How to Effectively Clean Pipelines: 

The fuzz about Dead spaces and Biofilm in pipes

Any process line consists of a series of equipment components linked together by pipework. There are many equipment components used in the food industry and this should be properly cleaned at the end of the production.  One of the many process equipment are the pipelines, and the only way to clean pipelines is through an effective CIP system. 

Turbulence in the cleaning solution would probably be around 75% of the CIP regime while 25% would be attributed to the chemistry behind the cleaning detergent.  Mechanical energy (turbulence) is generated by a pump.  This energy in the form of pressure energy is dissipated in the form of friction and turbulence inside the pipe to be cleaned. For CIP, the mechanical energy required is less than for the manual cleaning. Actions of manual cleaning, including scratching and brushing, require more energy than pumping. The mechanical energy is also more constant since CIP is not subjected to human intervention.

Dead ends/dead legs/dead spots on the other hand are areas outside the main bulk product flow where product can accumulate at the beginning of production, and may remain for an extended period of time. If the environmental conditions, such as temperature, are favorable, microbial growth may occur, resulting in recontamination of the bulk flow. It may also be difficult to clean and disinfect or sterilize such an area after production has finished, owing to the lack of fluid movement within the dead space. Most such problems occur as a result of the physical assembly, installation and integration of individual equipment components with connecting pipework: examples are T sections in pipes, incorrect orientation of equipment, and installation of sensors into pipework.

It is essential that the length of the dead ends do not exceed the equivalent of 2 times the pipe diameter when measured from the centre line of the pipe.  If measuring from the outside of the pipe then a rule of 1.5 times the diameter should be used. This is depicted in the diagram:

A process pipe work dead leg, is any “T” piece where the tee pipe length is more than ½ a pipe diameter in the “non flow” direction, or 1 pipe diameter in the “flow” direction.  However, in a case that a branch pipe is installed along the main process pipe, then the branch pipe will follow the rule of >2.70 (3.0) times the pipe stem diameter of the side branch pipe is a dead leg.

If the dead leg exceeds these dimensions there will not be sufficient CIP mechanical action in the dead leg to remove soiling, and the sanitizer may not be able to contact the surfaces during the disinfection step, causing contamination in the next product processed. If the dead legs are excessively long, or configured downwards, then they may remain full of “stagnant” product.  Biofilm formation inside the pipe dead space will occur, and this we don't want to happen in our factory.  An example of a biofilm formation inside a pipe branch: 

A common error or misconception is to assume that a dead space will still be capable of being thermally disinfected or sterilized owing to heat penetrating into the stagnant zone even if the fluid cannot. A recent study by Asteriadou et al. (2006) has shown that, even with turbulent flow within a horizontal pipeline, the temperature within a vertical dead leg will fall rapidly with distance from the junction between the horizontal and vertical sections. This will potentially compromise the thermal process owing to a failure to reach the required minimum conditions for proper cleaning and disinfection, hence the required contact time and temperatures are not achieved.

Examples of uncleanable installations in the factory.  In order for these pipes to be properly cleaned and disinfected, eliminating the dead legs would only be wise or reconfiguration or reinstallation of the pipework/valve/instruments and ensure that hygienic standards are observed.

Ensuring that the CIP system is free from dead spaces or dead legs without the correct turbulence of the cleaning solution will not guarantee the cleanliness of the pipelines.  One should achieve at least the optimum flow velocity of the cleaning solution passing through the walls of the pipeline.  There are generally two types of circuit within which lengths of pipework have to be cleaned:  first, where the circuit is predominantly pipework such as product transfer lines; and second, where the pipework is only a minor part of the circuit. In either case the user will not be concerned solely with cleaning straight runs of pipe, but also with more complex geometries, including joints, bends, tees and valves. The design of the cleaning system should be based as far as possible on 1.50 m/sec (optimal), which results in substantial flowrates for larger-diameter pipework, in other words design the CIP flow requirements basing from the largest pipe in the CIP system.

Hygienically designed pipework can usually be satisfactorily cleaned at lower velocities, at the expense of an increased cleaning time.

CIP: Principles of Fluid Flow Dynamics

Introduction

The understanding of the basic fluid flow dynamics is important for an efficient cleaning during CIP of any food processing equipment like tanks and pipelines.  Fouling deposits will form during processing and also the storage, therefore the effective removal of all these deposits(soil), thereby leaving the surface free of chemical residues and micro-organisms, is essential for ensuring food safety and product quality.

