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D8+ Chain Hoists – BLUMANO
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D8+ Chain Hoists
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D8+ Chain Hoists
The Life
Many years ago, a German Code of Practice named SR2.0, forged
Expectancy of a
three simple abbreviations to describe the technical
Chain Hoist
characteristics of electric chain hoists and the implicit allowed
1 Apr 2019
Machinery
applications: D8, D8+ and C1.
D8 is the short for BGV D8 (formerly VBG 8), which is the name
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1 Mar 2019
1980, with the scope of regulating the design and use of winches,
hoists and pulling devices in industries other than entertainment.
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C1 is the short for BGV-C1 (formerly VBG 70 and now DGUV
17/18) that is also a German accident prevention regulation but
has the scope of regulating staging and production facilities for
the entertainment industry, including stage machineries (via DIN
56950).
It should be logical to deduce that D8+ (the + stays for plus) is the
abbreviation of BGV-D8+, another accident provision regulation:
well, sorry to disappoint you, but there is no such regulation in
Germany or in any other country we are aware of.
So, what is a D8+ chain hoist?
D8+ chain hoists are an interesting breed of hoist that can be
used to lift loads during the setup process with the hazard zone
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clear of people, and are hoists that are allowed to keep the load
suspended above people without the need of a secondary
suspension being installed. These electric chain hoists need to be
designed with speci c provisions in mind and must be tted with
supplementary safety-related elements to ensure an increased
level of safety.
However, due to the fact that their intended use is for motion
without people in the hazard zone, the safety measures related to
these machineries are a sort of a compromise between the basic
engineering requirement of industrial chain hoists and the
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restrictive provisions of stage machineries.
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 Case Studies
Where the D8+ chain hoist
originates?
 News
In 2005, the VPLT in cooperation with the Institution for Statutory
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Accident Insurance and Prevention in the Administrative Sector
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compiled a Code of Practice1 [CoP] named SR2.02 Electric Chain
Hoists.
The scope for the code of practice was to ensure a uniform level
of safety for the provisions and use of electric chain hoists in the
event industry, taking under consideration the established best
practices.
The CoP de ned a new type of electric chain hoist and named it
the D8+. The D8+ hoist was an electric chain hoist based on the
BGV-D8 speci cations, used to lift loads during setup and with the
special characteristic of being able to hold loads at rest above
people without using a secondary safety component.
In 2010, the CoP was revised and the name changed from SR2.0
to SQ P2:2010. The SQ P2:2010 had the extended scope to de ne
the D8 Plus chain hoist requirements and take under
consideration the travel and load mode conditions. The concept
of an Asynchronous and Synchronous group drive with group
stop – only mentioned in the SR2.0 CoP – was described as well as
many other common terms that were useful for a full
comprehension of the speci cations required.
The load systems – statically determinate and statically
indeterminate – were introduced, de ned and explained, with
references of hoist con gurations and drawing examples.
However, eight years later, the CoP was withdrawn and replaced
with
the IGVW SQP2:10/2018 also due to the con icts with the
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revised DIN 56950-1:2012 provisions. The new CoP IGVW
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SQP2:10/2018 was written bearing in mind the design provisions
as stated in prEN 17206:2018, therefore, we believe it is unlikely
that it will be revised after the publication of the new European
standard.
Figure 1 – 2018 o cial SQ P2 valid Code of Practice.
The D8+ chain hoist requirements changed during the years and
today they are very di erent from the initial provisions; many
users identify the D8+ chain hoist as an electric chain hoist with
double brakes and a bigger chain (and other requirements they
struggle to remember). In reality it is exactly those “other
requirements” that make the electric chain hoist ful l (or not) the
D8+ condition.
Let’s analyse each requirement, what is still applicable and what is
not, and how the provisions evolved during the last 15 years.
