Silo Safety Alert

Background

A farmer entered a silo and then used an internal ladder to reach and dislodge clumped urea.

A crusted layer of urea collapsed under the farmer’s weight, causing him to fall through the material and become engulfed in the lower conical section of the silo.

Safety issues

Entering silos is a high-risk activity on farms. Having internal ladders fitted as a special request to manufacturers’ makes entry more likely, and increases the likelihood of having to manage confined space entry on your farm.

Confined space entry 

The management and control of confined space entry requires:

• a suitable entry permit system, including related training and documentation
• procedures to indicate entry and ensure exit 
• emergency procedures and practices and suitable ongoing training 
• air monitoring where required.

Or, alternately, restrict all silo entry points by: 

• locking hatches 
• posting highly visible warning signs and labels
• totally restricting entry to the silo.

Click here for more information about confined spaces on farms.

About urea

Urea attracts and absorbs moisture from the surrounding environment. This absorption then increases the likelihood of urea clumping and sticking to the silo walls. Granulated urea has higher bulk density and flow characteristics when compared to other commodities such as grains and stock feeds.

When exposed to moisture, dampness, or excessive heat, urea can hydrolyse and break down into ammonia gas (off-gassing). 

• Ammonia is a toxic irritant that can create severe atmospheric dangers inside a silo at high concentrations. 
• Heat or dampness makes ammonia off gassing more likely.

Employees or other people who enter a silo containing urea, risk being: 

• engulfed by urea 
• overcome by ammonia gas, or 
• caught in moving parts such as augers.

When urea sticks to the silo walls it can create increased loading on the wall, which can cause the silo to collapse unexpectedly. In this instance, the product formed a layer that gave way when the farmer stood on it, causing him to fall through the material.

Striking, hitting or throwing objects against the silo wall to dislodge stuck material may cause dents or other damage to the wall. This can increase the risk of the silo wall failing under the load of stored material.

Employees and any other people nearby may be at risk of:

• being engulfed by escaping material, or 
• crushed by the silo structure should it fail.

Risk control

Silos designed specifically for storing urea can be purchased. Contact silo manufacturers or fertiliser retailers to discuss the safest way to store fertiliser. 

It is the employer’s responsibility to ensure they have safe systems that eliminate or control the risks associated with silos.

Different fertilisers may pose significantly different risks. Before storing urea or another fertiliser in a silo, employers, employees and self-employed persons should ensure the following actions or assessments have been undertaken.

• The silo is appropriate for storing the selected material.
• They have read the product’s safety data sheet. Manufacturers and suppliers will indicate whether a product is suitable for storage in silos.
• The manufacturer’s specifications for material density are not exceeded.
• The silo’s sidewalls are smooth. This will improve material flow when unloading.
• The outfeed cone is appropriate for the flow characteristics of the material being stored.
• The silo can be appropriately sealed to prevent moisture entry.
• The structure is regularly inspected for damage including rust and damaged sealant and repaired by a competent person when required.
• Ensure no internal ladders are fitted to the silo or, if fitted in older silos, they cannot be accessed.
• Where access ladders are fitted to the outside of the silo, they comply with AS 1657-2013 Fixed platforms, walkways, stairways and ladders - Design, construction and installation.

Safe silo entry actions

Below are some of the actions you need to take before entering the silo.

• Read and understand confined space entry requirements and complete documents required to enter a confined space. (link to confined space entry guidance).
• Silo correctly identified.
• Filling conveyor isolated and locked out.
• Discharge auger isolated and locked out.
• Stored product/engulfment hazard controlled.
• Atmosphere tested, where required.
• Safe access/egress established.
• Standby person in position.
• Communication method functioning.
• Rescue equipment and procedure ready.
• Entrants have been appropriately trained.

Urea storage solutions

Where current farm silos are not suitable for storing urea, consider:

• alternative storage methods including well-ventilated storage sheds 
• third-party warehousing
• bulka bags
• just-in-time bulk delivery
• installation of new silos that are suitable for urea storage.

Legal duties

Employers and self-employed persons have duties under the Occupational Health and Safety Act 2004. 

Additionally, the Occupational Health and Safety Regulations 2017 (OHS Regulations) sets out specific requirements in relation to confined spaces. When working in a confined space, employers and self-employed persons who have management or control of the space must, so far as is reasonably practicable, identify all hazards associated with work in a confined space. You must control any risk associated with work in confined spaces, so far as reasonably practicable.

The OHS Regulations defines a confined space. A confined space is an enclosed or partially enclosed structure or space, including a silo, that:

• is likely to be entered by any person, and has limited or restricted entry or exit that makes it difficult to get in and out of, and
• is, or intended to be, at normal atmospheric pressure while a person is inside, and
• may contain one or more of the following:
  • an atmosphere that has a harmful level of any contaminant, or
  • an unsafe oxygen level, or
  • a stored substance, except liquids, that could cause engulfment

If the space on your farm meets all 4 parts of the definition, then the space is a confined space.