Installation of Metallic Expansion Joints and Flexible Hoses

1. Purpose

1.1 This global engineering specification defines for the contractor the minimum requirements associated with the installation of expansion joints and flexible hoses.

2. Scope

2.1 This specification applies to all projects having expansion joints or flexible hoses supplied separate from equipment packages. This specification applies to shop-fabricated skids or cold boxes as well as field piping.

2.2 The contractor shall furnish all labor, services, tools, materials, and equipment (other than that specifically called out on the contract drawings as being furnished by Air Products) necessary to install expansion joints and flexible hoses.

3. RELATED DOCUMENTS

3.1 Air Products Engineering Documents 4WPI-SW70003 Oxygen Clean (Class AA) Inspection and Acceptance Requirements

4. METAL Expansion Joints

4.1 General

4.1.1 Expansion joint assemblies are used to absorb thermal movement in piping systems. A typical assembly consists of stainless steel convoluted bellows, either a single bellows or a double bellows, with tie-rod attachments. Tie-rod attachments extend across the bellow(s) and are welded to the piping attachments or flanges at each end. Tie-rods are provided to restrain the unit from pressure or vacuum thrust. The bellows may be covered with a shroud or shield for protection against external damage.

4.2 Expansion Joint Installation

4.2.1 Before installation, expansion joints shall be visually inspected for damage during shipment, preferably upon delivery on-site. The site inspection shall include: checking the unit for overall cleanliness, inspecting the bellows for any damage such as cracks and dents, and ensuring that the tie-rods are not bent or damaged in any way. While stored on-site, expansion joints shall be adequately protected from damage. Expansion joints used for oxidizer service shall have been Class AA cleaned to 4WPI-SW70003 (oxygen clean).

4.2.2 Expansion joints are delivered with yellow shipping bars that are tack welded to the joint. These yellow shipping bars must be removed from the expansion joint following final installation in the piping system but before the pressure test. Removal of the shipping bars before final installation might result in the expansion joint being installed with offset for which it was not originally intended. If the shipping bars are not removed before plant operation, they will restrict the bellows from deflecting because of thermal expansion, thereby causing excessive loads on piping and equipment.

4.2.2.1 Shipping bars are not designed to carry the forces that can be generated during a pressure test. That is the purpose of the tie rods on the expansion joint. Shipping bars are not designed to stabilize an installed expansion joint during the shipment of a cold box or skid. If required, temporary shipping supports shall be provided for that purpose by the skid or box fabricator.

4.2.3 Expansion joints must be installed with the flow arrow pointing in the direction of process flow. The flow arrow is marked as part of the tag information supplied with the joint. The orientation of the joint in the process shall agree with the flow direction indicated on the flowsheet. The direction of the flow arrow shall also agree with the orientation of the liner inside the bellows, in that the open end of the liner does not oppose the direction of flow. Any discrepancies regarding the flow arrow direction shall be immediately reported to the Air Products field representative who will verify with Piping Stress Engineering.

4.2.4 Expansion joints are specified with tie-rods for restraint of vacuum or pressure thrust. Expansion joint tie-rod assemblies are factory-installed items consisting of lugs, tie-plates, or flanges welded to the joint. One set of nuts is tack welded to the rod on the outside face of the tie-plate to restrain the pressure thrust (the bellows would stretch and burst without the tie-rods to restrain them). If the expansion joint is designed for vacuum service, an additional set of nuts is tack-welded to the rod on the inside face of the tie-plate to restrain the system to keep the bellows from collapsing under extreme vacuum. The nuts are tack welded to the tie-rods by the manufacturer for reasons pertaining to safety. They must not be loosened, removed, or tampered with by anyone during installation, pressure test, or operation.

4.2.5 Expansion joints are supplied with different types of protective covers, both temporary and permanent, to guard against damage during construction or plant operation. A description of the three types of covers and their application is provided below. A shroud painted yellow must be removed before the pressure test and plant operation.

