Pump Nozzle loads

Rajesh

You asked that pump nozzle loads are cause of pump failure. Normally for any rotary equipment it is decided by agreement with the pump vendor how much load will be allowed to his nozzles. 2 times Nema/API allowable or more. By pipe stress analysis we are supposed to check how much load is coming to the nozzle due to piping. If it is more and cannot be reduced it has to be sent to the pump vendor for his checking. Nozzle loads are case of mutual agreement. Breaking that agreement from either side is not acceptable. Normally pipes are installed after installing of the equipment and piping field welds are provided accordingly. First support from the nozzle for pump piping is kept adjustable type to take care any vertical misalignment.

My personal discussion with some field construction guy and my experience gives a horrible picture. Sometimes they do not care about reasons for field welds or by mistaken FW has been missed in drawing. As a result there is a misalignment. In that case construction people will work in the middle of the night and pull the pipe to connect the flange to the nozzle. Actually that creates the problem. This gives more loading on the shaft than it is designed for. Since the shaft is a rotating object this will give an unbalanced force. Hence your bearings and shaft will fail. But things are changing now as QC are doing a better job nowadays and quite strong.

For compressors I feel they are relatively very sophisticated equipment and needs a lot of care. There piping loads may not be the main cause of failure. But it is advisable for few pipe supports adjacent to the compressor/turbine nozzles to be of spring support type.

Tanmoy Saha

Senior Mechanical Engineer

McDermott, Dubai

++971 4 8043132

[Non-text portions of this message have been removed] Received on Tue Jul 05 08:17:00 2005