01 / Set the design boundary before sizing any detail
The customer owns the chemical process, medium, operating and cleaning conditions, mixing objective, agitator selection, speed and control range, impeller arrangement, shaft design, design loads, tank geometry, support concept, governing requirements, maintenance method and approval of all design changes. Those inputs determine the opening, structure and clearances that the tank must provide. StelTank can review the supplied package for manufacturability, coordinate the named tank and support interfaces, fabricate the agreed scope, assemble customer-approved items where included, and perform checks stated in the approved order.
A fabricator should not infer agitator duty from a motor outline or copy an opening from a similar tank. Torque, bending, thrust, mass, starting conditions, upset conditions, dynamic behavior, seal reactions and maintenance loads can affect the interface in different ways. The responsible designer and agitator supplier must identify the load cases and application points that govern the tank and support design. A generic drawing checklist cannot create those values.
Define the supplied assembly boundary. State whether the drive, gearbox, shaft, seal, coupling, impeller, baseplate, support stool, guards, fasteners and local instruments are customer-supplied, agitator-supplier-supplied, installed by StelTank, shipped loose or excluded. State which party confirms compatibility between the current agitator revision and the tank drawing. If the machine has not been selected, keep the interface provisional and identify the information required before release.
Published mixing studies illustrate why process performance and mechanical interface definition cannot be collapsed into one shop assumption. Kordas and colleagues studied mixing time for a particular rotating and reciprocating agitator arrangement [3]. Their experiment does not select an agitator for a StelTank project or validate a customer process. Its bounded relevance is that mixing behavior depends on the actual equipment and operating conditions, which must come from the responsible process design.
02 / Control one complete agitator input package
Start with a document index. List the tank general arrangement, nozzle schedule, support drawing, agitator general arrangement, supplier data sheet, load table, shaft and impeller envelope, seal information, mounting detail, electrical or instrument interface documents, maintenance instructions and applicable project specifications. Record the identifier, revision, status and authority for each. Reference-only data should not be mistaken for released manufacturing input.
Identify which artifact controls when the supplier model, PDF drawing, data sheet and tank drawing disagree. A three-dimensional envelope may show physical shape while omitting loads, tolerances or service removal requirements. A data sheet may contain loads while using an obsolete mounting dimension. The drawing package should not ask the floor to choose. Record the conflict, stop the affected release and obtain a controlled answer.
Use a change register that links agitator and tank revisions. A changed shaft length can affect impeller elevation, bottom clearance and installation route. A changed baseplate can affect bolt pattern, nozzle diameter, support stiffness and guard access. A changed seal can affect stand-off height, drain or flush connections and maintenance space. Each supplier revision should trigger a review of connected features rather than a title-block update alone.
Define the release maturity. The tank shell may be released while the agitator remains unselected only when the responsible project has deliberately controlled the risk and frozen enough interface information. Otherwise, an early shell opening can turn a provisional assumption into expensive rework. Mark hold points for nozzle cutting, reinforcement fit-up, support fabrication and final assembly against the documents that must be approved first.
03 / Establish a coordinate system that connects tank and machine
Locate the agitator interface from customer-approved tank datums. For a vertical tank, the package may need a tank axis, support or foundation plane, orientation zero and top reference surface. For an offset or angled mounting, it also needs the direction and sign convention that define the shaft axis. Do not dimension a critical nozzle only from a formed edge or welded attachment whose final relationship is not controlled.
Show the viewing direction for angular locations. "At twelve o'clock" is ambiguous without a stated viewpoint and zero. Plant north, drawing up, a seam and a support leg are not automatically the same reference. Tie the agitator, manway, nozzles, baffles, internal supports, platforms and connected services to one coherent orientation scheme so that clearances can be reviewed across documents.
ISO 5459:2024 addresses datums and datum systems in geometrical product specifications [5]. ISO 129-1:2018 addresses presentation of dimensions and tolerances in technical product documentation [4]. Their official records are cited only to identify those normative subjects. This page does not reproduce protected requirements or establish a project datum scheme. The responsible design authority must supply the applicable editions and drawing rules.
