Section 8 — Heat Transfer Equipment

Tube Bundle Replacement

IPE Engineering Practice IPE-EP-8-1-3

Document number: IPE-EP-8-1-3 · Section: 8 — Heat Transfer Equipment

SCOPE

• This Practice governs the general requirements for the fabrication and materials for replacement tube bundles for use in chemical process services. Replacement tube bundles governed by this Practice are defined by either of the following:
• A bundle that is built, or partially rebuilt, identical to an existing bundle from existing drawings.
• A bundle built to the existing drawings of an existing bundle with a modification in tube metallurgy or wall thickness.
• Replacement bundles not defined by paragraphs 1.1.1 or 1.1.2 of this Practice are considered a thermal redesign, and shall be built to EP 8–1–1.
• The purpose of this Practice is to cover the majority of replacement tube bundles that the Owner utilizes. Specific requirements for components such as integral channels, floating heads, fixed tubesheet exchangers, single pass tube side, etc; are covered in EP 8–1–1.
• The requirements in this Practice are a minimum. More stringent requirements may apply in specific instances.
• Any deviation to this Practice or Practices referenced herein must be approved by the procedure given in EP 1–1–3.
• An asterisk (*) indicates that a decision by the Owner or Owner’s Engineer is required, or that additional information is provided by the Purchaser.
• A revision bar indicates all changes made to this Revision.

2.0 REFERENCES

The latest edition of the following standards and publications are referred to herein.

STANDARDS AND PUBLICATIONS

STANDARDS AND PUBLICATIONS (CONT.)

DEFINITIONS

• Contractor – Company or business that agrees to furnish materials or perform specified services at a specified price and/or rate to the Owner.
• Hydrogen Rich Service – A service defined as a combination of hydrogen partial pressure and temperature at or below the curve for carbon steel per Figure 1 of API Publication 941, latest edition, and with a hydrogen partial pressure greater than 100 psia.
• Hydrogen Service – A service defined as a combination of hydrogen partial pressure and temperature above the curve for carbon steel per Figure 1 of API Publication 941, latest edition.
• Inspector – A Inflection Point Engineering, LLC appointed engineer or inspector.
• Manufacturer – The recipient of a direct or indirect purchase order for materials and/or equipment. In this context, a direct order is one issued to a Manufacturer by a Contractor or the Owner. An indirect order is one issued to a Manufacturer by a vendor (recipient of a direct order) for materials, fabricated components, or subassemblies.
• Owner – Inflection Point Engineering, LLC
• Owner’s Engineer – A Inflection Point Engineering, LLC appointed engineer.
• Purchaser – The party placing a direct purchase order. The Purchaser is the Owner’s designated representative.
• Rotatable Bundle – A tube bundle designed to be rotated 180º without affecting shell or tubeside flow patterns, heat transfer or pressure drop.

COMMUNICATION OF HAZARDS

• (*) The Purchaser shall provide the Manufacturer with all information concerning the fluid services of the tube bundles. Any potential hazards associated with trapped gases or harmful scale in the bundle shall be communicated to the Manufacturer.
• (*) MSDS information for the fluids shall be provided by the Purchaser when the fluids are either flammable, corrosive or toxic.

DATA SHEET, DOCUMENTATION AND PURCHASING REQUIREMENTS

• (*) The Purchaser is responsible for supplying the Manufacturer with pertinent IPE Engineering Practices or sections from IPE Engineering Practices that are referenced herein.
• (*) Original bundle drawings and Data Sheet shall be provided to the Manufacturer by the Purchaser. Tube material or thickness changes shall be noted on the Data Sheet.
• (*) The Manufacturer shall supply new fabrication drawings for replacement bundles, even when the bundle is identical to existing drawings. When any change has been made to the design, these fabrication drawings must be submitted to the Owner’s Engineer for approval. Detailed fabrication drawings shall include as a minimum:
• Tube layout and baffle details
• Tube to tubesheet joint details
• Tube bending schedule
• Longitudinal baffle details
• Other fabrication details as required
• (*) Four copies of the partial data report must be provided for all replacement tube bundles when specified by the Owner’s Engineer. In the State of Pennsylvania, partial data reports are required and must be signed by an inspector who has a PA commission.
• (*) Four copies of the partial data report must be provided for all replacement tube bundles when specified by the Owner’s Engineer.
• Four (4) copies of the mill certifications shall be provided for all new pressure parts, including tubes.
• A reproducible plus four (4) sets of bundle “as built” drawings shall be supplied.
• Four (4) copies of the heat treatment records shall be supplied.
• The above records shall be separated and bound in separate packages.

MATERIALS

• Tube material and selection for replacement bundles shall be in accordance with EP 8–1–1.
• When the tube material is selected to resist corrosion from the shellside fluid, all other tube bundle components, such as tubesheets, baffles, tie rods and spacers shall be of similar corrosion resistance to, and compatible with, the tube material. Baffle material shall be compatible with the shell material to prevent galvanic corrosion.

• (*) Clad or overlayed tubesheets are acceptable when approved by the Owner’s Engineer and shall be in accordance with EP 7–1–6.

