Tank Frequently Asked Questions/Answers
Confused about tanks, codes, stamps, etc? A lot of our customers ask us the same questions so we created this page to help address your concerns. If you still have a question, please contact us. We are more than happy to assist you.
What is the ASME Code?
On March 20, 1905 in Brockton, Massachusetts at the shoe factory a boiler exploded killing 58 people, injuring 17 people and completely leveling most of a city block.
Unfortunately, boiler and pressure vessel explosions were fairly common and considered to be an "Act of God". There was no standard or agreement in the industry on what was considered an acceptable design or a safe way to operate the equipment. In 1911 the "American Society of Mechanical Engineers" (ASME) formed the Boiler and Pressure Vessel Committee to address the situation. In 1915 the committee issued the first "ASME Rules for Construction of Stationary Boilers and for Allowable Working Pressures" or as it is known today the "ASME Code".
Since 1915 many changes have been made and new sections added. The code changes almost yearly and is kept up to date by sub-committee made up of hundreds of volunteer industry professionals and engineers. And it covers everything from relief valves to nuclear power plant construction.
What is a code shop?
The American Society of Mechanical Engineers does not approve, rate or endorse any pressure vessel. A code shop is a manufacturer who has been issued a Certificate of Authorization to apply the ASME code symbol stamp to a pressure vessel and a Certificate of Authorization to register a pressure vessel with The National Board of Boiler & Pressure Vessel Inspectors.
Both of these certificates have to be renewed every three years.To receive these Certificates of Authorization the shop must contract for inspection services by an authorized inspection agency, and then apply for authorization to the ASME and the National Board. A joint review is then scheduled at the shop location to review a demonstration of the shop's Quality Control System. The shop's Q.C. system must incorporate engineering design, material ordering and certification, production control, welding procedures, and non-destructive testing.
When you consider that the shop's Q.C. Program is continuously monitored by an outside independent inspection agency, there are very few industrial quality systems that are this ridged.
What is a code tank?
It is a tank that has been designed, manufactured, tested, inspected and registered by an ASME shop.
Step 1 - The manufacturer designs the tank in accordance with ASME Pressure Vessel Code requirements. Taking into account pressure temperature ratings, corrosion allowances, and material thickness needed to withstand the pressure, joint designs and external loadings.
Step 2 - The design is shown to an outside "Authorized Inspector" (AI) who is licensed by the National Board of Boiler and Pressure Vessel Inspectors. The AI verifies that the design meets ASME code and sets "Hold Points" in the manufacturing process for the AI to witness the vessel being produced.
Step 3 - Manufacturing begins using only pressure vessel quality materials with complete traceability. All welding is performed by ASME qualified operators using certified procedures.
Step 4 - Final Hydro test of completed vessel is witnessed by the AI and the nameplate is stamped with both ASME and National Board Stamps.
Step 5 - The National Board registration papers are filled out listing the tank's serial number and design criteria. Signed, countersigned by the AI and submitted to the National Board for further review and then kept on file permanently.
What are the basics of pressure tank design?
Usually tanks are cylindrical in design because pressure does not like flat surfaces. Flat surfaces are quite thick in relation to cylindrical shells. That is why aerosol paint cans have concave bottoms even though they only have a few ounces of pressure.
The larger the diameter of the tank, the thicker it must be to withstand the same pressure.
Example: In a tank with the same volume and pressure rating, a long skinny one is much lighter than a short, fat one.
Remember: Never put an opening in a weld seam.
Call us, we can answer all types of questions.
Do we need a "code" tank?
Maybe. Insurance requirements, state and federal safety requirements and liability concerns generally demand them. Imagine the catastrophy if a tank or boiler exploded. However, in some circumstances, a quality-built "non-code" tank can be suitable and more cost effective.
We have never worked with tanks before. Any pointers?
Sure. Let us design the tank for you, based upon your application. Typically we need a sketch or list of requirements like size, capacity, pressure, bracket types and their locations, openings, etc. We will work with you to make the job easier.
We need a tank manufactured to SAE requirements. Can you do those?
No problem! We do them also.
How about tanks made to DOT specs?
Generally, an ASME tank meets all DOT regulations.
We have a "code" tank that needs another outlet. Can this be done?
A pressure vessel should only be modified by a shop with an R stamp issued by the National Board of Boiler and Pressure Vessel Inspectors. An R Form will have to be filed with the National Board listing what exactly was done to the vessel.
What's a "CRN" number?
All provinces of Canada have adopted the ASME Code and require vessels to be stamped with a provincial registration number in addition to the ASME symbol and National Board stamping. Before construction begins, one requirement has to be met in all provinces of Canada. We must submit blueprints and specification sheets in triplicate of all designs for approval and registration by the chief inspector of the province in which the vessel is to be used.
After the chief inspector receives the drawings, they are checked by an engineer to determine their compliance with the Code and also with provincial regulations. A CRN number is assigned and must be stamped on the vessel in addition to the ASME symbol and National Board stamping.
Once the design has been approved and registered, any number of vessels of that design can be built and used in the province where it was approved. This process is repeated for each province. The Canadian provinces also require their own manufacturer's affidavit form, with the registration number and the shop inspector's signature on the data sheets. Finally, when a vessel is delivered to a purchaser in Canada, an affidavit of manufacturer bearing registration number and the signature of the authorized shop inspector must be sent to the chief inspector of the province for which it is intended.
Can we register an existing non-code tank?
Our max. pressure is 150 psi. Should I order a 200 psi tank to be sure?
Typically we find it is a waste of money. You can be sure that a 150 psi-rated code tank is plenty safe. Just be certain that, as in any pressurized system, there is a safety release valve installed.
I have a code tank that needs repair. Is this possible?
Never weld or repair a pressure vessel. This should be done by a shop with an R stamp issued by the National Board of Boiler and Pressure Vessels. Hays Fabricating can do that for you!
The Nameplate was lost on our tank, how do we get another one?
The attachment of the nameplate is the culmination of an intensive quality control process and registration traceability. Therefore, simply getting another nameplate is virtually impossible.
What is corrosion allowance?
It's a term pressure vessel engineers use to describe a safety factor incorporated into the design to allow for safe operation of a corroded or rusty tank. Usually it is an increase in material thickness.
The corrosion allowance is listed on the Data Report. A vessel that is pitted gouged or corroded deeper than the allowance is unsafe and should not be used.
When Hays designs a pressure vessel, we count on you, the customer, to tell us what your operating conditions are and what is a realistic corrosion allowance for the life expectancy of the vessel. Of course, we can help you determine that.
What tank material and coating should I use?
Material: Pressure, temperature, atmosphere and contents all play a roll on the tank material used. We routinely work with carbon steel boiler plate, stainless steel and aluminum.
Coating: We would bet that the vast majority of tanks made all over the world are still simply painted. Sometimes we get requests for more durable coatings and we do that; however, many times the more durable coatings come with sharp increase in application costs. On a number of occasions simply switching from a carbon steel to a stainless steel makes sense.
My quality control department wants copies of weld procedure specifications and material certs. Does Hays provide them?
While we keep copies of that on file and can provide copies, it begs the question "why"? After all, that is whole purpose of the ASME Code Stamp and Vessel Registration process. The process is overseen by an outside independent inspector.
Do you routinely request that info on other components such as motors and pumps?