Users from the power generation, petrochemical and industrial chemicals industries are frequently confronted with extreme pressure differentials in their plants – differentials up to 400bar are not rare in this regard.  It is a suitable system for start-up and boiler-feed water recirculation.

Nevertheless, or rather precisely for this reason, these customers desire continuous, harmonious, steady-state curves with appropriate flow characteristics, long and uniform service life, as well as low maintenance costs.

The valves that will be implemented must therefore satisfy certain prerequisites, such as accommodating solids in liquid media, and prerequisites relative to high sound pressure levels, high temperatures, cavitation formation, and corrosion. Now Flowserve Essen GmbH offers solutions with an interesting technological new development.

Traditionally Flowserve Kämmer is involved with design and manufacturing technologies that are indispensable for production of control valves for particular application cases. More than half of all the Kämmer valves that have been shipped have been manufactured according to customer- specific requirements. 

High pressure differentials

With Multi-Z (Fig.1.) a new special valve series has been developed that is primarily used in power plants, however it is also used in applications where the occurrence of solids and high-pressure differentials play a role.

For instance such applications occur in oil production, in refineries, and in the chemical industry.

Type Multi-Z valves are used if solids occur in the medium and if there is a possibility of cavitation formation.

In addition this multiple stage valve is capable of reducing high-pressure differentials via a multiple stage relief process. Flowserve reduces pressure via division in partitions – a course that is different than that pursued by other suppliers.

The major advantage is a noticeable reduction in wear combined with an extremely low-noise control valve. Likewise deviating from conventional procedures, in order to avoid cavitation a physically optimised technology has been implemented that achieves significantly better results.

The high-pressure boiler feed water example (Fig.2.) shows the use of a feed water pump return flow valve (Multi-Z).

For example, if a fault should occur in the large high-pressure circuit of the customer application then this valve can appropriately reduce the pressures (delta-P) in the small upstream circuit accordingly without problem.

Reduced noise levels

The advantages are in the area of continuous pressure relief. In addition cavitations, deposits or obstructions, do not form and the noise level is noticeably reduced.

The valves are configured on the basis of customer specification so that the valve is optimally tailored to the special operating conditions.

In this regard we do not rely on standard values, rather specially matched seat-cone fittings are used in each case.

The individual stages of the cone are configured in such a manner that cavitation is impossible.

Through the appropriate design of transitions and passages in the cone, solids in the process can be safely managed without destroying the fittings or the valve.

Increased outlet pressure

A Venturi nozzle in the outlet increases the outlet pressure of the final stage of the cone and thus acts as a non-changing, external reduction stage. This offers additional protection against wear for the retracted cone.

The design of the linear/same per centage multiple stage cone results in a greater adjustment ratio and outstanding regulating characteristics for the installed strokes.

Depending on the model solids of up to 13mm in size are managed. The valves are available in a wide variety of materials and connection types in nominal widths DN25 to DN300 (1-in to 12-in) and pressure stages from PN40 to PN400 (CL300 to CL2500) in

full-way or angle form. For example these pressure stages enable maximum pressure reduction of 400bar to 1bar. 

Range of materials

The body is available in angle or globe configurations. The range of materials extends from C- via CrNi- to

Cr-Mo steels and nickel based alloys. For instance seat/linear and cone are made of 1.4122/1.4112 or 420C/440C. Custom options and configurations are available.

There are two proven drive alternatives, a membrane stainless steel drive (KP) for feed air pressures up to 6 bar, or a double acting piston drive (Valtek VL) made of aluminum for pressures up to 12bar.

Enter 17 or  at www.engineerlive.com/epe

Bernd Kujawski is with Flowserve Essen GmbH, Essen, Germany. www.flowserve.com