State the product condition for each dimension. The shell before support installation, the supported empty tank, the shop assembly with a trial fixture and the final installed tank are different measurement states. If the agitator axis must be verified after support fit-up or in the installed orientation, say so. A flatness or position result taken on an unstably supported shell may not represent the agreed interface state.
Distinguish nominal geometry, basic definition, reference information, fabrication targets and final acceptance. Do not apply overlapping dimensions from incompatible origins. If a temporary machining, trim or fit-up allowance is approved, identify when it is removed and which final requirement controls. A process target should not silently replace the product requirement.
04 / Define the nozzle and mounting surface as a complete interface
The detail should show opening geometry, neck or transition, mounting face, bolt or fastening pattern, orientation, stand-off, required facing or surface condition, reinforcement relationship, weld definition and connection to the surrounding shell or top structure. It should identify which dimensions come from the agitator supplier and which come from the tank design. Do not depend on a general-arrangement silhouette for a machine mounting interface.
Coordinate the usable bore, not only the nominal nozzle size. The shaft, coupling, impeller sections, seal components, installation tooling or removable parts may pass through different envelopes at different stages. Show the approved installation and removal path and any component that must be assembled inside the tank. If the impeller is split or removable, identify who controls that design and how its assembly state is verified.
Protect the mounting face from surrounding interference. Adjacent nozzles, manways, clips, lifting features, railings, insulation, guards, piping and cable routes can block fasteners or seal service even when their centerlines do not collide. Draw the wrench, lifting and removal envelopes supplied by the equipment and maintenance plan. Confirm whether the drive can rotate for alignment or must hold one fixed orientation.
Define sealing and mating responsibilities. State who supplies the mating base, gasket or seal, fasteners, washers, locking provisions and any adapter plate. State which surface is shop-finished, protected for delivery or completed by another party. If a supplier requires limits on face condition, run-out, flatness or coating, carry the approved requirement into the tank drawing and inspection plan rather than relying on a detached manual.
ISO 1101:2017 addresses geometrical tolerancing of form, orientation, location and run-out [6]. The official record is cited only for its public title and normative subject. It does not set a tolerance for this interface. The customer, responsible designer and equipment supplier must define the characteristics, values, datum references and verification rules appropriate to the approved design.
05 / Show how every approved load reaches the tank supports
The load table should identify each load case, coordinate system, application point, direction, sign convention and whether values are operating, starting, stopped, maintenance, transport, test or another approved condition. Separate forces and moments and state whether they are simultaneous, alternating, transient or governed by another combination rule supplied by the responsible engineer. A single unlabeled "agitator load" is not enough for structural review.
Research on stirred equipment reinforces the need for application-specific mechanical data without providing project values. Ando and colleagues studied drive-shaft torque in a horizontal stirred vessel [1]. Shi and colleagues examined bending moment acting on an overhung shaft in a stirred vessel [2]. Those studies do not size a tank nozzle, support or agitator here. Their limited relevance is that torque and bending behavior are real parts of a specific agitator system, so the responsible supplier must communicate the design actions rather than leaving the fabricator to infer them from mass or motor power.
Trace the load path on the assembly drawing: machine base to mounting face, nozzle or top plate, local reinforcement or support stool, shell and frame, then foundation or customer support boundary. Identify which components are permanent structure and which only stabilize fabrication or shipping. If a separate bridge or frame carries the agitator independently of the shell, show the relative movement and interface assumptions that the design permits.
Do not let reinforcement detail stop at a local plate outline. The responsible drawings should define its geometry, relationship to shell seams and attachments, joining requirements, access, inspection and any machining or final surfacing state. Check whether the support obstructs drainage, cleaning, insulation, venting or access to adjacent connections. The approved structural assessment remains outside this generic manufacturing note.
Include temporary states where they can govern fabrication. A heavy drive may be absent during shop checks and installed only at site. A trial fixture may reproduce mass or geometry but not dynamic loads. A shaft may be supported temporarily during insertion. Clearly state what each shop setup represents and what it cannot prove. A fit check with a light template is not evidence of operating structural adequacy.
