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Tom Wolf                          twolf5165@gmail.com                                    (281)565-4038

 

Hydrocracker Technical Issues

 

T.E. Wolf, Sugar LandTexas

 

(Please note this is copyrighted material, it is provided for your information.  Please feel free to use it, but please don't abuse the copyright.  Thank you.)

 

 

OVERVIEW

 

 

Hydrogen is a difficult gas to contain under any conditions, but at the elevated pressures and temperatures encountered in hydrocrackers, the problems are considerably magnified and present issues that, although my not be unique to these units, are exacerbated and demand close attention, planning, coordination, and execution.

 

Hydrocracker units are very special processing units combining high temperatures, high pressures, and toxic, corrosive, and aggressive compounds.  Even for construction and engineering personnel familiar with the special needs and requirements of these units, the fact that several years may lapse between building one unit and another, a method for documenting these numerous issues is required.

 

This document is intended to be an aid in this effort by addressing hydrocracker specific piping systems, equipment, and materials issues.

 

  • Construction and design of hydrocracking units, just to enumerate a few, combine the challenges of:
  • Flammable hydrocarbon streams
  • Highly toxic gases
  • Explosive gases
  • Strong acids
  • Elevated temperature
  • Elevated pressure
  • High Pressure closures
  • Alloy systems and systems combining different alloys
  • Large, heavy equipment

 

The organization of the report is such that the information is segregated into four major groupings: 

 

          1. General considerations, primarily materials of construction.
          2. Piping systems.
          3. Equipment.

 

1.0                GENERAL CONSIDERATIONS

 

1.1                Material Selection Criteria Basis

 

Hydrocracker Service

  • flammable hydrocarbon streams
  • highly toxic gases
  • explosive gases
  • strong acids
  • strong caustics
  • elevated temperature
  • elevated pressure

Corrosion is caused by:

  • Hydrogen sulfide
  • Hydrochloric acid
  • Hydrofluoric acid
  • Sulfuric acid
  • Caustic
  • Water

 

Hydrocracker units contain at least three of the six corrosion causing substances.

 

Corrosion due to hydrogen sulfide can be expected to occur in hydrocracker effluent streams.

 

Corrosion due to sour water can be expected in reactor effluent and light ends sections of hydrocrackers.

 

Corrosion due to high temperature sulfide can be expected upstream of the hydrogen injection line.

 

Embrittlement caused by high temperature hydrogen attack (increases with increasing hydrogen partial pressures), stress cracking due to presence of hydrogen and sulfides, and temper embrittlement can occur in hydrocrackers.

 

Early in design, and in deed throughout design, engineering needs to be confirming systems and portions of systems requiring special metallurgical attention. 

 

1.2                System Depressuring and Relief

 

In the specification and design of the relief system, the conditions governing design of the system include:

 

  • Refinery power failure
  • Substation failure
  • Cooling water failure
  • Hydrogen system dump
  • Hydrogen supply interruption
  • other

 

1.3                Positive Material Identification

 

Safety and the installation of correct material go hand in hand in hydrocracker units.  With the broad use of several alloy materials, to ensure the installation of the correct material in the right place, a positive material identification (PMI) program is required.

As part of the construction quality control and quality assurance program, all material and equipment requiring alloy material should be checked under the PMI program.

However, with the high cost and long delivery of these alloy materials, waiting until the construction quality check to determine if the materials and equipment have been supplied correctly is generally considered too late.

Even though it may appear to be more costly, a more effective PMI program will require the materials to be checked at each stage in the supply cycle.  Elimination of potential delays is the counter to the apparent increase in cost.

Therefore, when planning the positive material identification program, consideration needs to be given to specifying its requirements be implemented at the raw material manufacturer’s facility and/or material supplier’s warehouse before shipping, at the fabricator’s facility prior to shipping, and finally at the site.  Consideration should be given to each type of material and equipment for special cases which might require additional intermediate PMI verification.

 

2.0               PIPING SYSTEM

 

2.1                Access Routes and Space

 

All required access routes and space for maintenance, inspection, operation, and safety should be modeled and included in the interference checking procedure.

 

2.2               Acoustical Insulation

 

Requirements Identification - Some projects require acoustical insulation.  However, the specific need for acoustical insulation can not be determined until the equipment and the piping systems are designed.  Unfortunately, this is too late as the isometrics have been issued for fabrication and construction.  This is unfortunate because the need for acoustical insulation results in wider spacing of piping components and additional space in the rack.  Therefore, for projects requiring acoustical insulation, consider adding this potential thickness (and subsequent increased equipment and plant spacing) early in the project.

 

Planning, Design - Acoustical requirements need to be discussed and resolved early in the project, as the requirement affects pipe spacing and clearance just as thermal insulation.

 

2.3               Induction Bending

 

Overview

 

Bends save welded joints, but increase plot space requirements, that is, normal pipe bends have 1.5 X radius, but bends have up to 5.0 X radius.