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One of the most important requirements for a D8+ hoist was the
size of the load chain. Chain hoist manufacturers select load
chains such that the relation between the load chain MBF and the
declared hoist rated capacity is above 4:1 in order to ful l
Machinery Directive requirements.
Basically, they apply the MD 2006/42/EC requirement as stated in
point 4.1.2.4 which requires that lifting chains must have a working
coe cient chosen in such a way as to guarantee an adequate level of
safety. As a general rule, this coe cient is equal to 4.
An example of such approach would be a nominal size 8 mm load
chain with a MBF of 80.4kN, for a hoist with a rated capacity of
1600 kg with 8 m/min max speed (the ratio also considers an
average 20% of dynamic forces).
However, the CoP argued that the provision stated in the
Machinery Directive concerning the coe cients to be applied for
lifting people (the mechanical strength of load-bearing lines),
should have also been applied for equipment left suspended
above people. From MD 2006/42/EC, chapter 6.1.1: The working
coe cients for components set out in sections 4.1.2.4 and 4.1.2.5 are
inadequate for machinery intended for the lifting of persons and
must, as a general rule, be doubled. This approach found its
con rmation in national standards (BS 7905-1, DIN 56950, NEN
8020-10, etc.), which adopted a similar criterion in order to
implement the passive redundancy in load-bearing elements.
In SQ P2:2010, the requirement stated that the operating
coe cient of the load-bearing material (tensile strength) should be at
least 10. At the time, the uno cial interpretation of the loadbearing material was referred to load-bearing lines as
suspensions.
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A couple of years before, in 2008, a CEN 15902-1:2008 technical
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used to carry loads should meet the requirements for a safety
factor of 8 at characteristic loading3. The concept of characteristic
loading listed in the CEN 15902-1:20084 explained that the
characteristic loading was the Safe Working Load5, plus the load
carrying device (equal the system load), plus the dynamic forces.
SAFE WORKING LOAD (SWL)
+
WEIGHT OF LOAD CARRYING DEVICE
=
SYSTEM LOAD
+
DYNAMIC FORCES
=
CHARACTERISTIC LOAD
In the case of a D8+ chain hoist, with the intended use of keeping
loads suspended above people, the dynamic forces were
excluded from the characteristic load calculation due to the fact
that in that condition, the load was at rest when people were
allowed to be in the hazard zone. The conclusion was that for D8+
chain hoists based on CEN 15902-1:2008, a load chain static
safety factor of 8:1 was su cient.
In 2012, the DIN committee published a revised standard as a
backbone for the BGV-C1 German regulations: the DIN 569501:2012. Concerning load chains, the DIN 56950-1:2012 matched
the CEN 15902-1:2008 requirements and stated that round steel
chains used to carry loads shall meet the requirements for a safety
factor of 8 at characteristic loading6.
The SQP2:2010 requirement “operating coe cient of the loadbearing material of at least 10” therefore automatically became in
con
ict with the DIN 56950-1:2012 – 8 at characteristic load.
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Nonetheless, this con ict was addressed and in the new SQ
P2:2018, the provision is that a static coe cient (at rest) of 8:1 is
su cient for the load chain7. The CoP also states that during a
lifting operation, it’s admissible for the safety factor of the chain
to go below 8:1 since there are no people in the hazard zone
during motion8.
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AUGUST 2019
The static coe cient (at rest) of a D8+ load
chain is 8:1.
Group Mechanism
In 2005, table 3.1.1 of SR2.0 stated that the dimension of a D8+
chain hoist lifting mechanism should have been 2 x rated load
and the group mechanism should have been minimum 1Bm. For
dimension of the mechanism, the CoP referred to the gearbox
and transmission elements and the 1 Bm class was related to the
expected lifetime of the hoist9.
In 2010, the Engineering Requirements were renamed as
Constructional Requirements and the “dimension of the motor” was
set to double the lifting capacity.
The “dimension of the motor” created controversial opinions in
the industry.
