J&E Hall Danfoss AKS 41 Manuel utilisateur

Section 9

Publication 9-45

Issue 1 : 10/11

Section 9 Publication 9-45

Issue 1 : 10/11 Page 1 of 18

Danfoss AKS 41 Liquid Level Transmitter

Contents

About this Publication ................................................................................................. 3

1.1.

Safety Warnings and Symbols................................................................................................3

1.2.

Units of Measurement.............................................................................................................3

1.3.

Terminology............................................................................................................................3

1.4.

Ordering Extra Copies ............................................................................................................3

Application................................................................................................................... 4

Operation .................................................................................................................... 4

Technical Data ............................................................................................................ 5

Installation ................................................................................................................... 6

Adjustment .................................................................................................................. 8

6.1.

Setting for the Refrigerant.......................................................................................................8

6.2.

Calibration for Minimum and Maximum Liquid Level ..............................................................9

6.2.1.

Calibration for Minimum Liquid Level....................................................................................10

6.2.2.

Calibration for Maximum Liquid Level...................................................................................10

6.3.

Calibration for Minimum and Maximum Points Other Than 4 mA and 20 mA.......................10

6.3.1.

Minimum Calibration When Minimum Liquid Level Different From 4 mA ..............................10

6.3.2.

Maximum Calibration When Maximum Liquid Level Different From 20 mA ..........................11

6.4.

Signal Damping ....................................................................................................................11

6.5.

Restore Factory Default Settings ..........................................................................................12

Commissioning.......................................................................................................... 12

Maintenance.............................................................................................................. 12

Faults and Remedies ................................................................................................ 13

10.

Spares....................................................................................................................... 14

11.

Appendix 1 AKS 41 Early Version ............................................................................ 15

11.1.

Measuring Test Voltage........................................................................................................15

12.

Adjustment (Early Version) ....................................................................................... 16

12.1.

Setting AKS 41 for the Refrigerant (Early Version)...............................................................16

12.2.

Calibration for Minimum Liquid Level (Early Version) ...........................................................16

12.3.

Calibration for Maximum Liquid Level (Early Version) ..........................................................16

12.4.

Calibration for Minimum and Maximum Points Other Than 4 mA and 20 mA.......................16

(Early Version)

12.5.

Signal Damping (Early Version)............................................................................................17

List of Figures

Fig 1 Principle of Operation ....................................................................................................................4

Fig 2 Wiring ............................................................................................................................................6

Fig 3 AKS 41 and AKS 41U Liquid Level Transmitters...........................................................................6

Fig 4 Calibration for the Refrigerant........................................................................................................8

Fig 5 Calibration for Minimum and Maximum Liquid Level .....................................................................9

Fig 6 4 to 20 mA Output Signal Damping .............................................................................................12

Fig 7 AKS 41 (Early Version) Internal Layout of Transmitter Housing and LED Function ....................15

List of Tables

Table 1 Technical Data...........................................................................................................................5

Table 2 Common Faults and Remedies ...............................................................................................14

Danfoss AKS 41 Liquid Level Transmitter

Publication 9-45 Section 9

Page 2 of 18 Issue 1 : 10/11

J & E Hall International

2011

any means, electronic or mechanical, including photocopying, recording or by any information

storage or retrieval system, without permission in writing from the copyright holder.

The copyright in this publication shall be and remain the sole property of J & E Hall International.

Danfoss AKS 41 Liquid Level Transmitter

Section 9 Publication 9-45

Issue 1 : 10/11 Page 3 of 18

1. About this Publication

These instructions have been prepared according to the following

standards:

BS 4884 : Technical Manuals:

Part 1 : 1992 Specification for Presentation of Essential

Information.

Part 2 : 1993 Guide to Content.

Part 3 : 1993 Guide to Presentation.

BS 4899 : User’s Requirements for Technical Manuals:

Part 1 : 1991 Content.

Part 2 : 1992 Presentation.

BS 4899 is based on the principles of BS 4884.

BS 5378 : Part 2 : 1982 Safety Signs.

1.1. Safety Warnings and Symbols

The system of safety warnings and symbols is based on BS 5378 :

Part 2 : 1982 Safety Signs and BS 4884 : Technical Manuals : Part 1 :

1992 Specification for Presentation of Essential Information.





WARNING

This denotes an immediate hazard with a high likelihood

of personal injury or death if instructions, including

recommended precautions, are not followed. There is

also a potential risk of damage to the product, process

or its surroundings.





CAUTION

This draws attention to instructions which must be

complied with to avoid damage to the product, process

or its surroundings.

