Favorie stupid

"No-compromise design"

 

I am glad I cpr'ed this thread.

 

What do you mean you want me to take a "field sobriety test" on the water?

 

Sleeps six comfortably...

 

I read somewhere that a man was seen walking his son round a marina one day. His son spotted the wind vane generator and asked what is that?

His Father said when the wind gets low and the boat wont move they turn on the fan.

 

wipe on, rinse off, removes rust stains, oxidation, oil, marine growth .........

 

Some assembly required, using common hand tools . . .

 

Er......then it is a little misleading if 30 hp can outdo 167 hp on the same job, no ? Doesn't make sense to class each unit by hp if that is the case.

 

What do you intend by "head" here? Is it not a pressure?

 

I thought when the wind wouldn't blow and the boat couldn't go, they got Carter, the farter, to start 'er ?

 

Ten lb oil base drilling mud is a solution of diesel mixed with iron bearing clay so one gal weighs 10 lbs. There isn't always oil under gas but there is ALWAYS gas above oil. The gas has 2000psi pressure or more, because weight of earths crust pressing on it. In order to drill 1000s of feet deep and not have the gas blow out of the well at mach 2 velocity, exploding into fireball the minute it hits the air, you need a liquid cork in the well pipe. Thats what drilling mud is.

A supply boat pumps mud and other products up to the rig. The rig usually stands on legs above the water. The mud tanks and engine room of OSV (Oilfield Supply Vessel), are below waterline/sea level.

Verticle distance from the pump outlet to the hose connection on rig (all downhill after that) is the head. Usually 60 ft or more.
GPM is rate and head psi is pressure at delivery at verticle lift height.

 

You are right.. thats really stupid

 

Yobarnacle, an HP is an HP. Be it provided by electric or diesel motor, or by mine and your hands. It's always the same HP, 550 pounds of force at 1 ft/s. Always. So a diesel HP is the same as electric HP, by definition.

The difference in the pressure value (for the same mass/volume flow?) you have witnessed can be simply explained by the fact that a diesel and an electric motor have their max torque placed at different RPMs (at 50% of the maximum RPM for the diesel, around 70-80% for the electric motor). So your particular pump was better matched by the electric motor, not the diesel one.

To sum it up - an HP is always the same HP, whether it is produced by an electric or a diesel engine. The difference, for a particular application is made by the torque curve, and where is the peak torque located in the RPM range of the engine.

Cheers

 

static head pressure is weight of column of liquid on discharge side of pump when pump is stopped. A 5in ID hose holds a gallon+/- every linear foot. 60 feet head @ 10 lbs per gal, means these pumps have to restart fighting 600psi static head.
Eletric motors are torque motors. So are steam engines. They can produce torque, working against a static load when stalled. Piston engines (with exception reciprocating steam) produce no torque when stalled.
A diesel engine is rated at its max rpm. At start up rpm, its hp and torque are hugely reduced. Electric motors are rated at continuos power and provide same torque at startup as at 3500 rpm.
The 471 is rated at 2800 rpm, but no engineer would stand near it at that speed. It's about to fly apart. 2200 rpm is usually "maxed".
Can you see how a lowly 30hp hi-torque electric motor can do more usefull work than a diesel of much higher rating?
Of course these are direct drive centrifugal pumps. The diesel does have a PTO or it could never start.

 

On paper and in mathematics hp is hp. I agree.
The purpose of inventing hp, was as a measure of work.
When 2 different machines can do same or similar amounts of work, then their true work capacity is similar.
If the varios mfgs assign hp ratings that make these machines appear un-equal, who is to blame?
Are we to blindly accept their assessment as gospel? Or are we inteligent enough to observe, this works and ignore mfgs marketing tactics.