[huubhubregtse]

Hi Gary and other persons.
Yes, the impact of the wind is big due to the rocketing effect of the fan during wind.
This has an impact on the outgoing bearing. The high speed pinion is on the motor side and should not be affected by the wind.
To withstand the forces due to the wind we always specify an extra heavy bearing on the outgoing shaft, service factor 2.5 or higher.
we recently invstigated a failure of the high speed pinion.
It appeared to be a lubrication problem. The oil level should be just halfway if by some reasons this is not the case, the bearing overheats and get damaged.
the result of this case was a complete failure of the gear box.
Huub Hubregtse

[huubhubregtse]

Hi,
I can tell you a lot about ACC cleaning.
In 1993 I developped the first ACC cleaning system for the Rye House ACC in the Uk
this system has been improved over the years and is now used worldwide.
1. the frequency of cleaning is normally once a year. If the ambient is dusty cleaning can be done more often.

2. we use rails and a moving rig. Cleaning is not adviced to be done by hand. The high pressure water beams with a pressure of about 90 bar can damage the fins, therefor the spray angle must be fixed, which is impossible to be done by hand.

3. Cleaning should be done from the outside towards the inside. Most fouling is on the inside bundle surface with a dept of about 50 mm. By cleaning from the outside the fouling is directly washed away in the direction it came from.

4. we often make a small thermal calculation before and after the cleaning. This indicates the effect of the cleaning. A simple way to check the effect of the cleaning is to measure the static pressure in the planum compared to the ambient. The operator can make this measurement on a monthly basis and record the increase of static pressure. From expeience he can that indicate the time cleaning is required.

5. As the performance depends on A. the air flow, which can be reduced by fouling, B. the ambient temperture and C. the steam flow. The performance curves can help to determine the performance. We often make a thermal calculation with a computer model. When the computer model is made, we just fill in the ambient temperature and the steam flow and calculate the back pressure. This can then be compared with the actual back pressure.

I hope this explains the cleaning process.
if you need some more information just send me a mail.

[huubhubregtse]

The control logic is based on the following two temperature differences.
1. is the temperature difference between the condensate leaving the ACC and the steam temperature at the turbine exhaust. If this temperture difference is below a certain limit the control system can increase the fan speeds, if possible. if the temperature difference is too big fans have to be reduced in speed or switched off as we are undercooling.

2. the second temperture difference is the temperature difference between the extraction of the incondensables and the steam temperture at the turbine exhaust. if this difference is too big the fans of the secondary cells have to be reduced in speed as the secondary bundles are cooling the steam too much.

[huubhubregtse]

HI

the bellows are installed in the steam duct.
they consist of a SS bellows welded to CS rings.
Some of them are Multi ply where the inner sheet gives the sealing.
the other sheets are mostly having holes to avoid pressure between the sheets.
if the innner ring get a hole due to fatique there is a entrance for air into the ACC.
We have seen this problem before

Huub

[huubhubregtse]

Hi Amir,
if you want to eliminate possible leaks of the hogger and or holder you keeep them in operation. during operation no air can flow into the condenser via this route.
If al the ejectors are in operation and the vacuum drop is still unacceptable the leak is not in the extraction section.

Huub

[huubhubregtse]

Hi Amir,
helium leak detection is a difficult job.
It took the Rye House power plant 6 weeks to find the leak. (Loose flange of a pressure test line)
Helium leak detection is the best way to find leaks but sometimes it takes time to find it.
we have experienced leaks in bellows as well, especially with multi layer bellows.
Also the turbine exhaust area could give problems, such as near the gland steam or the casing.

Huub

[huubhubregtse]

Hi,

we had similar problems with a wet cooling tower.
according to Hansen it was a lubrication problem and bearing tolerance.
The gearbox was repaired in the factory and works fine now.
as our office is about 50 miles from the factory personal contact is not difficult.
I could get some information about this problem from them if you like.

Huub Hubregtse

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