Concurrent call web service encounter error message when waiting for web service response.

 Hi all,

We have an issue when we are going to call web service by using concurrent program.

If web service response immediate, then concurrent complete normal.
But if web service process for a while, concurrent program always end with error at 1.5 mins always.
Always stop at 1.5 mins.

Here is the part of package code, any comments will be appreciating.
=====================================================
BEGIN
     soap_request := '<?xml version="1.0" encoding="utf-8"?>
<soap:Envelope xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/">
  <soap:Header>
    <GDWSoapHeader xmlns="http://gxxxt.intra.xxxx.com/xxxxGDW/