IPE-TM-400-06 — Strength Welded Tubesheet Joints

1. Purpose

This procedure provides guidelines for determining which situations require strength-welded tube to tubesheet joints.

2. General

Reference Strength Welded Tube to Tubesheet Joint and Crevice Free Type Tube To Tubesheet Joint Requirements in Tool, .

3. Guidelines

Strength-welded tube to tubesheet joints prevent or minimize the possibility of cross leakage. These joints also protect the mechanical integrity of high temperature applications that have an operating temperature that exceeds 1000ºF (538ºC), or a differential pressure between tubeside and shell side that exceeds 1000 psi (70.3 kg/cm2).

If a hair pin type (multitube/double pipe) is applicable, use a “separated head closure” design with a strength-welded tube joint for a multitube type.

Double tubesheet designs are not recommended because differential thermal expansion between the two tubesheets makes the design prone to leakage. Use strength-welded tube joints instead of a double tubesheet design.

Typical applications that require a strength-welded tube to tubesheet joint are listed in Section 5. For specific process units, review the strength-weld requirement with a Heat Exchanger Specialist and a Technology Specialist within the technology center.

Typically, admiralty tubes cannot be welded to naval brass tubesheets. When strength welding is required, the metallurgy needs to be changed to allow welding. The same is true with Type 410 materials. Titanium tubes always require strength welding due to its relaxation properties when just expanded.

4. Crevice Free Type Tube Joint

Crevice free type tube to tubesheet joints are required for exchanger services where potential coke formation between the tube to tubesheet crevice is possible. Examples are:

Oleflex – Hot Combined Feed Exchanger

Styrene – Hot Combined Feed Exchanger

Cyclar – Hot Combined Feed Exchanger

For these applications, a special crevice free type tube to tubesheet joint with inner bore welding is required. Strength welded type tube joint is not an acceptable alternate.

5. Applications

Process Unit	Applications	Reasons
Molex	Raffinate Column Reboiler 2) Extract Column Reboiler 3) Extract Splitter Column 4) Desorbent Splitter Column Reboiler 5) Desorbent Heater	Steam or hot oil leak could contaminate the adsorbent (Sieves)
Naphtha Hydrotreater	1) Stripper Reboiler	Steam could contaminate feed to Platformer
Kerosene Hydrotreater	1) Stripper Reboiler (Feed to Molex)	Steam or hot oil leak could contaminate the adsorbent (Sieves)
Platforming	1) Reformate Splitter Reboiler	Heavy feed from HDS unit may contaminate CCR
Olex/Parex/ MX Sorbex	Feed Preheater or Cooler 2) Raffinate Column Reboiler 3) Extract Column Reboiler 4) Finishing Column Reboiler 5) Start-up Heater 6) Desorbent Heater (Special Case) 7) Raffinate Heater (Special Case) 8) Paraxylene Cooler	Steam, hot oil or cooling water leak could contaminate the adsorbent (Sieves)
Xylene Fractionator	1) Xylene Rerun Column Steam Generator (Feed to Parex)	Steam or water leaks could contaminate adsorbent (Sieves)
Butamer/ Penex	Reactor Charge Heater 2) Regenerant Heater/Vaporizer 3) Deisobutanizer/Deisohexanizer O/H Condenser	Steam, hot oil or cooling water could kill catalyst
	4) DIB/DIH Side Draw Cooler 5) DIB/DIH Reboiler (w/dry DIB/DIH) 6) Isomerate Rundown Cooler (w/dry DIB/DIH) 7) Stabilizer Reboiler* 8) Stabilizer O/H Condenser* 9) Methanator Heater/Cooler	*Steam/water leak would be corrosive with the chlorides in stabilizer column
Catalytic Condensation (Motor Fuel or Cumene)/InAlk (SPA)	1) Feed Heater 2) Feed Cooler	Steam leak could fuse catalyst
HF Alkylation	Alkylation Reactor 2) Depropanizer Feed Condenser 3) Depropanizer Condenser 4) HF Stripper Feed Condenser 5) Drier Regeneration Heater 6) Isostripper Feed Preheater	Avoid acid/water mixture
Detergent Alkylate	Reaction Cooler 2) Acid Regen/HF Strip Condenser	Avoid acid/water mixture
	3) Benzene Column Condenser (normally air cooled type)
	4) Acid Regeneration Feed Heater* 5) Acid Regeneration Reboiler*	*Avoid contamination of synthetic oil with acid
THDA	1) Hot Combined Feed Exchanger	Special Design High Temp. (1400F) single pass with internal bellows
	2) Reactor Effluent Steam Gen. (Waste Heat Boiler)	Special Design High Temp. single pass; refractory lined; tube ferrules; internal bypass
Demex	DMO Separator Steam Heater 2) Solvent Heater	Steam is contaminant and could cause foaming
FCC/RCC	1) Catalyst Cooler	Special Design High Temp. bayonet type tubes for steam generation
Hydrogen Generation	1) Process Gas Waste Heat Boiler	Special Design High Temp. single pass; refractory lined; tube ferrules; internal bypass
Unicracking / Unionfining	1) RX Effluent Steam Generator 2) Feed-Effluent Exchangers (for ultra low sulfur diesel product requirements <50 ppm S) 3) Naphtha Splitter Reboiler (upstream of CCR Platformer)	Kettle steam gen. With differential pressure greater than 1000 psi Avoid contamination Avoid contamination of CCR catalyst by heavies.
All	Steam heaters/reboilers Steam generators Hot oil heated equipment	Avoid leakage and mechanical damage. Minimize hot oil losses.