The greatest benefit of a control valve (automatic control valve) is that it keeps process conditions such as temperature, pressure, and flow rate continuously constant without human intervention, simultaneously reducing quality variation and the effort required for adjustment. A manual valve’s role extends only to “opening and closing” or “setting it to an approximate opening”; keeping up with load fluctuations depends on the operator’s judgment and action. A control valve, by contrast, receives signals from sensors and continuously corrects its opening automatically, making it a configuration that tends to be advantageous in terms of productivity, stability, and labor savings. Below, we organize these differences and the way to think about deciding on adoption.
Key points of this article
- A control valve automatically follows load fluctuations and keeps conditions continuously constant
- The difference from a manual valve lies in “automated adjustment,” delivering quality stability, labor savings, and reduced energy waste
- Because the effect varies with the application, fluctuation range, and control method, selection must be based on first organizing the conditions
Differences between a control valve and a manual valve
The control concept is fundamentally different
With a manual valve, an operator decides the opening on-site and adjusts it as needed. On lines where conditions remain nearly unchanged during steady operation, this functions well enough, but when there is fluctuation in supply pressure or an increase or decrease in load, inspection and readjustment become necessary each time.
A control valve, on the other hand, has a control device feed back measured values such as pressure, temperature, and flow rate, and automatically corrects the opening according to the deviation from the target value (set point). The major difference is that it tends to keep conditions within the intended range without requiring a person to remain on hand.
How automatic control changes productivity
In terms of productivity, the following effects can mainly be expected. Since the degree of each varies with conditions, these are general tendencies only.
Quality stability is a representative benefit. By reducing variation in temperature and pressure, it becomes easier to suppress the occurrence of defects and rework. Next is labor savings. Frequent manual adjustment becomes unnecessary, allowing operators to devote time to higher value-added tasks. Furthermore, by curbing oversupply and wasteful discharge, it can in some cases lead to reduced energy loss of steam, cooling water, and the like.
Points to focus on when deciding on adoption
Automating every valve is not necessarily the right approach. As a guideline for judgment, first check the magnitude and frequency of load fluctuation. The larger the fluctuation and the more frequently adjustment occurs at a given location, the more readily the effect of automation tends to appear.
Next, clarify the quantity you want to control (whether it is temperature, pressure, or flow rate) and the precision required. On that basis, identifying not only the maximum flow rate but also conditions such as the minimum flow rate and differential pressure makes it easier to avoid an over- or under-sized bore or rangeability. Note that if you select based on bore alone while conditions remain vague, you may not obtain the intended controllability.
Frequently asked questions
Q1. Should I replace all manual valves with control valves?
A1. It cannot be stated categorically. For locations where conditions are nearly constant, a manual valve may be sufficient. It is realistic to begin considering it at locations with large fluctuations and a high frequency of adjustment.
Q2. Which controlled quantity should I consider automating first?
A2. It is common to prioritize quantities that are directly linked to quality or safety and also fluctuate greatly. First organize which of temperature, pressure, or flow rate you want to keep constant.
Q3. Does a control valve always improve precision?
A3. Not “always.” The intended controllability is obtained only when the selection of the sensor, control device, and valve, together with condition matching, is properly aligned. Consideration across the entire system is a prerequisite.
Q4. Should I match the bore to the pipe size?
A4. The pipe size and the valve’s appropriate bore do not necessarily match. Because the bore is calculated from conditions such as flow rate and differential pressure, we can advise on selection once the conditions are known.
Q5. What should I do if the minimum flow rate is unknown?
A5. Selecting based on the maximum flow rate alone can result in insufficient range. If the lower limit of the operating range is unknown, please consult us, including the anticipated operating patterns.
Q6. Can you also handle the replacement of existing valves?
A6. In many cases, yes. Knowing the existing model number, bore, connection specifications, and operating conditions makes it easier to proceed with selecting an equivalent or compatible product.
Summary
A control valve automatically follows load fluctuations and keeps conditions continuously constant, making it a configuration that tends to lead to productivity gains such as quality stability, labor savings, and reduced energy loss. However, since the degree of the effect varies with the application, fluctuation range, and control method, selection based on organized conditions is essential.
If you have concerns such as “I cannot judge whether the bore is appropriate,” “I know the maximum flow rate but not the minimum flow rate,” or “I want to select an equivalent to an existing valve,” please make use of Yoshitake’s technical and selection consultation. If you organize your operating conditions for us, we can propose a selection suited to your application. Please feel free to contact us first.