Richard Jaeger-Forzard

enie.

A TEREX BRAND

22"4 July 2014

Re: Coroner’s Report - Kimberly Depot Accident: 5"June 2013 / Genie Z135/70
Dear Sir,

The following is a response to the Regulation 28 Report issued on 30" May 2014. Following the
accident on 5" June 2013 at the Kimberly Depot in the United Kingdom, Genie Industries, Inc.
conducted a full investigation of the accident. In addition, Genie has thoroughly reviewed and
confirmed the design, testing and manufacturing procedures for the Z135/70. Based on the
information and data available, Genie believes that the machine became unstable because it was
mis-calibrated. These conclusions are consistent with the findings made by [I

On 29" July 2013, Genie issued a mandatory Safety Notice that requires all Z135/70 owners to
remove their machines from service and to confirm that the secondary boom angle sensor on all
machines is calibrated correctly before returning the machines to service in accordance with the
procedure set out in the Safety Notice. A copy of the Safety Notice is attached hereto. In
addition, through research and development efforts, Genie has updated the controller software
that, in the event of a mis-calibration, prevents machine instability. The following four updates
to the control system software are discussed below. These changes update the calibration and
operation of the secondary boom angle sensor.

Software Update No. 1 - Value too High Voltage Diagnostic. The voltage diagnostic
for a “Value Too High” has been recalculated based on the sensor range. Working in
tangent with software update no. 2 Secondary Boom Up During Extend, if the sixth point
is calibrated at a value lower than the maximum angle, the boom will continue to rise
until reaching the new closer “Value Too High” diagnostic. This diagnostic informs the
control system to stop functions associated with the diagnostic.

Software Update No. 2 - Secondary Boom Up During Extend. Secondary boom up is
energized for 20 seconds anytime the secondary extend function is activated. Looking at
the hydraulic system, if the boom is left in the raised condition and the oil is hot and
allowed to cool the boom potentially can lower a couple degrees due to the thermal state
change of the hydraulic oil. Thus, if secondary extend is activated, the secondary boom
up output is enabled at 50% for 20 seconds. This lifts and pressurizes the lift cylinder to
hold it at maximum angle.

Software Update No. 3 - Primary and Secondary Calibration Windows. The earlier
revisions of the software only required that all calibration points were ascending in output
voltage. The latest version has “windows” in degrees and voltage for each calibration
point. The windows were developed from a statistical analysis of data obtained from

1

a
enie.
A TEREX BRAND

existing production machines for angle vs. output voltage. Now each calibrated point
must reside in an expected range of output voltages.

Software Update No. 4 - Active Crosscheck Fault. Note: This update is not related to
machine instability or mis-calibration. If the output of the angle sensor remains constant
for more than 7.5 seconds while the boom up or down directional or proportional valves
are active then a fault will be declared. This cross-check should apply only if the angle
sensor is in the middle 80% of its range, the function input is greater than 50%, and the
auxiliary power is not active.

The updated software no longer tolerates an incorrect secondary boom angle calibration. If the
machine is mis-calibrated, the software faults the machine out in a stable and safe position as
designed. The fault interrupts machine movement automatically and prevents further boom
extension eliminating the potential for machine instability.

Genie requires operators to conduct a pre-operation function test from the ground controls before
entering the platform. Any errors in calibration or machine faults will be detected during this
inspection. However, in the event of a fault during operation from the platform, certain machine
functions will remain active, allowing the operator to lower the platform safely. Genie began
installing the updated software on the Z-135/70 manufacturing line on 1* April 2014. As of 14th
July 2014, Genie has made this updated software available to all Z135/70 owners. On the 14%
July 2014, Genie issued a Service Advisory to all Z135/70 owners. This advised owners to install
the software in a number of situations including when the secondary boom angle sensor needs to
be calibrated for any reason. A copy of the Service Advisory is attached hereto. Genie’s actions
have eliminated the potential for machine instability due to human error.

Genie has also carefully evaluated the design alternatives proposed by Kimberly, and adopted by

(discussed in detail below). Based on Genie’s analysis, evaluation and engineering
experience, the proposed alternative designs do not address or prevent the root cause of this June
2013 accident. As noted above, the accident occurred because the boom was mis-calibrated.
The designs suggested by Kimberly will not prevent mis-calibrations. The proposed switch can
be mis-calibrated or fail leading to instability

Genie installed and evaluated several switch ideas onto a prototype Z135/70 machine to examine
the implementation of this design. While the intent of the proposal was to prevent the type of
accident experienced, the switch will not prevent machine mis-calibration and requires a custom
installation due to the design tolerances between the secondary boom and the turntable
connection.

The proposed switch also adds to complexity and requires an additional, separate calibration
procedure. The switch would have to be calibrated after the angle sensors are calibrated.

enie
A TEREX BRAND :
Genie’s assessment is that the switch does not comply with Performance Level D requirements
of EN280 and EN ISO 13849. In general, safety-related parts of a control system that performs a
safety function must satisfy the following requirements:

© Well tried component;

e Be monitored for failure;

e If used in line with power to output, it must be normally closed forced open in an unsafe
condition;

e Be redundant. No single failure would result in the loss of safety.

The proposed switch does not meet any of these requirements. Unlike the dual (redundant) angle
sensors used on the Z135/70, this single mechanical switch operates separate from the control
system. If the switch is damaged or is improperly calibrated, the control system will not be able
to detect the problem.

In conclusion, Genie has appropriately addressed the issue of mis-calibration by updating the
software in the control system and making it available to all Z135 owners. The accident on 5m
June 2013 would not have happened had the machine been properly calibrated. If an error is
made during calibration, Genie’s updated software addresses this issue and prevents machine
instability. Kimberly’s proposed design modifications do not prevent machine mis-calibration,
are unreliable within the application of a Z-135/70, are subject to human error, do not comply
with industry standards, and add unnecessary complexity to the machine.

Sincerel

Joe George
Vice President & General Managing Director

Terex Aerial Work Platforms
Terex Global GmbH
Muhlenstrasse 26

8200 Schaffhausen, Switzterland

Tel:
Mob:
Fax:
Email:

Enclosures:

1 Mandatory Safety Notice dated 29" July 2013
2 Service Advisory dated 14" July 2014
3