MRO Magazine

Washdown Woes

It comes as a surprise to many that cleaning industrial equipment can be a very dangerous process. For example, in 1999, two young workers died on the job while cleaning dough mixers.


September 1, 2004
By Simon Fridlyand, P.Eng

It comes as a surprise to many that cleaning industrial equipment can be a very dangerous process. For example, in 1999, two young workers died on the job while cleaning dough mixers.

Sixteen-year-old Ivan Golyashov died when a dough-making machine he was cleaning was accidentally turned on by a fellow employee. The young man was inside the mixer when the rotors began to turn.

A very similar accident took place six months prior. David Ellis also died cleaning a mixer, on the second day of this new job.

“My son David was an 18-year-old boy with a whole career ahead of him, very similar to Ivan, eager to please,” says David’s father, Rob. “Most kids will put their heads down and work very hard and ask very few questions.”

Advertisement

Those unfortunate accidents could have been easily prevented. The Ministry of Labour in Ontario issued an alert related to the cleaning and operating of mixers and other process equipment. The alert includes the following recommended precautions and legal requirements:

Guarding

Mixing machines need to be guarded to prevent a worker from being exposed to the moving parts. The guard should be interlocked so that the equipment cannot be operated when it is opened for pouring or cleaning, or when the bowl is lowered. An appropriate lock-out must not should be in place. The interlock must not be used in place of an appropriate lock-out procedure.

The province’s Regulations for Industrial Establishments [R.R.O. 1990, Reg. 851], Section 24 states: “Where a machine or prime mover or transmission equipment has an exposed moving part that may endanger the safety of any worker, the machine or prime mover or transmission equipment shall be equipped with and guarded by a guard or other device that prevents access to the moving part.”

Section 76 of the regulation states: “Where the starting of a machine, transmission machinery, device or thing may endanger the safety of a worker, (a) control switches or other control mechanisms shall be locked out; and (b) other effective precautions necessary to prevent any starting shall be taken.”

Solvents

In many cases cleaning is done using flammable materials such as acetone, for example or other solvents. On top of the machine guarding requirements, fire and explosion safety issues must be considered, especially with the cleaning of closed systems such as a closed mixer or vessel.

Transferring acetone into the mixer could cause an explosion, since the liquid may generate static electricity while being transferred. Grounding and bonding the mixer is essential but not enough. The recommended way of safeguarding is through the control of the explosive concentration of vapour inside the mixer or vessel.

The safe way is when this concentration is below the lowest flammable level. For most solvents the level is below 2%. This could be achieved through the introduction of nitrogen or another inert gas into the mixer or vessel before acetone is added. Nitrogen will displace oxygen and will maintain the explosive concentration below the limit. But the opening of the hatch cannot not take place since the nitrogen is lighter than air and could be easily replaced, creating a flammable concentration.

The level of the lower explosive limit must be constantly monitored by sensors to ensure that the level of nitrogen inside the mixer or vessel is adequate. As far as the hazardous location classification of electrical equipment is concerned, if solvents are used for cleaning purposes only, the equipment will still be classified as such.

For cleaning of open systems (such as open mixers or vessels), Section 63 of the Regulations for Industrial Establishments requires that when a process is likely to produce a gas, vapour (e.g. acetone vapour), dust or fumes to such an extent as to be capable of forming an explosive mixture with air, the process must be carried out under the following five conditions:

1. The area where the process is carried out must be isolated from other operations. Note: When flammable liquids such as acetone are dispensed, the process must be carried out in a room or area that is isolated from other operations in the building.

2. The area must have a system of ventilation adequate to ensure that the gas, vapour, dust or fume does not reach a hazardous concentration. Note: Mechanical ventilation must be provided at a rate capable of reducing the vapour concentration below 25% of the lower explosive limit of the solvent vapour mixture in the air. When practicable, the dispensing process must be interlocked with the ventilation system, so that if the ventilation system is stopped or fails, the dispensing process also is stopped.

3. The area must have no potential sources of ignition. Note 1: Potential sources of ignition include open flames, smoking, hot surfaces, electrical sparks, static electricity, cutting and welding, radiant heat, and frictional heat or sparks. Note 2: Electrical installations used in dispensing areas must be inspected on site and approved by the Electrical Safety Authority as safe for use in hazardous areas.

4. The area must have provision for explosion venting.

5. The area must have, where applicable, baffles, chokes or dampers to reduce the effects of any explosion.

Dispensing flammable liquids

Subsection 22(4) of the regulation states that an area where flammable liquids are dispensed must have mechanical ventilation from floor level to the outdoors at the rate of 18 cubic metres per hour per square metre of floor area; and containers and dispensing equipment must be bonded and grounded when flammable liquid is dispensed.

