Guidelines for planning and setting up very narrow aisle warehouses

Guidelines for planning
and setting up very narrow
aisle warehouses
Table of contents
Floor................................................................................................. 6
Specifications for the floor....................................................................7
Height differences and evenness tolerances.......................................8
Racking.......................................................................................... 14
Assembly tolerances for racks and permissible deformations..........16
Safety distances in the rack................................................................18
Guide systems............................................................................... 19
Mechanical guide: rail guidance.........................................................20
a.) Design and assembly of guide rails...................................... 20
b.) Overview of rail types.......................................................... 22
Inductive wire guidance......................................................................24
a.) Laying an inductive guide wire............................................ 24
b.) Entering and exiting the aisle/changing aisles.................... 26
c.) Frequency generator............................................................. 27
Driver assistance system.............................................................. 28
1. Systems for determining vehicle position......................................29
a.) Magnets...................................................................................30
b.) Reflected light sensors............................................................31
c.) Bar code...................................................................................32
d.) RFID..........................................................................................32
2. Safety functions in the very narrow aisle......................................33
a.) End of aisle protection.......................................................... 33
b.) Height-dependent cut-off.......................................................34
c.) VNA navigation........................................................................35
Personnel protection systems...................................................... 37
Legal regulations.................................................................................38
Stationary protection...........................................................................38
Mobile protection................................................................................39
Standards...................................................................................... 41
3
Guidelines for planning and setting up.
very narrow aisle warehouses
Narrow aisle warehouses have a particularly high space utilisation rate
through very low spatial requirements and high lift heights. These
aspects require special attention in planning and implementation.
These guidelines provide you with a tool which should help you in
building the most economical, safe, and functional narrow aisle
warehouse. They also utilize your floor space and spatial resources
efficiently and ensure optimum implementation for truck, racking, and
flooring interfaces in your premises.
Our recommendations and directives in the following should prevent
bad investment as well as deficiencies in construction, leading to
professional solutions.
4 5
The floor
High rack storage areas where man-down narrow aisle trucks are
used are technically advanced systems today. The use of highlevel order pickers, racking trucks and order picking trucks in such
warehouses not only requires technically highly developed industrial
trucks, but also floors of above average quality. They must be capable of carrying loads, level, and horizontal, and meet the strictest
tolerances for travel paths of the VDMA directive (the tolerances
according to DIN 18202 apply for all remaining surfaces).
6 Only compliance with the VDMA directive requirements can guarantee the full performance of the trucks and their associated productivity. Testing the floor surface for evenness should be done directly
after installing the floor, and before beginning any subsequent work.
Proof of compliance with the tolerances is provided by the floor
installer or a neutral surveyor office
(also see: www.VDMA.org/Branchen/Logistiksysteme).
Linde VNA Directives // Floors
Specifications for the floor
The following listed values and tolerance ranges are essential for
permissible driving speeds, diagonal driving heights, a smooth ride,
and positioning accuracy for the trucks used. Therefore, pay special
attention to the “floor tolerances”. To avoid possible misunderstandings, we recommend you to make these directives part of your
agreement with the floor installer and racking manufacturer.
Sub-flooring:
• The supporting subsoil is designed according to DIN EN 1045 part 1
and two using a concrete quality of at least B25 and DIN 18202.
Use-surface (top layer):
•The load group II (middle) DIN EN 18560, part 7, table 1 (resistant against oils and grease) requires an approx. 10 –30 mm thick
industrial flooring.
•The surface must be anti-skid (approx. µ 0.5), anti-slip, free of
fluids, dirt, and oil films and must not exhibit plastic deformation
under load in order to achieve the braking distances according to
ISO 6292. The resistance to earth RE must be a maximum of 10^6
ohm (per DIN EN 1081).
Sub-concrete
Iron reinforcement
Grinding the floor
Milling or grinding individual travel paths in the aisle to achieve
the necessary evenness standards is permissible for inductive or
mechanical guidance, assuming it does not result in any visual or
tangible height differences.
•Make sure that the overall traffic surface never exceeds the
allowed tolerances and meets the required level of technology
(honing the floor finish over levelled guide rails typically does
not guarantee the necessary floor tolerances for trucks).
•Discontinuities in the flooring, such as channels or shafts, require
a minimum spacing of 200 mm to the travel paths and should be
avoided in the aisle whenever possible.
7
Linde VNA Directives // Floors
Evenness tolerances
Table 1: Permissible height differences crosswise to the travel path
This specification is based on the VDMA directive “Flooring for use by
very narrow aisle industrial trucks”. Stricter requirements apply for
travel paths in very narrow aisle warehouses than in all other areas
of the warehouse. Tolerances per the VDMA directive must be complied with (see tables 1+2+3) in very narrow aisles and everywhere
travelled with an increased load. The evenness of other surfaces
must meet those tolerances of DIN 18202, Tab. 3, line 3.
