What should be taken into account when installing control valves and flow meters together? Are there any standards or guidelines?

The flow meter is upstream, and the control valve is downstream, to ensure accurate full-pipe measurement. The requirements for the straight pipe sections of flow meters can be found in the clause explanations of GB 50093-2013 Code for Construction and Quality Acceptance of Automatic Instrument Engineering.

It seems that in all the examples I’ve seen, the control valve is located at the front, but I don’t think there’s any specific requirement for this; at least I’ve never heard of such a requirement in actual production settings

The control valve and flow meter are installed together, with their order determined by the control requirements. The basic principle is: the flow meter should be installed at the end where the pressure remains stable after passing through the control valve, with the required straight pipe sections provided ； If the pressures before and after the control valve are both relatively stable (or both not very stable), install it in front of the valve. For example: ● For the control valve in a pressure regulation system, if a flow meter is required, it should be installed on the side of the pressure system from which samples are taken (i.e., the side where the pressure is regulated by the control valve) ； ● Flow regulation system: If there is a pump upstream of the valve and equipment for pressure regulation downstream of it, then both the pressure before and after the valve remains relatively stable. Usually, a flow meter is selected in front of the valve ； 　　However, when there are multiple branches at the pump outlet supplying fluid in different directions, it is necessary to consider the stability of the pressure before the valve; if needed, a flow meter should be installed after the valve ； 　　For situations where the pressure downstream of the valve is uncontrolled, it is preferable to have the flow meter upstream of the valve. ● There are various conditions regarding the level and temperature control systems; these can be determined by referring to the flow rate. Exception: The flow meter has been determined. At this point, one can only determine which end of the control valve is more suitable for the operating conditions required by the flow meter ； 　　　For flowmeters that do not require consideration of operating pressure, as long as the straight pipe section requirements are met, it doesn’t matter which end is installed. .