Manual-Acid Digestion Vessel

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MANUAL/Manual Acid Digestion Vessels Page 1 of 10

Instruction Manual for

Acid Digestion Vessels

Designers & Manufacturers

High Pressure Lab-Autoclaves, Pressure Leaf filters & sparkler Filter Press

(An ISO-9001 Certified Company)

6, PARMAR INDUSTRIAL ESTATE,

BEL BAZAR, KURLA (W),

MUMBAI400 070. INDIA.

Tel. : (91)

22

2512 9273 / 6755 3029 / 28

Fax:- : (91) - 22 2510 95 65

Email :- amarequip@ amarequip.com

Website :-http:///www.amarequip.com


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INDEX

SR. NO. PARTICULARS PAGE NO.

1.0 INSTALLATION OF AUTOCLAVE 32.0 SAFETY PRECAUTIONS BEFORE STARTING 33.0 WARRANTY CLAUSE 34.0 SCOPE 45.0 PREVENTIVE MAINTENANCE 46.0 ASSUMPTION OF RISK 57.0 NATURE OF PTFE 58.0 POTENTIAL HAZARDS 69.0 SAMPLE SELECTION 710.0 PRESSURE & TEMPERATURE LIMITS 811.0 OPERATING PROCEDURE 912.0 SETTING UP THE VESSEL FOR USE 1013.0 TROUBLE SHOOTING & REMEDIES 1014.0 HYDROSTATIC TEST CERTIFICATE 1115.0 SUPPLIED SPARES LIST 1216.0 SPECIFICATION WORK SHEET 13


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1.0 INSTALLATION OF THE VESSEL:

We thank you very much for selecting anAMAR product & wish you all the very best to get the

maximum out of our vessel. Kindly go through the manual thoroughly before using the vessel to ensure

efficient & safe working with longer life. Also read the trouble shooting chapter & warranty clause carefully

before making any call.

First unpack the vessel completely (if packed in a wooden crate). The vessel is already in assembled

condition. Fix the vessel position on a leveled surface. The vessel should be placed in a room with adequate &

effective ventilation. It is preferable to have a hood with an exhaust fan over the vessel. This is the most

effective arrangement to vent off any accidental leakage of hazardous gases. Any parts or equipment given

separately should be bolted or mounted as instructed during the trials or read the respective headings in the

manual.

2.0 SAFETY PRECAUTIONS BEFORE STARTING:

2.1The area of operation should be well ventilated.2.2There should be no open flames in adjacent areas.2.3A continuous watch should be kept on reactions which are (i) Exothermic (ii) Involving highly reactive

compounds such as Acetylene, Ethylene Oxide, Oxygen etc. (iii) dealing in flammable gases.

2.4Chemicals of corrosive nature with material of construction of autoclave should not be used in thisapparatus.

3.0 WARRANTY CLAUSE:

The apparatus is warranted for 12 months from the date of supply for any bad workmanship or any

defective materials. The warranty does not include the parts that are subjected to constant wear due to

running i.e, teflon beaker, rupture disc etc. However, if any damage is done to the equipment by (i)

mishandling (ii) using corrosive chemicals (iii) carrying out explosive / out of control reactions (iv) failure due

to non-compliance with the instructions mentioned in the manual. or (v) Any subsequent design

modifications carried out without our permission. M/s. AMAR EQUIPMENTS PVT. LTD. will not be held

responsible/liable for this damage or injuries. Parts / Material which are irreparable at site under


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warranty may have to be sent at our works for repairs / replacement. Any free replacement if necessary

shall be given only after inspection of the faulty part / material.NOTE :

1) Check the work order sheet enclosed to see the specification of vessel & optional accessories ordered &supplied to you.

2) Whenever the word optional is attached to any part or items, it means the item shall be provided only ifordered optionally. These items do not form part of standard equipment.

3) The specification & rating of the autoclave & material of construction : All the internal & external wettedparts of the autoclave shall be as per your purchase order, our specification work order sheet & our

quotation unless specified.

4) P. No. : Part No. from drawing enclosed.5) Refer nozzle orientation plan to locate the desired valve / nozzle.

4.0 SCOPE :

These instructions are to acquaint the user with the procedures to be followed and the precautions to be

taken when using Acid Digestion Vessel, PTFE-lined digestion vessels provide a convenient means for dissolving

analytical samples rapidly in strong acids or alkalis, it is important that the user understand the capabilities and

limitations of the equipment and will be well aware of the safety precautions to be observed in its operation. The

user should read these basic instructions carefully before starting to use any of these vessels It must be

understood that the excellent mechanism for sample digestion and dissolution provided by these vessels can be

hazardous if a vessel is misused. Therefore, careful reading and full compliance with these instructions must be

observed in all applications.

5.0 PREVENTATIVE MAINTENANCE:

Periodic cleaning may be performed on the exterior surfaces of the instrument with a lightly dampened

cloth containing mild soap solution. There are no user serviceable parts inside the product other than what is

specifically called out and discussed in this manual.


