About non-linearity of piping system

Dear all,
sometime I facing some problem about non-linearity of piping system.If a piping system have only +y and guide support and,
i have not given any mu for guide support,i provide mu for only +y support.If a support having both of them I have given any mu for that node no.But then also sometimes while running it show non-linearity type.I dont know why it happens?then if delete some mu then its working.But i want to know how can i know that where i should not provide any mu?

Ujjwal

Use the [Search] option to the right, just above the Calendar. Search for "+friction +convergence", without the quotation marks. (Change the search period to 5 years instead of 1 week.)