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SOLVING SYSTEM CONTAMINATIONS.
IT'S THE LITTLE THINGS!

When you are a firm like HBW, who touts its abilities in sanitary process design, it is imperative that there is a good understanding of the why’s behind sanitary piping. When a client comes to you with a challenging problem, you had better be able to get to the bottom of it and solve it, particularly when it comes to preventing microbial contaminations.

Below are three unique cases where HBW assisted a client in overcoming microbial contamination failures.

4” Process Line Suppled by a 1.5” CIP feed

Case 1: Filter Skid Contamination

In the microfiltration step of a process that makes proteins for the alternative food/protein market, the client’s product was being contaminated by residual bacteria. After a thorough evaluation of both the process piping and the cleaning recipe, the two major issues below were defined and dealt with:

A 4” DIA header retentate recirculation header was utilized for six microfiltration skids. The 4” header was required for capacity of the six skids, but the cleaning flow velocity for parts of the header wasn’t being met due to it being supplied with CIP solution through a 1.5” process line. The piping needed to be redone so that as the retentate header diameter started smaller and then progressively increased based on the process flow.
A biofilm had developed on the microfilters themselves. HBW put together a cold sterilant program to kill any of the microbes and then designed a new cleaning recipe, selecting a good chemical set to use for maintenance of the skid during CIP.

CIP Program Considerations

The following are critical practices within CIP Programs for bioburden maintenance:

Flow Rate:

Line velocities maintained at greater than 5 ft/sec and tank overall spray device flow rate in GPM of (2.5 x foot of tank circumference). Increased line velocities assist with cleaning by providing more turbulence and energy applied to the piping surface being cleaned.
Post-Sanitization Contamination Prevention:
In systems where it is critical to limit potential for microbial growth, it is important to keep the overall systems as “closed” as possible. This includes steps where drain valves are opened for long durations of time with non-pressurized flow or opened for any duration where a localized vacuum may be in effect.
Chemical Concentration and Contact Time:

After a year and half, the client hasn’t had a single instance of contamination and their production has doubled out of the facility.

Case 2: Bioreactor Sterilization Issues

This next case involved a production bioreactor that would get intermittent contaminations. This was in a multi-product facility and it was limited to runs with one product and there would be microbial hits on and off with no rhyme or reason. Our task was to find the source of the contamination and recommend modifications to correct it. HBW did an inspection of the steaming circuit drawings and told the client the first thing to do would be to check pipe slopes. We knew that one of the transfer panels had a loop on the back side that was flat and had the team start with it. When inspected, a low spot in the piping was found. It appeared someone may have used the piping as a step stool. Once the slope was corrected, the issue went away.

Piping System Considerations

When evaluating a piping system for biofilms, it requires a holistic approach. Here are the consideratnos to be applied:

Piping Slopes:

Any low point in the system that is non-drainable can retain water and provide a breeding ground for bacteria. As biofilms grow, they will help retain nurients from the product in the matrix that is formed, providing food for the organisms to survive.
Internal Piping Roughness:
If there is any pitting in the piping system, there is opportunity for bacteria to colonlize. Stainless steel systems that have been exposed to repeated, elevated leels of bleach do have a higher risk of corrosion.
Dead Legs:
These are piping dead ends where flow stagnates. Piping dead legs in CIP systems do not allow full cleaning and can trap process soil.
Line Sizes:
A minimum of 5 ft/sec is the recommended velocity for cleaning process piping systems. Cleaning issues can arise when supplying CIP solution to process equipment using undersized line diameters or in systems where looped headers are used that are improperly sized to ensure equal flow rate distribution around the loop. If there is not sufficient flow rate, additional contact time for cleaning may be required.
Open Pathways:
To prevent microbial contamination, it’s important to keep the process system as closed as possible. If there are any open pathways into the piping system, microbes can be introduced.

Case 3: Cleaning Issues

We were part of a special project to help a new contract pharmaceutical manufacturer determine issues with their processing systems. HBW performed a HACCP of each equipment set within their production system that was focused around CIP. As part of the HACCP, it was recognized that there were restricted CIP supply line sizes into certain tank inlets. We asked the client for their microbial count data when sampling with flow of water through each inlet. Sure enough, at each inlet that had undersized CIP supply lines, there was a high microbial count left over after CIP completion. The piping was modified for the appropriate line sizes and the issue for that equipment set never occurred again.

HACCP Example

Step

Unit operation/
Process Parameter

Biological,
Chemical,
Physical

Hazard
Description

Control
Measures

Pre Rinse

Filling of Rinse Tank

Water supply quality - Microbial CFU

Sanitary Piping Design
Water Drops are able to be flushed and sanitized

Water supply quality - Chemical Contamination

Purified Water Loop Controls

CIP Unit Rinse Tank Sanitization

Hot Water through Spray Device

Overpressurization or Overflow

Fail Open Vent, Vent Filter Heat Trace

Cross Contamination of Streams

Double Block and Bleed Arrangement

Do not pipe purified water/WFI directly into process piping, always use a break to atmosphere between the loop and the tank being serviced. Prevent back flow.

Rinse to Drain

Flow Velocity

Spray Pressure
and Pattern

Soil Remaining due to laminar flow in piping

Tank Flow Rate vs. Line Flow Rate Required

Insufficient Flow Rate for Pattern/Pressure

Flow Control Valve/CIPS Pump Speed

Tank Nozzle L/D > 2, may cause shadowing

Riboflavin Test Coverage

Spray Device Installation

Do spray devices have locating pins?