Lift height (m)
Zslope
dz = Z x Zslope
bis 6
2.0
Z x 2.0 mm/m
10
1.­5
Z x 1.5 mm/m
15
1.0
Z x 1.0 mm/m
Lift heights >_ 6 m require interpolation (see Fig. 2)
Zslope
Permissible slope crosswise to the path between the middle of the
load wheels of the industrial truck (a, b) in mm/m (the value of
Zslope is specified dependent on the lift height)
Specifications for evenness for the very narrow aisle range are defined for three different areas:
a.) height differences crosswise to the travel path
b.) height differences longitudinally along the travel path
c.) rippled variations in height differences
Z
Dimension between the centres of the load wheels of industrial trucks
(a, b) in m
These three factors have a decisive influence on the driving performance and non-compliance can lead to a reduction in handling
performance.
dZ
Maximum permissible height differences between the centres of
load wheels of industrial trucks (a, b)
Height differences crosswise to the travel path
The following tolerances crosswise to the travel path apply per
VDMA, deviating from DIN 18202 (see Tab. 1):
Fig.1: Diagram, height difference crosswise to the travel path
a
b
dz
Z
8 Height difference = dz
Track width = Z
Load wheels = a, b
Linde VNA Directives // Floors
Example for determining Zslope:
Assumption: lift height = 8 m; travel path Z = 1.5 m
Calculation of Z slope using Fig. 2:
Lift height = 8 m; Z slope = 1.75 mm/m
Calculation of dz using Fig. 3:
dz = Z x Z slope = 2.625 mm
The maximum permissible height difference (dz) in this case
must not exceed 2.625 mm.
Fig. 2: Example for determining Zslope
Zslope (mm/m)
2
1.75
1.5
1
0.5
8
5
10
15
T lift height (m)
Fig. 3: Example for determining dZ
Zslope
2
dZ (mm)
1.75
4
1.5
1.25
3
2.625
1.0
2
1
0
2
0.5
1
1.5
2
2.5
Z (m)
9
Linde VNA Directives // Floors
After determining the maximum permissible height difference dz, the
lateral deviation of the truck at a specific height can be calculated
using a formula.
The general formula for determining the lateral deviation
(see Fig. 4):
Lateral deviation at the maximum height =
Delta X = dz (mm/m) x Hx (m)
Fig. 4: Determining the lateral deviation of point X
Example calculation for lift height 10 m and track width 1.0 m
(see Fig. 5):
A lift height of 10 m and a track width of 1.0 m produces a dz value
of 1.5 mm/m
Hx = height of point X = 10 m
Delta X = 1.5 mm/m = 15 mm lateral deviation of point X
Fig. 5: Example calculation for lift height + 6.0 m
and track width up to 1.0 m
X
Delta X
Delta X
Point X
Hx
+ dz
Zero line
Track width
Ast
– dz
Ast
Hx = height of point X
above the floor
b1 = safety distance
10 Ast = aisle width
Linde VNA Directives // Floors
Evenness tolerances longitudinally along the travel path
The evenness tolerances per VDMA longitudinally along the travel
path are the following (see Tab. 2):
Example:
The inside micrometer below a 2 m long straight edge must not be
greater than 3 mm (see Fig. 6).
Table 2: Evenness tolerances longitudinally along the travel path
Distance between measurements l
Gap under the ruler t
1m
2 mm
2m
3 mm
3m
4 mm
4m
5 mm
Testing the evenness is done per DIN 18202.
Fig. 6: Example of evenness tolerances longitudinally along the travel path
l=2m
t = 3 mm
11
Linde VNA Directives // Floors
Ripple variations for industrial flooring in very narrow aisle
warehouses
In addition to the requirements for absolute height differences in
very narrow aisles, there are also requirements for regularly reoccurring uneven surfaces.
No rippled uneven surfaces or regular changes in lateral inclination
may occur, as they lead to the industrial trucks swinging. Ripple variations are defined by the height differences between two adjacent
points along the travel path and are measured in “ripple variation
factor Fx”. This is determined from a series of height differences of
multiple adjacent readings according to a specified algorithm. The
smaller the Fx value, the larger the ripple variation at greater amplitudes or the more uneven the floor.
In the VDMA directives, the calculation of this key figure is described
in detail; a table calculation is also offered for download, enabling
automatic calculation from the raw data.
The directive and the calculation tool mentioned can be found on
the home page of the VDMA (www.vdma.org/Branchen/Logistiksysteme).
The ripple variation factor Fx calculated in this way must be complied
with as per table 3.
Table 3: Ripple variation factor Fx
Lift height (m)
/-FX
Fx or O
15
>_ 525
10
>_ 400
up to 6
>_ 300
Lift heights > 6 m require interpolation (see Fig. 5)
12 Linde VNA Directives // Floors
Measuring procedure for ripple variation
The exact measuring method is defined in the VDMA directive
as mentioned. You can find assistance in determining Fx in the
schematic drawing below (see Fig. 7).
Example calculation:
Assumption: lift height = 8 m; travel path Z = 1.5 m
Calculation of Z slope using Fig. 2: 1.75 mm/m
Calculation of dz using Fig. 3: Z x Z slope = 2.625 mm
Calculation of Fx using Fig. 6: Fx >_ 350
Fig. 7: Example for determining Fx
Fx
550
500
450
400
350
300
250
5
8
10
15
Lift height (m)
13
The racking
Racking systems available on the market can be adapted exactly to
the most varied requirements and room characteristics. Thus, the
weights and load dimensions used, the loading equipment, and the
industrial trucks used are the most important parameters for designing racking. Today, pallet racks are primarily used for very narrow
aisle systems. They have the advantage that they can be used both
manually and automatically, and facilitate direct access to all items
and also order picking.
