WOHLER DTEST Evaluation Of Dust Surface Density Instruction Manual

WOHLER DTEST Evaluation Of Dust Surface Density Instruction Manual

General EN

Information about this operating manual

This operating manual will enable you to safely and reliably use the DTEST Set to determine the dust surface density / level of cleanliness of air guiding surfaces according to DIN EN 15780:2012-01 and VDI 6022:2011. Please keep this operating manual in a safe place for future reference.
The DTEST Set is to be used by professionally trained personnel exclusively for the purpose for which it was designed.
To be entitled to conduct measurements to VDI 6022 Part 1.3: 2015 it is necessary to absolve training in accordance with VDI Guideline 6022 Part 4, Category A.
We accept no responsibility for any damage or loss resulting from any failure to observe this op- erating manual.

1Symbols used in this operating manual

WARNING!
Highlights important information. Any failure to observe this information risks injury.

CAUTION!
Highlights information about hazards that can lead to material damage.

NOTE!
Highlights tips and other useful information.
The scales are designed exclusively to determine smaller masses up to 50 g.

Proper use of scales

Safety information

WARNING!
Use solvents only in well-ventilated areas. Do not breathe in solvent vapors. Avoid contact with skin and clothing.

The DTEST Set Scope of supply

Fig. 5: Scope of supply

2 AAA 1.5 V batteries
1 calibration weight

50 g

Test cloths| 30: 110 x 190 mm
Test canisters| 2
Magnetic disk| 1
Marker pen| 1
Acetone| 2 bottles each contai- ning 50 ml
Isopropyl alcohol| 2 bottles each contai- ning 50 ml
Disposable gloves| 30
Plastic case| 1

Disposal

Do not dispose of electronic equipment along with household waste. Dispose of electronic equipment in accordance with valid environmental regula- tions.
Batteries are considered hazardous waste. Dis- pose of batteries at the collection points provided.

Technical data

Max.

weighing capacity

| 50 g
Resolution| 0.001 g
Accuracy| ± 0.001 g
Weight units| g, oz, gn, ozt, dwt, ct
Power supply| 2 AAA 1.5 V batteries
Operating temperature| 10 °C to 30 °C
Auto power off| After 3 minutes inacti- vity
Dimensions| 65 x 115 x 32.5 mm
Description| Details
F (inner circle)| 100 cm2
Description|
Acetone, Isopropyl

alcohol

|
Description|
100% polypropylene / microfiber|

Digital Mini Scale

ATTENTION!

Never load the scale with more than the maximal capacity. Overloading will permanent- ly damage it.
Avoid any exposure to extreme heat or cold.
Avoid shaking, dropping or otherwise shocking the scale.

Device components

Fig. 6: Device components – scales

Diagram key

Top Cover

1. Weighting pan
2. LC display
3. Keys

Control panel

Fig. 7: Control panel

Diagram key

Inserting and replacing the batteries

Open the battery compartment cover in the backside of the scale. Insert two AAA 1.5 V batteries.

CAUTION!
Observe correct polarity when inserting the batter- ies. The position of the batteries is marked in the compartment.
Close the battery compartment cover.

CAUTION!
Before replacing the batteries, ensure the top cover is closed.

Preparing to weigh

Place the scales on a stable, flat and vibra- tion-free surface. Ensure there are no drafts.

NOTE! Due to the high level of sensitivity of the scales even the slightest draft can affect the weighing result, for example caused by breathing out in the direction of the weighing pan.

NOTE! t is recommended you calibrate the device before weighing.

• To switch on the scales, press the ON/OFF button briefly. The device performs a function test for approx. three seconds, during which all display options are displayed. Then 0.000 g is displayed (if the unit g is selected).
• Wait approx. one minute before you begin weighing.

Selecting the weight unit

• Press the MODE button repeatedly to toggle between the units g, oz, ozt, dwt and ct. The weight unit last selected is active when the device is turned on.

Weighing Put the scales are in a stable position.