In the German version, the phrase Dimension des Triebwerks
meant
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Rightsthe dimension of the engine implied that the engine was
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both the gearbox and the electric motor, instead of only just the
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dimension of the motor. As a result, the requirement was that the
entire “engine” should have been dimensioned to lift and support
twice the characteristic load. The motor groups should have been
at least at M3, and this requirement referred to FEM 100110.
Figure 2 – Machinery mechanism and transmission gears.
In 2018, the Engineering or Construction requirement table
disappeared and now there are other recommendations. As
reported from the DTHG Technical Committee, “the chain hoist
load-bearing parts need to be dimensioned to bear twice the
characteristic load with the machinery at rest” [the German term
ruhedn11 means resting, dormant, stationary]. “There is no
demand for the D8+ hoist to be capable of lifting twice the
characteristic load for a minimum of 400 hours as de ned in prEN
17206 or DIN 56950”.

AUGUST 2019
When the chain hoist’s load-bearing
elements are at rest, they should be able to
keep suspended twice the chain hoist’s
characteristic load.
Friction Clutch
The allowance of a friction clutch, its location and use has been a
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controversial point of the D8+ chain hoist requirement’s history.
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In 2005, the SR2.0 table 3.1.1 stated Friction Clutch: no. Hence, a
friction clutch was not permitted, unless it was located outside
the load path when the electric chain hoist was disconnected
from the power supply. Annex IV of SR2.0 explained in detail the
position of the friction clutch for electric chain hoists. A friction
clutch was allowed as an overload device and chapter 3.1.3 of
SR2.0 also stated that the required shutdown condition could be
ful lled by means of a friction clutch.
NOTE: In 2005, the de nition of friction clutch meant any
friction coupling device installed between the lifting wheel
and the load securing devices (the brakes).
In 2006, the EN 14492-2 was published, explaining the concept of
a Direct Acting Rated Capacity Limiter12 (a friction clutch) as a
di erentiation from a Friction Coupling Device.
The international community debated for years about the
provisions related to the clutch inside (or outside) of the load
path (on the load side rather than on the motor side) and the
de nition of load modes, meaning the multi-hoist con gurations
had the potential of shifting loads in statically indeterminate
scenarios.
The debate led the German technical community and the VPLT
Chain Hoists Working Group to review the SR2.0, and issue a
review in 2010: the IGVW SQ P2:2010.
In 2010, the provisions for clutches were that a slip clutch was
allowed provided the conditions below were met:
a. In statically determinate mode, the slip clutch was
admissible on the load side, between the lift wheel and the
brakes.
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b. In statically indeterminate mode, the slip clutch should not
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have been used as protection against overload and other
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means should have been used to cut-out the hoists in the
group if 120% of the lifting capacity was reached.
The SQ P2:2018 states that direct-acting hoisting force limiters – no
matter if they are inside or outside the load path – cannot be
considered as overload devices for the D8+ chain hoist. Overload
monitoring can only be achieved with Indirect Acting Capacity
Limiters (sensors). The CoP also states that for D8+ hoists,
adjustable direct acting force limiters should be set higher than the
D8+ lifting capacity in order to be used as a lifting mechanism
protective device rather than as an overload device.
Friction clutch, slipping clutch, friction force limiter, friction torque
limiter and direct-acting capacity limiters are some of the many
names you can call a friction coupling device.
De nitions are related to the engineering solution, the device’s
function, its behaviour or simply what a device is normally called
in the market.
It is important to analyse the de nitions present in the original
Standards in German language, and the related translation in
English in order to make sure there are no misinterpretations.
