Permit-Required Confined Spaces are dangerous places, and to safely enter one, three CRITICAL PATHS have to be done near perfectly every time. These are:
- Space preparation (cleaning and isolation),
- Atmospheric Testing/Monitoring, and
- Permitting
In this article, I want to highlight these three areas and highlight some small but critical details that can make a HUGE difference in worker safety.
Space Preparation
If at all possible, the space should be as clean as possible. This may mean using less hazardous materials, such as sodium hydroxide (NaOH) or diluting acid to acid/caustic wash the space to react out any remaining material. In some spaces, steam cleaning may be the optimal method to clean the space. PLEASE KEEP IN MIND this cleaning is DONE FROM OUTSIDE the space, and no one is breaking the plane of the space during cleaning. Some spaces may be equipped with “spray balls” that can be used to clean the space. We cannot forget that some of our cleaning agents may themselves create a hazard within the space, so we should not be fooled by the mere fact we are calling this “cleaning” the space. This is especially true if a solvent was used to clean the space, as the vapors can linger long after the liquid has been drained, and the vapors are deadly – NOT the liquid! Once we have the space DRAINED and CLEANED, we then focus on isolating the space from all potential energy sources. I like to train personnel to imagine the space is suspended in air, and there is NOTHING attached to the space, AND the ONLY way anything can get into the space is through the entry permitting process. In the USA, OSHA accepts ONLY three (3) such means of isolation:
- Blinding/Blanking,
- Double Block and Bleed, and
- Disconnect and misalignment
Here are a few items to consider when using these three energy isolation methods.
ALL pipes, hoses, ductwork, and tubing TO & FROM the space MUST be isolated using one of the following methods:
- Blanking/Blinding,
- Disconnect and Misalignment,
- Double Block and Bleed
Don’t be fooled with “drain lines” and “discharge lines” that normally convey materials away from space – these lines, too, MUST be isolated, as liquids and vapors can travel in ALL DIRECTIONS! “ALL pipes, hoses, ductwork, and tubing ” means even those unused nozzles to the space. In 1996, I had a PRCs incident at my plant when a worker mistakenly hooked up a caustic hose to a space on the first floor and began pumping caustic into the space and onto the workers. Everyone yelled for the worker to be fired, but the investigation found that the three (3) identical vessels were not labeled on the first floor; the entry was being made on the 3rd floor, so he had no way of knowing anyone was inside the space, and lastly, and most importantly, he did not violate LOTO since the nozzle he attached the hose to was not locked or tagged out. This is why EVERY nozzle/connection on the space MUST BE ISOLATED using one of these acceptable methods. If this is done properly, there will be no way any hazards can enter space, except through the permitting process, which will then be identified and measures put in place to manage the risks.
Blinding and Blanking are defined as
the absolute closure of a pipe, line, or duct by the fastening of a solid plate (such as a spectacle blind or a skillet blind) that completely covers the bore and that is capable of withstanding the maximum pressure of the pipe, line, or duct with no leakage beyond the plate.
We should blank/blind the flange CLOSEST to the space, preferably the nozzle flange on the tank. We should leave the valve(s) that were locked out when installing the blanks/blinds locked out for added safety during the entry process; after all, the valves will have to be locked out to pull the blanks/blinds. Any blanks/blinds already in place (e.g., process flow control or for QC purposes) MUST be pulled and inspected BEFORE being used as an isolation device. There have been many occasions where blinds/blanks left in process streams catastrophically failed, and no one ever knew until the incident investigation! A GREAT book to read for examples of this happening is “What went wrong?” by Trevor Kletz. We should LOCK blanks/blinds in place with chain and lock if possible; if not, tag it out so that it is CLEARLY identified as an energy isolation device so that others will not tamper or remove it. This is a widespread oversight, as we find a lot of blinds/blanks that are listed on energy isolation worksheets but are not identified as isolation devices in the field. This is sort of like closing a valve and not locking it or tagging it out! If blinds/blanks are used, the facility should utilize some type of system (e.g., blinding log, energy isolation worksheet, PSSR, etc.) to ensure all blinds/blanks have been pulled BEFORE the space is returned to service.
Double block and bleed is defined as
the closure of a line, duct, or pipe by closing and locking two in-line valves and by opening and locking or tagging a drain or vent valve in the line between the two closed valves.