 

With fewer weld joints, dimensional tolerance of bent pipe is very crucial.

 

Pipe bends

  • Reduce non-destructive testing.
  • Decrease the number of pipe fittings.
  • Decrease the number of piping components to be bought and delivered.
  • Reduce handling cost.
  • Reduce warehousing cost.
  • Reduce the number of shop welds.
  • Minimizes fabrication time.
  • Promotes timely delivery.

 

Cost - Possibly reduce overall piping cost versus conventionally fabricated piping

  • Weld ells are eliminated (reduced material cost, possible schedule savings if fittings are in short supply, reduces warehousing and material control requirements).
  • Welds are eliminated (reduced labor cost, reduced non-destructive testing cost).
  • Increased system integrating (higher safety, reduced cost).

 

Design Impact - Pipe radius and impact on plant layout.

  • Conventional weld ell radius is 1.5 times pipe diameter (1.5D).
  • Pipe bend radius is typically 3 times pipe diameter (3D) for large diameter pipe.
  • Pipe bend radius can be as low as 2 times pipe diameter (2D) for small diameter pipe, and up to 5 times pipe diameter (5D).
  • Result:  Decision to use Pipe Bends must be made early due to the impact on spacing to accommodate pipe bends versus weld ells.

 

Pipe Stress Impact - Wall thickness and impact on pipe stress.

  • There is evidence pipe flexibility is positively effected by utilizing induction bent pipe.
  • Since maximum moments due to thermal expansion normally occur at bends and supports, the use of induction bent pipe allows welds to be located much further from areas of maximum moment.

 

Properties Impact - Physical and metallurgical changes in the pipe.

  • Mechanical properties will be changed in the heating, bending, and cooling process; sometime for the better.
  • Austenitic stainless steel strength is reduced by induction bending
  • Austenitic stainless steel corrosion resistance in the heat affect zone adjacent to the bend is reduced and may require attention.

 

Dimensional Tolerance - With fewer weld joints, dimensional tolerance of bent pipe is very crucial.

 

2.4               Heavy Wall Piping - General

 

Inside Diameters - In heavy wall piping systems, the inside diameters are significantly smaller than normal wall thickness pipe, consequently friction losses and pressure drop, particularly in the recycle gas compressor piping, must receive special attention.  Additionally, on small bore piping and fittings, the inside diameter may be too small, requiring the next size larger pipe; special attention is required as normally this is not a problem.

 

Clearance and Accessibility - See comments for hydrotesting heavy wall piping systems below, particularly those labeled Clearance and Accessibility.

 

Interference Checking - During design, not only should the clearance for insulation (heat conservation, safety, and/or noise) and thermal growth be considered, but also the test position of the pipe to ensure clearance with adjacent structures, fireproofing, platforms, handrail, cable tray, instruments, high pressure control valve operators (gears, motors, hydraulic cylinders, etc.) and their ancillary devices, etc. 

 

2.5               Flanges Versus Welds

 

Flanged Connections - Large diameter (greater than 28”) flanged connections mating flanges of dissimilar material have a leakage potential, particularly during operational transient conditions, due to

  • Differential thermal expansion
  • Radial movement and expansion
  • Flange rotation.

 

Welded Connections – Dissimilar metal (bimetallic) welds have been utilized for many decades.  Particularly in the case of high hydrogen partial pressure contents with high operating temperatures, where minimizing the number of flanged connections is thought to be a safety precaution.  However, there have been some reports of dissimilar metal weld failures.

 

Minimization of Flanges – In hydrocracking service, it is typical to require flanges to be minimized for safety reasons and to be included for maintenance purposes only.  This may cause such problems as requiring a hydrotest against a closed valve, testing through equipment, and, particularly, in a line containing a spec break (material change) with one part limiting the hydrotest pressure.  Plan hydrotest carefully.

 

Spec Break Problems – Also in hydrocracker units, because of metallurgical requirements, there will be material specification changes in a circuit requiring one of the following alternatives, either:

  • Flanges of dissimilar material, or
  • Welds connecting dissimilar material.

Neither of these are ideal situations, each present their own special concerns.

 

Flanges of Dissimilar Material – In the case of mating flanges of dissimilar material, the problem is differential thermal growth, primarily during transient conditions, such as start up and shutdown, tending to cause the connection to leak at the gasket face.

  • When the mating flanges are of dissimilar material, thermal conductivity of each material will be different, resulting in differential thermal growth.
  • The differential thermal growth will, directionally, adversely effect the joints ability to remain seated at the gasket surface. 
  • The differential thermal growth will be in the
  • Radial direction, which will cause the gasket seating surfaces to move differentially.
  • Longitudinal direction, which will cause the force on the bolts to increase/decrease depending on the heating/cooling cycle.
  • And the differential thermal growth will affect the gasket seating due to flange rotation stress changes.