SR2.0
Chapter 3.1.1: Rutschkupplung (translated: Friction clutch)
Annex IV: Anordnungen der Rutschkupplung bei Elektrokettenzügen (translated: Position of the friction clutch for electric
chain hoists)
SQ P2 2010
Chapter 4.1: Rutschkupplung (translated: Slip clutch)
SQ P2 2018
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Chapter 4.2.1.2: Direkt wirkenden Hubkraftbegrenzer (translated:
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direct-acting force limiter device, or direct-acting load limiter
device)
Chapter 4.2.1.1: Einstellbare direkt wirkende Hubkraftbegrenzer
(translated: adjustable direct-acting force limiter device, or
adjustable direct-acting load limiter device)
In all the de nitions above the friction coupling device is intended
as a torque limiter, which means an automatic device that protects
mechanical equipment, or its work, from damage by mechanical
overload.
Usually a torque limiter may limit the torque by slipping (as in a
friction clutch or slip clutch) or uncouple the load entirely (as in a
shear pin, used for other kind of machineries).
The fundamental point to be considered in order to understand
what is allowed and what is not, is the intended use of the friction
coupling device.
Slip/friction clutches used to prevent the machinery from
lifting more than the rated capacity are technically called
friction torque limiters or rated capacity limiters.
These devices should be located outside the load path (limiting
the force ow, on the motor side).
Device used to protect the lifting mechanism from damages
by mechanical overload, also when chain hoists are
disconnected from the power supply, are friction coupling
devices or mechanical protector devices.
These devices are allowed within the load path, but they need to
be rated much higher than the permissible load capacity 13.
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AUGUST 2019
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Adjustable friction clutches, slip clutches,
direct-acting force limiters located outside
the load path are allowed but they cannot
be considered an overload protection
device.
Friction coupling devices located inside the
load path/force ow are allowed provided
they are set higher than the D8+ rated
capacity (prEN 17206 provisions are that the
setting should be at least twice the rated
capacity).
Load Securing Devices
The benchmark requirement for a D8+ chain hoist has been the
presence of two load securing devices, which means two
mechanical devices that can bring the load to a de ned stop and
prevents unintentional movement (for example, brakes,
dynamically irreversible worm gears, shut-o valves, etc.). The
most common way to implement such a redundancy requirement
is to t the electric chain hoists with a double brake system,
although there are chain hoists in the market which have one
brake and one irreversible worm gear lifting mechanism.
SR2.0 in 2005 explained the requirement as such: Safety brake or,
alternatively, dynamic transmission brake: 2 x, basically either “two
electromagnetic brakes” or “one electromagnetic brake + one
worm gear” (provided it was a self-sustaining worm gear with at
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least 85% of non-reversibility).
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SQ P2:2010 read more or less the same: Numbers of brakes (or
self-locking gearbox): 2.
SQ P2:2018 reiterates the same concept of the need for two load
securing devices although it also states that an electric chain hoist
equipped with double brakes and used for half of its capacity can
be considered to meet the D8+ requirements14.

AUGUST 2019
A D8+ chain hoist must be tted with two
load securing devices (for example brakes
or dynamically irreversible worm gears).
Figure 3 – How big does the chain need to be?
Load Monitoring
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Monitoring the load, overload and underload conditions, has
been a requirement for D8+ hoists since the beginning.
In 2005, SR2.0 stated: Overload Monitoring: Shutdown and
Underload Monitoring: no.
The requirements were mainly referring to the friction clutch.
In 2010, the requirement was updated to: Overload Monitoring:
Protection against overloading and Underload Monitoring: no.
In 2018, the concept has been better explained, therefore, chain
hoists with built-in friction coupling devices rated at 200% of the
rated capacity, will be suitable to become D8+ hoists, provided
they are always put into service together with a load monitoring
system capable to shut-o the hoist in motion once they reach
120% of the rated load. The load monitoring system will act as an
Indirect Rating Capacity Limiter, suitable for overload protection,
and the protector kit will be considered an admissible friction
coupling device.

AUGUST 2019
D8+ chain hoists must be tted – or put into
service – with an overload system capable
to shut down all the hoists in motion if an
overload condition of 120% occurs. In other
words, the D8+ chain hoist’s machinery
movement should be stopped when the
load exceeds 1,2 times the characteristic
load.
