Once you've decided where to put your bolt, you have to actually physically
place and set it. The methods used differ substantially depending on whether
you are using hand bolts (spits) or drilling using Hang Fix anchors.
Martin Green coorindated a complete appraisal of anchors
for the 2020 expo, but Covid pandemic meant that it was 2022 before it was put into practice. We discussed the issues intensely for more than three years, and did experimental tests.
Why change?
We have been having a failure rate of a
couple of hangers per year.
Current anchors are intended for hanging
air ducts on uncracked concrete, not
humans on limestone.
Local cavers have expressed concerns
regarding our current anchors.
Experience shows that with current
anchors, they can all be underset, risking
all the anchors of a pitch pulling out.
Current anchors rust, reducing tread
strength. With time they will need
replacing and we have limited pitch head
real estate.
Decision
That we standardise on Raumer M8 Hang Fix anchors: M8 HANG FIX inox M8L (ØM8x78).
These are stainless steel (A4 aka 316) 'through bolts'
have thick sleeves reducing the likely hood of failure due to corrosion of the
sleeves
have big spikes on the sleeves, reducing risk of failure to set the anchor, due to it
instead rotating in its hole rather than setting
have combined nuts and washers, making placement easier and risk of use
without a washer.
have bumps on the back of the nut/washer, which almost eliminates the nut loosing
itself
have an effective depth of ~50mm
complies with BS EN 959:2018
tightened and set using a spanner not a hammer - for better control
uses existing 13mm spanners in personal kits
We can change over to these through bolts for existing caves, as most
of our normal hangers can be used with them, by removing the rubber O-ring and the
bolt. This requires the nuts are left in situ, and that we do not have too many circlips
on our hangers.
Unused Hilti HKD anchors and setting
equipment must be retired
Petzl ‘ring’ hanger must be retired, as:
– They require longer bolts than other hangers
to be safe,
– Having both steel and stainless steel rings is
likely to lead to confusion
We have been doing this a while now
Wookey using our first drill in 1990 - Click for more details
