Buchi K-424 Operation Manual

1

Digestion Unit K-424

Contents

Contents

Read these instructions thoroughly before you use the
Digestion Unit K-424. Store these instructions in the im­mediate vicinity of the apparatus so that they may be consulted
at any time.
The unit must only be connected to the mains and switched
on after having completed all necessary preparations.

Chapter 2 contains important safety information. Knowledge
of this is imperative for the safe operation of the Digestion
unit.

Subject to technical change without notice. No part of these
instructions may be reproduced in any form whatsoever or
processed, reproduced or disseminated by means of
electronic or optical systems without the express written
permission of Büchi Labortechnik AG. All rights reserved.
Copyright © Büchi Labortechnik AG 2008

en, Version E Order No.

K-424 Operating instructions 96711

1 Scope of delivery 2

2 Safety 3

2.1 Symbols 3

2.2 Requirements for the operator 3

2.3 Regulation use 3

2.4 Non-regulation use 3

2.5 General hazards 4

2.6 Safety measures 4

3 Function 6

3.1 Principle of operation 6

4 Putting into operation 7

4.1 Setup location 7

4.2. Unpacking 7

4.3 Connection to the mains 7

4.4 Hose connections 8

5 Operation 9

5.1 Operating elements 9

5.2 Operating elements and their function 9

5.3 General information 9

5.4 Execution of the Kjeldahl disintegration 11

5.5 Malfunctions 11

6 Maintenance 12

6.1 General information 12

6.2 Upkeep 12

6.3 Gaskets 12

6.4 Replacing the insulation 13

6.5 Replacing the O-rings 13

6.6 Fuses 14

6.7 Customer service 14

7 Taking out of operation 15

7.1 Storage/Transport 15

7.2 Disposal 15

8 Replacement parts 16

9 Appendix 17

9.1 Technical Data 17

9.2 Materials used 17

9.3 FCC requirements 18

9.4 Declaration of conformity 19

2

Digestion Unit K-424

1 Scope of delivery

1 Scope of delivery

Fig.1: Overview K-424

Description Order No.

Versions:

K-424 standard 120 V 50 / 60 Hz 37963

K-424 standard 230 V 50 / 60 Hz 37962

Table 1: Versions

Enclosed parts:

4 Digestion tubes 37377

1 Rack 26730

1 Upper insulating plate 26736

1 Suction module complete 26842

1 Connection to suction module 26875

1 Digestion tube holder complete 38080

1 EPDM Hose 8mm 26275

1 Mains cables:

Type CH 10021

Type Schuko 10029

Type GB 17833

Type AUS 17834

Type USA 33756

1 Operating instructions in one of the

following languages

German 96710

English 96711

French 96712

Italian 96713

Spanish 96714

1 Packaging 26799

Table 2: Enclosed parts

Accessories:

Water jet pump plastic 02913

Glass cap 17396

Gasket PTFE to suction tube 22442

Collection tube for suction tube 27737

Condensation bottle complete 25100

Suction module for H2O2 digestion 37399

Büchi B-414 Scrubber 37876

Suction pipe with condensation gutter 26880

Non Kjeldahl digestion set 43677

Suction pipe with ball joint 40158

Table 3: Accessories

3

Digestion Unit K-424

2 Safety

The apparatus has been built in accordance with state-of­the art technology and recognized safety regulations.
Nonetheless risks and dangers can arise from the
apparatus:

• If the apparatus is operated by insufficiently trained
personnel.

• If the apparatus is not used as directed.

2.1 Symbols

Stop

Information on dangers which can lead to serious damage
to property, to severe or life-threatening injuries.

Warning

Information on dangers which can lead to damage to health
or property.

Please note

Information on technical requirements. Noncompliance can
lead to faults, inefficiency and production losses.

2.2 Requirements for the operator

The unit is only to be used by laboratory and specialist
personnel and other persons, who, because of their training
or professional experience, are able to assess the dangers
which can result while operating the equipment.

2.3 Regulation use

The unit is conceived and built as a piece of laboratory
equipment. Its regulation use is the heating of concentrated
sulfuric acid used in the oxidation of organic samples.

2.4 Non-regulation use

Any other use than listed as well as any use which does
not correspond to the technical data is a misuse. The
operator bears sole risk for eventual damage related to
such use.

In particular the following uses are not allowed:

• operation in explosion-prone areas

• operation with samples that can explode or ignite due to
impact, friction, heat or sparking.

2 Safety

4

Digestion Unit K-424

2.5 General hazards

General hazards arise from:

• Hot sulfuric acid

• Combustible gases or vapors in the immediate vicinity
of the apparatus

• Damaged glassware

• Location of the apparatus to close to the wall (see
section 4.1 Set up location)

• Hot surfaces

Except for authorized repair personnel it is forbidden to remove
covers using commercially available tools.
The device must not be put into operation with damaged
glass parts.

