Working Safely in Confined Spaces

What is a confined space?

 

Confined spaces have a number of key attributes:

• The space must be large enough for a worker to enter but be too small for continuous occupation

• The space should feature limited openings for entry or exit

• The space may be poorly ventilated

• There may be inwardly sloping walls or floor

Many confined spaces exist within a variety of industries including marine applications. Depending on the type of ship and the cargo, dangerous gas concentrations can form in the atmosphere at any time. Liquid gas, fuel, chemicals and other fossil fuels harbor a risk of explosion and there is a danger of suffocation from lack of Oxygen when using Nitrogen or other non-flammable gases for inerting. It is also important to be aware of dangers presented by toxic gases such as Carbon Monoxide from exhaust fumes, or Hydrogen Sulphide from the decomposition of organic compounds found in the briny water inside the ballast tank.

Likely hazards encountered in confined spaces

Typically, confined spaces can contain a variety of hazards including Hydrogen Sulphide (H2S), Carbon Monoxide (CO), Methane (CH4) and Oxygen deficiency.

• H2S - H2S is a toxic gas that is produced as a bi-product of microbial activity. This gas is highly toxic and at concentrations less than 30ppm is identifiable by its strong odour of rotten eggs. At concentrations higher than 30ppm, H2S paralyses the olfactory nerve, stopping the sense of smell. At concentrations of 500 to 700 ppm, death will occur within 30 mins to 1 hour.

• CO - CO is a toxic gas that is produced by the incomplete burning of fossil fuels such as oil, gas and coal. During normal combustion, Carbon Dioxide is produced (CO2) but when ventilation is inadequate, CO can be produced instead. CO is absorbed by haemoglobin in the blood and prevents Oxygen being absorbed, causing the victim to die of asphyxiation. At concentrations of 400ppm, CO will start to cause nausea, dizziness, headache and sickness. At concentrations of 800ppm, death will occur half an hour after exposure.

• CH4 - CH4 is a combustible gas that is produced by the decomposition of organic materials. CH4 is the main constituent of Natural Gas and as a result, leaks in gas pipes can be another source of Methane.

• Oxygen Deficiency - Normally Oxygen makes up 21% of the atmosphere and an Oxygen deficient environment is described as being one where Oxygen levels are 19.5% or less. Oxygen can be displaced by toxic or inert gases and microbial action, oxidation caused by rusting metal and combustion can also cause an Oxygen deficient environment. At 19.5% Oxygen the operator will feel drowsy. At 17% and less cognitive processes and coordination will be severely compromised. At levels of 6% or lower, death will occur quickly.

Although these are the most likely gases to be encountered in confined spaces, other gases can also be found.

Dealing with marine confined space entry

Before an operator enters a confined space, they will need to make a pre-entry check to determine the hazards in the area.

The use of a multi-gas portable gas detector, capable of providing simultaneous monitoring of H2S, CO, Oxygen and combustibles (%LEL) is essential for safe confined space entry (please note: the sensors used with any portable device must reflect the known hazards likely to be in the environment).

First the operator must perform a full test of the environment prior to entering. Once the area has been cleared for entry, continuous monitoring must continue to ensure the area remains safe from gas hazards.

Pre-entry check:

Testing at various levels of the confined space is essential because of the differing nature of gases and the fact that some are heavier than air, whilst others are lighter, than air.

Naturally, until the hazards are known and evaluated, it is not safe for the operator to directly enter the area. The use of a confined space gas detector kit makes stratified testing easy and generally includes a multi-gas monitor with pump, 10 foot sampling hose for pre-testing (longer lengths available).

Continuous monitoring

After initial testing is complete, the atmosphere within the space must be continuously monitored to ensure the area remains safe. If a hazardous atmosphere is detected during entry, employees should exit immediately, re-evaluate the space and take corrective measures.

What portable device?

The ideal portable device needs to offer simultaneous monitoring of 4-gases, and be rugged and suited to tough environments; especially when working in marine applications where water is likely to be present. This makes an IP66/67 rating preferable. Audible and visual alarms are also necessary to ensure that the operator is alerted to an issue, even in noisy environments.

The MARINE QUATTRO - portable multi-gas detector is ideal for the job being rugged and reliable with the World's longest continuous operation battery life.

Find out more about the MARINE QUATTRO.

The Importance of Portable Bump Testing

Bump Testing: The simple test that could save your life!

It’s important to do a bump test before you use your portable device, even if it has been recently calibrated. This is the only way to ensure accuracy and ensure that the device will alarm when exposed to specific quantities of gas.

Why bump testing?