14 Linde VNA directives // Racking
Pallet racks consist of vertical racks and horizontal bridge pieces (DIN
EN 15620). Support beams, grating, steel panels, or particleboard can
be placed on these, depending on application profile. If the distance
between the inside of the stored loads for double racks is less than
100 mm, a push-through guard is mounted for protection.
Free-standing pallet racks are not permanently joined to the building.
They can be set up flexibly, and can be used later for other applications by switching them around.
DIN EN 15512 “Stationary racking systems made of steel – adjustable
pallet racks – basis for static measurement” forms the basis for static
verification when building such racks.
Requirements for fire protection are an another important factor
when building racking storage. We recommend early contact with
the responsible agencies, construction companies, and with your
insurance partner, and taking into account the spatial requirements
for fire protection measures in terms of safety distances in the
racking.
Please also note the regulations for the load capacity of the floor.
Flooring in storage facilities and the trucks used must meet the requirements of DIN EN 15635, DIN EN 15512 and DIN EN 15629 so that
net weight and loads can be supported safely.
The p and d stations are normally formed from the overhanging support of the last rack. The use of centering aids at the p and d stations
is required for partial and fully automatic rack operation. Thus the
loads from the industrial trucks with freely moveable feeder can be
deposited in a specified position on the p and d station for the mandown narrow aisle truck.
15
Linde VNA directives // Racking
Assembly tolerances for racks and permissible
deformations
Per DIN EN 15620 pallet racks for very narrow aisle trucks are divided
into two different classes:
Rack class 300A:
Man-down narrow aisle truck with “man up” operation.
Rack class 300B:
Man-down narrow aisle truck with “man down” operation.
The assembly tolerances are shown in Fig. 8, the associated tolerance description per DIN EN 15620 can be found in table 4.
Fig. 8: Rack assembly tolerances
Front view
Side view
CX
CZ
Y-direction
GY
GY
JX
H1
H
JZ
HB
Detail
E1
H1A
M
X-direction
Z-direction
D
E
D
Top view
A1(n)
A
GZ
Side view detail
B0
B1
B2
B3
Bn
HY
F
Z-direction
F1
X-direction
16 F
Linde VNA directives // Racking
Table 4: Installation tolerances and permissible deformations of the racks according to DIN EN 15620
Horizontal tolerances for the XZ plane (mm)
Measurement specification and description of the cross deviation
Building cross deviation for
racking class 300
A
Deviation from the nominal size of the access width between two support uprights
in any beam height
+- 3
A1
Deviation from the nominal value for the total length of the racking, cumulative number “n” for
the fields, measured as close as possible to the base plate
+- 3 n
B
Misalignment of the supports in transverse direction, speed, cumulative for the Number
“n” the fields measured approximately at ground level. For this class 300A applies only
to the support uprights. Class 300B applies to the support uprights and the rear pillars.
+- 10 or for class 300A: +- 1,0 n
for class 300B: +- 0,5 n*
B0
Deviation from the nominal size of the racking front at the transfer aisle
the respective „reference line of the racking system Z ‚ measured near ground level
+- 10
CX
Deviation from the perpendicular of the frame in the X direction
+- H/500
CZ
Deviation from the perpendicular of the frame in the X direction
without fixed Hub: +- H/500
with fixes Hub: +- H/750a
D
Deviation from the nominal depth of the racking
(Single or double frame)
Single frame: +- 3
Double frame: +- 6
E
Deviation from the nominal size for the aisle width about ground level
+- 5
E1
Deviation from the nominal size for the width between the rails
+5
0
E2
Deviation between the supports on one side of the guide rail
+- 5
F
Deviation from the nominal size of the aisle straightness measured approximately
at ground level with respect to the “reference line aisle system X” or according
to the specifications of the truck supplier
+- 10
F1
Deviation measured between next to each other uprights around Ground level in the Z direction
+- 5
GZ
Straightness of the beam in the Z direction
+- A/400
JX
Straightness of the beams in the X direction between supports in
a distance HB from each other
+- 3 or +- HB/750*
JZ
Initial curvature of a stator frame in the Z direction
+- H/500
M
Deviation limits for the upper guide rail
Is set by the truck supplier or the
author of the specification
TW
Beam rotation in the middle of the field
1° per m
Vertical tolerances in the Y direction (mm)
Measurement specification and description of the cross deviation
Mounting tolerances for.
racking class 300
GY
Straightness of the beam in the Y direction
+- 3 or +- A/500*
H1
Deviation of the top level of any beam over the H1 lower support level
300A: +- 5 or +- H1/500
300B: +- 3 or +- H1/1000*
H1A
Deviation of the top edge of the lower beam on each upright against ground level
+- 7
H3
Deviation limits for the upper guide rail, if available
If available, set by the supplier or
manufacturer of the truck
HY
Deviation of the heights of the load unit between the front and rear beam
in one compartment
+- 10
H
Height from the top of the foot stand level to top of the racking support
HB
Height from the top stand level to the next higher stand level
*The greater of the following values is valid
a H/500 is also permitted, provided the overhang of the pallet skids or blocks at the front bars is 75 mm
or more and the skids or blocks are supported by the beams.
