High Lifter is not a
ram pump
And why it is usually
better
The High Lifter water pump is not a
ram. It uses a completely different principle and exhibits different operating
characteristics. These differences are essential when comparing rams with the positive
displacement High Lifter.
Hydraulic Rams: How they Work
The hydraulic ram is a device that has
been used for over 100 years to pump water uphill. It works on the "water
hammer" effect: i.e., it uses the energy of a column of water moving downhill in a
pipeline that is suddenly stopped by a valve in the ram. As the water column is stopped, a
pressure peak, or "hammer" is created, which can be used to force some of the
water uphill higher than the original source. After this sudden short peak of pressure,
there is then a depression or "valley" in pressure caused by the shock wave
moving from the ram back up the inlet or "drive" pipeline. This slight reduction
in pressure permits the valve of the ram to be opened up by means of a spring or weight,
thus allowing the process to begin again. Rams usually incorporate an air chamber to
assist in capturing the impulse or shock energy.
Although rams are usually mechanically simple, the
means by which they transfer energy from the downward moving column of water to the water
being pumped uphill is deceptively subtle. Since the shock impulse they use is very short
in duration and intense, the energy from it has a tendency to "leak" out. The
noise they make is a manifestation of this energy leakage (although not a large one),
since it is a shock impulse radiating out into the air. Likewise, the shock of each pulse
radiates out anywhere it can: out through the pipeline, through vibrations of the ram,
etc. The smaller the ram, the greater the percentage of this energy loss (due to a
reduction in volume to surface ratio). Consequently, every means must be employed to
reduce this wayward energy radiation if the ram is to operate efficiently at all. This
includes using steel pipelines, anchoring the ram to a heavy base, etc.
Efficiency
The efficiency of the energy transfer from drive
water to pumped water is dependent on lift height and inlet pressure as well as size of
the unit, etc. It tends to be limited in small and medium sized units to no more than 50%
and is often much less.
The operation of a ram is essentially a resonance
phenomenon and, as such, must be tuned. It uses the shock waves in the inlet pipeline
created by the water flow through the opening-and-closing valve and the
"elasticity" of the system to create the conditions necessary for its continuing
operation. If any of the factors in this balance are changed appreciably, this periodic
operation will stop. Thus, changes in water flow or changes in air volume in the air
chamber, for instance, can stop operation. The ram must then be restarted manually. Again,
smaller units are the most sensitive because they are the least efficient.
In Summary
Rams are a time-honored means of pumping water
uphill, and, although they possess some features that may be objectionable, such as noise,
tuning problems, installation difficulties, excessive water consumption, etc., they can be
very effective if used in the right set of circumstances. Ideal applications are usually
those of abundant water supply, low inlet pressure (very little fall), modest lift, and a
somewhat patient operator.
High Lifter Pumps
High Lifter pumps, because they use a positive
displacement pumping action instead of the resonating water hammer effect, are less
troublesome, since they don't require tuning and have a wider range of application than
rams. High Lifter pumps are more efficient, quieter, lighter weight, and easier to
install. They require less attention and are usually a better choice for most pumping
applications.
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