R&D programme
Research brief
Performance and installation criteria
for sanding systems
T797
Background
The installation of sanding systems onto multiple units is covered by
Railway Group Standard GM/RT2461 - Sanding Equipment Fitted to
Multiple Units and On-Track Machines, issue 1. Since this standard was
produced, the industry has gained significant operational knowledge
through service experience. From this there have been a number of
developments in the performance and operation of sanding systems.
This research project examined the relevance of the existing sanding
requirements. It undertook testing and research to propose and support
future changes to these requirements.
Aims
The aims of this research were:
• To understand the rationale for selecting the existing GB interface criteria
set out in GM/RT2461 Issue 1.
• To establish the equivalent interface criteria for sanding systems in other
European networks.
• To determine whether evidence already exists to support changing the GB
sander interface criteria.
• To understand the dynamic performance of the sand delivery systems and
to determine the optimum design parameters
• To determine the benefits of withdrawing the current GM/RT2461
requirement restricting the installation of the first active sander after the
leading bogie on multiple units of 2 or more vehicles.
R&D programme: Research brief T797 - November 2015
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• To identify the benefits of utilising distributed active sanding systems along
different arrangements of multiple unit formations and the most
appropriate distribution of sanders for the typical arrangements of GB
multiple units from single vehicles up to formations with 6 vehicles.
• To consider how to specify the interface criteria for the deposited sand
between the wheel and the rail at the point of delivery and also the
appropriate measures to ensure end of train detection.
Method
This project was delivered in 3 phases. Phase 1 reviewed legacy sanding
work and international requirements to understand the rationale for
selecting the existing GB interface requirements. Phase 2 conducted
laboratory based tests to understand the dynamic performance of sander
delivery systems and to determine the optimum alignment relative to the
wheel/rail interface. Phase 3 outlined recommendations to achieve
distributed sanding systems along different arrangements of multiple unit
formations, including recommendations for standards change.
The laboratory based tests investigated the effect that different setup
parameters of a sanding system has on performance.
The wheel rail test rig at the University of Sheffield was used. The rig was
modified to install a sanding system representative of that typically
installed on GB multiple units.
The scope of the tests was delivered in two stages:
Stage 1 - Preliminary and investigative tests
Stage 2 - Dynamic tests to determine the optimum alignment of sanding
nozzles relative to the wheel/rail interface
The aim of Stage 1 was to observe and assess the dynamic performance of
the three set-ups identified in the research project T796 Understanding the
current use of sanders on multiple units, to determine which appeared to
be most effective at getting sand into the wheel/rail interface. The most
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R&D programme: Research brief T797 - November 2015
effective setup and the impact of changing other setup parameters were
then investigated in more detail by modifying variables such as:
• Height of hose or nozzle above rail
• Distance of hose or nozzle from wheel
• Angle of hose or nozzle to rail
The aim of Stage 2 was to undertake a series of dynamic tests using the
optimum setup conditions determined in Stage 1 to investigate the effect
of the changes on adhesion and track circuit operation.
Findings
Phase 1
The research found that the existing criteria were based on a specific set
of tests performed on two and three car diesel multiple units and that most
other countries do not have defined criteria for the installation and
operation of sanding systems. The research also identified recent studies
and testing activities which could support changes to the Railway Group
Standard once results have been validated.
Phase 2
The laboratory based tests identified a number of specific conclusions in
relation to the performance of sanders:
• Fitting a plain nozzle to the end of a wide bore hose focuses the sand more
effectively towards the wheel/rail interface and increases the amount of
sand passing through this interface.
• A 25% reduction in sand flow rate from 2kg/min to 1.5kg/min when passing
sand through a 25mm bore hose results in a disproportionate reduction in
the amount of sand passing through the wheel/rail interface.
• The most effective set-ups were those where the sand hose or plain nozzle
was set at a shallow angle to the rail (10° to 15°) and aimed just in front of
the wheel and rail contact. As the angle to the rail increases the amount of
sand passing through the nip decreases.
• The addition of a plain nozzle compared to a plain hose allows the sand flow
rate to be reduced whilst still achieving the same amount of sand passing
through the wheel/rail interface as the plain hose.
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• For a given set of test conditions, use of a nozzle with a horizontal or vertical
chamfer does not affect performance compared to a plain nozzle.
• For a given hose length, the use of a narrow bore 19mm hose requires a
significantly higher air pressure to achieve the same flow rate as a 25mm
bore hose of the same length. However, the narrower bore hose appears to
achieve a better performance in terms of the amount of sand passing
through the wheel/rail interface.
• As the longitudinal distance and height of the sand hose from the wheel/rail
interface increases the performance of the sander reduces.
• Performance of the sander is affected by the lateral offset and twist of the
sand hose or nozzle and the optimum performance is achieved when the
sander is longitudinally aligned with the centre of the wheel.