Imagine the following scenario; an operator picks up his portable device, which has just been calibrated. He is scheduled to undertake some sandblasting of rusted pipe work in a confined space onboard a ship.
The area he is working in poses a potential hazard for H2S, Oxygen depletion, CO and flammables and his portable device uses catalytic bead detection to monitor for flammable gases. Whilst undertaking the sandblasting, his device is bombarded with minute particles, and some get forced into the sensor’s sinter, partially blocking it up. This means that the sensor is no longer working correctly.

According to his usual equipment maintenance schedule, the engineer does not plan to re-calibrate the device for 3 months. When he next uses the device, he assumes it is working well, but in reality its ability to detect flammable gases has been severely compromised.

Bump testing explained

As the previous example highlights, regular bump testing is essential to ensure that a device is online and able to do the job it is designed to do every time it is used by an operator. There are two main ways to bump test a portable device:

1. Manual method: This involves using a 4-gas mix cylinder (four gases that are being monitored all contained in one pressurised cylinder) and a bump testing kit, consisting of a gas flow regulator and tubing. The operator uses the tubing and regulator to expose the device to the mix of gas from the canister.

2. Automatic method: This involves using a device that provides automatic portable test and calibration. Typically these devices contain an integrated gas supply and easy dock aspect that allows a portable to be tested and calibrated in a few minutes, at the touch of a button.

What’s the benefit?

The table below provides a good comparison for manual testing and automatic testing, but how does this translate into customer value in terms of cost savings?

When it comes to time management, even the smallest changes can equate to considerable savings over time. A small change such as reducing the bump test time from five minutes to two minutes can translate into a labour cost reduction of 60%. When additional aspects such as auto data logging and auto calibration are also included, this percentage rises to an approximate saving of 75% by making small time efficiencies.

MPA Singapore Rule Out Use of Motion Sensors on BNWAS for Their Vessels

The Maritime and Ports Authority of Singapore has clarified the issue of use of motion sensors as a method of confirming OOW activity to reset a BNWAS on Singapore registered vessels.

MPA Singapore has taken a similar viewpoint to Lloyd’s Register in that they do not see motion sensors as providing an indication of the awareness of the Officer of the Watch (OOW).

MPA Singapore state:

“A motion sensor would not meet the design criteria for reset function in accordance with MSC.128(75). As stated in paragraph 6.2.2, "Reset devices should be designed and installed so as to minimise the possibility of their operation by any means other than activation by the OOW.

In the case of BNWAS, the OOW may not be the only trigger for the motion sensors, in particular, in consideration that the ship is moving, and in rough seas the rolling could be severe, resulting in curtains swaying, falling objects in bridge, etc, all which may trigger the motion sensors. Also, having motion sensors would add an additional device to the alarm system, which would then require testing and approval that they can function properly in a shipboard environment as part of the alarm system.

The intent is also clearly stated in the above para 6.2.2, that the activation by the OOW positively is preferred, not via a passive means such as motion sensors. The resolution also actually provides an example of where the reset button could be located, eg chart table or ECDIS, where the OOW would be for considerable periods of time and therefore could easily reach out to reset the alarm. The aim is to include simple reset devices which would not be prone to false resets or failure and for the OOW to have complete awareness of the need to actively reset the alarm. Motion sensors will take away this awareness.

Please refer to our shipping circular no. 21 of 2010 on BNWAS.”

Navgard™ - Lloyd’s Register (LR) Type Approved BNWAS

The LR Type Approved version of the Navgard™ BNWAS has been designed and approved to operate without the use of motion sensors. Instead, the system operates with manual push buttons to reset the BNWAS at the prescribed intervals to meet with LR requirements.

The criteria that the systems meets for Lloyd’s Register Type Approval also means that it is ideal to meet the requirements of the Singapore MPA.

Find out more about Navgard LR Type Approved BNWAS.

Lloyd’s Register Requirements for BNWAS

An updated version of this article is now available - click to view updated article.

Anyone who has any of their vessels classified by Lloyd’s Register of Shipping should be aware of one very important requirement that the classification society has stipulated for BNWAS.

While many BNWAS use passive infra red (PIR) sensors to detect movement on the ship’s bridge as a way of automatically resetting the BNWAS, LR do not recognise this technology as an acceptable method of determining the awareness of the OOW.

In their Rules and Regulations for the Classification of Ships, Part 7, Chapter 9, Section 4.2 – Navigational Arrangements and Integrated Bridge Systems, LR state:

4.2.3 Acknowledgement of any alarm is to automatically reset the time interval between warnings. Manual adjustment of controls may also be used for this purpose. Manual adjustment of controls and navigation equipment is to automatically reset the watch safety interval timer. Reset arrangements based on the detection of movement in the bridge are not considered to satisfy this requirement or to confirm well-being and watch-keeping awareness.

In further clarification on this issue Lloyd’s have said:

“Paragraph 4.1.3, 5.1.4, 6.2.2 & 6.2.3 of the performance standard adopted by IMO by its MSC. Res. 128(75) provides the requirement on the reset facilities of BNWAS.

