Furnace Audit

Inspection | Heat & Mass Balance | Repair Suggestions | Certification

GS Energy & Environment, Ltd., 100% affiliate of Glass Service, Inc. is providing Inspection & Audit services.


Glass manufacturers are under constant pressure to further reduce the melting costs and the costs for fuel and electricity in particular as well as emissions, mainly NOx, SO2 and Particlates, and since the majority of the energy consumption occur in the melting and refining process, it offers the largest opportunity for improvements.

The Furnace Audit is an assessment of the “present situation” of the glass melting at the given furnace – characterized by all process input and output variables – and includes, if applicable, the air preheating device and the batch and/or cullet preheating device.

The Audit mainly

  • points out the critical issues such as corrosion, failures or scaling and summarizes suggestions to repair,
  • recommends measures to economically and/or ecologically optimize the glass melting and
  • benchmarks the ‘results’ with the industry average.

The Audit can be subdivided into:

  • Inspection
  • Heat & Mass Balance
  • Repair suggestions
  • Certifications

Heat & Mass Balance

Heat balance calculations are needed to estimate the energy requirements and the cost of the process, as well as the operation preconditions. In fact, no process will work unless the heat balance is met.

Heat and mass balances are based on the most common enunciation of the first law of thermodynamics and can be described as:


Heat and mass balance calculations of the furnace process at steady state aim at two objectives:

  • Firstly, they aim characterising the operational efficiency of a given furnace based on measured results and
  • Secondly, they intend to predict future results of the same furnace under different operating conditions.

The accuracy of the heat and mass balance is much depending on the accuracy of the input data […].

The first calculations are based on all measured data. Briefly, this includes mainly the quantity, temperature and chemical analysis of all the materials entering (raw materials, fuel, electricity, oxygen etc.) or exiting (mainly glass, waste gass and losses) the furnace.

Based on the furnace data, knowing (all) the process variables, a forecast is very accurate. The fundamental idea behind is, that with the given parameters, the overall losses can be calculated very quickly without evaluating the furnace refractory conditions etc. in detail.
Within a specific forecast these losses will not change significantly. Even when the given parameters are not 100% correct, the forecast or trend respectively will be very accurate.

Possible variations are:

  • Electricity vs. Fuel as well as fuel changes
  • Batch and/or glass changes or Heat recovery modifications
  • Production increase (with additional electricity or oxygen)
  • Conversion from air fuel to oxy fuel combustion (or vice versa)
  • Recuperator or regenerator repairs

Repair Suggestions

With the results from the inspection (mentioned under section 1), GSEE will suggestion every type of repair observed and the repair time planning.


Inspections and Audits are often part of a certification respectively certification processes.
GSEE offers 3rd party certification / audits as well as supporting internal certification for the following Certification Standard Specifications.


  • DIN EN ISO 19011 – Guidelines for management system auditing


  • DIN EN ISO 9001:2008 – Increase efficiency and build confidence
  • TL 9000 – Improve Management System


  • (BS) OHSAS 18001 – Occupational Health and Safety Management Systems


  • DIN EN ISO 50001:2011 – Energy Management Systems
  • DIN EN 16247-1:2012 – Energy Audit


  • DIN EN ISO 14001:2009-11 – Environmental Management
  • EMAS III – Eco Management and Audit Scheme
  • QC 080000 – Hazardous Substance Process Management


  • ISO FSCC 22000 – Food Safety Management
  • HACCP – Food Safety


  • Various e.g. ISO 15504, ISO 22301 or ISO 27001