 

Welding Dissimilar Materials – In the case of having the mating flanges of the same material (eliminates situation discussed above), the pipe of one material is welded to a flange of another material, resulting in the dissimilar metal weld (bimetallic weld).  In the case of dissimilar metal welds, there have been some reported failures of this type weld which are generally accepted to be caused by thermal transients, thermal fatigue, and changes in mechanical properties by high temperature diffusion of carbon.

 

As there are only two methods for joining dissimilar metals, welding and flanging, and neither method is free of risk, judicious care is to be taken in either case.

 

2.6               Flanges, Gaskets, Bolts

 

Flanges – In hydrocracking service, it is typical to require flanges to be minimized for safety reasons and to be included for maintenance purposes only, e.g. flanged control valves, with butt welded block and by-pass valves. 

 

Flanges -  Over the years, different types of flanges have been specified in hydrocracker units and other severe service processes, including ring type joint (RTJ) flanges, proprietary (e.g. Grayloc, Destec, Cimex, Techlok) flanges, and raised face special finish (RFSF, 125 to 250 micro inches) flanges.  The raised face special finish is the currently accepted flange type.

 

Flanges – Proprietary flanges may warrant consideration, for these offer certain advantages over normal ANSI flanges:

  • Light weight
  • Speed and ease of assembly
  • Dimensionally as small as possible

 

Flanges – In order to prevent heat conversation at flange connections increasing the temperature and thus increasing the flange rating, flanged joints are not insulated in high pressure, high temperature insulated piping lines.

 

Flanges, Jacking Device – To facilitate isolation blinding and hydrotesting all Class 900 flanged connections should include a method for jacking the flanges apart.

 

Flanges, Spacer Rings – For piping with flexibility insufficient to allow the installation of test blinds and the testing of the pipe must be made in the installed location, a spacer ring (same thickness of the test blind) will be installed.  The use of spacer rings for slip blinds should be minimized to maximum extent.

 

Gaskets – Like flanges, over the years, different types of gaskets have been specified for hydrocracker units.  The current accepted gasket is the spiral wound flexible graphite filler with inner and outer compression ring (Flexitallic or equal).

 

Bolting – Check for clearance to attach and operate a bolt tensioner. 

 

Bolting - Check the bolt length required for bolt tensioners.

 

Bolting – Check the physical clearances in the vicinity of the bolt and nut to ensure bolt removal and bolt reinsertion clearance. 

 

2.7               Valves

 

Special Service Valves -  Typically, valves in the following services require special attention:

  • Hydrogen (with H2 partial pressure > 100 psi)
  • Hydrofluoric Acid
  • Dry Chlorine
  • Lethal (streams with H2S > 1000 ppm)
  • Wet H2S (sour water service)
  • Critical Service

 

Many hydrocracker unit valves fall into at least three of these categories, Hydrogen service, Lethal service, and Sour Water service.  Critical service is also a possibility.

 

The special attention to be given these valves include primarily:

  • External metallurgical compliance
  • Internals metallurgical compliance
  • Seal/Packing requirements
  • Heat treatment
  • Post weld heat treatment
  • Specification compliance
  • Material testing
  • Specified operating testing
  • Flow direction indication (if not bi-directional)
  • Noise data (if required)
  • Actuator and actuator size
  • Dimensional data
  • Temporary storage requirements
  • Special Installation and handling requirements
  • Certification and Documentation

 

Butt Welded Valves – Butt welded control valves, check valves, and block valves need special consideration:

  • Determine if internals can take heat of welding and/or heat treatment.
  • If not, ship valve internals separately to eliminate the need for field labor to remove internals.
  • Or, consider having valve vendor weld on a short stub at the manufacturing facility prior to installing the internals.  The stub should be of sufficient length to distance the internals from the heat affected zone.  If this is the selected alternative, then this determination needs to be made early in the procurement cycle to minimize design, cost, and schedule impact.
  • Make sure construction is completely aware of post-weld heat treatment requirements for all classes and varieties of butt welded valves.

 

Testing Against Closed Valves – Piping specifications forbid the hydrotesting of systems against closed valves.  In high pressure systems, particularly in systems requiring the minimization of flanged joints with butt welded valves, there may be no choice but to test against a closed valve.  These valves should be identified early, alternates proposed, evaluated, and if testing against the closed valve is required, the valve manufacture must be consulted and owner approval must be obtained.

 

Testing Butt Weld Check Valves – Determine if the check valve can be jacked to the open position.  If not, then either

  • The valve should have the internals removed, or
  • The valve should be removed and a spool piece installed, or
  • The filling and flushing of the line must be from the opening side of the valve.

 

Gatelet valves – do not specify gatelet valves on line sizes less than 4” as the required welds are too big.

 

Small bore valves – when doing small bore isometrics, do not dimension end-to-end on the valves.  These valves vary in length depending on the supplier and this information is not available soon enough.  Dimension only to one end with an overall dimension.

 

2.8               Turnover

 

Definition, System – A system can be a processing unit, part of a unit, and/or a utility system.

 

Definition, Turnover System – A turnover system is a part of a processing unit and/or a utility system identified to be turnover to the customer at one time.

