The lid won’t open! Solution for stainless steel container lids that do not open.

Posted on by nitto-kinzokukogyo

As you may have experienced if you have already used our stainless steel containers, the lid of the container may occasionally fail to open.

The most common cause is the difference in air pressure between the inside and outside of the container. When the temperature inside the container is cooler than when the lid is closed, the inside of the container becomes depressurized, and the lid will not open in any way.

This phenomenon has been introduced in a previous column, but this article focuses on the actual situation in which the lid fails to open due to the difference in atmospheric pressure and how to deal with the problem.

CONTENTS.

1. why does the lid stop opening in the first place?

2. how the lid looks when the contents have cooled down

3. how to open a stuck lid

4. summary

1. why does the lid stop opening in the first place?

When a container is filled with a liquid or other substance and then the contents cool down, the lid will not open. Again, this is caused by the difference in air pressure between the inside and outside of the container.

This is the same phenomenon that occurs in everyday life when the lid of a bowl becomes stuck.

 

As the inside of the container cools with the lid closed, the water vapor inside the container gradually cools and returns to water.

In addition to this, the air inside the container will lose its balance with the atmospheric pressure outside the container due to the property of air that its volume decreases as it cools.

 

Thus, the lid cannot be opened when it is pushed by a relatively strong force from outside the container.

2. Appearance of the lid when the contents have cooled

We actually tried to reproduce the phenomenon of being unable to open the lid.

First, fill our lever-band and catch-clip type containers about 1/7th of the water and bring it to a boil. Then, the lids are immediately closed and cold water is applied from the outside of the containers for about 10 minutes to cool them.

When the inside of the container is thus cooled, the lid is pushed with strong force from outside the container as explained earlier. If you actually look at the lid, you will notice that the center of the container is indented more than normal.
We placed a straight scale on the center of the lid to check the dent.

With this amount of pressure, the lid will not open even if you pull it forcefully. In the first place, it is not desirable to open the lid by force, since the contents may spill out.

3. how to open a stuck lid

So, how do you open the lid?

The following is an explanation for each lid shape.

For lever band type...

With the lever-band type, the lid can be opened by inserting a microspatula between the packing and the body, allowing air to enter the container.

Just as when opening the lid of a bowl, the lid will open if air is allowed to enter the container and the air pressure inside is equal to the air pressure outside. The details are described below, but unlike CTH, it is relatively easy to open the lid as long as you have a spatula.

Incidentally, the temperature of the contents (water) when the container was opened was 33.6°C.

For catch-clip type

In the case of the catch-clip type, its shape makes it difficult to open with a spatula. If you try to force it in, you may damage the packing or lid, or even the spatula itself.

If you want to open the lid of the CTH, heat the container to restore the air pressure inside the container. You can also wrap it in a warm towel or boil it in hot water, but this time we will heat it over an open flame.

In this experiment, the lid was closed immediately after boiling, so we waited for a while until the temperature reached that level. The lid did not move at the beginning of heating, but when we heard a rumbling sound from inside, the lid opened easily. Since the boiling point decreases in a depressurized state, the lid opened at 86.6℃.

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4. Summary

If you are having trouble opening an existing container, try one of the following methods

  • CTL (lever band type): Insert a spatula-like object to let air in.
  • CTH (catch clip type): Heat the container to the temperature at which the lid was closed to restore air pressure.

If you are planning to purchase a container from now on, you can easily open the lid by installing a valve or air vent hole on the lid. We can also provide the microspatulas mentioned earlier.

If there is a possibility of putting warm contents into the container, please consider these measures.

Pressure Vessel Classification in Japan

Posted on by nitto-kinzokukogyo

A pressure vessel is a container intended to apply pressure to the inside of a vessel.
In Japan, pressure vessels are classified into several types according to their specifications and contents. Therefore, this column explains the standards for pressure vessels in Japan, focusing on First Class Pressure Vessels and Second Class Pressure Vessels.

Contents of this article

  • Pressure vessels are divided into First Class Pressure Vessels, Second Class Pressure Vessels.
  • The key point is whether or not gas is generated inside the vessel when pressure is applied.
  • Pay attention to laws and regulations, and do not neglect inspections.

Pressure vessels can be dangerous under pressure, so standards are established according to the magnitude and conditions of the pressure.
If they are not strong enough, serious accidents can occur. In Japan, the Industrial Safety and Health Act and Ordinance on Safety of Boilers and Pressure Vessels specify the structure of pressure vessels in detail.

Vessels are classified according to their size and the amount of pressure they handle, and some vessels require certification.
Classifications include First Class Pressure Vessel, Small-sized Pressure Vessel, Second Class Pressure Vessel, and (simplified) vessels.

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Many results in the pharmaceutical industry. What is the highest grade of electropolishing?

Posted on by nitto-kinzokukogyo

What is electropolishing?