• Place the object to be weighted on the top of the scales.

Calibration oft he scale

• Turn the scale on and wait fort he display to show „0.000 g“.
• Press and hold the MODE key until the display shows „CAL“. Then
• Press the MODE key again The display will flash „50.000 g“.
• Place the calibration weight on the center of the

The display will show „PASS“, then return to normal weighting mode.

Troubleshooting

The primary reasons for inaccuracy or malfunction are low batteries, incorrect calibration, overload or
operating on an unstable surface. The following error messages can appear in the display\

Dust surface density / level of cleanliness in air ducts and air-guiding

surfaces

Background knowledge

Procedural feedback

A procedure comparable to that employed by the Japanese Air Duct Cleaners Association (JADCA) is used to determine the dust surface density and level of cleanliness. The wiping method can be carried out with or without the use of a solvent.
The difference between this method, based on the normed JADCA-procedure, and the laboratory method, is mainly the weighing. VDI 6022 1.3 states that the method is appropriate to control the cleanness of an HVAC system.

NOTE! The dust surface density to VDI 6022 1.3 and dust accumulation level to DIN EN 15780 detailed in the following are based exclusively on the wiping method in conjunction with a solvent.

NOTE FOR USERS IN GERMANY!
The reference to VDI 6022 in DIN 18379/ VOB Part C means this is written into practically every VOB contract (VOB = German construction con- tract procedures).
An assessment based on DIN EN 15780 should only be made when this has been expressly agreed with defined limit values in an individ- ual contract before the system was installed

The limit values to be applied for DTEST are stat- ed in VDI 6022 Part 1.3: 2015 (Table 3, Wiping method to JADCA specifications, with solvent, relevant collection efficiency (RCE) 0.8).
The values stated in DIN EN 15780 pertaining to dust accumulation levels are presently the subject of controversy in Germany with regard to both the amount and method-related restrictions; as a con- sequence they cannot be converted to DTEST or other methods of measurement. It is intended to modify the EN 15780.

Dust surface density / level of cleanliness in air ducts and air-guiding

surfaces

Please observe the information that will be pub- lished on our home page in due course.
To be completely clear, we wish to point that when using DTEST in conjunction with the wiping method without solvent the RCE is 0.5.
The wiping method with solvent should be pre- ferred due to the greater reliability it affords; as a consequence, all other explanations in this operat- ing manual will be based on this method.

Sampling

Generally, the sample has to be taken at repre- sentatives points of the air- guiding surfaces. Take the sample as follows:
To achieve a meaningful determination of the dust surface density we recommended a three-fold determination in accordance with VDI 6022 1.3.
Please note that samples should be taken from the duct floor at the beginning of the ductwork; however, this should be at a distance of at least five times the hydraulic diameter to fitted compo- nents and obstructions to flow. Alternatively, it is acceptable to take four samples and calculate the arithmetic average of the measurement results. Take samples in the middle of the ductwork width or as close as possible to the middle if it is not accessible. The following information is provided for determining the level of cleanliness to DIN EN 15780:2012: A representative number of samples from representative parts of and positions in the ventilation system are required. Take samples in areas where dust accumulations are obvious.
Before taking samples, choose appropriate points to take samples on a random basis with the aid of design and layout documentation.
The sampling points chosen should be in the main air ducts of the ductwork beginning at the central VAC handling unit, main ducts, riser ducts and branch ducts. The points where samples are tak- en should be in straight sections of ductwork as well in ductwork with changes in direction and at joints.
For further details please refer to currently valid VDI 6022 and DIN EN 15780 standards. We rec- ommend you determine together with the client, or at least discuss with the client, the points where samples are to be taken.

NOTE! Choosing the right sampling points has a far greater effect on the accuracy of the measur- ing process than the method of measurement. As a consequence, VDI 6022 1.3 2015 requires personnel who carry out measurements re- ceive training in accordance with VDI guide- line 6022 Part 4, Category A.

