A multi-server markovian queueing system including the concepts of balking and reneging under the restriction of nopassing is considered. In order to reduce the discouraging behavior of the customers, there is also provision of removable servers which turn on one by one according to a threshold scheme. The customers arrive according to poisson process and leave the system in chronological order. This restriction characterizes the queueing system with two types of customers wherein the first type of customers have zero service time and second type of customers have exponentially distributed service time. We derive the expression for queue size distribution. The expected waiting time of both types of customers and difference between their expected waiting times are also derived.