If you’re reading this then the likelihood is, you’re involved in the operation, management or maintenance of steam boilers. If this is the case then you’ll no doubt be looking for ways to achieve continued safety and greater efficiency in your plant. This is where I can provide a few pointers to help you get the most out of your boiler house. house.
There are five key tests that can be carried out that are designed to ensure the safety of boiler house operators and the safe operation of plant equipment. These tests can also highlight areas of improvement.
I’ve broken the five tests down into the following areas:
The main question to ask yourself here is, am I trained to the Boiler Operation Accreditation Scheme (BOAS) standard? I mention this as BG01 guidelines suggest that any person operating a (shell) boiler at their site should be trained to the BOAS standard. To find out more on achieving the BOAS standard, take a look at this course where the Spirax Sarco Technology Centre prepares operators like yourself for the BOAS accreditation.
‘Guidance on the Safe Operation of Boilers’ (BG01) Edition 2, published in March 2019, should be your go to guidance document when it comes to safely operating and maintaining your boilers. Additionally, it could help to achieve compliance with various legal requirements set out in the Health and Safety Executive’s ‘Safe Management of Industrial Steam and Hot Water Boilers’ (INDG436) document.
It’s worth taking the time to familiarise yourself with the guidance and standards outlined in both BG01 and HSE INDG436. Whether you have one boiler or multiple boilers across your site, you should be regularly checking them to ensure they remain compliant. Typical log sheet examples can all be found on pages 50-58 in the BG01 guidance document.
We support operators like yourself with compliance audits (called a BG01 audit). These are a very useful way to identify areas of improvement and also ensure that the necessary regular tests are being performed in the correct manner.
Depending on where your plant is located in the UK, you’ll be faced with either hard or soft water and will be combatting varying levels of Total Dissolved Solids (TDS). (TDS).
If faced with hard water, it could lead to hard-scale forming on the surface of the boiler furnace tube which may act as an insulator, causing the metal to overheat. This could, in a worst-case-scenario, result in catastrophic boiler failure which is something you definitely don’t want to happen. The solution is to deploy a water softener which will introduce sodium compounds into the boiler’s water supply to counter the presence of magnesium and calcium. Carrying out daily water tests will help you to see the level of TDS in your water so that you can determine the right amount of water softener to use. use.
It’s also important to carefully control the pH level of the water. The pH of the water should always be between 9 and 12 in the boiler. If your water is reading below pH 7, you’ll need to raise the pH so the water becomes alkaline rather than acidic. The oxygen is controlled in the hotwell tank by heating the water to between 80-85oC, and using an oxygen scavenger to remove the remaining oxygen from the water. Oxygen scavengers (or oxygen absorbers as they are sometimes known) are either a liquid or powder that are added to the water to remove or decrease the level of oxygen within the tank. tank.
On a weekly basis, the boiler must undergo an evaporation test to check the integrity of water level alarms and the results must be recorded in a log book. The test involves lowering the actual boiler water level to the first low through evaporation, and then blow down to the second low. This will ensure that the alarm is sounded at the right level when the level of the water drops slowly in the boiler. boiler.
In any shell boiler, sludge consisting of minerals, metals, organic material and salts forms and falls to the bottom of the boiler. Unless it’s removed, it can accumulate and potentially prevent heat transfer from the boiler fire tubes causing them to overheat and eventually fail.
To remove the sludge, I recommend opening the bottom blowdown valve as a minimum, using short sharp bursts, typically of a few seconds duration. The stored water volume and your boilerhouse risk assessment should determine how and when the boiler is blown down. This can be done manually or by an automatic bottom blowdown system that opens at a specific time for a set number of seconds leaving you or your team to focus on other critical areas. It’s worth noting here that any fluids leaving the boiler cannot enter a public sewer until it has been cooled to below 43oC. The use of a purpose designed blowdown vessel is recommended to facilitate this. The recently published guidance on BG03 (Blowdown systems) can provide more information.
If the valve doesn’t operate correctly, you’ll need to replace this immediately, so it’s worth checking the valve regularly.
Having reached number five on the list, you’re probably feeling quite confident that you’re already carrying out the correct testing procedures in your boiler plant. plant.
Ask yourself, what’s entering the boiler? What fuel am I using? How much fuel am I using? What’s in my feedwater? Do I know exactly what’s entering and exiting the boiler? By being able to answer these questions, you’ll have a much firmer grasp of what’s happening with your boiler and whether your energy consumption is being managed efficiently.
Energy monitoring systems such as the B850 Boiler House Energy Monitor can help you by providing the data necessary to understand the energy consumption by calculating the efficiency of the boiler based on measured inputs from the fuel, feedwater, steam output, condensate return and blowdown. This provides a ‘real time’ energy transfer efficiency from fuel to steam which can help you to identify issues that can be turned into efficiency gains.
In my experience, there has been a tendency for efficiency measurements to be taken using the burner efficiency as the metric. However, this approach disregards a number of potential energy losses that can occur, such as losses through boiler blowdown.
The surest means of guaranteeing efficiency readings is to meter all of the energy entering (through both fuel and feedwater) and compare this with the useful energy exiting the boiler through the steam.
For further advice and support when it comes to safe and efficient boilerhouse operation, the team at Spirax Sarco are here to help. Contact us today at email@example.com or call us on 01241 521361.
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If you are under pressure to reduce the running costs of your boiler house, then I have some tips you may find useful.
Steam is an incredible heat transfer medium. Every kilogram of steam contains around 2200 kj of condensable energy. That’s 26 times more usable energy than a kilogram of water in a typical heating system based on flow and return temperatures with a delta of 20oC.
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