The drain/vent valve must be locked or tagged in the open position, which is as important as the closed and locked block valves. DB&B is often used as it is thought that it is safer to put in place than blinds/blanks; however, this can be a DANGEROUS assumption, as we are “opening” the process when we open the vent or the drain, and if the process contains a highly hazardous chemical (HHC), this small release can have devastating results. We need to ensure NO tie-ins or connections between the two block valves. If there are, then we either cannot use the DB&B arrangement, or we have to apply one of the three isolation methods on the line that ties in between the two block valves to have proper isolation. The risk for this error increases the further the distance between the two isolation valves; hence some facilities have been known to limit the distance between the two isolation valves. Some facilities call out in their procedures that the valves must be “in view of each other at ground level” to be used in a DB&B arrangement. Lastly, we want to ensure that any connection between the block valves is locked or tagged closed, including ALL vents/drains and utility connections on the pipe. Lastly, using a DB&B arrangement should be reserved for lesser hazardous chemicals and not for highly toxic or flammable materials. After all, the whole idea behind DB&B is that the material will exit the pipe at the vent/drain and not apply force against the isolation valve. This means that if we fail within our arrangement, we will release a highly hazardous chemical into the atmosphere just outside the PRCS, which could endanger the entrants. I have seen chlorine actually be released outside of the space through a DB&B vent and blown into the space by the forced air ventilation!
Disconnect & Misalignment do not have an official definition, making them vulnerable to mistakes. I like to call it “disconnect AND misalignment” to indicate that BOTH MEASURES must be taken to be considered adequate isolation. Too often, I come across a situation where a valve was removed from the 3″ pipe, leaving about a 6″ gap in the pipe, and I, for one, feel this is not acceptable isolation. It is not impossible for many gases/vapors to travel across the 6″ gap and enter the space. I have always recommended that a distance of at least 2 feet be set as the minimum distance for this type of isolation when the pipe cannot be misaligned (e.g., rolling a spool piece). Misaligning 1.5″ or larger pipe should NOT be attempted or done as this can cause undue stress on the pipe and its flanges. Facilities use jacks, and pipe stands to misalign piping, which is not good practice. This isolation method is intended for hoses and tubing associated with the space. We would disconnect the hose/tubing from the space, which would meet “disconnect and misalignment” requirements. The KEY here is that workers need to be trained to place their lock or tag on the VESSEL CONNECTION and not the end of the hose/tubing. We want the connection to be isolated so that nothing can be attached to the vessel at that spot. Putting the lock or tag on the end of the hose only prevents that hose from being used, and we all know what will happen…the worker will go get another hose! When disconnecting and rolling down a spool piece, we should place a LOTO lock through the nozzle/flange bolt opening as a means to “lockout” this “energy isolating device.” Placing the lock through the bolt opening on the flange/nozzle prevents the spool piece from being rolled back into place.
Atmospheric Testing/Monitoring
It is easy to see (no pun intended) why atmospheric hazards are the leading killer inside confined spaces…often we cannot see, hear, feel, smell, or taste the hazardous atmosphere. Humans depend on our senses to inform us of danger(s). Since our senses do absolutely nothing to help us detect oxygen-deficient atmospheres, it remains to this day, the leading killer inside confined spaces. Hence, why atmospheric testing/monitoring is one of the critical paths in confined space safety. But there are a lot of flaws in the typical atm testing/monitoring programs. One major flaw is using the regulatory minimums on acceptable entry conditions.
Consider this…1% is equal to 10,000 ppm. The oxygen ranges set in most regulatory languages around the world use 19.5% Oxygen as the lower limit and 23.5% as the upper limit. The normal oxygen concentration in the air is 20.8% (at sea level). Suppose we have an atmosphere reading 19.8% Oxygen. In that case, we are within the acceptable limit set by most regulatory agencies, but here is the catch…we have 1% less oxygen in the atmosphere, which translates to 10,000 ppm of something else in the atmosphere within the space! How many chemicals does your facility have that have an IDLH limit of less than 10,000 ppm, and how many of these chemicals have POOR WARNING PROPERTIES?!?!?! If Oxygen is normally 20.8% (at sea level), why don’t we set our O2 limits at 20%-22%? If we are off the norm of 20.8%, we have something going on inside the space that needs to be analyzed further; just writing it down on a permit is NOT ENOUGH! Also, narrowing the range for O2 provides even more of a safety factor for the number one killer inside confined spaces. I always like to remind workers that “confined” spaces are usually small, and thus an atmosphere within them can change rapidly. Having a narrow range for atmospheric conditions will give more time to exit the space before a hazardous atmosphere is present.
How about explosive/flammable atmospheres? Are there any flaws with how we currently measure the Lower Explosive Limit? Oh yes, I have written about a major flaw several times before. Basically, the reading on your LEL detector is NOT the actual reading of the atmospheric concentration for the flammable gas/vapor. You see, meters are calibrated with a special mixture of gases, and depending on the flammable gas used in calibration, the meter reading will have to be “corrected” with a “correction calculation.” Each manufacturer has different “correction calculation” formulas and multipliers, so BE CERTAIN to use those provided in your meters owners/operations manual.
