very high pressure pump seals?

Thinking about very high pressure displacement pumps, 10,000psi to 40,000psi or so.
Seems they tend to use rods rather than pistons/cylinder seals, and the rod slides in a seal at one end of the cylinder.
Any idea about how they do that seal?
thx,
--Peter Fairbrother

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Would it be a common-or-garden square section hydraulic seal in a rectangular slot, the sort that twists to seal tighter as the pressure increases?

On 03/05/15 23:01, Mark Rand wrote:
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I believe that sort of rod seal goes up to about 6,000 psi normally, and maybe 10,000 psi on special occasions.
I'm more interested in around 30,000 psi or more.
-- Peter Fairbrother

Going back a number of years we used chevron packing 4 pieces with header and follower rings on hard chrome plated or ceramic plungers. worked well up to 15,000 psi. We never did get 20,000 psi working reliably but we used Aramid square section packing coiled like a spring.
We had for test a german pump that was rated to 65,000 psi that again used chevron packing but had a very slow plunger speed which may have been the key.
The above were all used on water.
What do you intend to pump ?
I expect the seal manufacturers are more genned up on these pressures than they were back then.
Regards Colin Docherty
On 03/05/2015 15:11, Peter Fairbrother wrote:
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