NOTE: draws attention to important additional

information.

1.2. Units of Measurement

Quantities are expressed in SI units or SI derived units.

1.3. Terminology

Terminology, abbreviations and acronyms are those currently in use

throughout the refrigeration and air conditioning industry.

1.4. Ordering Extra Copies

Extra copies of these instructions can be obtained from J & E Hall

International. For contact details go to www.jehall.com.

Danfoss AKS 41 Liquid Level Transmitter

Publication 9-45 Section 9

Page 4 of 18 Issue 1 : 10/11

2. Application

AKS 41 and AKS 41U liquid level transmitters are used to measure

refrigerant liquid level for control applications. The transmitter supplies a

4 to 20 mA signal in proportion to the level of liquid refrigerant. This

signal can be used with a suitable controller to control the level of

refrigerant within a vessel. The Danfoss EKC 347 liquid level controller is

dedicated for use with the AKS 41 and AKS 41U.

The location of the liquid level transmitter and level controller can be

found from the system schematic flow diagram and in Part A :

Specification in Section 1 of the plant instruction manual.

This publication is applicable to the latest version of the AKS 41 and AKS

41U fitted with one green LED. Information about the earlier version,

fitted with one green and one red LED, can be found in Appendix 1.

3. Operation

The transmitter comprises consists of two parts: an inner insulated

electrode and an outer tube with a space between, forming a capacitive

rod. Liquid refrigerant flows up between the tube and the electrode; the

length immersed in the liquid is registered and transmitted as a 4 to

20 mA signal. The principle of operation is illustrated and described in

Fig 1.

In its simplest form, an electrical capacitor consists

of two conducting plates insulated from each other.

In this case the insulation medium is free-air.

When this example is translated to the capacitive

rod, the outer tube constitutes one plate and the

centre electrode the other plate.

Fig 1 Principle of Operation

Section through transmitter

(capacitive rod)

Electrode of

ordinary steel

Gap between the outer tube and

the insulated electrode where the

liquid can rise

Outer tube of stainless steel

Electrode hermetically

sealed in a non-conducting

PTFE material (Teflon)

Danfoss AKS 41 Liquid Level Transmitter

Section 9 Publication 9-45

Issue 1 : 10/11 Page 5 of 18

The capacitive rod can measure the level of conducting as well as non-

conducting liquids.

If the rod is partially immersed in a conducting liquid, for example, R717

(ammonia) or R718 (water).

On the part of the rod that is surrounded by liquid, the outer tube is

short-circuited to the teflon insulation. This produces an effect as if

the distance between the outer tube and the centre electrode has

become smaller which will cause an increase in the rod’s

capacitance. This change of capacitance is converted into an

output signal between 4 and 20 mA.

If the rod is partially immersed in a non-conducting liquid, for example,

R134a.

When the liquid rises between the outer tube and the inner

electrode, it displaces the gas otherwise present. As the liquid has

a higher dielectric constant than the gas, a rising liquid level is

registered as an increase in the rod’s capacitance and hence

results in a higher 4 to 20 mA output signal.

4. Technical Data

ARAMETER

ETAILS

General

Enclosure IP 65

Max working press 100 bar g

Temperature range -60 °C to +100 °C

Refrigerant R717 (factory setting), R22, R404a, R134a, R744 and R718 (R717 and

R718 give the same output signal)

Materials

Thread: stainless steel AISI 303

Reference tube: stainless steel AISI 304

Inner electrode: steel, PTFE coated

Top housing: cast aluminium

Environment

-25 to +55 °C during operation, -40 to +70 °C during transit.

20 to 80 % Rh (not condensed).

No shock influence or vibrations.

Approvals

EMC directive 89/336/EEC

EMC directive 92/31/EEC

EN 50081-1 and EN 50082-1

Electrical

Power supply 24 V ac -15 %/+25 % 50/60 Hz or 24 V dc ±10 %

Power consumption 1.5 W

Transmitter output 4 to 20 mA

Max load resistance 500 Ω

Connection 4-pole plug DIN 43650

Nomenclature

X X X X X X

Consecutive number

Serial number

Production year

Production month

Product type (code number)

Version number

The nomenclature code can be found inside the transmitter housing.

Table 1 Technical Data

Danfoss AKS 41 Liquid Level Transmitter

Publication 9-45 Section 9

Page 6 of 18 Issue 1 : 10/11

5. Installation

Allow adequate space for transmitter removal.

Locate a gasket seal under the hexagon portion of the transmitter body,

insert into the level column taking care not to bend the transmitter.

