diff --git a/src/main/java/neqsim/process/processmodel/ProcessModel.java b/src/main/java/neqsim/process/processmodel/ProcessModel.java
index 46d0e510a..82358e5c2 100644
--- a/src/main/java/neqsim/process/processmodel/ProcessModel.java
+++ b/src/main/java/neqsim/process/processmodel/ProcessModel.java
@@ -11,8 +11,46 @@
  * @version $Id: $Id
  */
 public class ProcessModel implements Runnable {
-  ArrayList<ProcessSystem> processes = new ArrayList<ProcessSystem>(0);
+  ArrayList<ProcessSystem> processes = new ArrayList<ProcessSystem>();
+  private boolean runStep = false;
 
+
+  /**
+   * <p>
+   * isRunStep.
+   * </p>
+   * 
+   *
+   * @return a {@link java.lang.Boolean} runStep
+   * 
+   */
+  public boolean isRunStep() {
+    return runStep;
+  }
+
+  /**
+   * <p>
+   * runStep.
+   * </p>
+   * 
+   * @param runStep run in steps
+   * 
+   */
+  public void setRunStep(boolean runStep) {
+    this.runStep = runStep;
+  }
+
+
+  /**
+   * <p>
+   * add.
+   * </p>
+   *
+   * @param name name of process
+   * @param process process to add
+   * 
+   * @return a {@link java.lang.Boolean} success
+   */
   public boolean add(String name, ProcessSystem process) {
     processes.add(process);
     return true;
@@ -20,14 +58,30 @@ public boolean add(String name, ProcessSystem process) {
 
   /**
    * <p>
-   * runAsThread.
+   * run.
    * </p>
    *
-   * @return a {@link java.lang.Thread} object
    */
   public void run() {
     for (int i = 0; i < processes.size(); i++) {
-      processes.get(i).run();
+      if (runStep) {
+        processes.get(i).run_step();
+      } else {
+        processes.get(i).run();
+      }
+    }
+  }
+
+  /**
+   * <p>
+   * runStep.
+   * </p>
+   *
+   */
+  public void runStep() {
+    for (int i = 0; i < processes.size(); i++) {
+      processes.get(i).run_step();
+
     }
   }
 
diff --git a/src/test/java/neqsim/process/processmodel/CombinedModelsTest.java b/src/test/java/neqsim/process/processmodel/CombinedModelsTest.java
index 82bb57de9..d6304561b 100644
--- a/src/test/java/neqsim/process/processmodel/CombinedModelsTest.java
+++ b/src/test/java/neqsim/process/processmodel/CombinedModelsTest.java
@@ -3,6 +3,7 @@
 import java.io.File;
 import org.apache.logging.log4j.LogManager;
 import org.apache.logging.log4j.Logger;
+import org.junit.jupiter.api.Assertions;
 import org.junit.jupiter.api.Test;
 import neqsim.process.equipment.compressor.Compressor;
 import neqsim.process.equipment.separator.ThreePhaseSeparator;
@@ -63,10 +64,10 @@ public void testProcess() {
 
     ((Compressor) compressorProcess.getUnit("Compressor1")).setOutletPressure(100.0, "bara");
 
-
     ProcessModel fullProcess = new ProcessModel();
     fullProcess.add("feed process", inletProcess);
     fullProcess.add("compressor process", compressorProcess);
+    fullProcess.setRunStep(true);
 
     try {
       fullProcess.run();
@@ -74,8 +75,11 @@ public void testProcess() {
       logger.debug(ex.getMessage(), ex);
     }
 
-    ((Compressor) compressorProcess.getUnit("Compressor1")).getOutletStream().getFluid()
-        .prettyPrint();
+    Assertions.assertEquals(164.44139872, ((Compressor) compressorProcess.getUnit("Compressor1"))
+        .getOutletStream().getTemperature("C"), 0.1);
+
+    // ((Compressor) compressorProcess.getUnit("Compressor1")).getOutletStream().getFluid()
+    // .prettyPrint();
 
   }