17
Linde VNA directives // Racking
Safety distances in the rack
Free compartment dimensions are the distances between the loads
within the rack. A distinction is made between distances between
stored pallets and the next rack bridge piece (dimension Y) and between stored pallet and upright or the next standing pallet (dimension X) or also between the pallet backs to each other (dimension Z).
The more generous these values are measured to be, the faster the
pallets can be stored and removed.
Thus it is advisable at higher productivity to design the safety distances larger than the defined minimum distances.
Fig. 9: Minimum distances
Y
X
X1
Z
18 Minimum distances to be observed:
Dimension X (distance from pallet to upright): 75 mm
- For rack class 300B starting at 12 m lift height: 100 mm
Dimension X1 (distance from pallets to each other):
75 mm
- For rack class 300B starting at 12 m lift height: 100 mm
Dimension Y (distance from pallet to bridge piece):
75 mm
- For rack class 300B starting at 6 m lift height: 100 m
- For rack class 300B starting at 9 m lift height: 125 m
- Linde recommendation: minimum distance + 25 mm
Dimension X (distance from back of pallets to each other): 100 mm
(also take into account here the space requirement for sprinkler
pipes)
The guide systems
To take optimum advantage of the spatial requirements in the very
narrow aisle, the appropriate industrial trucks make work easier
with very short distances to the rack. DIN EN 1726 part 2 prescribes
a minimum distance of 90 mm between the supported load and the
pallet in the rack. Depending on parameters such as pallet size, truck
type, and guide system, larger distances are also needed sometimes.
Basically, there are two different guide systems: inductive wire guidance enables driving speeds up to 9 Km/h. Load pick up from the
floor is straight forward with inductive guidance. Mechanical guide
systems have high driving speeds up to 12 Km/h. Load pick up from
the floor is only possible with small rails and special forks.
19
Linde VNA directives // Guide systems
Mechanical guide: rail guidance
Ast
Aisle width, clear width between the loads or between the racks
The mechanical guide has rollers attached to the truck and steel
profiles mounted to the floor to guide the industrial truck. The laterally mounted rollers hold the truck between the profiles in the aisle
centre.
F = Ast/2
Permissible deviation of the aisle width from the centre line to 20 m
- F = +- 5 mm
Fig.10 shows the minimum width of the aisle (Ast) taking into consideration the relevant parameters.
b26
Clear width between the rails
b6
Truck width over guide rollers b6 = b26 – 5 mm
Permissible deviation:
- over the entire length: -0/+5 mm
- over 1 meter length: -0/+2 mm
Fig. 10: Minimum aisle width
F
F
Ast
Distance between the guide rails -b26Truck width over the guide rollers -b6-
Sub-concrete
2.5 mm
20 Iron reinforcement
2.5 mm
Linde VNA directives // Guide systems
Safety distances with mechanical guide
Distance of supported load to pallet in the rack (a21/a23)
DIN EN 1726 part 2 prescribes a minimum distance of 90 mm between the supported load and the pallet in the rack. Depending on
parameters such as pallet size, truck type, and guide system, larger
distances are sometimes needed also. The difference in lift height
guarantees maximum handling performance with maximum safety.
Distance from guide rail to load wheel
A minimum distances of 50 mm is prescribed between guide rail
and load wheel for the mechanical guide. In terms of safety and
handling performance, a safety distance of 100 mm (see Fig.11) is
preferable.
For mechanical guides, the following applies:
Lift height < 7 m -> a21/a23 = min. 90 mm
Lift height > 7 m -> a21/a23 = min. 120 mm
Fig. 11: Safety distance
a21/a23
min.
50 mm
21
Linde VNA directives // Guide systems
Fig. 12: The different rail guidance systems
Height of non-cast guide rails
Rail guidance types
There are multiple types of rail guidance. The most commonly used
profiles used in the market are L rails with a profile height of 100
mm (high rails) or 50 mm (low rails). Additionally, other heights can
be implemented up to the smallest possible rail height of 38 mm.
The profile rails can be both free standing as well as integrated in a
concrete base (cast guide rail).
Design and assembly of guide rails
To make it easier to adjust the tracks of the truck in the very narrow
aisle, the start of the aisle has a entry funnel of approx. 300 mm in
length with an opening angle of 15°. The strongest horizontal force
is achieved in this funnel and the first meters afterwards, the approx.
2500 mm long single track area. This force of up to 2500 kg occurs
in the single track area, as the industrial truck is only guided with
the front rollers. Then the rear rollers get into the rail guidance and
thus the forces are reduced as the aisle is travelled to approx. 400 –
1000 kg.
Height of cast guide rails
To ensure secure track adjustment, we recommend using a funnel
with a high profile. The guide rails are anchored in the floor after
being installed. The different effects of force in the driving area and
single track area require different dowelling distances. In the driving
area, the distance is 500 mm. In the single track area, it is recommended to reduce it to approx. 300 mm for the first 4 dowels. This
dowel spacing also applies to the front of the rail for the changeover
aisle (see Fig. 13). The guide rail should be 8 mm to avoid deformations due to lateral forces.