 

Definition, Test Loop For purposes of hydrotesting and subsequent flushing, the piping of a turnover system is subdivided into test loops.  A test loop is the largest group of contiguous piping that can be hydrotested as an entity.  During hydrotesting, a test loop may be further broken down for construction purposes.  Typically, the objective is to make the test loop as large as possible.

 

Definition, Minimum Hydrostatic Test Pressure – The minimum hydrostatic test pressure for piping and is usually tabulated on the piping line list.

 

Definition, Maximum Hydrostatic Test Pressure – Test loops can comprise more than one line.  The loop hydrostatic test pressure is the highest of the minimum test pressures in the test loop.  Typically test loops are selected within a line class such that a component pressure rating is not exceeded.

 

Planning, Sequencing – Identify all turnover systems and their required turnover dates early and have all disciplines include impact of these systems in their schedule.

 

Planning, Turnover Package – When planning turnover and hydrotest packages, start with the complete definition of the turnover package, then make the test packages fit, at least, in the same boundary limits as the turnover package.  This will ensure there is no portion of the turnover package that can not be turned over and accepted.

 

Planning, Turnover Flow Sheets - The turnover system flow sheet is the best vehicle to visualize and communicate the extents, boundaries, and included turnover equipment. 

 

Piping Turnover Package – A typical piping turnover package for each turnover system contains the following data (the turnover team should early in the planning process define the acceptable contents for a turnover package):

  • Turnover System Routing and Status Sheet, including typical items shown in sample below.
  • Piping Pressure Test Record Summary
  • Piping Punch List Record Summary
  • Piping Isometric Drawings
  • Piping Support Drawings (applicable supports)
  • Piping Specialty Item Drawings (applicable items)
  • Line List (applicable lines)
  • P&ID (applicable) and this may be the Hydrotest Flow Sheet and/or Turnover System Flow Sheet.
  • Equipment Data Sheets (applicable equipment, if in system)
  • Equipment Drawings (applicable equipment, if in system)
  • Instrument Data Sheets (inline instruments)

 

Equipment Turnover Package - A typical equipment turnover package for each turnover system contains the following data (the turnover team should early in the planning process define the acceptable contents for a turnover package):

  • Turnover System Routing and Status Sheet, including typical items shown in sample below.
  • Equipment Pressure Test Record Summary
  • Equipment Punch List Record Summary
  • P&ID (applicable).
  • Equipment Data Sheets
  • Equipment Drawings
  • Instrument Data Sheets (applicable instruments)

 

Turnover Package Control - A turnover coordinator should be appointed to control packages, monitor status of packages, and have overall responsibility for all aspects of the turnover process.  Tracking of each package should entail every step of the process, who received the package last, when the package was received, and when the package was released from that part of the process. 

 

Water Systems – The demineralized water and condensate systems may need to be commissioned before flushing and hydrotesting can begin.

  

2.9               Cleaning, Flushing, and Chemical Cleaning

 

Requirements Identification - All cleaning requirements (citric acid, soda ash solution, chemical, steam blowing, detergent, air blowing, fresh water flushing, oil flush, boil out, etc.) should be resolved early in the project and the details indicated on the P&ID’s, including the start/stop points, removable spools, vents, drains, etc.

 

Planning – During the planning process, look at the possibilities for combining flushing, testing, and chemical cleaning activities on appropriate lines.

 

Planning, Water – Early in the construction effort, an estimate of the quantity of water to be required should be made and a source for this quantity and quality determined. 

 

Planning, Disposal - Disposing of flush and test water and chemical cleaning fluids is of equally importance.  Plan for the disposal of water and chemical cleaning fluids.

 

Planning, Exchangers – For systems requiring hydrotesting through installed u-tube exchangers (particularly vertical u-tube exchangers), extreme care must be exercised.  Consider using plastic plugs on tube ends, use low pressure water (so as not to dislodge the plugs) for flushing, and then vacuum debris collected on the tubesheet prior to removing plastic plugs.  Alternates to consider, testing and flushing at grade (with welded end caps).

 

Planning, Exchangers – For systems requiring hydrotesting through installed vertical exchangers, all water must be removed after test and flushing.  To ensure water removal, circulate a hot fluid (e.g. gas oil), then air blow.  If air blowing, plug tube ends with plastic plugs after blowing to ensure water does not re-enter the tube.

 

Planning, Furnaces – For systems requiring hydrotesting through furnaces, all water must be removed after hydrotest.  Consider boiling out during refractory dryout and/or nitrogen purge. 

 

Planning, Furnaces - Be aware there has been a report of at least one instance where preservation oil fouled the burners, resulting in an unplanned onsite burner cleaning.

 

Planning, Furnaces – Consider furnace hydrotest and flushing sequence as follows:

  • Flush individual coils before making the last connection.
  • Weld.
  • Hydrotest with demineralized water.
  • Air blow.
  • Remove balance of moisture during refractory dryout, circulating dry air or nitrogen through tubes.  (If this is the case, check to make sure appropriately sized nozzles are installed, and sufficient volume of dry air/nitrogen is available.)