Contact with electrically live parts presents a danger to life
and limb!

2.6 Safety measures

It is recommended that the apparatus be operated
exclusively under an exhaust hood.
The wearing of personal safety equipment such as safety
glasses, gloves and

ll

ll

laboratory coats is necessary.

As a necessary part of the digestion unit K-424, this instruction
manual must at all times be available to the operating
personnel at the location where the apparatus is being
used. This also applies to the further editions in other
languages which may be ordered seperately.

Modifications

Any modifications on the apparatus itself or on replacement
or accessory parts, and any use of replacement or
accessory parts other than those listed in these operating
instructions is permissible only with the express written
approval of Büchi Labortechnik AG.

Responsibilities of the operator

The operator is responsible for providing proper instruction
for his staff. For that purpose, these operating instructions
may also be ordered in other languages.
The operator must inform the manufacturer immediately of
any and all events relevant to product safety that arise
during his operation of the apparatus.
If assuming that a safe operation is not possible any more
the unit must be put out of operation and secured against
unintended further operation.

2 Safety

5

Digestion Unit K-424

2 Safety

It is to be assumed that a safe operation is not possible
any more

s if the unit is visibly damaged,
s If the unit is not functioning any more
s after long storage under anfavourable conditions,
s after being transported under difficult conditions.

The unit must not be operated with combustible substances.

If you need the assistance of Büchi Service, it is required
to indicate and declare eventually remaining dangerous
substances (e.g., as defined in EC guidelines L 360, 1976/
79 or VBG 16) in or on the apparatus for reason of on-the­job safety or pollution control.

6

Digestion Unit K-424

3 Function

3 Function

The digestion unit K-424 is suitable for digestions involving
concentrated boiling sulfuric acid at a temperature of
approximately 370° C.

3.1 Principle of operation

 Sample tubes

 Heating

 Suction module

 Hose to water jet pump or to Scrubber B-414.









Fig. 2: Principle of operation K-424

7

Digestion Unit K-424

4 Putting into operation

4 Putting into operation

4.1 Setup location

The digestion unit must be installed on a stable, clean and
flat base.
For reasons of safety, a gap of at least 30 cm must be left
open between the back of the machine and the wall or
other objects. Never place any containers, chemical
products or other equipment behind the digestion unit.

4.2 Unpacking

The original package must be kept for possible later
transport.
If the package has been damaged, check the machine
carefully for broken glass or damage to the housing.

Make certain that the socket voltage is the same as that
shown on the machine nameplate. Always connect the
machine to an earthed (grounded) socket. This avoids risks
due to an internal defect.

4.3 Connection to the mains

Before switching on the K-424 for the first time check that
the voltage on the socket corrsponds to the voltage
indicated on the apparatus identification plate.
Always connect the apparatus to a grounded (earthed)
socket.
External couplings and extension cords must contain a
protective conductor ( 3-pole couplings, cables, and plug­in devices). Any and all interruptions in the protective
conductor are forbidden. This avoids risks due to an internal
defect.

8

Digestion Unit K-424

4 Putting into operation

4.4 Hose connections

Mount the safety shield (A) with the fitted hoses on the unit
(see photograph).

Assemble the connection to the suction module (B) and install
on the hose (C) and on the suction modules (D).

Connect the EPDM hose to the scrubber B-414 or to the
water jet pump (e.g. made from plastic) Art. No. 02913.

When working with a water jet pump unpleasant odours
may escape into the environment if the suction is not power­ful enough.

Fig. 3: Hose connections enlarged section

Fig. 4: Connection to fume exhaust

A

026757

002073

026240 003577

B

D

B

Scrubber

E

C

9

Digestion Unit K-424

5 Operation

5 Operation

5.1 Operating elements

 Main switch

 Energy regulator

 Heater pilot lamp

 Mains connector

5.2 Operating elements and their function

Main switch 

Switching the apparatus ON/OFF. In case of an mains load
over 12 A a bimetal switch cuts the circuit causing the
mains switch switching to OFF.
After switch back to ON the apparatus is ready to operate
again.

Energy regulator 

Regulates the heating in stages from 1 -10.

5.3 General information

The heating process heats the digestion tubes uniformly
from the side, leading to good boiling behaviour (no
retardation of boiling). Boiling chips are used only when
larger quantities of water (>10 ml) are evaporated (no glass
beads used).

It is important that the condensation zone of the sulfuric
acid does not rise too high ( maximum 5 cm under the
glass rim).

For the digestion of approx. 1 g of organic material, normally
18 - 20 ml H

2SO4

are used.
For each additional gramm of organic material an addition
of 3 - 5 ml (by fat or mineral-oil 5 - 10 ml) H

2SO4

has to be

used.

