Factors that affect the changing speed of steam pressure are: 

1. The boiler load changing speed: the load change makes the mass balance of steam supply and evaporation damaged, it is the main factor for the steam pressure to change. The faster the Load changes, the faster the steam pressure changes too. In order to limit the changing speed of steam pressure, the changing speed of load during operating must be limited. 

2. Heat storage capacity of the boiler:  heat storage capacity refers to the heat to be absorbed or released by the temperature changes of the corresponding working medium inside the boiler, the metal of heating surface and boiler wall  due to the changes of saturation temperature, when the boiler steam pressure changes. Heat storage capacity  has buffer effect to the change of steam pressure, such as when the steam pressure drops, the saturation temperature drops, the heat storage capacity will be bigger, generating additional steam and slowing down the reduction speed of steam pressure. Therefore, the bigger the boiler heat storage capacity is, the slower the steam pressure changes; The smaller the heat storage capacity is, the faster the steam pressure changes. 

3. The inertia of combustion equipment: the inertia of combustion equipment refers to the time required from when the fuel amounts begins to change to when the new heat load is established inside the boiler in order to adapt the demand of external load. If the inertia of combustion equipment is big, the time required by the new load to be established inside the boiler in order to adapt to the changing of external load will be long, the changing speed of the steam pressure will be faster. The capacity of combustion equipment inertial is related with the fuel types, combustion mode and the types of coal pulverizing system etc.