|jacking oil pump |
A.C. power must be available for the jacking oil pump electric motor.
Er moet wisselstroomvermogen beschikbaar zijn voor de elektrische motor van de vijzeloliepomp.
jacling oil system - vijzeloliesysteem
jack - opvijzelen
according to technical geniuses over here
de vijzeloliepompen, de pompen voor de vijzelolie
Het gaat zo te zien om het pompen van ashefolie, niet het heffen dat de oliepompen doen
2402 - 2408 : Vijzelolie
Uiterst geraffineerde hydraulische minerale olie, onontbeerlijk voor een goede werking van de hydraulische buigmachines van Virax (ref. 2402/2408). Uiterst krachtige smeringscapaciteit en gaat roestvorming, corrosie en slijtage tegen. Concentratie bij 20°C : 0,87 tot 0,89. Viscositeit bij 40°C : 22 mm2/s. Uiterste stollingspunt: - 42°C.
Note added at 5 days (2018-03-27 20:35:33 GMT)
6.9 Jacking oil systems
When a turbine-generator shaft is rotating very slowly, the normal lubricating oil supply cannot ensure that a hydrodynamic oil wedge will be maintained. Also, additional lubrication measures are required to prevent bearing damage and to minimise breakaway torque when starting a turbine-generator from standstill.
In both circumstances the jacking oil system provides high pressure oil to the base of the bearing and floats the rotors on a film of oil. Until the turbine shaft speed is capable of sustaining an adequate bearing oil wedge (above 200 r/min), the jacking oil system and the normal lubricating oil system are run in parallel.
The oil pressure used to lift the rotors is around 300 bar and with the use of mineral oil in close proximity to high temperature components, this represents a fire hazard unless special precautions are taken. Older units used a single pump with long pipelines to feed each bearing and with this arrangement oil leakage does occur. On modern units, the high pressure pumps are mounted in or on the bearing pedestals (see Fig 2.66). Details of the pumps used are given in Section 6.2 of this chapter. A pressure relief valve is fitted in the discharge line from each pump in order to prevent over pressurisation and overload damage. Jacking oil is also provided to the turning gear journal bearings during start-up and shutdown.
Note added at 5 days (2018-03-28 02:55:46 GMT)
CIRCOR Pumps and Systems in Power Generation Applications
Bearing lift pumps provide the necessary high pressure “jacking oil” to lift the turbine generator shafts within the sleeve bearings on horizontal machines and to the lower thrust bearing of a vertical turbine prior to starting the rotation of the hydro turbines.
Crescent Internal Gears are a common choice here for their low initial cost and superb reliability.
Q: Sometimes Jacking Oil Pumps (to lift the shaft) are provided to Steam Turbine & Generator and some times only to Generator.
On what basis do we decide to provide the Jacking Oil?
Is it the mass of the shaft?
A: It's the mass of the shaft and the type/design of bearings and shaft journals. For example, horizontal tilting pad bearings usually need a little "help" at low speed and for turning gear operation. Journal bearings can be designed such that they don't require jacking/lift oil, but again it does also depend on the weight (mass) of the shaft and the space available for the journals and bearings. If the design of the bearing/journal is such that a sufficient oil wedge/lubrication can't be established to prevent bearing/journal damage during low-speed and/or turning gear operation then the decision is usually made by the manufacturer to add a jacking/lift oil system to the turbine and/or generator.
>On what basis do we decide to provide the Jacking Oil?
Since we don't know much about your position/experience, I presume you are writing from an operations/technical perspective. I don't believe operators decide when to provide jacking/lift oil; that's done by the turbine- and/or generator manufacturer(s). And, the unit control system should automatically start/stop the jacking/lift oil pump(s) as appropriate.
Hope this helps!
In the early years of operation of these units, many methods were applied in an attempt to minimize the friction and damage during start-up conditions. In 1912, American engineer Albert Kingsbury, who invented a tilting pad thrust bearing, found that scraping the babbitt surface on the thrust bearings reduced the start-up friction. During this same time frame, many operators of hydroelectric generators would manually jack up these vertical units, allowing fresh oil to flow between the operating surfaces. The load was manually released and the unit was started quickly in an attempt to beat the time required for the rotor weight to squeeze out the oil. As individual unit capacities grew, engineers recognized the need for a more elegant solution to minimize start-up wear.
A reminder of the principles at work in these bearings is helpful. In a hydrodynamic bearing, internal pressure is developed as a result of the interaction of relative movement of the rotor and bearing, a converging clearance space, and a viscous fluid. This pressure then, acting over the area of the bearing, supports the load. In a hydrostatic bearing, oil is injected into a bearing at a high pressure, developed by an external pumping system. This pressure then, acting over the bearing area, supports the load. The logical solution was to develop a bearing that could start as a hydrostatic bearing and then convert to hydrodynamic operation once there was sufficient relative velocity (or more correctly, sufficient hydrodynamic pressure) to fully support the load. This is the model that is still in use today. The engineering challenge was and still is to create a high-pressure lift system that is as robust as the fluid film bearing it is intended to enhance.
The real world
I recently visited a hydro plant with a large horizontal generator. The rotor was heavy enough that the OEM had applied high-pressure jacking oil to reduce the friction and minimize the wear during start up of this large machine. The OEM had also included a combination check valve/nozzle to achieve the gains noted above, namely: eliminating the possibility of bleeding back hydrodynamic pressure and keeping the high-pressure oil away from the babbitt bond line of the bearing.
A thrust bearing failure on one unit, which had experienced a significant rise in thrust bearing temperatures, was attributed to contamination of the lubrication system but actually arose from failure of the sealing washers in the high-pressure jacking oil system.
The sealing washers in the high-pressure oil jacking system of one unit were identified as the culprit causing a unit shutdown.
On the contrary, remember that the delivery port on any high-pressure jacking oil system is located at the most critical point on the bearing. Leakage of hydrodynamic oil, no matter how small, from this location will immediately impact the load-carrying capacity of the bearing.
In short, a high-pressure jacking oil system extends the life of a rotating machine with fluid film bearings and makes maintenance easier when properly installed and periodically inspected. Careful inspection and installation of the individual components is critical to keeping this valuable system from becoming the root cause of a bearing damage outage at your plant.