Due to the different heights of guide rails, the side guide rollers on
the industrial truck require different heights:
40 – 65 mm for high guide rails
20 – 23 mm for low guide rails
Low guide rails
22 Linde VNA directives // Guide systems
Fig. 13: Design and assembly of guide rails
b26
Ast
500 mm
500 mm
300 mm
300 mm
300 mm
300 mm
300 mm
15°
23
Linde VNA directives // Guide systems
Inductive wire guidance
The inductive wire guidance replaces the guide rails. A wire loop
routed in the floor epitomises the guide line. The guide wire is fed
from a frequency generator with AC (low voltage). The magnetic
field formed around the guide wire is scanned by antennas. The
downstream electronics evaluate the signals and control the servo
unit. This makes the truck always move centred over the guide wire.
Laying an inductive guide wire
The guide wire is laid as a closed loop, and its beginning and end are
connected to the frequency generator. An uneven number of aisles
requires installation of an additional return (see Fig. 14).
Technical data
Standard frequency: 6.25 Hz
Current strength: 80–120 mA
(additional frequencies and current strengths on request)
Fig. 14: Laying inductive guide wires
Rack
Frequency generator
Return of an inductive
guide wire
Distance between t wo
guide wires with the same
frequency: min. 1200 mm
Tolerances with inductive wire guidance
= Ideal wire guidance
± 5 mm
24 = Maximal permissible deviation
Linde VNA directives // Guide systems
Tolerance with inductive wire guidance
Fig. 15: Minimum distance
Deviation of the guide wire from the theoretical centre line over
the entire aisle length +- 5 mm (see Fig. 14) is within the tolerance
range. In order for these deviation tolerances to be achievable per
DIN 15185 part 1, the guide wire should be routed after the racks are
assembled.
140 mm
Distances for inductive guide wire
As a rule, the distance from the steel reinforcement to the guide wire
(c) must be at least 50 mm. A lower distance between reinforcement
and guide wire is possible but must be determined using field measurement. Metal (cable ducts, expansion joint angle, etc.) must be
kept at least 200 mm away from the left and right of the guide wire.
Safety distance
With inductive wire guidance a minimum distance of 140 mm is
required (see Fig. 15) between load and truck cabin.
Distance between two guide wires
of the same frequency: min. 1200 mm
(see Fig. 16). If this distance is not met, the magnetic fields may malfunction (exception: return lines that are not used as a travel path).
Fig. 16: Functional principle
Receiver antennas
Transmitting antennas
(coil)
Guide wire
10 mm
50 mm
6 mm
Iron reinforcement
Sub-concrete
25
Linde VNA directives // Guide systems
Entering and exiting the aisle/changing aisles
Entering the aisle
With inductive wire guidance, the changeover aisle width compared to the alternative rail guidance must be enlarged by approx.
1000 mm (see Fig. 17).
In the changeover aisle, the forklift truck driver drives the truck at
a sharp angle in the direction of the guide wire and switches to
automated operation. The smaller the tracking angle, the faster the
truck lines up (displayed by an optical and acoustic message). The
guide wire should be pulled in as far as possible in the changeover
aisle. The minimum dimension here is a truck length plus 500 mm
(see Fig. 17).
Exit from the aisle
After exiting out of the aisle, the driver switches back to manual
mode and the truck can be driven again freely.
Fig. 17: Entering the changeover aisle
Select the changeover
aisle to be 1000 mm
larger than with the
mechanical guide
Maximum tracking
angle 60°
500 mm minimum distance
between sensor and end
of guide wire
26 Optimum tracking
angle 45°
Position of the inductive
guide wire
Linde VNA directives // Guide systems
Frequency generator
The frequency generator has connections for a max. of 8 separate
loops with each up to 2000 m summing up to a total of 16000 m. It
feeds the guide wire with high frequency AC. If a single driving loop
is damaged this loop then fails entirely. Therefore it is recommended
to reduce downtimes by splitting of the wire guidance in a warehouse in different loops.
The supply voltage is 230 V AC at 50 Hz or 115 V AC voltage at 50 Hz.
The frequency can be specified between 300 Hz and 20 kHz in 10 Hz
steps. Either 35 mA, 80 mA or 100 mA can be selected as adjustable
loop current.
A protected, easily accessible position in the storage area should be
selected for assembly of the frequency generator. If there is a power
failure, an independent power source (buffer battery) can be used
as emergency power supply and sustain operation for approx. 2 additional hours.
27
The driver assistance system
Driver assistance systems support the driver when operating the
truck and are especially used for safety in storage areas. Part of the
driver assistance system is the end of aisle safety functions, heightdependent shut-off, as well as the Linde navigation system. Whereas
end of aisle safety features and driving speed reduction are prescribed by DIN 15185 part 1 or DIN 15185 part 2, the Linde navigation system is a supplementary system, which can increase both the
handling performance as well as avoid incorrect storage.
