Alternative Technologies and Avoiding Entry
Robotics and high power vacuum systems are just two of many options for cleaning, repair, or inspection that might require an entry.
I have never actually entered a confined space, and to be honest, I have never really wanted to. I have, however, been responsible for ensuring the safe and effective entry into literally hundreds of confined spaces. One thing is for certain: The safest entry is no entry at all!
The purpose of this article is to review the various reasons that one may have for entering confined spaces, and then to offer a variety of alternative technologies and approaches for avoiding entry in the future. While it is unlikely all organizations can eliminate the need for confined space entry, it is very likely many organizations can at least reduce the frequency of entry.
Let's begin by reviewing the definition of a confined space. A confined space is "A space that is large enough and configured in such a way that an employee can enter and perform assigned work. It also has limited or restricted means of entry or exit (e.g., tanks, vessels, silos, storage bins, hoppers, vaults, and pits are spaces), and is not designed for continuous employee occupancy."
The implication of the definition is that entrants into a confined space where hazards are present have greater risk because of the work conditions. With that as a basis for our discussion, let's proceed.
Reasons for Entry
There are many reasons why confined space entry may be required (at least at first glance). Some of these might include:
- Product removal: A site may have to remove a product from a tank, silo, vault, or similar space for reprocessing, or there may be a need to change out production to a different product.
- Spills: Spills or releases may flow to vaults, sewers, catch basins, pits, or similar locations.
- Maintenance: Confined spaces of all types may require entry in order to perform repairs, complete inspections (regulatory, post-incident, and or good engineering practices), provide for new installations, etc.
- Cleaning: Cleaning may be required for decommissioning of equipment, as a follow-up to product removal or spills, or in preparation for maintenance activities.
Why Not to Enter
Despite the many reasons why confined space entry may be required, there are overriding reasons why not to enter. Consider, for example:
- Chemical exposure: Many entries are into spaces containing, or formerly containing, hazardous chemicals. Obviously, work in an area with reduced natural ventilation increases the potential for exposure through inhalation, and because of the nature of the space, physical contact may be more likely, as well.
- Physical hazards: Entry into confined spaces can subject the entrants to entrapment, engulfment, mechanical hazards, heat, cold, and a host of other hazards.
- Equipment requirements: Entries require the use of specialized equipment, including extraction devices and other rescue equipment. Much of this specialized equipment is of no use for other workplace activities.
- Personnel requirements: A safely performed entry will require at least three people, and possibly more. Other personnel, including those assigned to rescue services, will necessarily be on standby. The overall commitment of employee resources for these activities can be quite significant.
What Are My Alternatives?
So, you ask, if I have tasks to perform, and yet I have all of these risks and reasons not to enter, what are my alternatives? Let's consider several specialized pieces of equipment, as well as common and not so common techniques.
Product/Material Handling Equipment: High Power Vacuum Systems
In order to remove material from a confined space without entry, one option might be a high power vacuum system (see Figure 1). These systems can be truck- or trailer-mounted, can achieve air flows of 500 to 7,000 cfm, and are capable of establishing 15 to 30 inches of Hg vacuum. The units can be equipped with suction lines of up to 8 inches in diameter, allowing for removal of even large debris, and will move material up to 1,000 feet laterally. They can be operated in wet or dry mode and may be further equipped with HEPA filtration. Other special options include explosion vents, special interior coatings, internal wash down systems, swing out cyclone collection, and specially designed drop-out collection containers. With a high power vacuum system you can move abrasives, brick, catalysts, cement, chemicals, oil, sludge/slurries, clay, coke, and virtually any other debris from virtually any confined space.
Specialized Cleaning Equipment
There are several options available for cleaning without entry. These can include water jet cleaning, abrasive blasting, and chemical cleaning.
