The Hydraulic Nut is a permanent fixture, replacing the conventional nut and retaining the high bolt load and extension in small space envelopes where there may not be sufficient space to use tensioners. The nut can be retrofitted to existing plant and is a simple and accurate solution to mechanical jointing problems.
The locking for hydraulic nuts is different from common nuts. When the hydraulic nut is locking, it causes ultra-high pre-tightening force by hydraulic pressure (about 200 MPa), which can get close to the yield point of the bolts. It will not loosen even if it is in vibrating condition.
Hydraulic nut is especially suitable in the fastening for the coal miners and roadheaders in underground mining where the space is very narrow. It can also be used in the machines for metallurgy , chemical industry and engineering machinery.
Working principle of hydraulic nuts :
Hydraulic nut is a kind of locking device which relies on pre-tightening force that can make the connecting nuts longer. So the high-strength two head nuts above 10.9 grade must be used.
Schematic diagram ( picture 1). Firstly, the hydraulic nut pre-tightens, ulltrahigh pressure manual pump injects the high pressure oil to the cylinder block of hydraulic nuts by ultrahigh pressure hosepipe which will make the bolt longer.
There will be a gap between the back bolt and the cylinder(picture 2-2), now turn the back bolt so that it will get very close to the cylinder(picture 2-3), and then tighten the back bolt.
Forcing system of hydraulic nuts :
The forcing system of hydraulic nuts are mainly made up of ultra high-pressure Manual oil pump, ultrahigh pressure flexible pipe, hydraulic nuts and high-strength bolt (picture 3)
1.ultrahigh pressure manual oil pump
Ultrahigh pressure manual oil pump is a power equipment which offers hydraulic nut high pressure oil, it is mainly made up of plunger pump, oil storage tank, ultrahigh pressure gauge, high-pressure unloading valve, low-pressure unloading valve, oil filter.
2. Ultra-high pressure flexible pipe
It is made up of ultra high-pressure hosepipe, filter joint, quick coupling.
3. The connection of hydraulic nuts and ultrahigh pressure hosepipe
It connects very quickly by quick joint and filter joint, it is very convenient in operating and moving.