Steam Quality and Testing

Steam is one of the critical and essential utilities in the pharmaceutical industry used to derive most of the pharma processes and equipment. It delivers thermal energy to its intended point of use, which in turn performs the desired functionality of a process or equipment.

Like all components of the pharma industry, the steam must be delivered in its purest and quality state to fulfill regulatory guidelines and product safety. Another critical reason for quality steam in the pharma industry is the fact that steam comes in direct contact with the product or container in which a product is packed.

While pharma industry work hard to generate quality steam, it is also required to monitor its quality to prevent and rectify any faults during its generation.

Steam quality testing determines the acceptability of steam for pharma applications and points out any shortcomings.

What is steam quality?

Steam quality is the function of the following

● Moisture content in steam (expressed as the percentage of steam in the mixture) ,

● Superheat, and

● Dryness.

Standard values of the above mentioned parameters in a given steam sample indicates a quality steam.

The addition of other concentrations, contamination or foreign body affects the steam purity. It is because, during steam generation phases (i.e., water preparation and conversion into steam), it is possible that water adds to the steam, degrading the thermal efficiency of steam and can result in the following.

● Boiler Water Carryover

● Failure of steam trap

● Insulation problem in steam piping

Boiler Water Carryover

Steam is generated by an equipment called a boiler. A steam's purity can be affected when anything besides steam leaves the boiler, and is contaminated with moisture traces.

When this problem occurs, moisture from boiler enters into the pharma process.  

There can be many causes of boiler carryover, such as

● Improper boiler design and un-match boiler specifications

● Erratic operational parameters

● Improper chemical parameters and dosing values

● Different contaminants, such as grease and oil

Failure of Steam Trap

Steam Traps are valves that automatically filter away non-steam components, and are responsible for removing condensate and non-condensable gases from the steam network, if somehow they have entered the piping network.

If steam trap fails to perform its function, the condensate or moisture content will increase in the steam, decreasing the steam quality

There can be many reasons for steam trap failure, such as

● Contamination in the water feed(to the boiler) injects contamination into steam, which affects the steam trap working

● Incorrect installation in the line

● Design failure

Insulation problem on steam distribution piping

Steam is distributed from the boilers in different parts of the pharma manufacturing plant through an extensive network of piping. This network can span large areas where steam travels to its intended location.

The main aim of steam is to deliver heat, which is generated at high temperatures. Piping is insulated to prevent heat loss to avoid temperature drop and heat loss. It helps to reduce heat loss and provides the desired steam pressure.

If piping is not insulated correctly, it will result in condensation in steam due to heat loss, which will decrease the steam quality. Additionally, the volume of condensate will be more for the traps to handle, resulting in their failure to trap the condensate from reaching its endpoint.

Importance of steam quality in pharma

Let's discuss why it is essential to maintain steam quality in the pharmaceutical industry.

Effective sterilization depends on the Steam Quality

Sterilization is one of the most critical applications of steam in the pharmaceutical industry, and its effectiveness depends on the quality of the steam being used. Steam provides the necessary thermal energy to kill microorganisms and remove contamination, which in turn depends on the steam properties.

During sterilization, steam penetrates the items, transferring the thermal energy and killing microorganisms or removing other contamination. The steam penetration success depends on the steam's quality.

On the contrary, if steam is not of the required quality, the moisture will act as a barrier, failing sterilization in an autoclave.

Incorrect temperature and pressure values

The success of steam for any application depends on the optimum temperature and pressure values. If these values are lower than the standard, it will affect the application's performance to which it is being supplied.

Several factors affect the steam's temperature and pressure value; among them is the steam quality or the amount of moisture content in it.

More significant than the standard moisture content will lower the standard steam temperature and its ability to transfer heat, affecting the relevant process.

The relevant application or equipment component will force to apply more time or steam to achieve the required temperature, resulting in increased resource consumption and in-efficient process execution.

Water hammering in piping

Water hammering in piping is a phenomenon in which water driven by steam at high speed is suddenly stopped by a valve, fitting, or pipi surface, and a pressure shock occurs originating from the point of impact because steam can accelerate the water velocities at higher rates.

Water hammering can result in a noise or movement of the pipe. In most severe cases, it will leak the pipe (at the point of impact), destroying the piping structure and resulting in steam leakage.

Introducing steam with appropriate steam quality will control the steam's moisture content. It will prevent water hammering from occurring, saving the piping network and preventing costly steam production.

It becomes more critical for the pharmaceutical industry as the piping is often made of stainless steel, which is costly compared to other materials. The piping deployment, welding, and testing for pharma applications are also critical compared to other industries, increasing the overall cost.

Additionally, if piping is damaged and steam leaks in a critical production area, it will affect the area's requirements, cleanliness, and environmental parameters. I will also require more time to test the area after repairing the faults in the piping.

How to test the steam quality

Steam quality test consists of measuring a sample steam for three components

● Non – Condensable Gases

● Steam dryness test

● Superheat test

Non – Condensable Gases

The noncondensable gas test determines the amount of noncondensable gases in the steam supply. These gases can enter the steam supply at several stages, such as during water treatment before supplying to the steam generator or during shutdown and startup.

This test is performed by condensing the sample test to lower temperatures. Upon condensing, any noncondensable will not be condensed and will separate from the sample steam and can be collected. The amount of noncondensable gases collected is compared with the amount of sample steam or condensate.

Super Heat Steam

Superheat steam is a steam at a higher temperature than its vaporization temperature (at absolute pressure). This steam occurs in a vapor state and acts as hot air. Under this condition, the steam cannot condense for successful sterilization.

A steam supply containing abnormal superheated components will require higher than average temperatures and longer holding times for adequate sterilization results.

For quality testing for superheated value, attach a test tube to a chamber expansion tube that can collect the stem. Start the sterilization process with only regular items in the chamber. After the vacuum pulses and the steam exposure cycle, during the final steam exposure cycle, record the temperature in the steam supply pipe (nearest to 0.1⁰C) and the expansion tube (nearest to 1⁰C). The superheat temperature can be calculated by subtracting the expansion temperature from the boiling point of temperature.

If the superheated temperature is less than 25⁰C and the temperature in the steam pipe is within  3⁰C of the temperature in the steam pipe.

Steam Dryness

The dryness test determines the amount of moisture or liquid phase water in the steam. Moisture is calculated by dividing dry steam's weight in the steam mixture with water droplets. For example, 99% quality indicates that the steam mixture contains 1% moisture. Steam is also tested for dryness and superheated, which have implications on the process.

Moisture in the steam can be developed for many reasons, as discussed in the above article. As a result, the wet steam provides favorable conditions for microorganism growth, mollifying the sterilization effects. The standard value of steam dryness should be ≥ 0.95.

The dryness value is determined using a calorimetric experiment by calculating the heat energy transferred. It is the ratio of change in mass against the temperature change.

For testing, take an empty flask and weigh it after filling it with water of about 650ml. Also, measure the temperature of the flask and keep the temperature probe/sensor in it for further measurements.

Now, introduce steam in the flask through appropriate tubing in such a way that water in the flask is fully exposed to the steam from the tube. Continue the steam exposure until the water temperature in the flask rises to 80⁰C.

When the water temperature reaches 80⁰C, stop the steam introduction into the steam and weigh the flask & water temperature.  

The following equation can obtain the dryness value

About the Author:

Muhammad Asim Niazi

Muhammad Asim Niazi has a vast experience of about 11 years in a Pharmaceutical company. During his tenure he worked in their different departments and had been part of many initiatives within the company. He now uses his experience and skill to write interested content for audiences at PharmaSources.com.