trigger for approval process

trigger Call_AprovalProcess_In_Trigger on Account (before insert, before update) {

 for(Account acc:trigger.new){

    if(acc.AnnualRevenue < 2000){

       approval.ProcessSubmitRequest aprlPrcs = new Approval.ProcessSubmitRequest();      

       aprlPrcs .setComments('Submitting record for approval.');

       aprlPrcs.setObjectId(acc.id);

       aprlPrcs.setNextApproverIds(new Id[] {UserInfo.getUserId()});

       approval.ProcessResult result = Approval.process(aprlPrcs);

    }

 }

}