Tighten with a spanner on the hexagon flats provided.

Wiring connections to the probe are shown in Fig 2, also refer to the

control panel wiring diagrams specific to the application. Segregate

control wiring from power wiring, do not run together.

Fig 2 Wiring

AKS

41U AKS

ODEL

NSERTION

ENGTH

A W

EIGHT

ODEL

NSERTION

ENGTH

B W

EIGHT

AKS 41U-6 152 mm 1.32 kg AKS 41-3 280 mm 1.7 kg

AKS 41U-8 203 mm 1.41 kg AKS 41-5 500 mm 2.0 kg

AKS 41U-12 305 mm 1.55 kg AKS 41-8 800 mm 2.4 kg

AKS 41U-15.3 389 mm 1.72 kg AKS 41-10 1000 mm 2.7 kg

AKS 41U-19.2 488 mm 1.82 kg AKS 41-12 1200 mm 3.1 kg

AKS 41U-23.1 587 mm 1.96 kg AKS 41-15 1500 mm 3.5 kg

AKS 41U-30 762 mm 2.22 kg AKS 41-17 1700 mm 3.8 kg

AKS 41U-35 889 mm 2.38 kg AKS 41-22 2200 mm 4.6 kg

AKS 41U-45 1143 mm 2.71 kg AKS 41-30 3000 mm 5.8 kg

AKS 41U-55 1397 mm 3.1 kg

AKS 41U-65 1651 mm 3.5 kg

AKS 41U-85 2159 mm 4.3 kg

AKS 41U-105 2667 mm 4.93 kg

AKS 41U-120 3048 mm 5.7 kg

Fig 3 AKS 41 and AKS 41U Liquid Level Transmitters

EKC 347 Electronic

Liquid Level Controller

4 to 20 mA

Signal

24 V dc or

24 V ac 50/60 Hz

24 V ac

DIN Plug

Connection

Danfoss AKS 41 Liquid Level Transmitter

Section 9 Publication 9-45

Issue 1 : 10/11 Page 7 of 18

Fig 3 (continued) AKS 41 and AKS 41U Liquid Level Transmitters

Gasket Seal

Outer Tube

Plug can be

mounted in

four different

positions

Transmitter

housing and

tube can be

separated

without

emptying the

standpipe

1” BSP (AKS 41)

¾” NPT (AKS 41U)

Transmitter

Housing Assembly

DIN Plug

Connection

Calibration Cover

Green LED (‘flashes’ slowly

during normal operation)

LED Bar

Graph (option)

Inner Tube

Calibration

Cover

Calibration

Push-button

Danfoss AKS 41 Liquid Level Transmitter

Publication 9-45 Section 9

Page 8 of 18 Issue 1 : 10/11

6. Adjustment

6.1. Setting for the Refrigerant

The AKS 41/AKS 41U will not need setting if is used with R717

(ammonia) or R718 (water) and the length of the transmitter corresponds

to the actual refrigerant measured range.

For refrigerants R22, R404a, R134a and R744, set the AKS 41/AKS 41U

for the refrigerant as follows; refer to Fig 4. This procedure can be

carried out before the transmitter is mounted on the plant.

(a) Dismantle the cap on the DIN connecting plug and pull it back a

little on the cable to gain access to the four screw terminals inside

the plug where the four wires are connected. Connect a meter

between terminals 2 and 3 so that the 4 to 20 mA output signal can

be measured.

(b) Enter setting mode by removing the DIN plug so there is no voltage

to the level transmitter.

Press the calibration push-button and keep it depressed while

refitting the connecting plug. Release the push-button; the green

LED is extinguished until the push-button is released.

NOTE: this sequence must be observed. Restoring the

supply before the push-button is pressed will change

the signal damping.

of flashes and the 4 to 20 mA output signal; refer to Fig 4.

(d) Press the calibration push-button to select the refrigerant. Each

press steps to the next refrigerant according to the table in Fig 4.

When the measured output current corresponds to the required

refrigerant, wait 10 seconds until the green LED is constant

illumination (not ‘flashing’). This indicates that the required

refrigerant has been selected.

REEN

LED

UMBER

‘F

LASHES

’

UTPUT

IGNAL

EFRIGERANT

1 5 mA

R717 or R718

2 6 mA R22

3 7 mA R404a

4 8 mA R134a

5 9 mA R744

Default (factory setting)

Fig 4 Calibration for the Refrigerant

20 mA

4 mA

43 mm

30 mm

Danfoss AKS 41 Liquid Level Transmitter

Section 9 Publication 9-45

Issue 1 : 10/11 Page 9 of 18

(e) Remove the meter from the DIN plug and reassemble.

