Packing rings

Q - We bought a surplus irrigation pump. On start-up the pump developed some
leakage around the stuffing box area. We tightened the gland bolting to stop the
leakage. Soon after the packing rings seized on the shaft and there was smoke
coming out of the stuffing box. What went wrong?

A -  Pumps with packing rings are supposed to have some leakage to provide
lubrication and cooling to the packing rings. Stopping the leakage by tightening
the gland bolting will result in heat build-up in the stuffing box due to friction.
Excessive heat build-up will eventually cause the packing rings to melt and seize
on the shaft.

Q - We have an engine-driven water pump fitted with packing rings normally
running at 2000 RPM. Due to an increase in water demand we decided to
increase the engine speed to 2300 RPM. (The vendor advised that the pump can
safely run up to 2400 RPM.)

After a few minutes of operation we noticed that steam is coming out of the
stuffing box. Not wanting to damage the pump, we quickly reduced the engine
speed back to 2000 RPM. What was the is likely cause for the "steaming" and is
there anything we can do to run the pump safely at 2300 RPM?

A - When the pump ran at the higher speed of 2300 RPM the surface peripheral
speed of the packing rings also increased. This resulted in higher friction that
caused the heat build-up in the stuffing box. Excessive heat can eventually cause  
some of the leakage flow to form into steam.

One solution to this problem is to accelerate the cooling by increasing the leakage
in the stuffing box to dissipate more of the heat. Slowly increase the number of
leakage drop until the steam disappears.

Q - How much of a leakage on the stuffing box does a typical packed pump
require for effective cooling and lubrication of the packing rings?

A - The answer to this question is available on request.

File: packing rings

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