 

Planning, Furnaces – There may be a limitation on the use of flanges in the vicinity of the furnace (Area Classification requirement); beware this limitation may impact design and testing.

 

Planning, Cleaning Connections - Make sure all chemically cleaned lines have connections for chemical in and chemical out, show these connections on P&ID’s, and check for hose access.

 

Planning, Design - During design, ensure a complete line can be flushed and chemically cleaned.

 

Purging Requirements – During the planning and review phase identify all purging requirements and methods, and plan for adequate supply.

 

Visual Inspection Program – Prior to final closure for flushing, hydrotest, and chemical cleaning (if required), there should be a formalized piping internal visual inspection program to ensure the piping system is clean and clear of debris to minimize flushing.  Because of the potential cost and schedule ramifications, consideration should be given to designating a responsible party to sign off prior to final closure.

 

Visual Inspection Program – The visual inspection program should be a combination of shop and field visual inspection.  The piping fabrication request for quotation and purchase order should stipulate these requirements: shop cleaned, inspected, protected prior to shipment, protected during shipment.  After receipt at the construction site, the visual inspection continues through receipt, field fabrication, and erection.  Consider establishing a special pipe cleanliness visual inspect team, including signoff procedure.

 

Sandblasted Pipe - Piping which has been internally cleaned by sandblasting should be tested with a water solution containing a rust inhibitor.  After test, drain and blow dry with air or nitrogen.  A corrosion inhibitor not in conflict with the process should be used.

 

Water - With the high utilization of alloy materials, determine the maximum chloride content allowed for flushing and hydrotest water.

 

Flushing Flushing normally follows hydrotest, but with some test systems including equipment (particularly exchangers) consider reversing the order.

 

Flushing Large Lines – Obtaining adequate flushing velocities can be problem in large lines, an aeration device (blind flange with water and air connections) can be utilized effectively.

 

Chemical Cleaning – For lines requiring chemical cleaning, hydrotest, chemical clean, pickle, passivate, air dry, then put line on a nitrogen blanket.

 

Injection Points – Make sure the injection pipe is retractable or able to be cleaned after test and flushing.  Holes in the injection nozzle can be quite small and become plugged during the test and flushing operation.

 

2.10            Hydrotest

 

Planning, System Identification – define these systems early in the design phase, and include all disciplines (construction, commissioning and start-up team, scheduling, piping, and process) in the development of these systems and include impact of these systems in their work plan.

 

Planning, System Identification – When planning turnover and hydrotest packages, start with the complete definition of the turnover package, then make the test packages fit, as a minimum, in the same boundary limits as the turnover package.  This will ensure there is no portion of the turnover package that can not be turned over and accepted.

 

Planning, Hydrotest Flow Sheets – Piping test system extents, piping test pressures, and included equipment allowed test pressures need to be checked for consistency and hydrotest system breaks indicated appropriately.  The hydrotest flow sheet is the best vehicle to visualize and communicate these data.  Consideration should be given to indicating isometric breaks on these flow sheets, as this information has proved helpful in the planning process.

 

Planning, System Definition – During the planning process, look at the possibilities for combining flushing, testing, and chemical cleaning activities on appropriate lines.

 

Planning, Water - With the high utilization of alloy materials, determine the maximum chloride content allowed for hydrotest and flushing water.

 

Planning, Water – Estimate the quantity of water required, the quality (water specifications) of the test water, the source for this quantity, storage, and disposal requirements. 

 

Planning, Equipment – For systems requiring hydrotesting through installed equipment, consider the effect on installed internals and take necessary precautions.

 

Planning, Equipment – For systems requiring hydrotesting through installed equipment, be aware of minimum test water temperature requirements and take necessary actions.  Be aware that minimum test water temperature requirements may vary depending on type of equipment (e.g. minimum test water temperature for vessels may be different from minimum test water temperature requirements for furnaces).

 

Planning, Exchangers – For systems requiring hydrotesting through installed exchangers, consider the maximum differential pressure allowed across the tubesheet.  Consider making temporary connections between the shellside and tubeside to eliminate the differential pressure.  If temporary piping is to be used, make sure engineering is involved in the discussion, decision, and design.  If temporary piping is not used, extreme care must be exercised in using two pumps (one for the shellside and one for the tubeside) to ensure the maximum allowable differential pressure is not exceeded.  Consider using both pressure gauges and pressure recorders.

 

Planning, Exchangers – For systems requiring hydrotesting through installed u-tube exchangers (particularly vertical u-tube exchangers), extreme care must be exercised.  Consider using plastic plugs on tube ends, use low pressure water for flushing, and then vacuum debris collected on the tubesheet prior to removing plastic plugs.