Determining the start- ing weight

Fig. 8: Test canister

• Place a single test cloth in each of the respec- tive test canisters, before moistening it with
• Use the scales to determine the weight of the test
• Use the marker pen to write the starting weight on each test canister.

Sampling

NOTE! Use sufficient solvent in particular when it is not possible to gather enough dust and dirt for sampling, for example oily or old deposits of soiling.

Select a suitable solvent. Isopropyl alcohol and acetone are suitable for metallic

CAUTION! Acetone can damage plastic materials. If neces- sary, check resistance lists of the surface material where the sample is to be taken!

• Apply either small amounts of solvent to the respective test cloth or more to a larger area of the cloth depending on the level of
• Collect all dust/soiling on the inner surface of the magnetic disk. Use the test cloth mois- tened with solvent, and apply sufficient pres- sure when wiping.
• First, use one cloth per 100 cm² surface of the respective magnetic disk; use both sides if Evaluate this measurement. In case of few dust pollution, see chapter 4.6.
• Allow the solvent to evaporate completely in still air (acetone will require approx. 20 minu- tes, isopropyl alcohol at least 30 min at 22 °C).

NOTE! If required, it is possible continuously check the weight throughout the drying process us- ing the scales. That method is a particularly recommendable when working in low ambient temperatures.

Determining the final weight

• After sufficient drying time has elapsed, place the test cloths in the respective, assigned test
• Now determine the final weight using the

Sampling

To increase measurement accuracy when the dust accumulation level measured is below 3.0 g/m², you should greatly increase the sur- face area to be wiped with a test cloth.

Recommendation! > 3.0 g/m² : Three-fold test to VDI 6022 **< 3.0 g/m² : Three-fold test, but with the same test cloth < 1.0 g/m² : Mind. 2 x three-fold test, but with the same test cloth**

Using the same test cloth to wipe several surface areas is the same as averaging the results, and is in practice equivalent to a three-fold determination to VDI 6022 1.3.

• Affix the magnetic disk at the predetermined sampling points one after the other and wipe the additional surfaces using the same test cloth (if necessary, dampen the test cloth again with solvent).
• Optionally the surface to be wiped can be defined or marked in another way. It is im- portant that it is exactly 100 cm2.
• If it is necessary to increase accuracy follow- ing intermediate weighing, it is possible to use the same test cloth to wipe a further 100 cm² of surface area of the constructional element being examined

Recomandations

• Determine the difference in mass by subtract- ing the starting weight from the final weight of every test cloth:

A: Evaluation with a test cloth per 100 cm² surface of a magnetic disk:

• To obtain the level of cleanliness, multiply the difference in mass by the surface factor

Limit values for DTEST

Acceptable level of dust concentra- tion to VDI 6022 Part 1.3: 2015:

Upper limit value – cleaning is required| Value of successful cleaning| Value of news com- ponents before put- ting into operation
---|---|---
4.0 g/m2| 2.0 g/m2| 2.0 g/m2

VDI 6022 1.3 assumes that a cleaned surface has the same dust level as a new component.

NOTE! Choosing the right sampling points has a far greater effect on the accuracy of the measuring process than the method of measurement itself

NOTE! Wiping several 100 cm² surfaces with the same test cloth increases the accuracy of the measurement process.

 Warranty und Service

Warranty

• If used properly, the warranty period will be 12 month from the date of sale. Consumables (e.g. batteries, cloths, marker pen and magnet disc) are not covered by this warranty.
  This warranty does not cover the freight and pack- ing costs when the device is sent to the factory for repair.
  Service by non authorized personnel or making modifications to the analyzer voids any warranty.

Service

Wöhler has built our reputation on excellence in customer service. Therefore, of course, we are readily available to assist you after the warranty period ends.

• Send us the device and we will repair it and return it to you with our package
• Immediate help is provided by our technical staff over the

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References

• Wöhler France SARL
• Wohler USA Inc.

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