F.E. Lewis, discipline authority, process engineering
BP America Inc., Houston, Texas

Add bleed valves

Given the situation described, the easiest solution would seem to be the installation of a "T" above Valve A with a bleeder valve installed on the "T." At the very least, this would allow a controlled release of the pressure on the trapped pipe before the line was broken. If the material in the pipe is of concern, another "T" could be installed above Valve B to allow the contents of the pipe to be blown out to a receiver at the opposite end. If the material is safe, the second "T" and bleed valve would allow the pressure to be removed if any of the three valves shown were in need of service.
Dan Iezek, manager, engineering and maintenance
Pfizer Global Manufacturing, Franklin, Ohio

Break flange for non-hazardous fluid

Several mechanisms exist for resolving this problem. From a safety perspective, bleed valves should be in the piping for the relief of the pressure in the line, unless the fluid is not hazardous and breaking the flange (loosening the bolts away from the mechanic) to relieve the pressure is acceptable.
Michael Hartzes, senior process engineer
CDI Engineering Group Inc., Houston, Texas

Lock Out/Tag Out

Energy isolation, or LOTO, requires both isolation of the energy and bringing the energy to a zero state. The energy isolation/LOTO permit should have an isolation device listing and a drawing of the piping. Included in the instructions and training for LOTO should be directions to walk the line/do a physical visual tracing of the line from isolation Valve 1 to the correct isolation Valve 2. If the line cannot be walked/visually traced from grade, then access to the overhead pipe rack must be provided. Color coding process lines and labeling valves will provide assistance, but cannot replace the physical/visual verification. The piping section does not show any vent/drain valve connections between the proper isolation valves. This requires an interim step before maintenance can begin. After closing the valves, either operations, or maintenance under the direction of operations, wearing the proper personal protective equipment and taking a defensive position, must break a flange between the correct isolation valves to vent the process before issuing a permit for the valve repair. The design of the fine adjustment Valve A should be reviewed to assure that compressed gas is not trapped in the bonnet by the valve position. The mechanic can then verify the proper isolation and zero energy state during the safe work permitting process. A safe work permit can then be issued for the maintenance. If recurring maintenance will be required on Valve A, a vent valve should be added to the line during the maintenance.
Rob K. Riley, senior reliability rngineer
Air Liquide America LP, Geismar, La.

Depressure line safely

Before any attempt is made to operate on a section of piping, a procedure for the work to be performed, including the isolation process and blowdown, should be written. This documentation should be reviewed by at least two other individuals not performing the work but who are knowledgeable of the operation. They should independently check the document for accuracy and operational soundness. The document should be used by the workers performing the piping work during the repair process and they should not deviate unless for safety reasons. (The deviations should be documented.)

After the pipeline has been isolated, the section should be blown down using a controlled process, preferably a small isolation valve. If a valve for control is not available, flange bolts should be loosened to allow the gas pressure in the pipe to escape safely. If the pipe is too large or long to allow timely depressurization of the line safely, an adequately sized valve should be installed onto the piping and tapped to allow safe depressurization of the pipeline. Safety is paramount in depressurizing any pipeline and should be performed efficiently before any consideration of time and money.

After the piping work has been repaired and put back into service using a documented repressurization process, all documentation should be signed and dated by the workers. The signed document should be submitted, reviewed and filed for further reference.
Karl Watson, P.E., C.E.M., C.E.P., sr. engineer
Abbott Laboratories, Abbott Park, Ill.

Several suggestions
Since there is no mention of any label or signage on the pipes and valves, color-coding with a unique ID would be the logical and least expensive first choice. You could actually use colored tape and apply a strip along the entire length of the pipe. Then, of course, a proper LOTO procedure that incorporates a second check by another qualified tag signer should be used. Another more expensive, and maybe less effective, option would be to relocate the "extra" pipe so that "three from the end" in the center of the room is actually "three from the end" on the wall.
Thomas Hinckley, senior process engineer
Texas Polymer Services Inc., Orange, Texas


Diane Dierking is senior editor for Chemical Processing magazine. E-mail her at ddierking@putman.net.