28 Linde VNA directives // Driver assistance system
Systems for determining position
General
Assistance systems in very narrow aisles such as traction and lift
cut-outs can be implemented with different systems. The currently
available systems are magnet operated switches, reflected light sensors, bar codes and RFID Tags. Whereas magnets and reflected light
sensors can be used for traction and lift cut- outs, the functionality of
bar codes and RFID is expanded somewhat further and can be used
with VNA navigation.
End of the
aisle safety
features
Lift and .
raction.
cut-outs
VNA.
navigation
Magnets
x
x
Reflected light
sensors
x
x
Bar codes
x
x
x
RFID
x
x
x
In the following, we would like to provide a brief overview of the
various systems. Each of these systems has advantages and disadvantages so that no general recommendation can be given.
29
Linde VNA directives // Driver assistance system
Magnets
Linde magnets are very small (31 mm diameter, 25 mm height)
and thus very simple and cost-effective to install. Two magnets are
installed in the floor at approx. 6 cm distance, one behind the other.
Depending on if the south pole or the north pole magnet is driven
over first, the truck detects in which direction the truck is moving
and thus, if and how the truck must brake. To be able to represent
different functions, there is also the option to place the magnets 150
mm or 300 mm off centre. Magnets are ideal in storage areas where
simple traction and lift reductions are necessary.
Fig. 20: End of aisle safety features using floor magnets
Open end of aisle
Closed end of aisle
N
1000
N
S
30 N
S
Absolute stop with
positioning move
Beginning of aisle end zone
Vmax
V-Check/
Beginning of aisle end zone
Temporary stop
A
Aisle detection with inductive
guidance using reflector
(A or alternative B)
Vred
300
S
Temporary stop
Middle
of aisle
Vred
150
Drive direction
Start of the rack
Vmax
Linde VNA directives // Driver assistance system
Reflected light sensors
Linde reflectors are attached at eye level to the uprights. Attachment
to the racks is cost-effective and fast. The reflectors are grouped into
A, B, C, D. These each have a different function:
A reflector: aisle detection, or beginning of the aisle end zone
B reflector: aisle detection (alternative when A reflector is not
possible).
C reflector: testing the reduced target speed
D reflector: absolute stop with positioning move
Fig. 21: End of aisle safety features using reflected light sensors
Open end of aisle
B
Closed end of aisle
C
A
Specify
on site
1000
Start of the rack
D
A
Absolute stop with
positioning move
Beginning of aisle end zone
Vmax
Beginning of aisle end zone
Vred
V check/temporary stop
A
Vred
Middle
of aisle
Aisle detection with inductive
guidance using a reflector
(A or alternative B)
Lrack
Drive direction
Vmax
31
Linde VNA directives // Driver assistance system
Bar codes
Linde bar codes are attached approx. 50 cm above the floor on
all rails. The truck scans the bar code and can determine its exact
position in the storage area. Exactly determining a location makes it
possible to assign various reactions from the truck to a location. In
this way, the most varied and complicated truck functions such as
lift and driving restrictions can be implemented. Exactly determining
a location is also the basis for Linde‘s very narrow aisle navigation
system as it supports the driver during storage and removal of the
correct pallets and avoids errors.
32 RFID
Linde RFID tags are especially small and can be installed very quickly
and easily in the floor with a standard drilling machine. They work
at a frequency which enables fast reading and writing on the tags.
Even if the tags get wet, they are protected and retain their function.
The truck reads the RFID tags and can exactly determine its position
in the storage area. Exactly determining a location makes it possible
to assign various reactions for the truck to a location. In this way, the
most varied and complicated truck functions such as lifting and driving restrictions can be implemented. Exactly determining a location
is also the basis for Linde‘s very narrow aisle navigation system as it
supports the driver during storage and removal of the correct pallets
and avoids errors.
Linde VNA directives // Driver assistance system
End of the aisle safety features
End of the aisle safety features mean stopping or braking the industrial truck without input by the operating person at the end of the
very narrow aisle. This measure also applies to cross aisles with the
exception of those expressly provided as escape routes which cannot
be entered from outside.
Please note that the above mentioned “End of the aisle safety features” system is an emergency solution. There are other braking options (depending on model) available to the driver such as generator
brakes, reverse current braking, and the mechanical braking on the
drive wheel.
Zones and functions
Driving speed reduction
From the beginning of the aisle end zone to the end of aisle, the
speed is reduced from Vmax to Vred = 2.5 km/h.
When driving out of the aisle Vred = 2.5 km/h.
Driving stop
Temporary stop
At the beginning of the aisle end zone the truck is braked to a standstill. After 2 seconds, there is a new drive release in the direction of
the end of aisle with Vred = 2.5 km/h.
Absolute stop
Braking with absolute stop is done when the end of aisle is closed.
When braking is finished, the truck is stopped. A positioning move
in the direction of the end of aisle can be done using the “Q“ button
(acknowledgement button pressed and held) with Vred = 1 km/h.
Speed check
Additional control point: testing the reduced target speed Vsoll<Vmax/2
(only for systems with reflected light sensors).
33
Linde VNA directives // Driver assistance system
Height-dependent cut-offs
When system-dependent components, such as joists, pipes, and
cable racks restrict the effective range and height of the industrial
trucks, lift-height dependent cut-offs must be provided.