CONSTRUCTION

• General
• If there is a change in metallurgy of the tubesheet, the Manufacturer shall compare the code allowable working stress of the new material with the old. If the new material has a lower allowable working stress, then the Manufacturer shall submit to the Owner’s Engineer a complete set of calculations concerning the mechanical integrity of the tubesheet and tubes. The Manufacturer shall review with the Owner’s Engineer any changes in thickness that may affect field installation of the bundle.
• (*) If there is a change in the tube metallurgy or tube thickness, the Manufacturer shall supply a complete vibration analysis to verify that problems are not being introduced into the design of the bundle. The criteria listed in EP 8–1–1 shall be followed. All information required to perform the vibration analysis shall be provided to the Manufacturer by the Purchaser.
• Bundles

All bundles shall be stamped with 1/2 inch numbers on the stationary tubesheet peripheral edge indicating a plant record number and serial number for the replacement bundle.

• Tubesheets
• (*) Unless otherwise specified, stationary tubesheets shall be supplied with lifting lugs or tapped holes for eye bolts located radially on the peripheral edge of the tubesheet to aid in the removal of the tube bundle from the shell. The opening in lifting lugs shall be at least 2 inches in diameter. When bundles are designed for 180º rotation, lifting lugs or tapped holes shall be provided on both the top and the bottom of the tubesheet. If the existing design and/or drawings do not include provisions for these lifting facilities, the Manufacturer shall add them to the new or retubed bundles. These lifting facilities are in addition to the tapped holes for pulling eyes required by TEMA.
• Cladding and overlaying requirements for tubesheets shall be in accordance with EP 7–1–6.
• Tube hole tolerances shall be in accordance with EP 8–1–8.
• (*) Threaded bolt holes in full diameter tubesheets are no longer permitted for new equipment. For existing or replacement bundles, consideration should be given to eliminating threaded tubesheets. This must be approved by the Owner’s Engineer.
• A 1/8 inch deep scribe line shall be provided in the outer face of the stationary and floating tubesheets at the 3 and 9 o’clock positions to insure correct alignment when matched with similar scribe lines on the channel, shell, and floating head.
• Tubes

Tube design, material and selection requirements shall be in accordance with EP 8–1–9.

• Tube Installation

Tube installation, tube–to–tubesheet joint design and fabrication requirements shall be in accordance with EP 8–1–8.

• Baffles and Sealing Devices
• (*) Longitudinal baffles for TEMA Type F shell removable bundles shall be continuously welded on both sides to the stationary tubesheet. The longitudinal baffles may be recess gasketed to the stationary tubesheet, if specified by the Owner’s Engineer.
• Leaf (Lamiflex) seals on longitudinal baffles shall not be reused.
• Replacement of Leaf seals must be of equal number and thickness. The Owner will not allow reducing the number of seals by making them thicker.
• Sharp corners at tube holes and on the periphery of exchanger cross baffles and support plates shall be broken (chamfered). All burrs shall be removed from both sides of the tube holes. This applies to all baffles on new or retubed bundles.
• Close fit baffles shall not be used because they may cause scoring of the tubes. However, baffle and support plate holes shall be drilled and reamed in accordance with TEMA RCB–4.2 close fit requirements for the following:
• units with water on the shellside
• titanium tube bundles
• unsupported tube lengths exceeding 36 inches
• units where vibration is a concern
• units where the average tube wall thickness is 0.065 inch (16 BWG) or thinner
• (*) when specified by the Owner’s Engineer
• Seal bars and skid bars shall be welded to every baffle with full fillet welds to prevent bypassing. Two welds shall be made on opposite corners, 180 degrees apart. Seal bars and skid bars may be welded to every other baffle provided the baffle spacing is less than 12 inches (maximum unsupported tube length less than 24 inches).
• The minimum thickness of transverse baffles shall be in accordance with Table 1.
• The transverse baffle nearest the floating end, if vertically cut, shall be thick enough to support the floating end, with a minimum thickness of 1/2 inch.
• All TEMA Type “S” and “T” exchangers shall have a floating head support plate located 4 inches to 6 inches from the inside face of the floating tubesheet.
• (*) Unless otherwise specified on the Data Sheet of EP 8–1–1 DS, by–pass seal strips shall be provided as follows:
• Seal strips are required for all bundles when the radial distance between the outermost tubes and the inside diameter of the shell exceeds 3/4 inch. Seal strips are not required for kettle type reboiler bundles.
• Tube bundles with vertically cut baffles shall have seal strips installed to seal by–pass areas caused by the omission of tubes to provide adequate entrance and exit areas.
• Seal strips or dummy tubes are required to block pass partition by–pass lanes when these lanes are parallel to the shellside flow.
• Seal strips shall be 3/8 inch thick minimum and shall extend from the first to the last segmental baffle.
• One pair of seal strips or dummy tubes shall be provided for each 5 tube rows between baffle cuts. Minor adjustments may be made to suit actual tube layout.

• Baffle ears are required on vertically cut baffles to block longitudinal by–pass areas caused by the omission of tubes to provide adequate entrance and exit velocities.

