PRESSURIZED WELDING ENCLOSUREs
WHAT IS A PRESSURIZED WELDING ENCLOSURE?
A pressurized welding enclosure (PWE) is a fully enclosed area that is constructed to create a safe atmosphere where welding and burning can take place near classified or otherwise hazardous areas. SafeZone Safety Systems, LLC has a patented process that utilizes a PLC system that will control all atmospheric monitoring and welding equipment based on set parameters. The system is designed to shut down all hot work components any time a hazardous atmosphere is detected, pressure is lost, or emergency shut down is activated. This process is used both on and offshore in various industry applications.
The Bureau of Safety and Environmental Enforcement (BSEE) has a current regulation for offshore operators that prohibits welding within 10 feet of pressurized process equipment or the perimeter of the well bay unless the platform is shut-in. BSEE will allow a waiver of this regulation if a PWE is used, given the appropriate notifications to the agency are made. Once approval is granted a PWE can be constructed and hot work is allowed in classified areas without having to shut down production operations.
PWE’s are used in chemical plants, refineries, and other onshore locations to keep the facility running during hot work operations. They can be used for any emergency repair that needs to be made in between turnarounds or sensitive areas where additional safety barriers are needed. Enclosures are custom built to size and can be very large in order to encapsulate huge vessels if needed. PWE’s can also be used when welding within 100’ of a loading dock, where otherwise hot work is restricted to specific days. Approvals need to be granted by the Coast Guard and a hot work permit addendum would be issued.
An enclosure can be installed to encapsulate and isolate hydrocarbon areas such as well heads, valves, and flanges where the potential for hydrocarbon release exists. The PWE process is reversed to create a negative pressure around the known hazard, and hot work operations can continue in the nearby vicinity of an existing or potential leak.
MONITORING AND CONTROL SYSTEMS
SafeZone’s PWE control system utilizes a Programmable Logic Controller system (PLC) that performs all monitoring and control of the SafeZone Safety System used in a safe welding enclosure operation. The PLC system gathers data from the inputs of various devices, such as emergency stop stations, atmospheric gas sensor equipment, and positive pressure sensors, and executes an output to various pieces of equipment. This output function is automatically performed without any person or person’s manual control. The PLC will turn off all outputs to the associated welding equipment (welding machines, oxygen/acetylene sources, grinders and work tools, etc.), which ensures that all equipment inside the welding enclosure is immediately shut down.
Our control system can be used for area monitoring applications without the use of a fully pressurized enclosure as well. Atmospheric monitors can be set up in designated areas to detect any possible hazardous condition. If detected, these monitors send a signal to the PLC in order to shut in welding equipment without the need for human intervention.
Each panel is interchangeable and is 4’ x 4’ in size that will attach by a 4” thick flame retardant Velcro material. All panels have sewn on straps that allow them to be attached to the scaffolding frame. Penetration panels come in various sizes and are used to cope around any size pipe, beam, etc.
The floor of a PWE will consist of the scaffolding system, if it is not located on a solid steel deck. Our floor panels consist of a rubber flame retardant material that has stainless steel sheeting embedded inside to eliminate exposure to cuts. Floor panels are covered with a carbon fiber felt that is rated fire proof for additional barriers where high exposure to flammable materials exist.
PROGRAMMABLE LOGIC CONTROL
A programmable logic controller system (PLC) is used to control all aspects of the hot work process. Whether a hazardous atmosphere becomes present, loss of pressure occurs, or emergency stop initiated, a shutdown signal will be sent to the control system. When a shutdown input is received, the system is designed to automatically shut down all components used in hot work operations without the intervention of workers.
PWE’s are custom built and supported by use of a scaffolding frame. SafeZone will work closely with the scaffolding crew on location to install the proper size frame needed for the enclosure. The base of the scaffolding system will function as the floor of the PWE unless it is located on a solid deck.
POSITIVE PRESSURE MONITORING
SafeZone safety systems monitor the differential pressure within the enclosure to maintain a positive pressure, so that outside gases cannot enter the welding area. Blowers are placed in unclassified areas of the facility to force clean air into the enclosure allowing for one air rotation per minute. If the differential pressure drops outside of the setpoints, the PLC will initiate a full component shut down of all hot work equipment.
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