POWER November 2013 - 20

the valve was compromised, which forced the staff to deal with
less-than-optimum operating conditions. The valve also proved
difficult to clean, which meant that after a certain period of
operational time, staff faced the problem of cleaning the scales,
as well as repairing or replacing the bearings.
After operating the butterfly valves for several years, it was
decided to abandon them and convert to fixed blend disks. The
disks could be removed and cleaned without too much effort,
but they did not allow for the flow to be controlled in any way.
Therefore, the flow required from the wells was approximated
when the disks were installed. Disks with different diameters
were installed on different wells, depending on their flow rate.
Such disks, because of their fixed nature, did not allow the optimum
amount of brine and steam to the power plant, which led
to steam being wasted in the production process.
Neither the butterfly valve nor the fixed blend disks were
considered acceptable for long-term operation, so the company
continued to search for alternative solutions. Because
it is almost impossible to alter the chemical composition of
the brine to avoid scaling, the valves needed to adapt to the
conditions.
2. A section view of the Giffard injector. Courtesy: Reynir
S. Atlason
Hydraulic
control
Fluid control
cone
Diffuzer
throat
Outlet
Using Old Concepts to Develop New Designs
The Giffard's injector was invented as a replacement for the mechanical
pumps used to supply boilers with feedwater. Patented
in 1858 by Henri Gifford, its simple design and efficient operation
made previously used forced pumps almost obsolete. In essence,
it controlled the flow of the fluid or gas with a cone. A section
view of a Giffard injector can be seen in Figure 2. The Elli-valve
can be considered a derivative of the Giffard injector. This type of
valve has not been used under geothermal conditions before.
The Elli-valve
An employee who operated the steam equipment on a daily basis
developed the idea. The Elli-valve allows a cone, which can be
controlled remotely, to regulate the brine and steam flow through
a blending seat. The valve consists mainly of three parts. First is
the cone, shown as number 1 in Figure 3. The cone can be adjusted
to allow for the required flow from the well to the separators.
The cone is manufactured out of steel with a Stellite hard facing.
(Early designs had problems with vibration in the cone head, and
it would eventually become loose, but that problem was solved
by strengthening the attachments between the cone and the cylinder
it is attached to.) Figure 4 shows cones ready for use in the
valve.
Second is the seat, shown as number 2 in Figure 3. Adjusting
the relative opening between the seat and the cone controls the
4. Cones ready for installation. These cones produced by
Renniverkstaedi Jens Tomassonar ehf and Framtak ehf are used for flow
regulation in the Elli-valve. Courtesy: HS Energy and Reynir S. Atlason
Inlet of fluids or
gases
3. A 3D model of the Elli-valve. The arrows indicate the flow
direction. The model has been cut to show the moving cone. Courtesy:
Reynir S. Atlason)
3
5. A section view of the Elli-valve in a fully closed
position. Courtesy: HS Energy
4
1
2
20
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POWER | November 2013
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POWER November 2013

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