DE1809620A1 - Mechanical seal - Google Patents

Description

Mechanical seal Mechanical seals are known, consisting usually consisting of two slip rings, one of which rotating on the shaft, e.g. one centrifugal pump and the other stationary, e.g. with an O-ring as a secondary sealing element sealed on the housing, is arranged. In the case of hydrodynamic mechanical seals a ring made of a wear-resistant thread, the corresponding counter ring made of one less made of wear-resistant material. With non-contact hydrostatic mechanical seals Both slip rings are made of a highly wear-resistant material.

When starting hydrodynamic mechanical seals under pressure the sealing surfaces that adhere to one another first loosen, then pass through Area of mixed friction and only then reach the area in which as a result the micro-roughness on both sealing surfaces is more or less even Establishes a liquid film between the sealing surfaces.

Mechanical seals are already known in this context, by grooves of any kind on one of the two or both sliding surfaces or by similar measures due to the formation of jam edges even at lower speeds Generate a liquid film between the sliding surfaces and the mechanical seal hydrodynamic relieve. However, this type of relief only achieves optimum at higher speeds Values.

When the machine is at a standstill, the faces of the mechanical seal adhere also with these Bauar @@ u still on each other.

Other constructions are also known in which the hydraulic Locking forces through externally issued pressure from a separate pressure supply be generated in an annular space behind the stationary sealing ring. The disadvantage However, this known mechanical seals lies in their reliance on one additional independent pressure supply.

The object of the invention is therefore to create a mechanical seal arrangement, with hydrodynamic mechanical seals that the machine starts up at high Pressure is allowed with the least possible wear and with non-contact hydrostatic Mechanical seals a tarnishing of the mechanical seals due to too low differential pressure prevented when starting.

This is made possible by a mechanical seal one with the shaft, e.g. a rotary pump rot @ era @ den and @ ine @ @@ strt @ Ge @ äuse ab @@@ hteten Sliding ring, characterized in that a rear the stationary seal ring formed annulus with a space to be sealed pressure a built-in throttle is connected by a line and also with a room with low pressure via a valve in the throttle and a line connected is such that by opening the valve, the medium from the space to be sealed relaxes over the throttle and the annulus with lower than that to be sealed Pressure applied.

The mechanical seal assembly according to the invention that Stick together and duit the breakaway torque of the two sliding surfaces to a mininun reduced or canceled by the externally accessible control of the hydraulic Closing forces of the stationary sealing ring when starting up. Is a speed achieved in which there is a sufficient film of liquid between the sliding surfaces can form, this starting device is switched off and the mechanical seal continues to work in the previously known manner.

The known hydrostatic mechanical seals are usually used to seal very high pressures and work with defined pressure-free Leakage. However, there are also known applications in which a system at very high pressures in the operating point works, but the pressures in the start-up state are very small.

The stability of such seals depends on the value of the change in opening force in the gap per gap width change.

This value is considerably lower at low pressures to be sealed than with large ones. Therefore, when driving in the area of lower pressures, there is unrest in the waves the risk that the sealing surfaces wear out heavily on contact. Through the invention it is now possible to also close the gap width of these seals at low pressures to prevent the sealing surfaces from tarnishing and in the larger area Press the mechanical seal to operate in the known manner in the event of a small leak.

The figure shows the mechanical seal assembly according to the invention.

Through the seal housing 1 and the end flange 2, which means Screws 3 is attached to the seal housing, the seal space 4 is around the Shaft 5 passing through it is formed. As a sealing element between the seal housing The O-ring 6 is used for 1 and the end flange 2.

Inside the sealing space 4 is arranged around the shaft 5 the mechanical seal, consisting of rotating sealing ring 7, which is connected to a O-ring 8 is sealed against the shaft 5 and a stationary sealing ring 9, the sealed with an O-ring 10 against the end flange 2 and held in place by anti-rotation pins 11. The fixed ring is secured with a compression spring 12 is pressed against the rotating ring 7.

The fixed ring 9 has a larger diameter O-ring 13 is once again sealed against the housing. This creates a ring scanner 14 formed with the space 4 high pressure in front of the seal through a line 16, in which a throttle 15 is located, is connected. This makes the hydraulic Closing force passed on the fixed ring 9, which at the same time through the O-rings 10 and 13 is elastically mounted.

In the end flange 2 there is a bore 17 to which a discharge line 18 is connected to a valve 19 and a throttle 20.

If the mechanical seal is to be approached, a control pulse which e.g. can be interlocked with the oil supply of the pump, the valve 19 is opened and the liquid to be sealed penetrates from the space 4 through the throttle 15 and line 16, as well as the annular chamber 14, bore 17 and discharge line 18 through the valve 19 and the throttle 20, by the size of the throttle bores 15 and 20 is it now possible to print in'der Ringka; he pretend 14, and the hydraulic To reduce the closing force on the stationary ring 9. With hydrodynamic Mechanical seals mean a reduction in the adhesive force between the two Sliding surfaces. Reduced with hydrostatic, non-contact mechanical seals this reduces the risk of start-up. Through suitable shut-off devices and bypass lines the throttle 15 mounted outside the machine housing can also be used during of the operation quiet. The attachment of the throttle points 15 and 20 outside the Machine housing is preferable to installation in the machine housing e.

Claims (1)

Claim Mechanical seal consisting of one with the shaft, e.g. a centrifugal pump rotating and a stationary seal ring sealed on the housing, thereby characterized in that an annular space formed behind the stationary sliding ring (9) (14) with a space (4) to be sealed pressure through a line (16) with built-in Throttle (15) is in communication and also with a space low pressure over a valve (19), a throttle (20) and a line (18) is connected in such a way, that by opening the valve (19) the medium from the space to be sealed (4) Relaxed via the throttle (15) and the annular space (14) with lower than that to be sealed Pressure applied. L e r s e i t e