 

Planning, Exchangers – For systems requiring hydrotesting through installed vertical exchangers, all water must be removed after test and flushing.  To ensure water removal, circulate a hot fluid (e.g. gas oil), then air blow.  If air blowing, plug tube ends with plastic plugs after blowing to ensure water does not re-enter the tube.

 

Planning, Furnaces – For systems requiring hydrotesting through furnaces, all water must be removed after hydrotest.  Consider boiling out during refractory dryout and/or nitrogen purge.  Also furnaces, be aware there has been a report of at least one instance where preservation oil fouled the burners, resulting in an unplanned onsite burner cleaning.

 

Planning, Steam Rings – Testing of piping systems with steam rings at flanged connections should be tested before the steam rings are installed to minimize the congestion of the steam ring piping.

 

System Conditions – Hydrotest piping system’s pressure and temperatures need to be reviewed in detail to insure pressures and temperatures are not over stated, therefore requiring than necessary test pressures.

 

Design Consideration – In high pressure piping systems requiring the minimization of flanged connections, it is not uncommon for a spec break (material change, condition change) to occur at the weld (bimetallic weld).  In order to physically make this hydrotest, consider moving this break to a nearby flanged connection.  This may not be possible (a. there may not be a near by flanged connection, b. the material cost to do this may be prohibitive, c. there may be a process reason preventing this action).

 

Design Consideration – For compressors and steam turbines with inlet and/or outlet nozzles oriented down and mounted on table tops (particularly concrete table tops), make sure there is access space to install the test blind and make up the flanged connection, including the bolt tensioning device, or make other arrangements for testing this piping.  Include construction in this discussion and decision.

 

Golden Welds – Piping systems require a hydrotest in accordance with establish specifications and codes.  In high pressure piping systems, particularly systems with a safety requirement to minimize flanged connections, alternates may be limited to such an extent some welds may not be able to be subjected to a hydrotest.  Such welds are sometimes referred to as golden welds.  These situations require study to determine possible alternates, and should alternates not be available, special approval by at least the client representative is required.  These welds are then 100% x-rayed and ultrasonically tested.  (One alternate to requiring a golden weld is to add a flange set at the point in question.)

 

Testing Against Closed Valves – Piping specifications forbid the hydrotesting of systems against closed valves.  In high pressure systems, particularly in systems requiring the minimization of flanged joints with butt welded valves, there may be no choice but to test against a closed valve.  These valves should be identified early, alternates proposed, evaluated, and if testing against the closed valve is required, the valve manufacture must be consulted and owner approval must be obtained.

 

Testing Butt Weld Check Valves – Determine if the check valve can be jacked to the open position.  If not, then either

  • The valve should have the internals removed, or
  • The valve should be removed and a spool piece installed, or
  • The filling and flushing of the line must be from the opening side of the valve.

 

Valves Subject to Hydrotest – All valves which are in place during the hydrotest should be checked to be sure the seat test limits are not exceeded.  Also when testing through valves, bonnet test pressure should be checked especially in high pressure tests.

 

Design, Equipment – On some high pressure, heavy wall piping systems, the pipe is welded to the equipment nozzle, requiring the equipment to be tested with the piping system.  Ensure the equipment can be tested at the piping system pressure and that there are adequate vents and drains on the equipment (pay special attention to vertical exchangers).  If equipment cannot be tested at the piping system pressure, check the piping specification and code for requirements, as an example, ASME B31.3, paragraph 345.4.3.  This situation is caused by:

  • Difference between equipment and piping code hydrotest formulas (check applicable Codes)
  • Differences between equipment and piping material allowable stress.

 

Clearance and Accessibility, Pipe Testing – On some high pressure, heavy wall piping systems, because of clearance and accessibility, the pipe may need to be removed and tested at grade, resulting in double handling. 

 

Clearance and Accessibility, Pipe Testing – Consider testing pipe in the shop or in the lay down yard rather than in place.

 

Clearance and Accessibility, Test Blind Installation - With the design requirement to minimize flanged connection in these systems, removal of the pipe for hydrotest may not be possible, make sure it is possible to install the (thick) test blinds required for testing.  Heavy wall pipe is not flexible and test blinds are thick. 

 

Clearance and Accessibility, Alternate Interference Checking – If piping can be rotated away from equipment to fit hydrotest blind, check clearances on vent and drain valves in the hydrotest position; there may not be clearance for vent and/or drain valves, requiring these connections to be capped during the test and the valves welded on after the test (followed by 100% x-ray and ultrasonic test of the weld – golden weld).

 

Clearance and Accessibility, Planning - During design, ensure a complete line can be flushed, chemically cleaned, and tested.

 

Clearance and Accessibility, Interference Checking – During design, not only should the clearance for insulation (heat conservation, safety, and/or noise) and thermal growth be considered, but also the test position of the pipe to ensure clearance with adjacent structures, fireproofing, platforms, handrail, cable tray, instruments, high pressure control valve operators (gears, motors, hydraulic cylinders, etc.) and their ancillary devices, etc.  It is a good idea to model all of these and perform the several interference checks.  General Arrangement drawings, when finished, are another tool to visually check for these conditions.  Since isometric drawings are usually issued for fabrication prior to the issue of the General Arrangement drawing, schedule General Arrangement drawing issue for high pressure systems as soon as possible, to help find interferences prior to fabrication.

