Do you have dust in your cabin? Is the heating, ventilation and air conditioning (HVAC) system underperforming or not cooling as before? Has the machine been stood down often due to HVAC service or repairs?
If you answered yes to any of these questions, the main issue may be fine (respirable) dusts and the fact that for the most part these are invisible and can potentially remain airborne for days or weeks. Fugitive fine dust which become airborne is produced at mineral processing sites by blasting, shovelling, drilling, screening, crushing, conveying and handling.
Airborne Particulate Matter
Airborne particulate matter which has a diameter of less than 10 microns in size will pass through installed cabin filters easily that were never intended to mitigate against respirable dust in the first place. Settling dust may deposit inside the cabin surfaces, foot well and inside HVAC components (Evaporator). Hazardous conditions occur for the operator when internal deposited dusts are lifted by air conditioning-HVAC, machine vibration and operator body movements and consequently, internal dust contamination, become airborne inside the cabin without any means of capture. The installed cabin pressuriser- filtration system must be configured for respirable dust (Particulate) mitigation.
The best practice that applies and keeps an operator safe is the same practice and procedures that can be used to keep the HVAC system and the inside of the cabin clean. The same applies to reduce unexpected costs of unscheduled service cycles made up of components failures and/or HVAC system underperformance caused by fine dust contamination.
Reducing Service and Maintenance Costs
The following key points have proven effective in reducing service and maintenance costs:
- Keep the cabin environment clean (Aaways keep doors and windows closed & use a HEPA vacuum in the cabin at least twice a week)
- The cabin needs to be sealed tight against external particulate contamination
- Pre-cleaner should be used to expel coarse particles and extend filter service life
- Ensure fresh air pressurisation with a HEPA filter (High efficiency filter to control respirable particulate)
- Use computer control pressurisation (Precisely control cabin environment and extend filter service life)
- Employ computer cabin pressure controller with display and warning/alert for operator (Site management warning/alert by remote monitoring)
- Have a brushless motor, with an operating design range between 10000 to 15000 hours of operation (Maintenance free)
- Provide a HEPA return air filter to capture contamination from clothes and shoes (Keeps evaporator free from dust contamination)
- Use remote monitoring for analytics 24/7 (May be used to develop filter maintenance intervals)
- Maintain cabin integrity by replacing worn out seals (Audits as part of implemented dust management plan)
At site operations, a cabin is exposed to different concentration levels of dust. The operating environment may be subject to extreme levels of dust coupled with high ambient heat. When fine dust contamination begins to accumulate in the evaporator, the performance level decreases over time and eventually causes restrictions. This process of contamination increases heat load and it is the ultimate factor that causes HVAC failures.
The issue of occupational fine dust exposures has been studied and tested by NIOSH and OSHA in the US. Their findings are some of the key points discussed. There are further implications with silica exposure which is 20 times more toxic than airborne mine dusts and this has been a factor in the OSHA’s new ruling in the US which has significantly reduced the amount of silica dust exposure that a worker can be exposed to. The following is an excerpt form this legislation:
(iii) For measures implemented that include an enclosed cab or booth, ensure that the enclosed cab or booth:
(A)Is maintained as free as practicable from settled dust;
(B) Has door seals and closing mechanisms that work properly;
(C) Has gaskets and seals that are in good condition and working properly;
(D) Is under positive pressure maintained through continuous delivery of fresh air;
(E) Has intake air that is filtered through a filter that is 95% efficient in the 0.3-10.0 µm range
(F) Has heating and cooling capabilities.
Excerpt from: www.osha.gov/silica/constructionregtext.pdf
The same system that keeps the operator safe will in fact reduce costs of unplanned maintenance and costs of HVAC repairs caused by internal dust contamination. The cost of a BreatheSafe (HEPA) fresh air pressuriser system is actually the same as a standard system. However, BreatheSafe has developed procedures and technology to help maintain costs by keeping a clean cabin and HVAC system. Furthermore, BreatheSafe has developed long life brushless motors to assist even further with keeping costs down of air filtration systems. Talk to us about reducing costs of entire system maintenance over the entire lifecycle of the machine whilst ensuring the most important aspect: keeping the operator breathing zone safe from respirable dust (particulate).