Bridgeable intermediate lift limitation
In this interlock, the lifting movement is always switched off using
a switch before reaching the critical overhead clearance. The driver,
once he is convinced that the industrial truck is not in the danger
area, can continue the lifting movement by pressing an acknowledge
button and actuating the lift valve. When the highest height of the
industrial truck has exceeded the critical height, driving is only possible at creep speed.
34 Automatic lift or traction cut-out
The combination of height query on the lift mast and the systems for
determining position (magnets, RFID, etc.) allows this lift or traction
cut-out to be automated.
If an industrial truck enters such an area at a height that is currently
less than the critical height, he can continue without restriction at
the appropriate speed. If the industrial truck enters this area, stops
there, and the lifting movement is triggered, this is switched off just
before reaching the critical height. Bypassing this cut-off is not possible.
If the industrial truck enters this area at a height that is currently
greater than the critical height, the driving movement is braked and
the lifting movement is switched off. Driving further is only possible
after lowering below the critical height. Lift cut-outs are often combined with traction cut-outs.
Linde VNA directives // Driver assistance system
VNA navigation
Using Linde’s very narrow aisle navigation system can increase handling performance and at the same time, ensure secure storing and
removing of stock by preventing errors. Additionally, the navigation
system makes the work easier for the driver and also makes it possible for new drivers to quickly work efficiently.
The truck receives its transport or picking order via data transmission
from the warehouse management system on its truck terminal. Using
the navigation system, the truck can move in the fastest possible
way from its current position to the required pallet storage location. The driver only has to steer using the drive and lift lever. This
ensures that the driver has both hands within the truck contours
and thus cannot be injured. The truck moves in an ideal curve to the
specified pallet storage location. Storing or removing the pallet in the
wrong location is ruled out.
Operation of the very narrow aisle navigation is fast, precise, and
simple at the same time. The basis for all functions of Linde’s very
narrow aisle navigation system is the exact determination of the
truck’s position. Determining position can be done using RFID tags
and using bar codes (see Fig. 18).
Fig. 18: Functional principle VNA navigation
3. Assigned pallet location
2. Diagonal driving in the aisle using
a time-optimised path to the pallet
storage location
1. Locating the truck using
RFID tags or bar code
35
Linde VNA directives // Driver assistance system
This combination of position detection and detecting the required
pallet storage location makes the system efficient and prevents
incorrect storage.
Optimised operation using position navigation saves time by up to
25%. The green line in Figure 19 shows the fastest route with the
lowest energy and time consumption.
Fig. 19: Time savings with VNA navigation
36 Linde VNA directives // Driver assistance system
Personnel protection systems
To be able to operate a very narrow aisle warehouse, measures
to protect personnel in storage areas must be taken in Germany
in accordance with BetrSichV. The following two options can be
considered as standard: stationary and mobile protection. Stationary
protection uses a photosensor system which is mounted on the rack,
and which can distinguish between people and industrial trucks.
Mobile protection uses sensors mounted directly on the truck which
warning the driver as soon as someone or something is too close to
the vehicle.
37
Linde VNA directives // Personnel protection systems
Legal regulations
In accordance with the workplace regulation 1.8. , pathsways, point
(3) a side clearance for pedestrians on each side of the industrial
truck in a VNA aisle should be guaranteed . Although a defnite value
is not given the clearance taken as a guideline is 50cm on each side
which is derived from the DIN EN 349.
In BetrSichV, basic options to protect persons in very narrow aisle
warehouses are described as technical or structural measures. Structural measures typically do not suffice, thus only a technical solution
is offered. There is a distinction here between stationary (photosensor equipment on the very narrow aisle entrances) or mobile
(systems installed on the truck) systems.
Fig. 22: Truck detection
If you operate a very narrow aisle warehouse or want to start operation in a new very narrow aisle warehouse the protective measures
should be on an up to date standard. In germany they should meet
the performance level b.
Stationary protection
Each access of the very narrow aisle is individually protected with a
photosensor system. Emergency exits and access doors are normally
protected by swinging doors.
Fig. 23: Personnel detection
Photosensors for
truck detection
Controller
Controller
Photosensors for
personnel detection
38 Linde VNA directives // Personnel protection systems
“Person authorisation” mode of operation
In the “Person authorisation” mode of operation, the aisle is
free for access by persons, and every attempt at truck entry
would immediately trigger an visual and acoustic alarm. This
alarm can only be reset by an authorised person using a key
switch, who can see what is happening in the aisle.
“Truck authorisation” mode of operation
In the standard “Truck authorisation” mode of operation, the
truck is automatically detected when entering the aisle. In
this mode of operation, if a person enters the aisle, a visual
and acoustic alarm is triggered. This alarm can only be reset
by an authorised person using a key switch, who can see
what is happening in the aisle.
Truck detection by wide-angle photosensors
In this solution, two wide-angle transmitters are attached
on the left and right of the industrial truck and a receiver
with two receiving elements is attached to the rack. The
two transmitters detect the industrial truck, regardless if it
enters the very narrow aisle forwards or backwards.
Mobile protection
The industrial truck is equipped with laser sensors on both sides.