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6.0 ASSUMPTION OF RISK:

Amar Equipment Pvt. Ltd. offers its PTFE-lined Acid Digestion Vessels to skilled analytical chemists

as an attractive means for digesting and dissolving analytical samples for analysis. Amar designed and

manufactures these vessels to be as effective as possible when used within the limitations prescribed l. But,

since the pressures generatedwithin these vessels are solely dependent upon the nature of the materials

being treated, the filling level and the amount of heat applied to promote the reaction, Amar will not be

responsible for personal injuries or damage to the vessel, to the oven or to other equipment resulting from

the use of these vessels. As with all laboratory operations, the user must assume responsibility for and

institute safety procedures to protect all personnel from any hazards associated with this equipment. Rigidcontrols must be established to guarantee that the operator does not overcharge or overheat the vessel.

7.0 THE NATURE OF PTFE:

PTFE offers such unique inertness and high temperature usefulness that it is an obvious choice as

the material of construction for lining these acid digestion vessels. PTFE does, however, have two

characteristics which make it somewhat less than perfect for this application, and the user who understands

these deficiencies will be able to minimize the effect upon their work. First, PTFE has a tendency to creep orflow under pressure or load. This tendency is present even at room temperature and it is accentuated at

higher temperatures. At operating temperatures above 150C the creep effect will become more

pronounced, making it more difficult to maintain tight seals & resulting in deformation and shorter life for

the PTFE components. The extent of the creep effect will be roughly proportional to the maximum

operating temperature. Secondly, PTFE is a porous material. Although the materials and designs used in

Amar Acid Digestion Vessels minimize the effects of this porosity, users of these vessels can expect to see

evidence of vapor migration across the cover seal and through the wall of the liner itself.

The thick walls and long path seals used in vessel liners also help to overcome these undesirable

properties. Experiments have shown that the amount of solute lost in this manner during a normal digestion

is negligible, but vapor migration will occur and frequently it will be sufficient to produce noticeable

discoloration on the inner metal wall of the vessel body and the screw cap


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8.0 POTENTIAL HAZARDS:

While many thousands of these vessels have been used safely and routinely for treating a great variety of

samples with different digestion media under a broad range of operating conditions, it is possible to create

conditions under which these vessels will explode. The bulk of the reported incidents of this type have been

caused by failure of the operator to recognize one or more of the following potential hazards.

8.1 Excessive temperature: - When a vessel is overheated, two factors come into play: (1) the vapor

pressure of the materials in the vessel increases exponentially with temperature and (2) the strength of the

materials from which the vessel is made falls off (again exponentially) if the vessel is heated above its maximum

temperature limit. Dangerous overheating can be produced by ovens with defective temperature controls, by

water baths boiling dry or by operator inattention or carelessness.

8.2 Excessive Pressure: -Excessive Pressure can be produced not only by overheating, as but also from

uncontrolled gaseous reactions and from high pressure vapor pressure or explosive materials, otr from overloading

the vessel.

8.3 Excessive loading: -When organic materials are treated in these vessels, they may liberate gases as

well as heat. Since the PTFE liner is an excellent thermal insulator, this internal heat will be translated into

higher internal temperatures and pressures. The loading limits prescribed for these vessels are purposely

conservative to ensure that the energy released from the sample will not over-stress the vessel. The user must

also remember that when a water-based solution is heated to 250C it expands to fill a space approximately 25

percent larger than its volume at room temperature. If there is insufficient vapor space in the vessel to

accommodate this expansion, the tremendous hydrostatic pressure which will be generated will destroy the

vessel.

8.4 Explosive materials: -The nitro compounds produced when nitric acid reacts with certain organic

materials may have explosive properties capable of destroying the vessel, even when present in quantities well

within the normal recommended charging limits. Consider, for example, what might happen if nitroglycerin

were produced by reactions in the vessel. For this reason, fats, fatty acids, glycerin and similar materials must

not be treated with nitric acid in these vessels and cellulosic materials must not be treated with mixed nitric

and sulfuric acids. Similarly, because of its unpredictable nature, perchloric acid must not be used in these

vessels.


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9.0 SAMPLE SELECTION

9.1 Inorganic materials: -Most inorganic digestions proceed smoothly without unusual hazards, using not morethan 0.5 grams in the 100 ml vessel size. As in all reactions, the vessel must never be completely filled as there

must always be vapor space above the surface of the charge. To be sure that there is adequate free space, the

total volume of the charge must never exceed two thirds (66%) of the capacity of the cup when working with

inorganic materials. By observing these limits and taking precautions to prevent overheating, there should be no

unusual hazards in treating inorganic samples with mineral acids.

Ores, rock samples, glass and other inorganic materials can be dissolved in acid digestion vessels using

strong mineral acids: HF, HCl, H SO, HNO, Aqua Regia and others. Digestion times for these materials can vary

anywhere from 2 hours to several days. Ordinary glass materials (SiO) will mandate the use of HF, sometimes in

combination with HCl, or aqua regia. Temperatures in the range of 100 to 150C are routinely used. Alumina is

routinely digested using 10% sulfuric acid. Temperatures used for these samples are typically in excess of 200C. It

is advantageous, from the standpoint of minimizing the digestion time, to reduce the sample to granular or

powder form prior to digestion. The increase in surface area of the sample has a significant impact on the reaction

with the digestion aid.

