The Ultimate Guide To Pre-Commission Cleaning And Flushing
The pre-commission cleaning and flushing of pipework systems is a complex process. With many procedures to follow, it’s of paramount importance that it’s carried out correctly. That’s why we’ve written this guide to give you an overview of the topic.
Why Pre-Commission Cleaning Is A Necessity
Pre-commission cleaning purges a pipework system of waste and debris. This includes biofilm, oil, and grease. Chemical cleaning and flushing leave the surface clean enough to apply a corrosion inhibitor. This procedure helps prolong the life of the LTHW or chilled water system and ensures its optimal performance.
What Happens When Pre-Commission Cleaning Isn’t Carried Out.
If pre-commission cleaning isn’t carried out, there can be severe consequences. This applies to closed, open, hot water, and chilled systems.
A wide range of debris can accumulate in new closed-water system installations. If these systems aren’t cleaned at the pre-handover stage, this debris continues to build up. This gradually reduces the performance of the system and can lead to failure.
It can also cause erosion corrosion. This prevents the corrosion inhibitor from doing its job. Erosion corrosion can also be accelerated by chloride contained in some jointing compounds. Flushing the system with raw water won’t altogether remove it. Only a thorough chemical cleaning utilising an appropriate biocide will be successful.
Common issues include suspended solids, oil, and grease inside the pipework. These form a layer that the inhibitor cannot penetrate. Advanced corrosion can occur as a result.
Hot water and chilled systems are particularly vulnerable to blockages. Strainers, small bore heat exchangers, and control valves are common problem areas. The water system will require continued treatment once a flushing and cleaning project is complete. This helps prevent further contamination.
The Pre-Commission Cleaning And Pipe Flushing Guidelines
There is also a BSRIA BG29/2021 version. It has a few additions relating to thin-walled carbon pipes and CPC procedures.
These guidelines take you through the entire pre-commission cleaning and flushing process.
They also cover water sampling and who is responsible for what.
Before You Begin
There are a lot of factors to consider and tasks to complete before you start. Here’s an overview of the most important ones, so you’re informed beforehand.
Pre-commission cleaning and flushing involve many steps, and these need careful planning.
A typical system flushing project will include the following:
- Pipework flushing
- Circulation of chosen biocide
- Removing oxides
- Disposal via drains
- A dosing system with inhibitors
Because of the complexity of this process, keeping a record of all the details is crucial. Flushing velocity and water samples are two important examples. The samples should be taken from the whole system. This ensures the cleaning and flushing has been carried out thoroughly.
Pre-commission cleaning involves potentially harmful chemicals and specialist pipe flushing equipment. To adhere to all Health & Safety requirements, a risk assessment and method statement must be completed and signed off prior to carrying out any work.
Flushing Older LTHW And Chilled Water Systems
If your installation is an older system, there are three further steps required:
1. There must be a clear reason why the cleaning is required
2. The pipework should be examined to ensure that it can withstand a chemical flush
3. The history of the system needs to be known
Before using any chemicals, it’s also important to know whether the system suits them.
This means knowing:
- The system volume
- The debris within it
- The system type; open, closed, or partially closed.
- The pipes are made from; each material requires careful treatment, and reacts differently to each chemical.
- The scale within the systems’ pipe work, chillers, flow rate monitors, and small-bore control valves can be easily blocked.
- If antifreeze is used and it’s glycol-based, this can nourish bacteria if not properly maintained.
- Whether the system has been left as is since installation or if it’s been modified in any way
- How long it took to build the system – this affects how much debris may have accumulated.
- Data about how the system operates, the temperature, pressure, and flow rate will suggest the kind of treatment required.
There are many requirements to keep in mind when you’re selecting chemicals for pre-commission cleaning. Pre-commission cleaners used should be neutral in pH and high in polymer. They should also contain a surfactant and a chelant.
It’s critical the cleaning chemical utilised has a neutral pH, as this prevents the metals in the system from being damaged. The polymer ensures solids and biofilm can be flushed out, whereas the surfactant removes any oil and grease, and the chelant dissolves the corrosion within the system.
The amount of chelant in a pre-commission cleaner determines its iron plateau level. BSRIA BG29/2021 states 6ppm total iron and 3ppm soluble iron, but a lower level may be required if the system is older.
Biocides, effective inhibitors, and bio-dispersants are some types of chemicals required. When you use these, you’ll need to consider the minimum contact time. If you’re using a biocide, it should have a similar contact time to the chemicals used in the pipe flushing procedure.
Maintaining the right concentration is also essential when using a biocide. Knowing the system volume will help with this. The same calculation results and dosages should be used for three purposes. Calculate the system volume, the rates for the inhibitor, and the rates for any biocide you intend to use after the final flush.
The product should have a clear recommended dose so the system can be tested easily. It will be difficult to choose how much of the pre-commission cleaner to use if it doesn’t. You can sometimes compensate for a lack of time with higher doses, but this isn’t always true.
You’ll also need to ensure the product is supplied with environmental information. That helps dispose of it without any issues. Looking for one with low toxicity should help with this.
All this information helps ensure the chemicals are present long enough to clean the system thoroughly.
Assessing The Systems Pipework
Once you’ve completed the paperwork and researched the required pipe-flushing chemicals, you’ll need to inspect the pipework physically.
Several factors need to be assessed. These are:
- Water quality
- Drainage facilities
- Power supply
- System integrity
There needs to be enough water available for the pre-commission cleaning and flushing. A double-check non-return valve needs to be fitted as well.
Taking samples of water before beginning the flushing works is recommended to test its quality. As stated previously, you should take samples from the whole system frequently, which should be taken both pre-flush and post-flush.
If there are any issues with water quality, the water can be treated with biocide as it enters the pipe work.
The water system should be pressure tested and filled before work begins.
This ensures its integrity. You should also fit bypasses near valves as needed, place the units on bypass, and leave the main valves fully open. This will keep any debris away from the units.
A waste licence to use local drainage facilities will be required. That’s because the wastewater will be full of chemicals. As well as securing a licence, the drains used should be able to tolerate the volume of water you intend to pour down it. Keeping a record of where drains are on-site is also required before work commences.
Some older systems can have a large scale level, which is often most noticeable on heat exchangers. The best way to deal with scale is to dissolve it rather than apply the acid. Systems with large amounts of scale will need a specialist product.
Pumping the water is a necessity, and this requires power. You should ensure that your power supply is stable and have a backup to rely on, like a generator.
Calculations should be made to ensure the pumps can handle the pipe flushing velocity. You may need to add more pumps, but if you do, use isolation valves to reduce the risk of short-circuiting.
Ensuring Pre-Commission Cleaning And Flushing Is A Success
If you follow all the guidance above, you should have no issues with the process. They’re only a few reasons why the cleaning process can fail, and here they are:
- Lack of data
- Presence of oxygen
- Untreated water
- Excess refilling
- Failing to improve water quality
This is why carefully selecting chemicals, completing the paperwork, and assessing the system are important.
Once the cleaning is completed, you can take samples to see how much bacteria is present and the pressure level. It’s important not to top up the water because this could put bacteria back into the system.
Water systems can change quickly, and close attention must be paid to what’s happening. This includes before, during, and after cleaning. That way any issues can be spotted before they become too serious.
Require help with a Pre commission Cleaning and Flushing project?
Now that you know all the above, you might think there’s much to remember. And you’d be right. Each system has its own requirements and will need a unique approach.
The most efficient way to do these specialist works is to seek advice from trusted experts.
That’s why we offer specialist pre-commission cleaning and flushing services. We can cover everything that’s been outlined in this guide while saving you time and giving you peace of mind.