Fig. 6: Arrangement of the control and display elements rear









Fig. 5: Arrangement of the control and display elements front

Fig. 7: Condensation zone of the sulfuric acid

10

Digestion Unit K-424

5 Operation

This apparatus is used for procedures that require the use
of heat and hazardous sulphuric acid. Wear goggles and
protective clothing and exercises extreme caution when
working in this area.
Seal off unused connecting branches with the glass cap
(item n

o

17396)

It is essential, that the gaskets are fitted correctly on the
suction tube and are leaned symmetrical on the glass!

Regulation of the heating power depends on a variety of
factors such as the quantity to be digested, the types of
reagents, etc.
To carry out the digestion in the minimum time, the samples
are digested at full power.
The digestion time depends on the material to be digested
and must be determined by experiment. (Continue boiling
for about 15 minutes after the solution has become clear.)
After the sample has cooled, the digestion tube can be
connected direct to a Büchi Distillation Unit for carrying out
the distillation.

If a digested sample takes a relatively long time to cool, it
may solidify. Before it is distilled, the sample must be
liquefied again:

- by the careful addition of a small quantity of distilled
water, or

- by gentle heating in the Digestion Unit.

Fig. 8: Gaskets

Fig. 9: K-424

11

Digestion Unit K-424

5 Operation

5.4 Carrying out the Kjeldahl digestion

• Switch the unit on  and preheat for approx. 5 minutes

on stage 10.

• Wear protective goggles!

• Place the digestion tubes in the digestion tube holder

 on the rack  .

• Introduce the sample and reagents into the digestion

tubes  .

• Seal off unused connecting branches with the glass
cap (item No. 17396) .

Never install empty digestion tubes!

• Place the suction module  with the fitted gaskets on
the digestion tube holder.

• Turn on scrubber or water jet pump bevor any gases
can develop.

5.5 Malfunctions

Malfunction Possible cause Remedy

Heating elements do not 1. Mains plug not plugged in - Connect unit to the mains
heat up 2. Unit switched OFF - Switch ON

3. Energy regulator in position „0“ - Set to position "10"

4. Energy regulator faulty - Replace regulator

5. Heating elements faulty - Replace heating element

Lamp does not light up (H 1) Lamp faulty Replace lamp

Table 4: Malfunctions

Fig. 10: Operation of the K-424











12

Digestion Unit K-424

6.1 General information

The housing of the digestion unit K-424 ist made of metal
and is coated with an acid-resistant material.
In order to avoid damage to this synthetic coating, any
drops of acid which might fall on it should be wiped off
with a damp cloth.
Absolutely avoid any scratching of the surface whatsoever.

6.2 Upkeep

daily:

• Check glass parts for damage

• Clean the plastic parts with a damp cloth.

The glass parts are cleaned.

6.3 Gaskets

The gaskets are subject to wear and must be replaced
when damaged or at loss of closeness.

Inspection and maintenance duty

All specifications and regulations aimed at maintaining the
digestion unit K-424 in a proper working condition must be
followed.
This includes periodic cleaning and checking for damage.
After any repair work the operator must check the proper
function bevor putting back into operation.

6 Maintenance

5 Maintenance

13

Digestion Unit K-424

6 Maintenance

6.4 Replacing the insulation

To avoid contact with live parts, components may only be
replaced when the apparatus has been isolated from all
supply points.
Electrical and electronic components are to be replaced
by skilled engineers.

No components may be replaced when the apparatus is
warm or hot. Allow the apparatus to cool down!

Replacing upper insulating plate

This insulation is freely accessible and can be replaced
without tool.

6.5 Replacing the O-rings

• Cut damaged O-ring with a knive or a scalpel

• Remove tube holder

• Fit new O-ring over the suction module (see Fig. 11)

• Insert tube holder and fix with O-ring.

➬

1

2

Fig. 11: Replacing the O-rings

➬

14

Digestion Unit K-424

6 Maintenance

6.6 Main fuses

Please change the main fuses as follows:

• Pull out mains cables

• Pull out fuse holders 

• Replace the defective mains fuse by a new one with same

performance :

- 230V: T 5A L250V

- 120V: T10A L250V

• Insert again fuse holders

6.7 Customer service

Any intervention on or in the apparatus may only be carried
out by authorized service technicians. These are persons with
a sound technical training and knowledge of the dangers
which result from not observing safety regulations. Authorized
Büchi serve centers have available to them a special service
manual for this apparatus. That manual can only be obtained
by authorized personnel.

The addresses of the official Büchi service centers are
shown on the last cover page of these operating
instructions. Please contact these service centers whenever
you have a malfunction, technical questions, or problems
in using the equipment.

Büchi’s customer service is prepared to offer the following
services:

•• Replacement part service

•• Repair service

•• Maintenance service

•• Technical consultation.