The Ontario Ministry of Labour recommends the following precautions for the dispensing of flammable liquids.

Use pumps or self-closing valves designed in accordance with good engineering practice in the dispensing of flammable liquids.

When the receiving containers have small openings, install flexible metal or conductive rubber hoses on the faucet to reduce spillage. If drums are in the horizontal position for dispensing, use a flame-arrestor bung vent.

Make sure that workers wear clothing and footwear that dissipate static electrical charges during the dispensing process, because man-made fibres and regular footwear generate static.

As required under the WHMIS (Workplace Hazardous Materials Information System), all containers of hazardous products must be labelled and adequate product-specific training must be provided to workers. The material safety data sheet (MSDS) for the product should be consulted for information on safe handling.

Electrical equipment washdown

When washing down takes place, it is very important that the enclosures for the electrical equipment are properly selected. The following are the definitions of various enclosure types as classified by National Electrical Manufacturers Association (NEMA) standards.

NEMA 1 — Enclosures constructed for indoor use to provide a degree of protection to personnel against incidental contact with the enclosed equipment and to provide a degree of protection against falling dirt. Note: All the NEMA standards following include provision of a degree of protection to personnel against incidental contact with the enclosed equipment.

NEMA 2 — Same as NEMA 1, but including protection against dripping and light splashing of liquids.

NEMA 3 — Enclosures constructed for either indoor or outdoor use to provide a degree of protection against falling dirt, rain, sleet, snow and windblown dust, and that will be undamaged by the external formation of ice on the enclosure.

NEMA 3R — Same as NEMA 3, but excluding protection against windblown dust.

NEMA 3S — Enclosures constructed for either indoor or outdoor use to provide a degree of protection against falling dirt, rain, sleet, snow and windblown dust, and in which the external mechanisms remain operable when ice laden.

NEMA 4 — Enclosures constructed for either indoor or outdoor use to provide a degree of protection against falling dirt, rain, sleet, snow, windblown dust, splashing water and ho
se-directed water, and that will be undamaged by the external formation of ice on the enclosure.

NEMA 4X — Same as NEMA 4, but including protection against corrosion.

NEMA 5 — Enclosures constructed for indoor use to provide a degree of protection against falling dirt; settling airborne dust, lint and fibres, and to provide a degree of protection against dripping and light splashing of liquids.

NEMA 6 — Enclosures constructed for either indoor or outdoor use to provide a degree of protection against falling dirt, against hose-directed water and the entry of water during occasional temporary submersion at a limited depth, and that will be undamaged by the external formation of ice on the enclosure.

NEMA 6P — Same as NEMA 6, but including protection against the entry of water during prolonged submersion at a limited depth.

NEMA 7 — Enclosures are for indoor use in locations classified as Class I, Groups A, B, C or D, and shall be capable of withstanding the pressures resulting from an internal explosion of specified gases, and contain such an explosion sufficiently that an explosive gas-air mixture existing in the atmosphere surrounding the enclosure will not be ignited. Enclosed heat-generating devices shall not cause external surfaces to reach temperatures capable of igniting explosive gas-air mixtures in the surrounding atmosphere. Enclosures shall meet explosion, hydro-static and temperature design tests.

NEMA 9 — Enclosures are intended for indoor use in locations classified as Class II, Groups E, F or G, and shall be capable of preventing the entrance of dust. Enclosed heat-generating devices shall not cause external surfaces to reach temperatures capable of igniting or discolouring dust on the enclosure or igniting dust-air mixtures in the surrounding atmosphere. Enclosures shall meet dust penetration and temperature design tests, and those for aging of gaskets (if used).

NEMA 12 — Enclosures constructed (without knockouts) for indoor use to provide a degree of protection against falling dirt, circulating dust, lint and fibres, and against dripping and light splashing of liquids.

NEMA 12K — Same as NEMA 12, but including enclosures constructed with knockouts.

NEMA 13 — Enclosures constructed for indoor use to provide a degree of protection against falling dirt, circulating dust, lint and fibres, and against the spraying, splashing, and seepage of water, oil, and non-corrosive coolants.

Safety is everyone’s business. The terrible fate of Ivan and David could have been prevented. We must know and understand hazards associated with the washing down process. Corporate governance mandates us to exercise due diligence in whatever we do.

Simon Fridlyand, P.Eng., is president of S.A.F.E. Engineering, a Toronto-based company specializing in industrial health and safety issues and compliance. He can be reached at 416-447-9757 or simonf@safeengineering.ca. For more information, visit www.safeengineering.ca.