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January 2008: Property Loss Prevention in Glass Manufacturing Plants

There are various types of glass manufacturing plants, and the processes and associated hazards differ significantly. One thing they have in common is that business interruption potential is higher than other types of occupancies, since the glass plants typically operate continuously for years.

The glass forming operation, if applicable, can present the greatest fire hazard within the operations since significant quantities of lubricating oils, mold release oils or combustible binders can be handled near the glass furnaces that are operated at high temperatures.

We address below some loss prevention issues that are critical for glass manufacturing plants such as Utilities, Construction, Operation, and Automatic Fire Protection.

Utilities

Since glass furnaces are operated continuously for years, reliability of the related utilities is the key issue. A minor event such as damage on a main power supply cable can stop production for the entire plant, and can result in a longer-than-expected business interruption if the remaining glass is not drained out from the furnaces in a timely manner.

Redundancy of the production and utility equipment
Single loss of any piece of production or utility equipment should not stop the production for an extensive time. The plant should be designed based on "N+1 philosophy" (i.e., at least one back-up utility or critical piece of equipment should be available at any time).

Oil insulated transformers should be separated by fire walls if they are grouped so that they will not expose each other and will not be lost in single fire event.

Back-up tanks for natural gas or LPG (for running the glass furnaces) should be preferably installed on site to prepare for a potential interruption although having tanks on site will present a fire or explosion hazard. They should be installed with adequate separations from the important buildings or structures and placed parallel to the main plant.

Maintenance
Plant power supply systems should be inspected and maintained properly. Infrared surveys have been proven very effective to find potential problems and should be conducted annually for key electrical equipment items. In some plants, high voltage power cables should also be inspected for their entire length.

Preparation for emergencies
A power outage can still occur for well designed and redundant power supply systems. In case of such an event, glass furnaces should be shut down safely. To do so, all associated utilities should be operable (such as cooling air systems, cooling water systems, process or temperature control instruments, pollution abatement, waste water treatment, etc.). The emergency power capacity and duration should be studied well in advance. The emergency generators should be tested at least monthly under a full load.

Emergency procedures for shutting down or inspecting utilities should also be prepared for other possible events such as fire, earthquake, flood and hurricane, etc. Training should be conducted based on pre-planning.

Others
Pollution abatement systems, through which the burnt natural gas or LPG will be treated before releasing to the atmosphere, are mandated in most countries. They are typically taller than other buildings or structures and can be damaged if they are not properly designed against the expected wind-speeds, or they can catch fire if the insulation materials are of combustibles.

A fire can damage waste water treatment facilities if there are combustible construction or contents (i.e., tanks, etc.). Gas detection is recommended where flammable gas can be generated from waste water.

If these facilities are lost or damaged, the authorities having jurisdiction may not allow the plant operations to be continued. Back up plans should be made in advance to prepare for the possible scenarios.

Construction

The temperature of glass furnaces can be operated as high as 1,400°F (760°C) which is high enough to ignite combustibles if used for building construction.

Building construction
Where glass furnaces are installed, the building construction should be non-combustible. Fire ratings should be determined based on the equipment arrangements and code requirements, if applicable.

Molten glass
Molten glass, if released from the glass furnaces, can expose the steel members or legs of the furnaces themselves, and surrounding occupancies especially the gas manifolds, safety equipment, and combustion controls. Bunds should be provided underneath and adjacent to the glass furnaces in order to confine the whole volume of a molten glass spill. Legs or any other steel members within the bunds should be fireproofed and process equipment should not be located within the bund areas.

Gas
Oxygen fuel headers should also be protected from molten glass.

Operations

Glass furnaces are a special item that can be only found in glass manufacturing plants. They are run mostly by oil or gas.

Combustion Control
The glass furnace should be provided with the basic combustion controls like any other furnaces such as manual shut-off valves, gas pressure regulators, safety shut-off valves (SSOV), high or low gas pressure switches and combustion controls.

Inspection/maintenance/monitoring
Refractory is made of ceramic materials designed to resist high temperatures over an extended period of time. It looks like a brick and is used in the furnace enclosures for insulation purposes. The refractory should be visually inspected daily to find hot spots and other problems. Some plants use thermographic (infrared) cameras for inspections. If there is a developing weakness in the refractory, the adjacent area can be directly exposed to very high temperature. The refractory temperatures should be continuously monitored with thermocouples and should send an alarm when abnormal conditions are found. Loss of or insufficient cooling air or water should also send an alarm.

Cleaning
Combustible residues, created due to the forming operations, should be cleaned up on a regular basis. The frequency of cleaning depends on the amount of residue.

Automatic Fire Protection

Like any other manufacturing plants, automatic sprinklers (or other types of automatic fire suppression systems) are necessary wherever combustibles/flammables are stored or handled. They are typically found in the following areas.

1) Glass forming operation areas where lubricating oils, mold release oils or combustible binders are used.
2) Warehouse areas where packaging materials or finished goods are stored, and oil storage areas.
3) Electrical rooms or areas where the cable concentration is high. Cable coating is an alternative.
4) Emergency generator rooms.
5) Other areas where the combustible loading warrants.
6) LPG tanks and oil insulated transformers should be protected by automatic water spray systems.
7) Cooling towers if fill materials are combustible.
8) Office areas and other general plant areas.

Risk Logic has the capability to evaluate property loss prevention risks and recommend ways to improve them in glass manufacturing facilities.