 

Sandblasted Pipe - Piping which has been internally cleaned by sandblasting should be tested with a water solution containing a rust inhibitor.  After test, drain and blow dry with air or nitrogen.  A corrosion inhibitor not in conflict with the process should be used.

 

Trim Piping – Usually trim piping is excluded from a hydrotest, but in high pressure piping systems this may not be the case.  If included in the test, consider how this piping is to be tested, will the instruments be included or not, impact of test on instruments, how piping and instruments will be flushed, etc.  This piping will be tested against closed valves.

 

Utility Systems – For any project, whether containing high pressure piping systems or not, determine which utility systems will be service tested, and if these systems are to be tested as a complete system or on a unit basis.

 

Punch List - Consideration should be given to integrating the punch list team to include both contractor and owner.  Advantage: time will be saved in that there is only one cycle for rework and recheck required.  Disadvantage: more problems will be observed by owner (if there is an adversarial relation, this approach will not work).

 

Punch List – A punch list coordinator should be appointed to control packages, monitor status of packages, and have overall responsibility for all aspects of the punch list process.  Tracking of each package should entail every step of the process, who received the package last, when the package was received, and when the package was released from that part of the process. 

 

3.0               EQUIPMENT

 

3.1                Reactor Transportation

 

Planning – Start the planning process for transport at the time of initial design.  Include consideration of transport from manufacturer to port of debarkation, marine transport, port of arrival, land transport, plant access, and erection.  Then continue to revisit the plan as design is developed, as supplier(s) identified, locations are determined, etc.  Include all affected parties in these coordination and planning discussions, e.g. plant representatives, construction, engineering, procurement, contracts, cost/scheduling, vessel vendor, hauling contractors, dock representatives, ship representatives, lifting contractors, etc.

 

Purchase Terms – To minimize the planning and execution, consider purchasing the equipment on a FOB/FAS (Free On Board/Free Along Side) exit port basis.

 

Lifting Lug – Consider buying separate lugs for duplicate vessels.  Initial cost is small compared to having crews and cranes waiting on lug removal and reinstallation.

 

Lifting Lug – Consider buying extra nuts and bolts in case of damage or loss.

 

Weight Calculations – Drawings should not only have fabricated, empty, operating, and test weight, but also various shipping weights, that is, weight with saddles (land transport weight may be different from marine transport weight), erection weight (not necessarily either fabricated or empty, but an intermediate weight); check.  If vessels are to be shipped dressed or partially dressed, the appropriate weight needs to be included in the various shipping weights.  Wrong weights can cost extra if too high, cause delays if too low.

 

Center of Gravity(s) – For each weight calculated make sure the associated centers of gravities are shown on the drawings.

 

Lifting Points – If special designs are included in the vessel design for lifting points, have these conspicuously identified on the finished vessel.

 

Strapping – Consider welding small pieces of shell plate circumferentially around outside of shell at regular intervals prior to heat treatment.  These pieces will help secure the strapping during land and marine transport against expected pitch and roll.

 

Shipping Saddles – Shipping saddles design needs to be coordinated; many time the vessel fabricator is responsible for this, their engineers may not be aware of or consider ocean going forces.

 

Documentation – Plan, coordinate, and clearing identify responsibility, and include these requirements in the appropriate request for quotations, request for bids, purchase orders, and contracts, for providing:

  • Saddle design
  • Saddle drawings
  • Lifting/tailing lug design
  • Lifting/tailing lug supply
  • Spreader beams design
  • Spreader beams supply
  • Shackle
  • Slings
  • Strapping
  • Loading/unloading drawings
  • Transport (sea and land) drawing
  • Transport routing
  • Loose material inventory
  • Etc.

 

Testing and Documentation – Ensure that necessary authority and client representative review and approval of designs, testing, certifications, etc. are identified in advance, performed in a timely manner, documented and reported by the appropriate responsible party.

 

Shipping Documentation – Ensure timely requirements identification and instructions are given relating to bills of lading, packing lists, invoices, etc.

 

Loose Material Inventory – This inventory is to include not only process equipment internals that may be shipping with the vessel, but also:

  • Saddles
  • Lugs
  • Spreader bars
  • Slings
  • Straps
  • Shackles
  • Bolts and nuts
  • Spare bolts and nuts
  • Drawings
  • Test Certifications
  • Etc.

 

Loose Material Availability – At each hand off point, designate a responsible party to ensure all required parts and pieces are available before that operation is started, after that operation is complete, and if parts and pieces are to be transported to the next hand off point, these are included on the Loose Material Inventory, safely on board the carrier, and conspicuously identified as part of the shipment.

 

Responsible Party – Ideally, one person, familiar with the entire process, should be available at each hand off point to ensure requirements are met and last minute details, upsets are resolved expeditiously.