Figure 12: Device plug, inserted





15

Digestion Unit K-424

7 Taking out of operation

7 Taking out of operation

In order to avoid the risk of endangering people with
hazardous substances the unit must be emptied and
cleaned thoroughly before taking out of operation.

7.1 Storage/Transport

The unit has to be stored and transported cleaned and its
original packaging.

7.2 Disposal

To ensure as ecologically sound a disposal of the apparatus
as possible, the Appendix in Chap. 9 contains a list of the
materials used in its most important parts.
This makes it possible for you to separate the parts and to
send them on for recycling.
For disposal of electronic parts, we refer you to official
regulations governing such action. In addition, all pertinent
regional and local laws must be observed.

16

Digestion Unit K-424

8 Replacement parts

8 Replacement parts

Only original Büchi accessories and replacement parts guar­antee safe use and reliable operation of the apparatus. The
use of other than Büchi replacement parts and accessories is
only allowed with the permission of the manufacturer. Replace­ment parts may be used only for purposes of assembly and
disassembly in connection with Chapter 6, Maintenance. Their
production using this manual is forbidden.

8.1 Replacement parts





























 Flat spring (12 springs) 38123

 Plug cap 17396

 Digestion glasses (4 glasses) 37377

 Rack 26730

EPDM hose 8 mm 26275

Fuses T10A L250V (10 pcs) 16952

Fuses T5A L250V (10 pcs) 33703

Suction pipe with ball joint 40158

Suction module for H2O2 digestion 37399

Rubber gukos for H2O2 suction module 44495

Funnel with frit for H2O2 suction module 44494

Table 5: Replacement parts

No.Description Order code

 Connection to suction pipe, complete 26875

 Seals Viton Standard (6 seals) 38122

Seal PTFE (1 seal) 22442

 O-Ring 26785

 Suction pipe 26755

 Glass holder set for suction pipe, 26877

including 2 O-rings (26785)

 Upper insulation plate 26736

 Contact guard 26797

 Digestion glass holder, complete 38080

 Cap for digestion glass holder 26791

17

Digestion Unit K-424

9 Appendix

9 Appendix

9.2 Materials used

9.1 Technical data

Dimensions (Width x Heigth x Depth) 275 x 600 x 570 mm

Nominal voltage 230 V ± 10%, 50/60 Hz

120 V ± 10%, 50/60 Hz

Connected load 1100 W

Power consumption 5 A

Weight (net) approx. 13,5 kg

Ambient conditions for indoor use only, below 2000 m.s.l.

maximum relativ humidity 80% for temperatures up to 30°C,
temperature 10 - 40°

Overvoltage category II

Pollution degree 2

Table 6: Technical data

Part Material Material code

Housing front and rear panels Polyurethane PUR

side panels Stainless steel / Perfluoralkoxy 1.4435 / PFA

Glass parts Borosilicate glass 3.3 DIN/ISO 3585

Safety shield Polyphenylensulfrole PPS

Insulation Saprolan 85K / Porextherm WDS Ultra

Metals Stainless steel

Hoses Ethylene propylene diene monomer rubber EPDM

Table 7: Materials used

18

Digestion Unit K-424

9.3 FCC requirements (for USA and Canada)

English:

This equipment has been tested and found to comply with the limits for a Class A digital device, pusuant to both Part
15 of the FCC Rules and the radio interference regulations of the Canadian Department of Communications. These
limits are designed to provide reasonable protection against harmful interference when the equipment is operated in
a commercial environment.

This equipment generates, uses and can radiate radio frequency energy and, if not installed and used in accordance
with the instruction manual, may cause harmful interference to radio communications. Operation of this equipment
in a residential area is like to cause harmful interference in which case the user will be required to correct the
interference at his own expense.

Français:

Cet appareil a été testé et s'est avéré conforme aux limites prévues pour les appareils numériques de classe A et à
la partie 15 des règlementation FCC à la règlementation des radio-interférences du Canadian Department of
communications. Ces limites sont destinées à fournir une protection odéquate contre les interférences nétastes
lorsque l'appareil est utilisé dans un environnement commercial.

Cet appareil génère, utilise et peut radier une énergie à fréquence radioélectrique, il est en outre susceprible d'engendrer
des interferences avec les communications radio, s'il n'est pas installé et utilisé conformément aux instructions du
mode d'emploi. L'utilisation de cet appareil dans les zones résidentielles peut causer des interférences nèfastes,
auquel cas l'exploitant sera amené à prendre les dispositions utiles pour polier aux interférences à ses propres frais.

9 Appendix

19

Digestion Unit K-424

9.4 Declaration of confomity

9 Appendix

BÜCHI Labortechnik AG
CH-9230

Flawil 1 / Switzerland

T [phone]
F [phone]

www.buchi.com Quality in your hands