Can 1.3MPa steam be used with 1.5MPa flanges and valves?

No, because at the temperature of steam, the allowable stress of the material decreases.

1.3 The temperature of saturated steam (gauge pressure) is 195, and a nominal pressure of 1.6 can be used for 1.3 saturated steam.

It is best to use valves with a pressure rating of 25 kilograms, leaving some extra headroom for safety; otherwise, leaks can be very dangerous.

It’s possible, as long as the maximum operating pressure of the flange is greater than the working pressure.

Surely not. If flanges made of material 20# are used, according to the pressure-temperature charts, a PN16 flange allows a maximum operating pressure of 13.0 bar at 150°C, and 12.6 bar at 200°C. Since the temperature in question is 195°C, the maximum allowable operating pressure must be below 13 bar. So it’s not possible.

At least some margin should be left; choose a valve with a pressure rating of 25 bar, as problems may arise over time.

Well, to put it this way: saturated steam at 1.6 MPa can be handled using valves and flanges rated for 1.6 MPa as well, but this poses safety risks. Generally, the pressure rating of valves and flanges should be 1.5 times the maximum operating pressure. For example, it’s 1.3 MPa at the site. In this case, the nominal pressure for the valves and flanges should be 1.95, but this pressure rating is not available. The closest options are 150LB (2.0 MPa, American standard) and 2.5 MPa (European standard); either of these pressure ratings will work. You should also take into account the pressure system used for valves, fittings, flanges, etc., in your company’s facilities. It’s advisable to include a safety factor when selecting valves and flanges, as this provides greater peace of mind. Moreover, the price difference between these pressure ratings isn’t very large, so there’s no need to cut costs in this area.