Changing to a larger horsepower pump
Changing to a larger horsepower pump
(OP)
I work at a power plant that uses river water for cooling. The water is brought in by (8)1000hp pumps. At all times at least 6 of these pumps must run. The problem is is that if one of the electrical feeders goes out - it takes out at least two of the critical 6 pumps. It has been suggested to replace the existing pumps with larger ones...like one 2000 Hp to replace (2) 1000 Hp.
What is the essential data required to determine if this is a feasible idea? I'm obviously not a mechanical engineer.
What is the essential data required to determine if this is a feasible idea? I'm obviously not a mechanical engineer.





RE: Changing to a larger horsepower pump
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RE: Changing to a larger horsepower pump
2 Cost of probably increasing the pipe diameters between pumps and headers (both suction and discharge) and header diameter.
3 I would guess, since I assume you're not changing system flowrates, only consolidating pairs of pumps into 1 unit, the delivery piping won't need major changing, but I sure can't tell from here.
4 Shutting down and ripping up the old foundations, putting in new ones, or can you build a new pump area with new piping power delivery feeders to that area? If shutdown is prohibited for one reason or another, you're probably better off looking at a new facility in a nearby area.
5 Will the new pumps & pipe arrangements fit into the space available?
6 Higher power requirements might affect your wire diameters
7 A larger pump starting may affect current drawdowns
8 A larger pump may affect transient pressures in the piping.
9 Soil must be suitable for foundations carrying higher loads without adverse settlements. Check underground for clearance for new fdtns. Replace any underground services that are affected.
10 Can you get the larger pump into the space available and still have access and lift out parts for maintenance?
11 Don't forget the auxiliary equipment may be larger too.
12 valve and fitting costs in any pipe segment that requires a new diameter.
13. watch the space required for making piping turns with the new diameters
14. pipe support elevations may need changing
15. pipe stress may need to be checked
That should get you started.
What makes you think that 2 big ones won't go down?
http://virtualpipeline.spaces.msn.com
"We can't solve problems by using the same kind of thinking we used when we created them." -Albert Einstein
RE: Changing to a larger horsepower pump
http://virtualpipeline.spaces.msn.com
"We can't solve problems by using the same kind of thinking we used when we created them." -Albert Einstein
RE: Changing to a larger horsepower pump
If it were me with this problem I would be investigating modifying electrics and not replacing pumps which is probably cheaper by a huge margin and will give you better pump coverage.
RE: Changing to a larger horsepower pump
RE: Changing to a larger horsepower pump
Actually the plan will likely be to modify the electrical - as in installing (3) lineups of switchgear, 3 pumps each gear all installed from a different feeder. It's still going to be expensive but as the responses show...probably not as much as replacing the pumps.
RE: Changing to a larger horsepower pump
RE: Changing to a larger horsepower pump
Don't you have a couple of big Diesel pumps?
Mike Halloran
Pembroke Pines, FL, USA
RE: Changing to a larger horsepower pump
rmw
RE: Changing to a larger horsepower pump
Have you seriously considered adding a couple of emergency diesel driven pumps as mentioned above ?
Presumably, your electical problems will not last too long and the diesels can buy you a few hours/days worth of repair time.
There are some used diesel driven fire pumps on the martket in the size range that you require.
-MJC
RE: Changing to a larger horsepower pump
The new electrical system we are proposing has 3 different feeders, each capable of running the minimum (6) requied pumps at once. In normal operation each feeder would assume 1/3 of the load, and auto switch if it lost power to another feeder.
I'm not following why you think adding a couple of deisel driven pumps would be more reliable. Please explain. Thanks.
RE: Changing to a larger horsepower pump
Adding the diesel-driven pumps will not increase the reliability of your system but instead will provide you with backup to take over if there is a failure that takes out more than two pumps.
RE: Changing to a larger horsepower pump
Say the probability of failure of any given unit is 0.1
and you must have 1 unit running to operate the system.
If you have 1 unit, the probability of system failure = 0.1
Reliability_1 (Probability of running) is 1-.1 = 0.9
If you have 2 independent units, the probability of both failing is 0.1 * 0.1 = .01, thus System Reliability (needing only one operating is) = 1 - 0.01 = 0.99
System Reliability has been increased.
http://virtualpipeline.spaces.msn.com
"We can't solve problems by using the same kind of thinking we used when we created them." -Albert Einstein
RE: Changing to a larger horsepower pump
RE: Changing to a larger horsepower pump
http://virtualpipeline.spaces.msn.com
"We can't solve problems by using the same kind of thinking we used when we created them." -Albert Einstein
RE: Changing to a larger horsepower pump
I wouldn't worry about diesels to run the pumps, if you loose power you have probably lost power to run other essential equipment in the plant ( like hot well pumps, closed cooling water, seal water etc. etc. )
A Black start is starting the plant with all external power lines de-eneggized. The plant is isolated from the grid.
RE: Changing to a larger horsepower pump
Pumps are not apples. One two thousand HP pump doesn't necessarily equal two one thousand horse power pumps so unless you just happened to have some pump choices that were made in heaven halving the pumps might not be the answer.
Second, even if there were some perfect selections in the pump catalog that would offer you that solution, the infrastructure - the piping, foundations, suction pits, and lots of etcetra would have to change with the pumps so it would be major major surgery.
You are trying to solve a symptom of the problem. The symptom is that you lose two critical pumps when you lose a circuit. Solve the problem of losing the circuit and the pumps you have will do just fine.
Now an added comment. I'll bet any plants in South Florida that had black start capability this afternoon were danged glad to have it (and probably used it to get back up.)
rmw