FABRICATION

• Subcontracted Work
• (*) Written approval must be obtained from the Owner before any welding, preparation for welded fabrication, machining, or forming (including bending and rolling) is subcontracted to others.
• (*) Owner approval will cover the extent of the work to be subcontracted and the qualifications of the subcontractor under consideration.
• Machining
• Tubesheet gasket surfaces shall be machined to the flatness tolerances shown in Table 2.
• All tubesheet gasket surfaces on retube bundles shall be refaced to a surface finish within the range of 125 to 250 inch arithmetic average, (Ra).
• Heat Treatment
• Heat treatment requirements for replacement tube bundles shall be in accordance with EP 7–1– 5 and the additional requirements of this Practice.
• PWHT is required for all carbon steel and chrome–moly (P1, P3, P4, P5) exchanger floating heads regardless of thickness.
• Heat treatment requirements for tube U–bends and tube end welds shall be in accordance with EP 8–1–9 and EP 8–1–8, respectively.

INSPECTION AND TESTING

• General
• Inspection and testing requirements for tube bundles of shell and tube heat exchangers shall be in accordance with EP 8–1–1 and the additional requirements of this Practice.
• The Manufacturer’s Quality Control Plan shall be available for review by the Inspector.
• All new and reused material and fabrication are subject to inspection by the Inspector. Rejections by the Inspector are final. The Owner’s inspection does not relieve the Manufacturer of the responsibility for complying with this Practice.
• Replacement tube bundles are subject to the Owner’s inspection. The Manufacturer is to advise the Owner or their inspection representative, 5 working days before fabrication is to begin and 5 days before testing.

• Items to be checked or witnessed by the Inspector shall include but shall not be limited to the following:
• Owner’s Engineer approval of drawings and welding procedures before fabrication starts.
• Welder and welding operator qualification documents and mock–up.
• Copies of certified materials, test reports, or certification of all materials and correlation of these data with materials actually used.
• Dimensional tolerances and conformance with design and specifications.
• Heat treatment records.
• Hydrostatic tests.

• (*) When reusing tubesheets, the inside diameters of 25% of all tube holes shall be measured to determine if they have become oversized due to previous rolling. If the tolerances given in TEMA have been exceeded, the Owner’s Engineer shall be notified to determine whether or not the tubesheet may be reused. Tube hole inside diameter measurements shall be documented and given to the Owner for inspection records.
• (*) If the inspection in paragraph 9.1.6 above shows that the tubesheets holes are too large, and because of time constraints, the tubesheets must be reused, then the Owner’s Engineer shall be consulted to determine if tube end welding is required.
• (*) When retubing an existing bundle the Manufacturer shall notify the Owner’s Engineer if:
• The tubesheet or any parts that were to be reused are damaged.
• Internal tubes are severely bent indicating that a thermal shock has occurred.
• Tubes show signs of wear at the baffles indicating that a vibration problem may exist.
• There is any excessive corrosion to parts that are being reused.
• Tube end thinning indicates the need for tube ferrules.
• Tube outside diameters show signs of corrosion or erosion.
• (*) When retubing an existing bundle and when specified by the Owner’s Engineer, the Manufacturer shall save a sample of the original tubing (preferably the most corroded or damaged protion) for the Owner’s Engineer.
• Magnetic Particle and Dye Penetrant Inspection

The entire surface of all stainless steel weld overlay including machined surfaces shall be liquid penetrant inspected after completion and when applicable, after final PWHT. All machined overlaid surfaces shall be checked with a saturated solution of copper sulfate to confirm that the overlay has not been machined off.

• Hydrostatic Testing
• (*) A hydrotest in accordance with Sec VIII, Div. 1 of the ASME Code shall be performed, unless otherwise specified in the purchase agreement. Hydrotest shall be held for at least 1 hour, and witnessed by the Inspector.
• Inhibited water shall be used for hydrostatic testing when the local water is brackish and contains impurities that might corrode exchanger parts.
• The water used for the hydrostatic testing of tube bundles containing austenitic stainless steel material shall be chloride free (less than 50 ppm).
• For titanium tube bundles, the hydrostatic test shall be maintained for 24 hours.

PREPARATION FOR SHIPMENT

• Each tube bundle shall be thoroughly cleaned inside and outside, and shall be free of grease, weld spatter, scale, slag, rust and all foreign matter.
• Machined surfaces and gasket faces shall be coated with heavy rust–preventative grease or other acceptable rust preventative and covered with sturdy wood or metal protectors.
• Bundles shall be properly supported on trucks. In no instance shall bundles be supported at the tubesheets alone. Bundles shall not be supported on the tubes.
• Leaf seal strips shall not be creased or mishandled. Bundles with this type of seal shall be shipped with wooden blocks wired or strapped to the bundle to protect the seal strips during lifting.

11.0 TABLES

TABLE 1

MINIMUM REQUIRED BAFFLE THICKNESSES

TABLE 2

FLATNESS TOLERANCES OF TUBESHEET GASKET CONTACT SURFACE

NOTES:

• The total tolerance on the peripheral gasket contact surfaces should not occur in less than 20 º.
• Special Service is defined as a design temperature > 850 ºF or pressure > 1000 psig.

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