A team from controls and instrumentation company Spirax-Mitech has supplied two twin pressure balanced 24-inch nominal bore ANSI Class 600 in ASTM A 217 WCB carbon steel valves, the largest valves supplied to date from Spirax Sarco South Africa, for installation in a UK-based pump test rig.

The valves will be used to establish pump curves during the testing stage of the pump manufacturing procedure. With a flow coefficient of just over 4 500, the valve is capable of taking 2 � t of water a second. This translates into 10 000 t/h.

The application demands that the full 50 to 1 turn-down of the valve be used with high-pressure drop, low-flow conditions at one extreme, and high-flow, low-pressure drop at the other.

The two units can operate with a maximum upstream pressure of 102 bar and a differential pressure of 16 bar and use nested cages to effectively control the energy conversion across the valve.

The capacity of the valve, the flow coefficient, was confirmed by computational fluid dynamics (CFD) after senior design engineer Peter Connan and his team carried out preliminary design calculations. They found that the claimed value and reality are very closely matched using this balanced approach. Using solid model- ing techniques in combination with CFD provides a global representation of the whole flow regime, including the flow characteristics through the valve, eliminating any undesirable issues in the field.

Magnetic particle examination of the body and bonnet together with dye penetrant testing of all machined surfaces was used to con- firm the integrity of the main components. Material certification and design reports provide the documentation to satisfy the European requirements of the pressure equipment directive.

With each valve weighing in at 4,5 t, each with hydro- static test pressures of 153 bar, 122,4 MJ of potential energy, building the valves posed a few issues for Samuel Mashava and his team to resolve during the assembly and testing procedures. The valve building stage, coinciding as it did with the opening of the new factory, provided a good opportunity to thoroughly test the 5-t overhead cranes and the special explosionproof test rooms, which form part of the new factory facilities. The valves passed through the hydrostatic test and then the seat leakage test without incident.

Spirax Mitech export sales manager Jeannette VandePeer, who worked to produce the commercial and technical bid is now confident that having proved the capabilities of the organisation, other similar projects will follow. Spirax Mitech can rank itself among the few organisations around the world that can confidently tackle this type of work, and deliver a product in a timely manner and at a competitive commercial price.

In the meantime, Spirax Sarco has unveiled two new versions of piston-actuated valves (PAV).

The type PF61G has a stainless-steel body and a polytetrafluoro-ethylene (PTFE) soft seat for tight shut-off, while the PF51G type has a bronze body and PTFE soft seat for tight shut-off.

A PAV is a pneumatically actuated piston, angle seat valve for on/off applications and suitable for the on/off isolation of steam, water, air and inert gases. The valves are also used in a few process control applications when used with a pulsed or positional controller.

Three configurations are available, such as normally open, normally closed and bidirectional.

For many applications, there is often a need for an interlink operation between valves and other equipment, such as in the case of pumps, mixers, other valves, and warning alarms. The optional inductive switch indicator operates on a magnetic volt-free switch principle, pro- viding the required switch indication of open- and closed-valve status.

A visual travel indicator positioned in the actuator cover indicates fully open or closed status.

A typical operation for the piston-actuated valve is from fully closed to fully open operation. Although this is ideal for most applications, there is a need under certain conditions to limit the maximum flow through the valve. This may be associated with load matching or to prevent thermal inertia of the process.

By fitting a manual flow-regulat- ing device to the valve, the maximum valve plug lift can be controlled to limit the maximum kilovolts. The flow regulator can also be used as a manual isolation device on normally open valves.

A visual indicator is provided in the top of the handle to indicate whether the valve is closed or open.

Spirax-Mitech also provides a range of globe control valves to the valve market. The Spirax-Mitech M-Series globe control valves are general-purpose control valves that can be engineered to solve both complex and basic requirements. The valves’ robust construction makes them long-lasting and easy to maintain, while a modular design makes them easy to specify, reducing spares inventory requirements.

The body materials are manufactured from carbon steel, stainless steel, bronze and chromoly and special alloys. This makes the valves ideal for high pressure and extreme temperature conditions. There is a choice of two-port globe, three-way globe, two-port angle and sweep angle, from DN15 to DN400, which translates into � inch to 16 inch.

The valve is versatile and eliminates noise or cavitation problems, and can also be adapted for corrosive fluids. Positioners can be pneumatic, electropneumatic or smart.

The entire Spirax-Mitech range of control valves uses the clamp-in-place, free float design. All trim components are designed to clamp in place, so that the valve can be quickly configured to the user’s specific pro-cess needs. The free float of the seat and plug during assembly means that stem, plug and seat alignment is easily achieved. When compared with alternative designs, the free float designs provide the user with longer stem seal life and better valve shut-off performance.

The simplicity of build also means that maintenance is quick and easy, with no special tools required to achieve the design performance of the valve.

The M-Series has been specially designed for applications within the petrochemicals, min- ing, food and beverage, pulp and paper and power generation industries.