The negative impact of dynamic forces
Nozzle load is the sum of all forces and movements acting on rotating machinery which are caused by thermal expansion, pipe strain, additional heavy loads (e.g. silencers) and everything else which will affect the operating performance of your asset. There are of course dynamic forces acting also on other types of machinery, but in this text we talk about rotating equipment like for example pumps and compressors.
Thermal expansion is a machine condition where the temperature of one of the aligned assets rise significantly compared to another. For example, a pump aligned to an electrical motor. The operating condition of the pump might be hotter than the condition of the electrical motor due to the temperature of the pumped media. Hotter conditions will expand the housing of the pump and consequently move the rotating centre of the shaft, causing misalignment. This is an example of a dynamic force.
Pipe strain is when the pipe flange is misaligned to the machine inlet or discharge flange, thus distorting the housing of the machine. Housing distortion puts tension on all internal parts and affects the functionality of lubrication, bearings, seals and other items, and will also lead to misalignment.
We recognize two types of pipe strain: static pipe strain and dynamic pipe strain. Static pipe strain is the condition when the pipe flange is misaligned to the inlet/discharge flange. This is due to a poor assembly procedure or inadequate pipe support, and maybe because no flexible connections/compensators are installed. Dynamic pipe strain occurs when the system is in operation, and is due to thermal expansion, plus weight and pressure of the media/fluid, plus inadequate pipe support.