Electropolishing is a polishing method in which metal ions are eluted from the metal surface to smooth the surface.
This process adds functions to the metal surface such as “removing oil, buffing powder, and other contaminants” and “inhibiting the adhesion of microorganisms.
For stainless steel, it also increases the chromium concentration on the metal surface and improves corrosion resistance.

Electropolishing is essential for pharmaceutical manufacturers who seek to avoid contamination and corrosion resistance from the surface, from the perspective of GMP and validation.

Electropolished stainless steel has a slightly shiny black surface (tank in the center of the photo).

When electrolytic polishing is applied, the surface of the metal will melt in a wisp.
It does not melt so much that you can tell by touching it with your hand that it has become flimsy. The thickness of the surface is about 1/3 of a sheet of copy paper. (20 to 30 μm)

The surface is thinly melted to add functionality, so it may be easy to imagine it as “reverse plating”.

Advantages of Electropolishing

Electropolishing has the following advantages

  • Removes stains that cannot be removed by normal cleaning
  • Resistance to residual stains and easy removal of stains
  • Improves corrosion resistance and rust resistance

Removes dirt that cannot be removed by normal cleaning

This product can remove (degrease) oil stains from stainless steel rolled, pressed, or buffed after welding.

These contaminants are embedded in the intricately deformed surface of stainless steel and are difficult to remove by normal cleaning.
Electropolishing melts the stains from the convex surfaces to a smooth surface, allowing the stains to surface and be easily removed.

Image of the surface

Material Surface
(Rough surface)

Buffing surface
(buffing powder, oil stains)

Electropolished surface
(smooth surface without contamination)

Less likely to leave stains and easier to remove

It is not only when the product is new that it remains clean.

As you can see from the image above, the electropolished surface is very smooth and has a smaller surface area.
Compared to the buffed surface, where the surface is uneven and has many small gaps, the new surface remains clean and easy to remove dirt even after repeated use and washing.

In addition, research conducted by the U.S. Department of Agriculture has shown that electropolished surfaces are less likely to retain biofilm (a collection of microorganisms).

Thus, electropolishing can easily maintain hygienic metal surfaces.

Improved corrosion resistance and rust resistance

As with the opening sentence, electropolishing increases the concentration of chromium on the metal surface. This is called chromium richness, and the metal surface is then covered with a strong passive film, which improves corrosion resistance.

The passive film prevents the iron contained in stainless steel from combining with oxygen (i.e., rusting). This is inherent in stainless steel itself, but the chromium richness makes it stronger.

Disadvantages of Electropolishing

Electropolishing itself does not have any negative effects on metal surfaces, but it does have a secondary disadvantage (risk).

  • Expensive.
    In our case, the price is about 2 to 3 times that of a buffed container.
    There is a risk of electrolytic solution getting into the gaps.
  • It is necessary to consider the application of electrolytic polishing from the design stage, and to make a structure with a small number of gaps.

Are there different grades of electrolytic polishing?

Electropolishing has no direct disadvantages and is a good thing, but if the proper technique is not used, the desired effect may not be achieved.

Have you ever had any of the following problems with electropolished stainless steel containers?

  • The container cannot be used without repeated washing.
  • White tablets became dirty and blackish.
  • Red rust (rouge) occurred.

These phenomena are caused by insufficient electropolishing.
The difference is caused by the way electropolishing is applied.

As a stainless steel container manufacturer, we would like to introduce our commitment to electropolishing.

General Electropolishing Methods

Electrode plates are placed on both sides of an electrolytic tank containing electrolytic solution (a mixed acid solution of phosphoric acid and sulfuric acid), and the product is placed between them.
When the product is connected to the + electrode and the electrode plates to the – electrode, an electric current flows through the electrolytic solution and the product is electropolished.

This method is suitable for electropolishing small parts, but not for stainless steel containers such as those we handle.
Although it is desirable to apply electropolishing firmly to the inner surface, which is in direct contact with the contents, with this method, the electric current flowing to the inner surface is weak, which means that electropolishing can only be applied weakly.

How Nitto Kinzoku Kogyo Electropolishes for High Grade Finishes

Nitto Kinzoku Kogyo uses a method that allows for firm electrolytic polishing to be applied to the inner surface of the container.

The difference from the general method is in the electrode plate.
Electropolishing is performed using special electrode plates that are dimensionally matched to the inner surface of the container.
This allows for stronger and more uniform processing, and the container is finished by taking full advantage of the benefits of electropolishing.

We are able to provide dedicated electrode plates tailored to each container because we are able to perform the entire process of container design, production, and electropolishing.
This is the secret to Nitto Kinzoku Kogyo's high-grade electropolishing.

We have delivered many electrolytic polishing products to pharmaceutical companies

Electropolishing certificates can be issued, please contact us.

Examples of electrolytically polished stainless steel products

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