 

Transport Contractor(s) – Ensure timely contact and contract with the transport contractor for suitability of equipment and availability.

 

Ship Owner(s) - Ensure timely contact and contract with the ship owner for suitability of equipment, special requirements, and availability.

 

Schedule – Starting with construction’s required at site date, work backwards through the entire sequence (land transport, marine transport, land transport, fabrication, material receipt, mill rolling requirements, etc.) to ensure timely orders, design, coordination, and execution.  Ship and/or crane availability may be a major issue; plan and coordinate contingency plans.  Monitor all parties’ performance and commitment to attaining their milestones.  Make sure each party is aware of the impact of their missing a milestone.  Consider incentives.

 

Routing Plan – The entire shipping route from manufacturer to foundation anchor bolts is to be planned, coordinated, and any special requirements identified and resolved, such as:

  • Saddles
  • Spreader bars
  • Private roads
  • Public roads
  • Plant roads
  • Public docks
  • Private docks
  • Loading
  • Off loading
  • Heavy haul
  • Heavy lift
  • Etc.

 

Marine Consultant – For marine transport, contract with a marine transport specialist (if this is not included other contract) for specific designs and drawings, design and drawing checking, saddle and lashing design, ramp requirements and details, ship configuration and ramping, loading and off loading

 

Commercial Aspects – In all the planning, coordinating, and various execution phases, always be aware of the commercial aspects as well as the technical and logistical aspects.Payments – Coordinate payment requirements with each carrier and the funds transfer responsible parties to ensure schedules are not adversely affected by payment of money delays (ship owners typically require payment in full prior to ship departure).

 

Demurrage – Include extended demurrage time at loading and unloading points in purchase orders and contracts.

 

Communication – Consider weekly or bi-weekly status review meetings with the various parties to ensure timely coordination and communication.  Ensure proper and timely notifications and instructions relative to place and time are communicated and understood.

 

3.2               Equipment Analog Studies

 

Identify early all pumps and compressors requiring an analog study.

 

3.3               Compressors

 

The piping analog calculation must be performed as early as possible; but well in advance of piping design and isometric preparation.

 

When restriction orifices are required in compressor piping by analog studies, these should be kept the same thickness as the suction screen plates/temporary strainers that are replaced.

 

Piping hook-ups to compressors mounted on concrete table tops can be difficult from below the table top; hook-up room must be considered during piping and structural design.

 

Consideration should be given to fabricate the lube and seal oil systems in stainless steel piping; there is a higher initial cost but lower startup and maintenance cost, e.g. chemical cleaning requirements. 

 

3.4               High Pressure Pumps

 

The piping analog must be performed as early as possible; but well in advance of piping design and isometric preparation.

 

3.5               Steam Turbines

 

Check ‘run-in’ conditions, that is, unloaded, and put this information on both the P&ID and the Equipment Data Sheet; ‘run-in’ steam temperatures are greater on the exhaust side in the unloaded condition, sometimes requiring a specification upgrade.

 

3.6               High Pressure Exchangers

 

Stacked exchangers – check the bolt length required for bolt tensioners (longer than normal), including bolt removal and reinsertion clearance.  Also check for clearance to attach bolt tensioner.  One option is to make nozzle necks longer, but this may not be the best option.

 

3.7               Air Cooler Header

 

Care should be taken in specifying materials for the air cooled exchangers downstream of the reactor.  In the vicinity of the water injection point, chlorides may build up.  Check and specify higher alloy material.



This website’s goal is to provide a source for project management support, information, education, and training material for project managers and project engineers primarily in the refinery, petroleum, and petrochemical industries.  In the execution of these projects, the project manager or project engineer may find the need for additional information and support; most times this support will come from within his or her company.  But there are times additional sources are needed.  This website is intended to meet those additional needs.

 

Project success is a function of the people skills and a broad understanding of diverse subject matter of the project management team.  Scope definition, execution considerations, construction strategy, planning and schedule impact, resource utilization, overcoming difficulties and problem solving, etc, etc, etc, are just a few to enumerate even without addressing the technical side.  Then there is the cost, estimating, and estimate side, factor estimates, detail estimates, forced detail estimates, basis of estimate, construction wage rates, and so on.  Then there is the technical side, material issues, piping systems, equipment considerations, civil and structural, electrical and control systems, document control, specifications, standards, and regulations.  Then there’s the variety of processes both refining (hydrocrackers, delayed cokers, etc.) and petrochemical facilities, the list is almost endless.

 

Project management is as much art as science.  The key is to continue to learn and never stop learning.


 

 

Tom Wolf has over 40 years petroleum and petrochemical experience, including 25 years in project management.  He holds a BS degree in Mechanical Engineering.

 

 

 

© 2013 by Thomas E. Wolf.  All rights reserved.  No part of the information contained in these webpages may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or by any information storage or retrieval system without written permission of the copyright holder, except for the inclusion of brief quotations in a review.