.
A pH meter checks the alkaline solution in the tank and, if necessary, opens a solenoid valve to add more liquid soda.

Ingot production

INDUCTION MELTING PLANT TYPE FIM/15LING

The furnace is used to produce no. 20 Au ingots 1 Kg per hour.

A high efficiency of the electrical output that drastically reduces electricity consumption, maintaining the production rate, is obtained by the frequency conversion system used.
The modular construction of the electric circuit board greatly simplifies maintenance operations and guarantees high reliability even in the most demanding working conditions.
The highest technical standards used to design the inductors along with the modular construction and the use of only high quality materials guarantee maximum production even in the worst conditions.

A. MELTING FURNACE FOR 1 KG INGOTS

The furnace is fitted with two special crucibles to melt 1 kg of Au each. Each crucible has its own protection burner to protect the crucible and metal from oxidation during melting.
The crucible is removed by a special pedal system which raises the crucibles from the botton allowing the worker to pick the up with the special pincers.
After melting, the gold is then manually poured into the 1 Kg ingot moulds.

B. INGOT SOLIDIFICATION CONTROL UNIT

This special unit consists of :
• Water cooled work table on which the ingot moulds are placed
• Ingot solidification control unit – fitted with photoelectric cells and timed propane gas burner

C. STATIC FREQUENCY CONVERTER

• Power output : 15 kW
• Working frequency : 10 Khz
• Power-supply tension : threephase
• Power factor (cosF-i) : 0.9
• Required cooling power (generator/furnace) : 10500 Kcal/h
• Minimum water cooling capacity : 20 lt/min
• Min pressure for the cooling water pump : 3 Bars
• Cooling water inlet temperature : 30° + 35°C

⇒ The converter is fitted with a centrifugal pump to recycle the cooling water, fitted with a pressostat,
thermals, fuses and a timer to automatically stop the pump. You require only a storage tank for demineralised water or a water cooling plant.
⇒ Display monitoring of the working parameters of converter as tension and absorbed power.
⇒ Computerised alarm diagnostics for as many as 12 alarms or warnings which the worker must take note of for the system to work properly. Instructions and advice are shown on the display.
⇒ Closed ring power regulation which allows the system to absorb the set power regardless of the quantity and type of metal to melt.
⇒ The internal environment of the convertor is conditioned by an air-water exchanger
⇒ Threephase power-supply transformer :
• Nominal power: 15KVA
• Nominal tension : depends on where the machines
• Allowed fluctuation of the electrical mains : +/- 10%

Ingot moulds for 1 kg Au

Water chilling unit model FRIGO/51

These chilling units are ideal for all cases where it is important to keep the temperature of the cooling water within certain limits. Suggested uses are with :
• Water cooled induction melting furnaces
• Trichloroethylene degreasing machines
• Brazing belt furnaces
• Deoxidation furnaces
• Fumes condensors for hollowing and refining plants.

Technical characteristics

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