Here is the bottom line: if we use the regulatory limit of 10% LEL and the entry supervisor is NOT trained in the proper use and limitations of the meter, we may send workers into a “hazardous atmosphere.” Here is how this can happen: The meter reads 8% on the LEL sensor; this is below the 10% LEL limit, so the entry supervisor signs the permit, and entry is authorized. In reality, the meter was calibrated with methane, and the flammable vapor in the space is Toluene. The actual LEL percentage of toluene vapors in the space is 22.8%, MORE THAN TWICE the upper limit of 10% of the LEL. Some would argue that even at this level, the space is only 1/5 of the way to having enough vapor to burn/explode, and even with the “correct calculation” not being used, the space would only reach ~30% of the LEL when the meter alarm would sound at the 10% meter reading. But my argument is the same for the oxygen limits… atmospheres can change rapidly inside confined spaces, and unlike Oxygen Deficient atmospheres, there is NO PROTECTION suitable for a flash fire within a confined space; SCBA or not, chances of survival are slim to none! Another serious matter that MUST be considered when you have a vapor present within the space is Toxicity Exposure.
Considering 22.8% LEL from the toluene, consider this:
the LEL for toluene is 1.1%.
This means you’d have about 0.25% toluene in the atmosphere within the space, which translates to 2,500 ppm of toluene in the atmosphere…
The PEL for toluene is 200 ppm, so the entrants are at 10X the toluene PEL in this atmosphere
The IDLH for toluene is 500 ppm; the entrants are at 5X the toluene IDLH in this atmosphere
Source: NIOSH Documentation for Immediately Dangerous To Life or Health Concentrations (IDLHs)
Lastly, how many of your entry supervisors know why we test first for Oxygen, then LEL, then toxicity? How many of them think this order is because oxygen deficiency is the leading killer in confined spaces and thus first on the list? We actually test for oxygen first, as our meters are oxygen-dependent. Many of the meters today have minimums of 8-10% oxygen for them to operate in and provide reliable results. Click Here to read a more detailed article on the flaws of direct reading gas meters.
One more critical subject for atmospheric testing is depth and time. Entry supervisors need to know that gases and vapors have different densities and, therefore, will be located in different locations within the space. Most of your hydrocarbon vapors will be heavier than air and will be found at the bottom of spaces, but there are a lot of flammable gases that are lighter than air, and these will be found at the top of spaces. How about the depth of a space…will this have any effect on atmospheric testing? You bet it will! How many entry supervisors know the capabilities of their meter sampling pumps? Do they know how long they need to leave the sample hose in the space when sampling a 40′ vertical vessel vs. a 10′ vertical vessel? How long does it take to sample the space, 2 minutes, 5 minutes, 10 minutes? Will each space take the same amount of time?
Your entry supervisors should be able to answer these questions correctly and in a timely manner.
Permitting
If we have done all the items above PROPERLY, we are now ready to do our final checks to verify all conditions on the permit have been met. Through proper cleaning and isolation of the space, we have assured ourselves that the “process hazards” have been eliminated; however, workers create many hazardous atmospheres within confined spaces. Using flammable liquids/gases, chalking materials, cleaning solutions, etc., can create hazardous atmospheres just as deadly as process hazards. This is why so many facilities are now using “continuous monitoring of the atmosphere” rather than the initial check and “periodic checks” throughout the entry. The permitting task is often viewed as a “paperwork burden” rather than a critical path for safety. The entry supervisor plays a VITAL ROLE in ensuring safe and successful entry, and it is through the proper issuance of the entry permit that he/she does this. When I say every “i” needs to be dotted and “t” crossed, it will never ring more true than when issuing and approving an entry permit. Completing and VERIFYING the permit entries is the FINAL INSPECTION before we send workers into a space that all too often becomes their grave! Entry supervisors need to be extremely picky in what they allow to be taken into the space and the activities allowed to be conducted inside the space. This is even more serious when dealing with potentially flammable atmospheres, as we want to limit the available ignition sources within the space. I have also seen different crews within the same space create serious hazards for each other by their work activities not meshing well (e.g., making repairs using welding while inspectors use a solvent-based cleaner to clean sections of the vessel). Lastly, the entry supervisors in the USA are required by 1910.146(j)(4) to “Verify that rescue services are available and that the means for summoning them are operable.” With so many facilities relying on their local FD to provide rescue services, this could be a bit tricky for the entry supervisors, as there will need to be some type of communications system in place for the entry supervisor to do this, as I am sure the facility will not want their entry supervisors calling 911 each time they approve a permit. Click Here to read a more detailed article on the topic of using FD for rescue and the drawbacks of this practice. If a facility succeeds in these three critical paths, then the likelihood of a safe entry is very high.
