Archive: Jul 2019
DFT® recently held a webinar on severe service control valves. To follow up on the information we presented, here are some answers to questions we’ve received.
Are you coping with corrosive aggressive services? Which materials do you use?
Our Ultra-Trol valve is designed to withstand corrosive media with a combination of metallurgy and controlling fluid conditions. It has replaceable liners, as well as wear-resistant materials, including Stellite, 440C, and Tungsten carbide.
How soon you can deliver a valve after receiving the PO?
We can deliver a valve within 10-12 weeks of receiving an order. Depending on our factory capacity at the time of the order, we can often accommodate faster delivery times.
How can digitalization help you predict integrity damage of a valve to take preventive measures before is too late?
As a preventive measure, we recommend a series of initial inspections. This will identify the wear rate, so you can predict integrity damage.
What is the preferred range of operation of a valve?
For the HI-100, the effective range of operation is between 15-90% open. The preferred range is between 30-85% open.
How do you select a valve?
To ensure you get the right valve, they are sized by DFT® engineering. To do that, they take into account temperature, pressure, fluid type, and flow.
What type of valve characteristic curve is preferred (e.g. equal percentage, linear, etc.)?
For the HI-100®, the valve trim characteristic is linear.
What is the max CV/min CV preferred value when selecting a valve?
DFT® engineering accounts for inlet pressure, orifice size pressure drop, and valve flow path to select a trim package that will result in max CV/min CV preferred value within the range of 30-85% full open.
What is the ease provision of trim replacement in Venturi style?
The HI-100® Straight-Through Venturi Style Control Valve is an in-line repairable valve, so replacing the trim requires a few simple steps. First, remove the valve bonnet, which will enable you to remove any internal component. The trim can be removed without any special tools. When the trim has been replaced, reassemble the bonnet. Be sure to follow the disassembly and reassembly instructions in the DFT® HI-100® maintenance manual.
Do you cover also 3-way valves and angle valves? Where are they used and what are their characteristics?
For more information on valve types and sizes we offer, take a look at our website. You’ll find DFT® catalogs, including those for Check Valves, HI-100® Severe Service Control Valves, and LSV-100® General Service Control Valves.
Catalogs have information on valve sizes, types, and material options. DFT® engineering sizes every HI-100® valve based on application data provided by the end user. You can find an application data sheet on page 13 of the DFT® HI-100® catalog or download the PDF here.
Can your valves be 4-20mA or 0-10V modulated and if yes, how does it work?
The controller package in the HI-100® valve/actuator/accessory assembly contains 4-20mA modulator capability. Although DFT® doesn’t manufacture controllers, we do mount them as a part of our complete assembly package. We are able to support a number of control protocols with a range of actuator and controller packages.
How do you isolate a valve during operation?
As it is a modulating control valve, the DFT® HI-100® can achieve Class V shutoff. This is a tight shutoff which is specially designed for isolation service, but not an isolation valve. For systems that require this function, we recommend that an isolation valve is installed upstream from the HI-100®.
Is the ball in the Venturi free to rotate in any position during operation?
During the initial opening of the valve, the HI-100® ball rotates less than 90 degrees, and then it drops during valve closure. As a result, the ball does not contact the seat in the same position, which reduces wear on the ball.
How do you deal with valves operated in parallel (e.g. 50-50% or other)?
In some cases, valves must be operated in parallel, known as “split range” control. One example is a 50-50% arrangement, where two valves each handle half of the total flow. In this case, the valve positioners are configured so they will accept 4-12 ma and 12-20 ma, respectively. This adapts to situations dealing with a large range of flows.
Does DFT® have motorized control valve with fast reaction time (<1sec)?
For a motorized control valve with fast reaction time, linear actuators that are capable of driving DFT® control valves in less than a second are available.
Price-wise, what is the difference when comparing a globe valve to the Venturi style of the same size?
If you’re comparing the prices of a globe valve with the Venturi style valve of the same size, there are a few factors to consider. Venturi style control valves can generate CVs that are 2-3 times greater than a globe control valve of a similar size. As such, you would need a much smaller sized Venturi style control valve in the same environment as a larger globe style valve. Since the Venturi style valve can provide much greater flows, it is more accurate to compare the price of a Venturi style control valve that can manage the goal CVs against the price of the globe style control valve that can achieve the same CVs.
How do you evaluate the opening/closure time for critical valves?
To evaluate the opening and closure time for critical valves, stroke times are specified in the quote. They will be accounted for in the design process, and we will test them in the factory before shipment.
How do you replace the wear bushings in case of a welded end connection? Can those be accessed by removing the bonnet?
The HI-100® is an inline repairable valve. First, remove the valve bonnet, which will give you access to all internal components. The wear bushings can be removed and replaced without using any special tools. Once that’s done, reassemble the bonnet. Be sure to follow the disassembly and reassembly instructions in the DFT® HI-100® maintenance manual.
See What DFT® Can Do for You
DFT® has been offering the best in valves since 1943. If you have additional questions or would like more information about one of our products, please contact us.