Feature: Suitable for explosive
 atmospheres

0

Graco’s EcoQuip vapour abrasive
blast equipment was thoroughly
tested for use in potentially
hazardous areas involving explosive
atmospheres

Abrasive blasting often has to take place in hazardous or explosive
 environments, such as the power 
generation, construction, oil and gas, shipping,
 petrochemicals and chemicals industries,
 and where flammable liquids, vapours or
combustible dusts exist.

In such environments,
it’s vital to use abrasive blasting equipment that 
has been fully tested to determine whether the 
blasting process might lead to an ignition.
 EcoQuip is Graco’s vapour abrasive blasting
 equipment. It’s been proven to be suitable in 
different industries for a range of applications 
such as the removal of paint, rust, corrosion,
industrial coatings and linings; for cleaning 
metal, stone and woodwork; and for building 
and site maintenance. In all these applications,
 EcoQuip has been demonstrated to reduce 
project costs and increase the speed, efficiency
 and productivity of blasting.

PUTTING ECOQUIP TO THE TEST
Gexcon AS of Bergen, Norway, a world-
leading company in the field of safety and 
risk management, and advanced dispersion,
 explosion and fire modelling, was asked to 
perform tests to determine whether sparks
generated by the EcoQuip system would be 
potential sources of ignition. The experiments
 were performed at Gexcon’s test site at 
Børnesskogen, Norway in May 2019.

EcoQuip is intended (and is ATEX approved)
 for use in atmospheres of flammable materials
in the Equipment Protection Level (EPL) 
Subgroup IIA. This subgroup of explosive 
gases includes diesel fuels, petrol fuels, hexane, 
methanol, propane, ethane, acetone, toluene,
benzene and methane.
For the purposes of this test, hexane was 
selected. At a concentration of only around 4%
in air, hexane is not only extremely sensitive to
electrical sparks, but is easy to ignite. It has an 
auto ignition temperature of 230 °C. Tests were therefore performed in explosive atmospheres
 with a rich concentration of n-hexane.
The tests were performed in a 50 cubic
meter testing vessel. It had to be relatively 
large due to the air coming into the system 
from the blasting equipment diluting the gas
mixture. Its large size would also permit a longer
 duration of the tests. The vessel was open at
one end, which was covered with a plastic sheet
 to contain the combustible gas/air inside the
vessel as well as to relieve the pressure of an
 explosion should one occur.
The vessel was equipped with a recirculation
system with a n-hexane evaporation system.

Pure n-hexane vapour was injected into the 
recirculation system to gradually increase
the n-hexane concentration inside the vessel.
N-hexane concentrations around 7% were
normally used as the starting concentration and
diluted to around 4% for all tests. The mixture
of n-hexane vapour and air inside the vessel 
was monitored with a binary gas analyser from
 Stanford Research Systems Inc.
EcoQuip was positioned on the outside of
the test vessel, while the nozzle was inside the 
test vessel. A Graco standard #7 blast nozzle
(7/16”, 11mm) was used during the tests. The 
nozzle was connected via a 15 metre hose to
the equipment. EcoQuip was earthed to the test
 vessel using its green earthing cable. The nozzle  
was mounted in rubber mounting brackets to
prevent it from being earthed
to the steel in the vessel in
order to best simulate a person
holding the nozzle. EcoQuip was
supplied with water from a 1000
 litre water tank standing on the
roof of the testing vessel, about
3 metres off the ground. Only
 gravity from this tank was used
to supply the system with water.
A Kaeser M122 air compressor
provided a steady pressure of
typically 7.5 bar (110 psi).
Five different abrasives were 
used with the Graco EcoQuip 
vapour abrasive blasting
 equipment during the test:
•

  • 30/60 mesh Garnet (GMA).
• 80 mesh Garnet (GMA).
•
  • Fine Copper Slag 0.2-1.0 mm
grit size (Star Grit).
•
  • Coarse Copper Slag 0.4-1.9
mm grit size (Star Grit).
•
  • Fine Crushed Glass 0.2-0.6
mm.

Blasting was performed on
 rusty steel and aluminium plates 
of approximately one square
metre. These could be moved 
during a test, making it possible 
to blast on new material. The
five abrasives were used on 
both steel and aluminium plates,
making a total of ten test runs.
The duration of each test run
 lasted between 3.2 and 7.5
minutes. The abrasives and 
blasting materials were chosen
to cover the typical worst-case 
combinations when it comes to
spark generation.

ECOQUIP PASSES WITH FLYING
COLOURS
None of the tests yielded an ignition. After the 
last test, the explosive atmosphere inside the 
vessel was ignited using an oscillating spark
in order to confirm that the atmosphere was
 indeed explosive. (It was!).
Gexcon therefore fully endorses Graco’s
EcoQuip vapour abrasive blasting equipment as
suitable for use in potentially hazardous areas 
involving explosive atmospheres caused by
gases and vapours of the Subgroup IIA. These
tests support EcoQuip’s ATEX ignition hazard
analysis for category 2 equipment in zone 1 explosive atmospheres. ■

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