4.2.5.1 A fiberglass shroud may be supplied as a permanent cover around the bellows for fire protection during welding and burning processes. This type of cover is also used for protection of expansion joints installed inside perlite-filled cold boxes to prevent perlite from filling the convolutions of the bellows. This cover, although permanent, is removable to allow for periodic inspection.

4.2.5.2 A permanent stainless steel or galvanized cover may be provided for protection of the bellows against piercing or cutting. This cover is attached to the expansion joint assembly via bolted connections to allow for periodic inspection.

4.2.5.3 A steel cover may be provided as a temporary cover to protect the bellows from being pierced or cut during shipping and installation. A temporary cover is painted yellow to indicate that it shall be removed before pressure test and plant operation. If left installed, a temporary cover might restrict the bellows from deflecting because of thermal expansion.

4.2.6 Expansion joints may be installed straight or with a predesigned offset. The amount of offset required, as well as the offset direction, will be indicated on the piping drawings. Expansion joint shipping bars are fabricated to accommodate an installation with a predesigned offset.

4.2.7 Expansion joints are not designed for gross piping or equipment misalignment. Misalignment greater than what is listed in the table below must be corrected in the piping, not by the expansion joint. Axial misalignment is not allowed since expansion joints with tie rods are not flexible in the axial direction. Expansion joint assemblies—including any installed shipping bars—shall not be modified in any way to accommodate installation misalignments. Any questions regarding the ability of an expansion joint to absorb minimal misalignment shall be directed to the Air Products field representative who will verify with Piping Stress Engineering.

Expansion Joints
Direction	Maximum Misalignment
Axial	0
Lateral	+/- 6 mm (1/4 inch)
Angular	1 degree

4.2.8 The Metal Expansion Joint Construction Checklist (Appendix A) is provided for documentation to ensure all requirements for installation have been addressed.

5. Flexible Hose Installation

5.1 General

5.1.1 Flexible metal hose assemblies are used to absorb thermal movement in piping systems of DN300 (NPS 12) nominal pipe size or less. A flexible metal hose consists of an internal convoluted bellows covered with a mesh of braided stainless steel. Flexible hoses may contain one layer of metal braiding or multiple layers depending on the system design pressure. The outer metal braiding of a flexible hose stabilizes the internal bellows under pressure and acts as a tie-rod to resist pressure thrust forces. It is of the utmost importance that the metal braiding be maintained taut upon installation into a piping system. To ensure this tautness, higher pressure flexible hoses are supplied with temporary bars to maintain the neutral length of the hose during fit-up and installation.

5.2 Flexible Hose Installation

5.2.1 Flexible metal hoses shall be visually inspected before installation for damage during shipment, preferably upon delivery on-site. The site inspection shall include: checking the unit for overall cleanliness and inspecting the outer metal braiding for any broken or twisted braids. While stored on-site, flexible hoses shall be adequately protected from damage. Flexible hoses used in oxidizer service shall have been Class AA cleaned to 4WPI-SW70003 (oxygen clean).

5.2.2 Certain categories of high-pressure flexible hoses are specified with yellow shipping bars tack welded to the hose. Although these yellow shipping bars are temporary, they must not be removed until the hose has been completely installed in the piping system but before pressure test. Removal of the shipping bars before final installation may result in the hose being installed in a compressed state or with excessive offset. If a flexible hose is installed in a compressed state, the outer metal braids will not be taut to restrain the inner bellows under pressure. Failure occurs when the inner bellows becomes unstable and “squirms” causing the hose to bulge outward. In this state, there is a risk of bursting, which can cause serious injury to personnel.

Note: If the shipping bars are not removed before plant operation, they will restrict the flexible hose from deflecting because of thermal expansion causing excessive loads on piping and equipment.

5.2.2.1 Shipping bars are not designed to carry the forces that can be generated during a pressure test. That is the purpose of the braiding on the flexible metal hose assembly. Shipping bars are not designed to stabilize an installed metal hose during the shipment of a cold box or skid. If required, temporary shipping supports shall be provided for that purpose by the skid or box fabricator.