In terms of insulation and dispersion, for clean dry rail and the specific low
speed test conditions, the laboratory based tests demonstrated that when
sand is laid at a rate of:
• 7.5g/m, normal wheel/rail contact is restored following the passage of 1
wheelset.
• 9.5g/m, normal wheel/rail contact is restored following the passage of 3
wheelsets.
• 11.5g/m, normal wheel/rail contact is restored following the passage of 7
wheelsets.
• 13.5g/m, normal wheel/rail contact not restored even after the passage of
10 wheelsets.
Track testing would be required to validate these laboratory based
findings.
In terms of adhesion improvement, the results show that:
• When sand is laid at a rate equivalent to 5.5g/m, the adhesion level
increases but it is inconsistent.
• When sand is laid at a rate equivalent to 7.5g/m or higher, the adhesion
level in the sanded area increases to approximately that of clean dry rail,
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R&D programme: Research brief T797 - November 2015
but rates higher than 7.5 g/m do not offer any further improvement in
adhesion.
Phase 3
This phase found that:
• Because of the small potential improvement in adhesion performance,
there are no real benefits from withdrawing the current GM/RT2461
requirement restricting the installation of the first active sander after the
leading bogie on multiple units of 2 with 8 wheelsets or more. This also
allows the leading wheelset to be used to detect low adhesion conditions to
trigger sanders.
• There are benefits of increased performance in low adhesion by using
distributed active sanding systems along different arrangements of
multiple unit formations. Potential arrangements for distributed sanders
have been proposed for typical arrangements of GB multiple unit
formations from single vehicles up to sets with 6 vehicles.
Adhesion Research Group (ARG), a subgroup of the Vehicle/Track System
Interface Committee, has considered 11 recommendations from the
research. How they are likely to be progressed is identified in the brackets
in the list below.
• R1: Investigate the performance of a single sander that varies its delivery
rate with speed compared to a single fixed rate sander and also the benefit
of 2 distributed fixed rate sanders. (Track testing)
• R2: For existing sander installations, try and quantify the amount of sand
lost when sanding at speed (the amount of sand deployed that does not
pass through the wheel rail interface) to determine how to make the
systems more efficient. (Track testing)
• R3: Optimise sanders on existing vehicles by implementing the actions
identified in a briefing note issued to industry in August 2013 Recommendations for simple checks and improvements to multiple unit
sander systems. (Briefing note)
• R4: Undertake track testing to verify the findings of the laboratory tests.
(Track testing)
• R5: Future revisions to the Railway Group Standard should allow the use of
distributed sanding systems. (Standards)
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• R6: Maintain the leading wheelsets free from sand to ensure front of train
detection whenever possible. (Standards)
• R7: If sand is applied ahead of the leading wheelset, in order to maintain
detection of the leading wheelset, the sanding delivery should be limited to
2.25g/m. Vehicle detection using the passage of following wheelset
permits higher sand delivery rates. (Standards)
• R8: Track testing is required to determine the upper limit of sand density (in
terms of g/m) that leads to a wheelset becoming isolated from the rail.
Tests can then be undertaken to determine how many wheelsets are
required to disperse sand laid at this rate before sand can be re-applied
(Track testing)
• R10: Further testing should be conducted as this is required to determine if
sanding with the leading car sanders on two coupled two car units during a
service brake application presents a risk to train detection. (Track testing)
• R11: Future revisions to the Railway Group Standard should allow the
additional use of dedicated traction sanders (where fitted) on single
multiple units when an emergency brake is demanded and low adhesion is
detected. The potential loss of train detection in these circumstances will
need to be reported to and managed by the signaller. (Standards)
Deliverables
The outcome of this research is fully described in three detailed research
reports along with a summary report that bring together all the results.
Additionally a briefing note that outlines recommendations for simple
checks and improvements to multiple unit sander systems has been
prepared and was issued to train operators in advance of autumn 2013
preparation. These reports are available via www.SPARKrail.org.
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R&D programme: Research brief T797 - November 2015
Next Steps
The outcome of the research was reviewed and accepted by the ARG and
the research was presented to industry during a cross industry RSSB
conference in May 2013.
The output of this research has contributed to a test specification to
enable track testing to be carried out to determine the performance of the
sanding equipment under normal and emergency operation, and the
possible trade-off from increased risk from loss of train detection.
It is expected that this validation work will provide the necessary evidence
needed to support proposals for standards change. Notwithstanding this
ARG has put forward proposals for standards change to allow the
additional use of dedicated traction sanders (where fitted) on single and
coupled multiple units when an emergency brake is demanded and low
adhesion is detected.
Recommendations relating to maintenance and optimising current
sanders are now being implemented by industry.
Contact
For more information please contact:
Operations Professional Lead
Research and Development Programme
RSSB
enquirydesk@rssb.co.uk
Floor 4, The Helicon
1 South Place
London
EC2M 2RB
R&D programme: Research brief T797 - November 2015
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