Problems with mechanical valve positioners

In a case like yours, you just need to set the output on the DCS to reactive

The forward and reverse actions of the positioner, as well as the air-open and air-close modes of the control valve, are designed to work together; they must not be changed arbitrarily.

From the diagram, this is a direct-acting actuator, so the travel knob must be pointed downward. Simply change the controller output characteristic to feedback.

The control valve is of the FO type; the DCS is set with reverse output, and under normal circumstances, the control valve positioners operate in a positive manner. Do not arbitrarily change the forward and reverse actions of the locator.

The action and reaction refer to the positive and negative effects of regulation and control; in manual mode, it is still the reverse

A poor linear performance makes it very difficult to adjust, indicating that the performance of the actuator is poor. If the valve’s operating direction meets the control requirements, it is sufficient to invert the DCS output; there is no need to adjust the feedback on the actuator.

1. Is a poor linear opening of the valve due to poor quality of the actuator? Answer: It can be said that if one can’t even achieve linearity, what quality can there be? ； 2. Currently, the opening degrees in the control room and at the site are opposite to each other. I want to change the locator so that its operation is consistent with those in the control room; I loosened the range-setting screw and adjusted it so that the knob faces upward. However, the valve does not move. I’m not sure what else needs to be changed Answer: Your changes are fine; generally, there’s nothing that needs to be altered. Just pay attention to the position of the feedback rod. 3. Inverting the DCS logic output can also achieve the same effect; I’m not sure if this is appropriate. Please advise. Answer: It is possible. In fact, it depends on the actuator, which corresponds to the safe position of the valve. If a safe location is not required, then there is no problem. I have to say that this thing is absolutely terrible; I’m worried that it won’t even be able to engage automatically during testing. Answer: It is indeed terrible – even better domestic mechanical positioners cost only a few hundred yuan. The imported ones cost a little over 1,000 yuan. To what extent of financial need is one forced to buy this junk?

1. Poor linearity is a problem with the locator； 2. The opening degrees in the control room and at the field are opposite to each other because it is a gas-operated valve; the control room displays the opening degree, so no change is needed to the positioner.

1. First of all, regarding this HEP15 model, you say its linearity is poor; I guess it’s because you haven’t adjusted it properly. I encountered a situation where a factory was using only such regulators, but after my adjustments, they worked very well. 2. The direction of the range regulator is not related to the main control signal but rather to the actuator of the control valve; for example, a valve that opens when air is applied operates in direct action, while one that closes when air is applied operates in reverse action. Once this setting is correct, it’s then possible to adjust the zero point and ensure linearity in the range adjustment. 3. This really doesn’t work; I’ll send you the detailed instructions later

Take a look; this guy is extremely durable:lol