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Other Requirements
Limit Switches.
SR2.0 stated: Emergency Limit Switch: no – Limit Switch: no.
SQ P2:2010 stated: Emergency Limit Switch: no – Operating Limit
Switch: possible. Although the emergency limits were not required,
the operational limits were possible.
In the SR2.0, the interpretation of the condition for the “Limit
Switch: no” could have been misleading and indicated that the
limits switches were not acceptable, rather than not required.
The SQ P2:2010 allowed the presence of the limit switches
although they were not necessary, but the provision was still
misleading. The same wording has also been used to describe the
underload requirement: Underload Monitoring: no. Common sense
suggests that the requirement is not necessary rather than
forbidden.

AUGUST 2019
Limitation of travel via limit switches is
required only where overtravel can result in
mechanical damage or failure.
Underload monitoring is not a necessary
requirement for D8+ chain hoists.
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There are a lot more details included in the SQ P2:2018, such as
the importance of a risk assessment as a tool to deviate from the
CoP requirements and the examination of how a “D8+ condition”
can be reached from a system point of view rather than using
already compliant D8+ machinery.
We believe that the clari cations contained in this case study are
su cient to allow manufacturers and users to understand the
D8+ scenario a little bit better.
If you ask to yourself, for how long the D8+ chain hoist
denomination will remain alive within the market, we may say
probably not for long. Apparently, new European guidelines will
replace this and other national regulations very soon, bringing
clarity and common approaches and introducing even a simpler
and rational denomination for all machineries used within the
entertainment industry. However, the D8+ chain hoist still serves
a very important part of the industry and riggers of any part of
Europe (and abroad) rely on this a ordable type of machinery for
their daily installation.
Tomorrow these chain hoists may be called di erent names, but
the long journey of the D8+ hoist is not in vain; this hybrid
equipment, created as compromise between industrial and stage
machineries, has been the bridge to ll in the gap between two
markets that are very di erent from each other.
And when a void between industries is lled, the pattern toward a
better understanding of its challenges… is already drafted.
1. The German word for “Code of Practice” is “Standard’. The German word for
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“Standard” is “Norm”.
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2. VPLT. SR2.0:2005 | Code of Practice for Event Technology – Provision and
Use of Electric Chain Hoists.
3. EN 15902-1:2008 Chapter 5.4.2.2 Chains.
4. CEN 15902-1:2008 Chapter 3.2 Loads and forces, Table 1.
5. CEN 15902-1:2008 Chapter 3.2.6 SWL is maximum load (mass) as assessed
by a competent person which an item of lifting equipment may raise, lower or
suspend under the particular service conditions.
6. DIN 56950-1:2012, Chapter 5.2.2.2 Chains.
7. Das Tragmittel (Kette) besitzt für den Zustand „ruhend“ einen
Betriebskoe zienten von 8.
8. Für den Zustand „in Bewegung“ sind niedrigere Betriebskoe zienten
zulässig, da sich in diesem Zustand keine Personen im Gefahrenbereich
aufhalten dürfen.
9. See the article “The life expectancy of a chain hoist”.
10. Booklet 2, chapter 2.1.3.1, stating that individual mechanisms as a whole
are classi ed in eight groups, designated by the symbols M1, M2, M3……M8, on
the basis of ten classes of utilisation and four classes of loading spectrum.
11. Für den Zustand „ruhend“ sind die Betriebskoe zienten aller sich im
Kraft uss be ndlichen Elemente des Elektrokettenzuges bekannt und
mindestens für die doppelte Tragfähigkeit des D8 Plus.
12. EN 14492-2:2006 – Chapter 5.2.2.2.2.
13. They need to be constructed in such a way that in the case of a failure of
plastic or rubber parts, there is a positive engagement by metal parts. EN
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14. SQP2:2018 Chapter 4.2.1.2, rst paragraph.
August 1st, 2019 | Articles, Case Studies
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