The typical water jet system (also known as hydro-blasting equipment), depending upon the pump and configuration, can produce a water jet of 1,000 to 100,000 psi at volumes of 1 to 100 gpm. This pressure can literally cut steel or concrete, and certainly, with the minimal volumes of water used, can be a creative cleaning solution. Water jet systems are in extensive use within a variety of industries, including pharmaceutical, chemical, petroleum, food processing, and transportation. In addition to "shotgun" cleaning wands, the units can be equipped with lances (for cleaning long portions of piping) and with cleaning heads that can operate at variable speeds and can further clean three-dimensionally over 360 degrees of coverage (see Figures 2 and 3). Specialized applications include telescoping booms (see Figure 4), retractable units for cleaning railcars or horizontal tanks (see Figure 5), and skid-mounted units for cleaning large-diameter pipes (see Figure 6). Water jet systems even can be included in a new engineering design to automate or semi-automate the cleaning process.
When someone mentions abrasive blasting, most people think of sandblasting. There are, however, several other options, the most intriguing being CO2 pellet blasting. The obvious advantage of CO2 as a cleaning medium is that during the blasting process the "abrasive material" sublimes, leaving only the residue of the material previously in the space, now ready for easy removal.
A number of companies specialize in chemical cleaning, using caustic or solvent cleaning materials to clean vessels, tanks, and other containers. Some of the cleaning materials are "off-the-shelf," but experienced companies can develop customized cleaning solutions, as well. Another chemical cleaning method is simple neutralization, which can be used quite effectively with acids and bases.
The increase in the use and availability of specialized robotics has created a wide variety of opportunities for avoiding entry into confined spaces. Mechanical cutting heads, remote welding capabilities, and guidelines combined with cameras allow for safer methods for repair and maintenance within confined spaces.
While IR and X-ray inspection or testing methods have been in use for many years, increased sensitivity and improved methods are creating rapid advancements in the use of these techniques as opposed to direct visual inspection. An added bonus, of course, is that these types of inspection actually yield more accurate results, allowing for better decision-making.
Another inspection technique that continues to advance is the use of opto-electronic equipment to inspect ducts, pipelines, drains, and sewers from 6 inches to 80 inches in diameter. This equipment allows for inspection of live water and live gas lines, which eliminates the need for downtime; it is joystick controlled and resembles a technical version of a modern video game.
Non-Entry by Design
Regardless of whether some of the specialized equipment described above is used or an alternative approach is taken, the best time to consider the prevention of the need to enter confined spaces is at the design stage. Consideration of approaches such as: removable agitators; fixed cleaning systems; oversized inspection plates/windows; and/or clean-outs (such as bottom take offs) can simplify cleaning, repair, and inspection and eliminate or at least minimize the need for confined space entry.
As an example of how creative approaches can improve task performance, consider the cleaning of a very large, heavy, oil storage tank. One approach, of course, is the "old method" of direct entry, which can be time-consuming and more than a bit messy (see Figure 7). One company specializing in this type of cleaning developed a very new approach utilizing steam lancing with a "fluff and stir" technology. A complex manifold system (see Figure 8) allows for a faster, cleaner process (see Figure 9), which also results in a cleaner tank. How creative can you get when considering your options for dealing with confined spaces?
Every modified approach, of course, has the potential to create new hazards that did not previously exist. High pressure water blasting introduces the possibility of liquid injection injuries; high power vacuum systems introduce new sources of physical injury and noise; solvent cleaning processes may create flammable atmospheres, while other cleaning agents present new chemical hazards; and CO2 blasting probably will result in oxygen-deficient atmospheres. A process safety review should be performed whenever changes in approach occur.
Specialized equipment, changes to procedures, non-entry by design, and customized/creative approaches can eliminate or reduce the frequency of the need to enter confined spaces. Plan now for later, and be creative. Just because it has always been done this way does not mean it must be done this way in the future.
Consider the new safety hazards that may be created, but always remember: The safest entry is no entry at all!
This article originally appeared in the February 2004 issue of Occupational Health & Safety.