06 / Protect the shaft, impeller and internal clearance envelope
Show the customer-approved shaft axis, shaft length, coupling location, impeller elevations, maximum assembly envelope and required clearances to the tank bottom, wall, baffles, coils, dip pipes, sensors, supports and cleanout path. Identify which dimensions are supplier-controlled and which are customer process geometry. Use sections that expose the closest relationships; a top view alone cannot prove vertical clearance.
Review the envelope through installation, operation and maintenance states. The component may need a larger path while being tilted, lowered, coupled or removed than it occupies in its final position. If an impeller or shaft section is assembled inside the tank, show the access opening, working area and sequence. If entry is proposed, the customer must provide the separate safety and operating basis; this article does not authorize personnel entry.
Coordinate baffles and internal attachments from the same datum scheme. Avoid placing a support weld, bracket or instrument in the path because separate drawings used different orientation zeros. Where clearances depend on as-built measurements, define the stage, method and acceptance owner before closure. Do not assume that nominal CAD separation remains after forming, fit-up and joining.
Define the cleanability and drainability implications supplied by the process design. A support stool, internal pad, shaft stabilizer or baffle connection can create retained regions or block access. The drawing should identify the approved surface, joint and access requirements without promising universal cleanability. The customer remains responsible for process validation and the cleaning method.
07 / Plan drive access, lifting and connected services together
Draw the complete external service envelope. Include motor and gearbox removal direction, lifting approach, coupling access, seal withdrawal, guard removal, fastener reach, platform position, headroom and temporary laydown area supplied by the maintenance plan. Check the envelope against roof steel, handrails, adjacent equipment, site walls, pipes and cable support. A mounting interface can be geometrically correct and still be unserviceable.
Identify the approved handling points and component masses supplied by the equipment documents. Do not use a tank nozzle, guard or process connection as an improvised lifting point. If the tank frame includes a maintenance beam, lug or removable rail, its design, marking, inspection and use must come from the responsible plan. StelTank can fabricate an approved detail but this page does not establish lifting capacity or procedure.
Coordinate seal support services, drains, flushes, lubrication points, instruments, electrical entries and local controls where present in the customer design. Show connection sizes and orientations only from approved supplier data. Identify flexible versus rigid interfaces and the boundary where another party takes over. Keep these routes away from hot work, removable covers, access openings and required movement.
Define what ships installed and what ships loose. Transport height, vibration protection, shaft restraint, weather protection and lifting constraints may require the drive or shaft to be removed. The delivery plan should preserve fitted relationships, identify loose parts and provide controlled reassembly instructions. A shipping decision must not silently invalidate a shop alignment result.
08 / Stage fabrication and assembly while correction remains possible
Plan the sequence from reference creation through opening preparation, nozzle or support fit-up, reinforcement joining, final surfacing, tank support installation, trial assembly and inspection. Identify which operations can influence the mounting face or shaft axis. Place checks after the relevant change, not only at the end when correction could require removing completed work.
Use a controlled fixture or template only for its defined purpose. A bolt-pattern template can check hole relationship but may not represent the supplier base flatness, bore, stand-off or removal envelope. A dummy shaft can help verify an axis and clearance but does not reproduce an operating machine. Identify the fixture, drawing revision, verification status and limitations in the inspection record.
If the actual agitator is shop-fitted, define receipt inspection, preservation, handling, installation condition and the checks performed. Protect supplier equipment from fabrication contamination and uncontrolled loads. Record whether the fit is temporary or final and what is removed for shipment. Return any mismatch to the approved disposition route rather than forcing the machine into the tank interface.
Protect the mounting face, bore, thread and datum targets between stages. Identify permitted temporary attachments and their removal state. Avoid using the finished interface as a storage surface, lifting contact or uncontrolled welding return. When coating or insulation is part of the scope, show masking, final thickness assumptions and the surfaces that remain available for mating and measurement.
09 / Verify geometry, access and documentation against the released state
The inspection plan should identify the characteristic, datum, product condition, method category, acceptance source, record and disposition authority. Typical project-defined characteristics may include mounting-face position and orientation, bolt pattern, bore relationship, nozzle height, support references, internal shaft envelope and clearances to named features. The actual list and tolerances must come from the approved drawings.