5.2.3 Flexible metal hoses may or may not be specified with an inner liner. Those hoses having a liner shall be installed with the flow arrow pointing in the direction of process flow. The flow arrow is marked as part of the tag information supplied with the hose. The orientation of the hose in the process shall agree with the flow direction indicated on the flowsheet. The direction of the flow arrow shall also agree with the orientation of the liner inside the flexible hose. If the liner design is a sleeve with an open end, the open end must not be on the upstream end of the installed hose. Any discrepancies regarding the flow arrow direction shall be immediately reported to the Air Products field representative who will inform Piping Stress Engineering.

5.2.4 Proper fit-up of a flexible hose is required to ensure that the outer metal braiding is installed taut, not kinked, bulged, or compressed. Once pressurized, a flexible hose is not flexible in the axial direction because of pressure thrust forces. The as-built overall length, supplied by the manufacturer as part of the tag information, is considered the neutral length of the hose. During installation, the fit-up dimension for the hose shall equal this neutral length such that the flexible hose is installed maintaining a neutral position. Misalignment greater that what is listed in the table below must be corrected in the piping, not by the flexible hose. (See paragraph 5.2.6 as well.) Consult with the Air Products field representative if the fit-up dimension on a prefabricated system does not equal the as-built length provided on the tag. The representative will inform Piping Stress Engineering.

5.2.5 Flexible hoses may be installed in a horizontal or vertical position, or with a predetermined offset. The amount of offset required, as well as the offset direction, will be indicated on the piping drawings. If no offset is specified, then the flexible hose shall be installed straight. Misalignment greater that what is listed in the table below must be corrected in the piping, not by the flexible hose. If there are shipping bars attached to the flexible hose assembly, the shipping bars shall not be adjusted to allow for misalignment. Any questions regarding the ability of a flexible hose to absorb misalignment shall be directed to the Air Products field representative who will verify with Stress Analysis Engineering.

Flexible Metal Hoses
Direction	Maximum Misalignment
Axial	0
Lateral	+/- 6 mm (1/4 inch)
Angular	2 degrees

5.2.6 A flexible metal hose will extend under pressure and the braiding must not be restricted from stretching. All supports in the area of the hose and the connecting piping must be installed according to the construction drawings. Before installation, any required deviations must be reported to the Air Products field representative who will consult with Stress Analysis Engineering.

5.2.7 The Flexible Hose Construction Checklist (Appendix B) is provided for documentation to ensure all requirements for installation have been addressed.

Appendix A Metal Expansion Joint Construction Checklist

Metal Expansion Joint Construction Checklist

EXPANSION JOINT IDENTIFICATION:

SITE DELIVERY INSPECTION

Date:

By:

Cleanliness – oxygen clean, if required?
Bellows Note any cracks or dents
INSTALLATION CHECKS
SHIPPING BARS
Yellow bars installed on joint? Shipping bars removed. Must be removed after installation and before pressure test.	Y	N
	Date:	By:
FLOW ARROW
Installed in direction of process flow?	Y	N
TIE-RODS
Nuts on outside face of tie-plate?	Y	N
Nuts on inside face of tie-plate?	Y	N
Are all nuts tack welded?	Y	N
Any signs of damage or tampering on rods, lugs or nuts?	Y	N
PROTECTIVE COVER (circle appropriate choice) Material (Fiberglass, Stainless Steel, Galvanized) Cover type Temporary or Permanent (Temporary cover is painted yellow) Temporary cover(s) removed. Must be removed after installation and before pressure test.	Date:	By:
ALIGNMENT
Installed with predesigned offset?	Y	N
Installed with offset required for fit-up?	Y	N

Appendix B Flexible Hose Construction Checklist

Flexible Hose Construction Checklist

FLEXIBLE HOSE IDENTIFICATION: