Mild steel-made differential pressure controllers are used to maintain steady differential pressure of any motor-operated control valve. This specific version of pressure control valves can be used at -20 degrees C to 120 degrees C operating temperature range and at 16 bar of operating pressure. A brass-made variant of this collection of pressure controllers is used to handle positive and negative pressure of anti freeze agent and water at +2 degrees C to 100 degrees C operating temperature. These pressure-controlling solutions are especially useful to minimize the pressure of noncorrosive grade gases.