Valves, Actuators & Pump Control


Blowdown applications using multi-stage trim

July 2018 Valves, Actuators & Pump Control

The Arca angle style control valves series 350 and 380 are proven under critical process conditions. If used in steam or other process gas applications at high pressure and temperature, in cavitation-free relaxation of liquids at high pressure differential or in handling of fluids with high solid content, the modular system of valve housings, bonnet and trim styles, in combination with a large range of materials, always offer an ideal solution.

The combination of high pressure ratio and solid-containing fluids is one of the most critical challenges for sizing, selection and design of a control valve. Due to the high pressure ratio, multi-stage valves are indispensable to avoid severe cavitation damages. However, as soon as the fluid contains solid particles, besides the normal fluid-dynamic sizing (determination of the number of throttling stages and their individual flow coefficient), the grain size of the particles has to be taken into account. The cross-section area of each flow channel in the valve must be the size and shape to allow all particles in the fluid (assumed to be of spherical shape) to pass.

Flow channel optimisation

Since the cross sectional area of each throttling stage is explicitly defined by the flow coefficient calculated from the fluid-dynamic valve sizing, only the shape of the flow channel remains to be optimised.

It is obvious that a circular shape is the optimum with regard to the permeability of spherical particles. The newly developed multistage trim MS4, which has only one flow channel at each stage, milled as a spherical calotte into a rigid, multiple guided control rod, approximates this ideal shape and is superior to any multistage parabolic plug in this regard.

Another special feature of this trim style is the protection of the seating surface (which is the most sensitive area in terms of erosion) against over-stroke of the valve. This ensures that the control stage of the valve only opens under conditions of low pressure differential and with a small flow velocity at the seating surface.

The rigid multiple guidance of the control rod is an effective prevention of the valve against mechanical vibrations and the resulting wear, even at extremely high pressure differentials.

Series 350 and 380 are available in sizes up to DN 250 and ratings up to Class 2500 (PN 400). Depending on the process conditions, MS4 trims can be delivered in valve sizes up to DN 100.

For more information contact Desmond Delport, Valve & Automation, +27 (0)11 397 2833, desmond.delport@valve.co.za, www.valve.co.za



Credit(s)



Share this article:
Share via emailShare via LinkedInPrint this page

Further reading:

Compact valve position indicator
Emerson Automation Solutions Valves, Actuators & Pump Control
Emerson’s new TopWorx DVR Switchbox is an entry-level addition to the DV Series of valve position indicators. It combines a durable resin enclosure, compact size, and a patented cam design that provides a reliable valve position feedback for water and wastewater systems, food and beverage production lines, and industrial utilities.

Read more...
New pilot-operated relief valve
Emerson Automation Solutions Valves, Actuators & Pump Control
Emerson has introduced a pilot-operated relief valve for installation on pressurised bullet tanks used to store liquid propane and anhydrous ammonia. This type of pressure relief valve is typically installed on tanks fabricated by OEMs for end users, engineering firms, or contractor customers.

Read more...
Case History 191: The weakest link.
Michael Brown Control Engineering Valves, Actuators & Pump Control
Which is the weakest link in a control loop? The answer, without any doubt is that, in most cases, the final control element is the weakest link.

Read more...
High-flow solenoid valve
Emerson Automation Solutions Valves, Actuators & Pump Control
Emerson has introduced the new ASCO Series 327C solenoid valve, which features a direct-acting, high-flow design that provides superior flow-to-power ratio. It permits high flows at minimum power levels, making it ideal for use in power plants, refineries, and chemical processing facilities.

Read more...
Selection of two-port valves: an open and shut case
SMC Corporation South Africa Valves, Actuators & Pump Control
Little consideration is generally given to two-port valves because they are often perceived as simple devices that only open and close to control downstream fluid supply. Although this is mechanically true, choosing the optimal two-port valve for your application can make a big difference, saving space, weight and energy consumption.

Read more...
Emerson software optimises maintenance
Emerson Automation Solutions Valves, Actuators & Pump Control
Emerson has announced the Plantweb Insight Valve Health Application, a powerful software tool that combines Fisher control valve expertise with advanced analytic algorithms. The new app makes it possible for users to visualise an entire connected fleet of valves, while prioritising actions based on the health index of each valve.

Read more...
New-generation vacuum pumps
Valves, Actuators & Pump Control
Busch Vacuum Solutions has introduced the new MINK MM dry claw vacuum pumps. This new generation stands out for its minimal operating costs, low energy consumption and reduced CO2 footprint through reduced raw material requirements.

Read more...
Noise solutions for valves
Valves, Actuators & Pump Control
Emerson has announced its innovative new Fisher Whisper Trim technology for use in both rotary and globe valves. This next generation of technology addresses noise issues by using additive manufacturing to create trim designs with increased capabilities.

Read more...
Valves for severe service
Valve & Automation Editor's Choice Valves, Actuators & Pump Control
Valve specialist, Valve & Automation supplies total valve and control solutions to a wide range of key process industries across southern Africa. Chemicals and pulp and paper are top of its list of industries with demanding process conditions.

Read more...
Pinch valves for efficient flow control
Bearing Man Group t/a BMG Valves, Actuators & Pump Control
Included in BMG’s extensive portfolio of industrial slurry valves is a range of pinch valves, which have been developed to control the flow of liquids, powders, solids and abrasives in many industries.

Read more...