The rotameter only sees the total water line pressure during operation which is 80-90 psi.  VanAire requires 140psi minimum air pressure to obtain the smallest bubbles.  Air travels from the air filter that has a metal bowl rating of 250psi, through the air regulator (regulator should be set to 140psi), gauge on the air regulator is 0-300psi, air then travels to the cash valve mounted on the header piping (cash valve MAWP is 250psi), once the pressure in the header is high enough it moves the valve in the cash valve to allow air to the rotameter (rotameter MAWP is 100 psi), air travels through the rotameter to the check valve (MAWP 580psi) and through the injector.  Since the header pressure is lower than the air pressure the pressure in the aeration system equalizes to the header pressure.  So, the rotameter is only seeing 90psi.  The only way the rotameter could see higher allowable pressure is if the system is deadheaded.  One could deadhead the pump, but the check valve will stop the pressure to the rotameter.  The air would need to be left on while trying to trouble shoot the pump to reach a higher pressure.