We understand these requirement as such that the reset functionality may be provided by either physical reset push buttons at Officer of the Watch(OOW)’s proper look out positions, e.g. conning position, navigation operation & watch station (radar & ECDIS workstation), wings, etc., or by input from other equipment on the bridge capable of registering operator’s action in positions giving proper look out, e.g. operation of radars or ECDIS.

Movement of OOW (or other thing) detected by the motion sensors in wheelhouse is not sufficient to demonstrate the OOW’s mental alertness as required by 4.1.3.3.

The BNWAS is required to be of a type approved by the Flag administration, therefore the justification of using motion sensors as reset facilities for BNWAS is to be given by the relevant Flag authority.”

Navgard™ - Lloyd’s Register Type Approved BNWAS



Navgard LR Type Approved BNWAS

Martek Marine’s Navgard™ BNWAS is available in versions both with and without PIRs. The version of the system that does not use motion detectors uses manual reset buttons instead and is fully Type Approved by Lloyd’s Register.

The version of the system that incorporates PIRs has Type Approvals from a range of other classification societies who have not interpreted the performance standards in the same way as LR and as such allow motion detection as a simpler and less stressful form of indicating activity on the bridge.

By having a system available in versions that can operate with or without PIRs and that has a full range of Type Approvals from all the major Classification Societies it means that you can source your BNWAS from just one supplier even if you have a variety of classed vessels. This can save you a great deal of time and effort.

Find out more about the Navgard™ BNWAS.

What Can You Learn from the Danish BNWAS Experience?

While the international shipping community is starting to turn its attention to how it will comply with the latest amendments to SOLAS V/19, Denmark has had a national requirement of a BNWAS on Danish ships for some time. The Danish implementation started in March 2003 for ships with gross tonnage below 500 and thereafter gradually for larger ships. By 1st March 2006, the national requirement was in force for all ships.

At the fifty-second session of the IMO’s Sub-Committee on Safety of Navigation looked at the human aspect of BNWAS. The Sub-Committee was asked to look at how they could enhance the safety of navigation while still taking into account the human element. In response to this, Denmark has taken a look at the use of BNWAS on Danish ships and on how navigators view the system they use.

In the winter of 2006-07, the Danish Maritime Authority issued a questionnaire to get feedback on the use of BNWAS on Danish ships. 237 responses were received from OOW’s familiar to the use of BNWAS.

Summary of Results

• 93% of the navigators answered “Yes” to the question: “Do you regard the BNWAS to be part of the safety equipment on the bridge protecting the ship and her crew?” This clearly indicates that the OOW’s generally regard the BNWAS as a factor that enhances the safety of navigation.

• In most cases the procedures and routines for Bridge Resource Management on board the ships had been changed to ensure proper use of the BNWAS.

• The number of times the BNWAS had been activated varied according to the way the alarm was reset. Approximately half of the received answers were given from ships equipped with reset button system only. A reset button must be activated manually in order to reset or postpone an alarm.

• On ships with a reset button system, an innumerable number of alarms were seen or heard.

• BNWAS was in many cases only reset after the alarm was activated. The OOW on such ships generally felt the BNWAS to be a source of irritation and distraction. In total, approximately 20% of the OOW’s found the BNWAS irritating due to the many alarms.

• On ships with a system including activity sensors that detects movement on the bridge, the BNWAS gave very few alarms. Furthermore, the OOW on such ships generally viewed the BNWAS to be reassuring. No element of irritation was found in the answers in connection with this type of BNWAS.

Conclusion

Based on the views expressed in the questionnaires, a BNWAS that incorporates activity sensors rather than only a reset button should be installed on your vessels. This will reduce the number of alarms and avoid unnecessary stress and inconvenience to the OOW. This, however, is not an option for any of your vessels that are classed by Lloyd’s Register who have advised that the use of passive infra red (PIR) motion sensors is not acceptable for compliance with SOLAS V/19. All other Classification Societies will accept this form of activity detection.

Only 0.1% of all alarms went to the second stage giving audible alarm in the back-up officer’s and/or master’s locations. No alarms went to third stage giving audible alarm in the locations of further crew members.

How Can Martek Marine Help You?

Navgard, Martek Marine's fully Type Approved BNWAS, is available either with or without the use of PIR motion detectors. This gives you the choice, should your class society allow it, of the most convenient method of compliance for your ships and their crew.

The system is Type Approved by all of the major classification societies, including Lloyd's Register, meaning you can find a BNWAS for your whole fleet from one supplier, even if your vessels are classed by a variety of societies with differing rules.

For more information, click on the links below:

Navgard - Fully Type Approved BNWAS

More information about BNWAS