(f) Leave setting mode by removing the DIN plug so there is no

voltage to the level transmitter. After a few seconds, refit the plug.

The level transmitter should now operate normally.

(g) For refrigerants other than R717 and R718, it is recommended to

check the minimum and maximum liquid level calibration

approximately 7 days after operation commences; refer to 6.2.

6.2. Calibration for Minimum and Maximum Liquid Level

Calibrating the transmitter sets the two outer limits of the measuring

range, i.e. the point on the capacitance rod where the output signal is to

be 4 mA and the point where the signal is to be 20 mA; refer to Fig 5.

Fig 5 Calibration for Minimum and Maximum Liquid Level

The active measuring range starts 30 mm from the bottom of the rod and

ends 43 mm from the top (gasket’s contact face). The liquid level

transmitter has been factory-calibrated to R717 (ammonia), so that the

entire measuring range is utilised, i.e. the transmitter’s output signal is

4 mA when the rod is out of the liquid and 20 mA when the liquid is

43 mm from the top of the rod.

If the transmitter is to be used with R22, R404a, R134a or R744 there is

no need to calibrate, simply set to the refrigerant used; refer to 6.1.

It is usually necessary to calibrate the AKS 41/AKS 41U if:

•The AKS 41/AKS 41U is used with a refrigerant other than

those listed in Table 1.

•The insertion length does not correspond with the refrigerant

measured level range.

•The transmitter housing assembly is replaced.

Calibration for minimum liquid level can be carried out without calibrating

for maximum liquid level at the same time. However, if one level is

changed on its own the other level will automatically move by the same

distance. For example, if the new calibration for minimum liquid level is

10 mm further down the rod, the maximum liquid level moves down by

the same amount.

(mA) Output Signal

Danfoss AKS 41 Liquid Level Transmitter

Publication 9-45 Section 9

Page 10 of 18 Issue 1 : 10/11

6.2.1. Calibration for Minimum Liquid Level

(a) Bring the liquid refrigerant to the level corresponding to the lower

limit of the measuring range. i.e. the point on the rod where the

transmitter’s output signal is to be 4 mA. The full length of the rod

should be used if possible, so calibrate the lower limit with the

liquid level below the end of the rod.

(b) Press the calibration push-button and keep it depressed for

approximately 5 seconds, until the green LED stops ‘flashing’, then

release.

once. After a few seconds the green LED illuminates begins to

‘flash’ slowly. The new minimum calibration has been saved to

memory.

NOTE: if the calibration push-button is not pressed

within 10 seconds, the AKS 41/AKS 41U will

automatically leave calibration mode and return to

normal operation.

The minimum output is now set to 4 mA and the AKS 41/AKS 41U

is operating normally.

6.2.2. Calibration for Maximum Liquid Level

(a) Bring the liquid refrigerant to the level corresponding to the

maximum limit of the measuring range. i.e. the point on the rod

where the transmitter’s output signal is to be 20 mA. The full

length of the rod should be used if possible, so calibrate the upper

limit with the liquid level 43 mm below the top of the rod (measured

from the gasket’s contact face).

(b) Press the calibration push-button and keep it depressed for

approximately 5 seconds, until the green LED stops ‘flashing’, then

release.

with a 1 second interval between each press. After a few seconds

the green LED illuminates then begins to ‘flash’ slowly. The new

maximum calibration has been saved to memory.

NOTE: if the calibration push-button is not pressed

within 10 seconds, the AKS 41/AKS 41U will

automatically leave calibration mode and return to

normal operation.

The maximum output is now set to 20 mA and the AKS 41/AKS

41U is operating normally.

6.3. Calibration for Minimum and Maximum Points Other Than 4 mA and

20 mA

The usual minimum and maximum calibration points are 4 mA and

20 mA, however, the transmitter can be calibrated at other points within

the signal range. This facility is especially useful if it is impractical to

bring the liquid level to the maximum and minimum limits.

6.3.1. Minimum Calibration When Minimum Liquid Level Different From

4 mA

(a) Dismantle the cap on the DIN connecting plug and pull it back a

little on the cable to gain access to the four screw terminals inside

the plug where the four wires are connected. Connect a meter

between terminals 2 and 3 so that the 4 to 20 mA output signal can

be measured.

(b) Bring the refrigerant liquid level to the desired minimum level.

approximately 5 seconds, until the green LED stops ‘flashing’, then

release.

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