Check in stages. Verify reference features before they are hidden, interface geometry after the operations most likely to influence it, and the final relationship in the agreed support condition. Where a site-installed drive changes the final state, identify what the shop record covers and what the site party must verify. Do not present a component check as acceptance of the assembled operating system.
Review service access with the complete configuration. Confirm that guards, fasteners, coupling, seal components and named removable items have the specified approach and removal path. This may be a drawing review, template study or physical trial according to the approved plan. Generated or representative imagery cannot prove access on the real project.
Reconcile the final documentation. The tank drawing, nozzle schedule, support detail, agitator revision, load table, loose-part list and inspection record should identify the same interface. Record approved deviations and fitted items. The handoff should state which equipment was installed or trial fitted, what was removed for shipment, which protections remain, and which site checks are required.
Stop the release when the agitator revision is unclear, loads lack a coordinate system, the shaft envelope conflicts with internals, the mounting face lacks a usable datum, service removal is blocked, the support path is incomplete, a shop fixture does not represent the required characteristic, or the acceptance value has no source. Closing those questions on paper is faster than recovering the interface after the shell is complete.
10 / Use an agitator-interface drawing checklist
| Drawing layer | Question to close | Controlled evidence |
|---|---|---|
| Responsibility | Who selects and approves the agitator, loads, tank structure and changes? | Scope matrix and named design authorities |
| Input package | Which supplier revision, load table and envelope control? | Document index and change register |
| Datums | How are mounting face, shaft axis, tank orientation and supports related? | Common coordinate and datum scheme |
| Nozzle | Are opening, mounting face, pattern, bore, reinforcement and mating responsibilities complete? | Sections, details and interface schedule |
| Loads | Where do approved forces and moments act, and how do they reach the support boundary? | Load table, cases and structural drawing references |
| Internal envelope | Do shaft and impeller clear internals through assembly and final states? | Controlled sections and installation sequence |
| External access | Can the drive, seal, guard and services be installed and maintained? | Removal, lifting and tool-access envelopes |
| Fabrication | Which stages can move the interface, and when are checks made? | Route, fixtures, hold points and protection notes |
| Verification | What is checked from which datum and in which product state? | Approved inspection plan and records |
| Handoff | What ships installed or loose, and what must be checked at site? | Packing list, fitted-item record and site instructions |
Read the checklist across the complete assembly, not only the top nozzle. Trace the shaft from the drive through the mounting face and tank interior. Trace every load from the supplier application point to the customer support boundary. Trace every maintenance item from its installed position to its removal path. Then reconcile those paths with the current document revisions.
For quotation, provide the tank arrangement, agitator supplier and selection status, current general arrangement, load cases, mounting detail, shaft and impeller envelope, support concept, internal arrangement, maintenance and lifting needs, delivery state and governing requirements. StelTank can then identify fabrication and assembly questions without taking ownership of process or mechanical design that remains with the customer and responsible suppliers.
References
- K. Ando, M. Goto, J. Sugita, T. Fukuda and K. Endoh, "Torque of Drive Shaft in Horizontal Stirred Vessel," Kagaku Kogaku Ronbunshu, 1978. https://doi.org/10.1252/kakoronbunshu.4.154
- D. Shi, T. Lu, A. Eaglesham and Z. Gao, "Characteristics of the Bending Moment Acting on an Overhung Shaft in a Stirred Vessel," International Journal of Chemical Reactor Engineering, 2014. https://doi.org/10.1515/ijcre-2013-0069
- M. Kordas, G. Story, M. Konopacki and R. Rakoczy, "Study of Mixing Time in a Liquid Vessel with Rotating and Reciprocating Agitator," Industrial & Engineering Chemistry Research, 2013. https://doi.org/10.1021/ie303086r
- ISO, "ISO 129-1:2018 - Technical product documentation (TPD) - Presentation of dimensions and tolerances - Part 1: General principles." Official ISO record.
- ISO, "ISO 5459:2024 - Geometrical product specifications (GPS) - Geometrical tolerancing - Datums and datum systems." Official ISO record.
- ISO, "ISO 1101:2017 - Geometrical product specifications (GPS) - Geometrical tolerancing - Tolerances of form, orientation, location and run-out." Official ISO record.