Cleaning - In - Place (CIP) is all about contacting the cleaning solution and sanitizers with soiled food processing surfaces, and involves the pumping of the detergent across the surface.  Therefore it is important to understand the principles of fluid statics and fluid dynamics.  Fluid statics deals with fluids at rest,  while fluid dynamics deals with fluids in motion or which we refer to (Mechanical Action).

Background information

Pressure - is defined as force per unit area. The SI unit of pressure is the pascal (Pa), which is a very small unit, So for convenience, the bar is often used, where 1 bar = 1,000,000 Pa. One bar is approximately equal to 1 atmosphere. Also used are kilopascals (kPa) and megapascals (MPa), whereas the Imperial units are pounds per square inch (psi)

Temperature - is a very important property, because it will affect viscosity and alter reaction rates, which is important for chemical detergents.  Temperature can simple be defined as the degree of hotness, it determines the direction of heat transfer: energy is transferred from high to a low temperature, and the rate of heat transfer (J/sec or W) is proportional to the temperature difference.  Temperature control is important, and hotter is not always better. In this context , accurate temperature measurement and periodic calibration of thermometers are important.  Energy is required in cleaning operations to bring detergents to the required temperature.  

Volumetric Flowrate - is defined as unit volume per time. the SI unit of volumetric flowrate is cubic meter per sec (m3/sec) and this will play a major role in the cleaning process.  Not enough volumetric flowrate for a particular pipe line or vessel would mean insufficient cleaning.

   

Laminar and Turbulent Flow - When a fluid flows through a pipe, the flow is one of two possible types: Laminar (streamline) flow or turbulent flow.  For cleaning operations and efficient heat transfer, turbulent flow is usually required.  The type of flow can be distinguished by a dimensionless group known as the Reynolds number (Re): this represents the ratio of the internal forces to the viscous forces acting upon the liquid.  When inertial forces predominate, the flow is turbulent, and when viscous forces predominate, the flow is streamline (laminar).  If the Reynolds number is less than 2000, the flow is laminar; if it is greater than 4100, the flow is turbulent. 

Streamline or Laminar flow  & Turbulent flow 

Fluid flow velocity - is defined as the distance traveled per time, (m/sec, feet/sec) this can be calculated using this equation:

where: v = velocity, m/sec

            Q = volumetric flowrate, m3/hr

            d = inside pipe diameter

            pi = 3.1416 (dimensionless)

            3600 sec = 1 hour

Pipe work: FLow velocity versus flowrate

Pipe CIP: Sub-laminar layer

The fluid velocity varies across the pipe diameter, high in the middle of the pipe, lower at the pipe wall due to friction, this is called the velocity profile.  The fluid velocity at the surface of the pipe is always "zero" this liquid layer is called the sub-laminar layer or the non-slip condition.

As the fluid velocity increases, the sub-laminar becomes thinner and soil on the pipe surface can be subjected to Mechanical Action, while the minimum required fluid velocity is 1.50m/sec for cleaning, inorder to satisfy the minimum required flow velocity at the sub-laminar layer of at least>0.30m/sec an ideal flow velocity of 1.80m/sec is highly recommended to compensate for flow velocity variations during the cleaning cycle.

With this phenomenon, It is therefore wise to increase the fluid flow velocity to at least 1.80m/sec to ensure effective cleaning every time anytime, of course this should be going along with the four other cleaning paramaters, (time, chemical, temperature and coverage)

Many of the cleaning problems encountered in the factory are fluid dynamic issues, however, since the quickest parameter to change are temperature and detergent concentration.  Without the required flow it will always follow in time that microbiological problems will occur.  Potential biofilm formation may happen in the production lines and will certainly lead to product quality issues and a risk to food safety standards.

How a Basic CIP System Works

How a Basic CIP System Works

The key objectives of an efficient CIP system are:

·                 Maximize safety — to avoid cross-contamination between product changes

·                 Minimize CIP time — to help speed up  time-to-market and reduce impact on plant production (downtime reduction)

·                 Optimize thermal efficiency — to avoid unnecessary heat loss and reduce energy requirements.

·                 Minimize water usage – Manage the solution interface.

The conventional CIP process that many of the food processing factories involves multiple cycles including an initial and final drain step, a pre-rinse, an alkali wash, and sometimes depending on the type of soil, an acid wash may be performed and a post-rinse. Rinse and wash cycles vary from five minutes to one hour. The process may include a “sanitize” cycle to reduce the levels of bacterial contamination using strong oxidants such as hydrogen peroxide, ozone, Peracetic Acid (PAA), chlorine dioxide or other chlorine-containing compounds. Thorough removal of these chemicals is required to prevent cross-contamination and to avoid corrosion of the stainless steel apparatus.