9.2 Organic materials: - Many organic materials can be treated satisfactorily in these digestion vessels but

careful attention must be given to the nature of the sample and to possible explosive reactions with thedigestion media. In all cases, the size of the sample and the amount of oxidant used must be carefully

controlled. For nitric acid digestions (Carius decompositions) of organic compounds, the dry weight of

organic matter must not exceed 0.5 gram in the 100 ml size. Notice that both minimum and maximum

amounts of acid are specified. If the sample contains less than the specified maximum amount of dry

organic matter, the amount of nitric acid must be reduced proportionately.

As stated above, fats, fatty acids, glycerin and similar materials which form explosive compounds in an

intermediate stage must not be treated with nitric acid in these vessels. Digestions involving other organic

materials must also be handled cautiously since it is impossible to list all of the potentially dangerous

combinations which might arise. For best protection, the user and their supervisor should study each reaction

carefully before proceeding to use the digestion vessel or any other pressure vessel, asking such questions as: Is

the reaction exothermic? What intermediate and final products might be produced and what will be their

behavior?


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When working with new or unfamiliar materials it is always advisable to run preliminary experiments

using small samples and observing the behavior of the reactants carefully. Organic samples are typicallytreated with concentrated nitric acid. Nitric - sulfuric mixtures are not recommended for digesting organic

samples due to the possibility of forming potentially unstablereaction products. Digestion with perchloric

acid can be dangerous, for the same reason, and must not be used. Typical heating times range from 1 to 8

hours. Temperatures in the 150 to 200C range are generally quite effective.

10.0 PRESSURE AND TEMPERATURE LIMITS

Maximum working pressures for each acid digestion vessel as shown in work sheet and orders. Extreme

care must be exercised to ensure that pressures do not exceed these prescribed limits. The user must

understand that in acid systems the solubility of gases as NO, HCL and SO will be reduced as the temperature

rises, having the effect of adding non-condensable gas to the vapor phase in a closed vessel. As a result, the

amount of acid present, the acid concentration and the free head space above the liquid will all have a

bearing on the pressure developed in a closed vessel. Free head space must therefore be provided in all

procedures, and the volume and concentration of the acid must be held to a minimum.

Maximum operating temperatures for each acid digestion vessel are shown in the individual listings. But

these limits must be used cautiously because, with certain acids, pressures higher than the allowable limit will

be generated if the vessel is heated to the listed maximum temperature.


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11.0 OPERATING PROCEDURE:-

Part No. Item Name Material Qty.

1. Body S.S. 316 1 No.2. Bottom False S.S. 316 1 No.3. Head S.S. 316 1 No.4. Body Clamp S.S. 316 1 No.5. Compression Ring EN8 1 No.6. Body Clamp Bolt H.T. 6 Nos.7. Rupture Disc S.S. 316 1 No.8. Beaker Cap PTFE 1 No.9. Beaker PTFE 1 No.10. Locking Plate S. S. 304 1 No.


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12.0 SETTING UP THE VESSEL FOR USE

12.1To open the Vessel:

Loosen the clamp bolts (P. No. : 6) in criss cross fashion with spanner provided & then unlock the

latches. Remove the two half sections of body clamp (P. No. : 4), the head (P. No. : 3) can be lifted out from

the body (P. No. : 1). Remove teflon beaker cap (P. No. : 8). Place the head (P. No. : 3) Carefully on proper

location. Charge the vessel as required. Do not fill more than 66% of the filling capacity.

12.2 Closing the vessel for operation:

First examine whether all fittings and teflon beaker are in good condition and correct position. If

body teflon cap has extruded into a thin edge around the inside and outside diameters, remove the

extruded portion with a sharp knife. Tighten the clamp bolts in a criss-cross pattern. Always keep the vessel

upright during assembly and closing operations. There must always be adequate free space above the charge

in the Vessel.

Place the vessel in a temperature controlled oven and follow the heating and cooling

procedure after digestion, allow the vessel to cool to ambient temperature on an aluminum plate or a

metal table top. It is not good practice to cool the vessel in cold water or in a freezer. The internal

forces will sometimes distort the liner, making it difficult to remove the liner from the vessel body.

Usually the liner can be dislodged by pressing the uncovered vessel against a brass.

13.0 TROUBLE SHOOTING & ITS REMEDIES:

SR.

NO.PROBLEM CAUSE SOLUTIONS

Leakage Problem

1. Leakage from body clamps Clamp bolt loose. Tighten them.

Other Problems

1.Pitting / Corrosion of wetted

parts

Chemicals / Acids corrosive to MOC

used

Use special MOC suitable to those

chemicals.

Documents

Manual-Acid Digestion Vessel