Stainless tank fabricators: what to spec so quotes line up

Start with the job the tank does

• Use: storage, mixing or batching, heating or cooling, fermentation, brite or holding tank, CIP supply
• Product: what goes in it, temperature range, and anything corrosive (salt, brine, vinegar, chlorides, high acid)
• Working volume and total volume, plus headspace you need
• Pressure or vacuum: atmospheric, or rated to a pressure (see ASME below)
• Cleaning: CIP, manual, or both, and your cleaning chemicals and temperatures

The spec checklist

Material

• 304 or 316L stainless for product-contact parts. 316L contains molybdenum and resists chloride and acid corrosion better, so it's often chosen for brines, salty or acidic products, and aggressive cleaning chemicals. 304 costs less and suits many products. Ask the fabricator to recommend and explain.
• Ask for material test reports (MTRs) for product-contact material.

Surface finish

• Specify interior finish as a roughness value (Ra, in microinches or micrometers), not just a name like "#4" or "2B." 3-A Sanitary Standards call for product-contact surfaces at least as smooth as 32 µin Ra (0.8 µm), including welds.
• Exterior finish (mill, brushed, or polished) is mostly appearance and price.
• Welds: ground flush and polished on product-contact surfaces; ask how they verify it.
• Passivation after fabrication, and how it's documented.

Shape and drainability

• Dimensions, orientation (vertical or horizontal), top and bottom heads (dished, coned, sloped, flat)
• Full drainability for sanitary use; slope toward the outlet
• Legs, adjustable feet, skirt, or load cells

Temperature control

• Jacket type (for example dimple, channel or half-pipe) and coverage area
• Heating or cooling medium (glycol, water, steam) with supply temperature and pressure
• Insulation and cladding
• Temperature sensor ports. For cooling with glycol, see our glycol chiller sizing calculator.

Mixing

• Agitator type, motor size, speed range or VFD, seal type, and mounting
• Product viscosity and what the mixing has to achieve
• Electrical supply and washdown rating for motors

Cleaning and connections

• CIP spray devices and coverage, CIP return
• Manway type and location
• Outlet, inlet and instrument ports: sizes and connection type (for example tri-clamp)
• Vent, pressure and vacuum relief, sample valve, level sensing

Site constraints

• Door and ceiling heights, floor loading, and rigging path
• Who installs, and whether the quote includes delivery, rigging, and startup

ASME and 3-A: when they apply

• ASME pressure vessels. ASME Boiler and Pressure Vessel Code Section VIII, Division 1 covers pressure vessels and excludes vessels at or below 15 psi internal or external pressure. If your tank will be rated above that, many states require an ASME-stamped vessel (and often National Board registration). Rules vary by state, so check yours and ask each fabricator whether they hold the ASME certificate of authorization for the stamp you need.
• 3-A Sanitary Standards are voluntary hygienic design standards, widely used in dairy. A fabricator can only put the 3-A Symbol on equipment after a third-party verification inspection. If your customer, inspector or a dairy program requires 3-A, ask for the specific 3-A authorization, not just "built to 3-A."

Documents to ask for

• General arrangement drawing for your approval before fabrication starts
• MTRs for product-contact material
• Surface finish verification (Ra readings)
• Passivation record
• Pressure or leak test record, and the ASME data report if stamped
• Agitator and motor documentation, and a spare parts list

What drives the price

• Size, material (304 vs. 316L), and material thickness
• Interior finish and polishing
• Jackets, insulation and cladding
• Agitators, motors and controls
• Number and type of ports, manways and fittings
• ASME stamping and inspection
• Documentation and testing
• Crating, freight, rigging and installation

What drives lead time

There's no standard lead time for a custom tank. It depends on:

• The shop's current backlog
• Drawing review rounds. Fast, clear approvals help the most.
• Stainless sheet and fitting availability
• Bought-in components such as agitators, gearmotors, and instruments
• ASME inspection scheduling, if stamped
• Freight for large vessels

Ask each fabricator for its current lead time from drawing approval to ship, and what it assumes about approvals and components.

Buying a custom tank in the Midwest

If your plant is in the Midwest, a regional fabricator can make it easier to attend a factory acceptance test and may reduce freight on a large vessel. But freight is a line in the quote, not a reason to skip a bid. Compare regional and farther shops on the same spec, with delivered pricing.

Questions to ask each fabricator

• What sanitary tanks have you built for food or beverage plants like mine?
• Do you hold the ASME certificate needed for my vessel, and 3-A authorization if I need it?
• How do you measure and document interior finish?
• What's included: agitator, controls, insulation, delivery, rigging, startup?
• What's your lead time from drawing approval to ship?
• What's the warranty, and what does it cover?
• Can I visit for a factory acceptance test?

How PostRequest helps

Write your tank spec once (or tell us what you know and we'll help fill it in). Our agents shortlist sanitary stainless fabricators, email each one your spec from a PostRequest address, follow up once, and line up the replies: price, what's included, lead time, and terms. Fabricators see your spec, not your name or company, until you choose to connect. During early access, a person on our team reviews every comparison before it reaches you.