The 5-Steps CIP process:                                              

1. Pre-Rinse
2. Detergent Wash Cycle (Ambient or Hot)
3. Intermediate Rinse
4. Disinfection (Sanitation) Cycle
5. Final Rinse

When the CIP process is initiated, pre-rinse water is sent through the circuit and “chases” the product. A timing sequence based on distances and flow rates will switch the valves at the proper time to minimize the interface between product and rinse water. Over 90% of the product residue is removed during pre-rinse, the pre-rinse step is terminated via turbidity of the rinse water, in order to minimize the use of washing chemicals. Proper cleaning  is a function of detergent strength, cleaning time, correct mechanical action, coverage and temperature (TACCT).

CIP - Redefined

What is CIP?  It means the cleaning of production plants without dismantling them or changing the operating status to assure consistency and sustainability.  There four cleaning elements that results to an excellent cleaning.  The Sinner's Circle cleaning elements.  

This is T.A.C.T. or Time, Action, Chemical and Temperature. All of the elements should be present at all times during any cleaning activity. 

Time - All chemical processes of dissolving soil deposits depend on  time factors: 

•

Corresponding to the chemical efficiency of the detergent, the soil is removed layer by layer Also with a higher concentration, a certain contact time is necessary before last remaining soil is removed 

•

 

Reaction time must be considered as the contact time of the cleaning solution with the soil at the correct concentration and correct temperature.

Action -  We understand that action is the physical conditions which are necessary for the cleaning.  We can also refer to it as Mechanical Action. This will refer to flow rates, flow velocity and pressure.  If you are cleaning the internal of pipes, you only have to consider two physical quantities: Flow rate and flow velocity.  The cleaning solution should be turbulent and not laminar flow in order to create that mechanical action.  We will be discussing more of this element in the coming blogs.

Laminar and Turbulent flow profiles inside the pipe

                                           

Static Spray Balls

When you are cleaning vessels or tanks then we only need to consider flow rate and pressure.  This will be dependent on what type of praying device is being used.  The most common spraying device used in the industry are the static spray balls.  Which we will also discuss in detail on how to choose the right spray device for your vessel.  How to attach it and how deep thus your spray device goes inside the vessel. For if any of these parameters are not correct, it will surely affects the cleaning efficacy of the CIP system.

Chemical - This refers to the chemical energy, or oftentimes also referred to the concentration of the cleaning solution.  The choice of the most appropriate detergent is determined by the  

following requirements:

• - Rapid and complete solubility in water

• - Rapid swelling and dissolving of specific soil components

• - High sequestrant

• - Good rinsability

• - Foam free or possibility to reduce foreign foam

• - Good compatibility with the wetted parts of the equipment being cleaned

 - Corrosion safe!

• - Biodegradable according to legislative requirements, with minimal effluent impact 

Temperature -  This refers to the thermal energy. The choice of temperature for cleaning will depend on: 

o

 - Heating facilities

o - Difficulty of removing the soil

o - Chemical formula of detergent

o - The materials of construction of the plant / equipment being cleaned

 

•10oC temperature increase doubles the detergent rate of reaction.

So, there you are the four elements of cleaning.  Eliminate one of them then no cleaning is achieved. All four should be present all the time.  You can however, vary the degree of each elements to achieve a certain degree of cleaning.  

Coverage - It is true that all four elements is a must in cleaning but without COVERAGE, another element I choose to include is one very important element.  Without good coverage then you can't even achieve good complete clean.  One example of coverage problems is the one illustrated.

So, there you go, In every cleaning needs remember T.A.C.C.T and you will never go wrong.  Happy cleaning guys.  Until next time.... 

     

Is Cleaning Important To You?

How important is cleaning to you? If you're a production/operations guy, then you know that the cleaning regime of your factory is as important as your production runs.  If you don't clean your factory, it means that you're not assuring the microbiological quality of your products that reaches your friends or even loved ones.

Many factories especially dairies, breweries and beverage plant  do CIP or Cleaning In Place.  But many of the people who actually runs the system doe s not know how a CIP system is done or at least understand the basic principle of CIP. Some of this operators only carry out the cleaning process as what their supervisors and or managers tells them to do.  The question is, are these people who are making the CIP protocols really understands how a CIP system cleans?

This blog will actually provide some basic knowledge on how this CIP systems will work for you the right way always. It will also provide tips on how to optimize your CIP operations inorder to be cost-efficient.  One of the objective of this blog is to provide FREE cleaning tips. 

I am hoping that to those who will be following this blog that you can learn from it and actually apply it to your operations and make cleaning operations easy and fun.