These monitor the travel path and detect when a person is in the
warning field or the alarm field. If a person is detected in the warning field, the speed is automatically reduced to creep speed (max.
2.5 km/h). If a person is detected in the alarm field, a alarm is
triggered and the truck is braked automatically until standstill. For
reasons of safety, the alarm can only be reset by the driver after the
truck is completely at a standstill. The monitoring equipment is not
active outside the very narrow aisles.
Assembly of the scanner
For reasons of space, the scanner can only be attached in most cases
to the front side behind the fork. This means that if the fork is lowered, there is no view and thus also no safety function. In this case,
the industrial truck may only drive at creep speed (max. 2.5 km/h).
A magnet operated switch on the lift mast will determine if the
scanner has an unencumbered view. The scanner is then activated.
If there are no other speed limitations (cross aisles or the end of the
very narrow aisle), the industrial truck can move at maximum speed
in the very narrow aisle.
39
Linde VNA directives // Personnel protection systems
Additional function
In order to have fully functioning mobile personal protection measures, e.g. detection of drive direction, end of aisle, cross aisles, or
exiting aisle, additional elements are required.
Drive direction sensor
A drive direction sensor is attached on one of the two non-driven
trailing wheels. This detects the direction of movement as well as the
speed and performs a distance measurement.
Additional functions
To increase safety, additional functions are implemented using the
drive direction sensor. At commissioning, the braking distance of the
industrial truck is measured from full speed to standstill. Braking distance and delay are then saved in the controller. During each braking
process the actual braking distance is measured and compared with
the stored braking distance. The driver is notified of diminishing
braking efficiency via the terminal. Afterwards, the truck can only be
operated at creep speed for safety reasons.
Position detection
Position detection can be performed using reflected light sensors
with coded reflection marks on the rack or using aisle magnets with
magnet operated switches. The first coding is located on the access
to the very narrow aisle. When this coding is detected, the protection
system is initialised, i.e. the drive direction sensor starts the distance
measurement and determines the drive direction. The protective
fields are activated.
Fig. 24: Mobile protection
Laser scanner
Alarm field
Warning field
40
Linde VNA directives // Standards
Standards
Cited standards
• ISO 6292: Powered industrial trucks and tractors — Brake
performance and component strength
• D
IN EN 1045 Part 2: Concrete, reinforced and prestressed concrete
structures - Part 2: Concrete - Specification, properties, production
and conformity
• DIN EN ISO 13849 Part 1: Safety of machinery - Safety-related parts of control systems - Part 1: General principles for design
• D
IN EN 1045 Part 3: Concrete, reinforced and prestressed concrete
structures - Part 3: Execution of structures
• DIN EN 349: Safety of machinery - Minimum gaps to avoid
crushing of parts of the human body
• DIN 18202: Tolerances in building construction - Buildings
• D
IN EN 18560 Part 7: Floor screeds - Part 7: Heavy-duty screeds
(industrial screeds)
• D
IN 15185 Part 1: Warehousesystems with guided industrial trucks;
requirements on the ground, the warehouse and other requirements
• D
IN 15185 Part 2: Industrial trucks - Safety requirement - Part 2:
Use in narrow aisles
Additional standards
• D
IN 15184: Power operated industrial trucks; industrial trucks for
rack operation, technical safety requirements and testing
• F EM 9.831 Calculation principles of storage and retrieval machines.
Tolerances. Deformations and clearances in the high-bay warehouse
• FEM 10.3.01 Pallet racks, tolerances, deformations, and clearances
• D
IN EN 1081: Resilient floor coverings - Determination of the
electrical resistance
• D
IN EN 15620: Steel static storage systems - Adjustable pallet
racking - Tolerances, deformations and clearances
• V
DMA directive “Floors for use with very narrow aisle industrial
trucks”
• D
IN EN 15635: Steel static storage systems - Application and
maintenance of storage equipment
• D
IN EN 15512: Steel static storage systems - Adjustable pallet
racking systems - Principles for structural design
• D
IN EN 15629: Steel static storage systems - Specification of
storage equipment
• D
IN EN 1726 Part 2: Safety of industrial trucks - Self-propelled
trucks up to and including 10000 kg capacity and tractors with
a drawbar pull up to and including 20000 N - Part 2: Additional
requirements for trucks with elevating operator position and trucks
specifically designed to travel with elevated loads
Linde Material Handling ranks among the world’s leading manufacturers. This position has been justly earned. Linde trucks
excel not only with their recognized innovative technology but especially their low energy and operating costs, which can be
as much as 40% less than competitors.
High quality in production is matched by the standard of the services we provide. With a comprehensive network of local
sales partners, we are at your call around the clock and around the world.
Engineered for your Performance
Linde Material Handling GmbH, Postfach 10 0136, 63701 Aschaffenburg, Germany
Phone +49.60 21.99-0, Fax +49.60 21.99-15 70, www.linde-mh.com, [email protected]
Printed in Germany . 031.e.0,1.1012.IndE.DD
Your local Linde partner offers you a complete single-source package. From qualified pre-sales consulting through the sale
to after-sales service; including finance packages matched to your business requirements. Leasing, rental or hire purchase.
Flexibility is maintained in your operational and decision-making processes.