WAIVER NO. 4

Exhibit 10.2(d)

EXECUTION COPY

WAIVER NO. 4

     THIS WAIVER NO. 4 is being executed and delivered as of May 31, 2006, by and among Chicago Bridge and Iron Company N.V., a corporation organized under the laws of the Kingdom of the Netherlands (the “Company”), certain Subsidiaries party thereto as Borrowers (the “Subsidiary Borrowers”), JPMorgan Chase Bank, N.A. (successor by merger to Bank One, NA) as Administrative Agent (the “Administrative Agent”) under the hereinafter identified and defined Credit Agreement and the lenders party to said Credit Agreement. All capitalized terms used herein without definition shall have the same meanings as set forth in the Credit Agreement.

W I T N E S S E T H:

     WHEREAS, the Company, the Subsidiary Borrowers, the Lenders and the Administrative Agent are currently party to that certain Amended and Restated Credit Agreement dated as of May 12, 2005 (as the same may be amended, restated, supplemented or otherwise modified from time to time, the “Credit Agreement”);

     WHEREAS, the Borrowers have requested the Lenders and the Administrative Agent to waive certain provisions of the Credit Agreement in certain respects;

     WHEREAS, the Lenders and the Agent have agreed to waive certain provisions of the Credit Agreement on the terms and conditions set forth in Section 1 hereof.

     NOW, THEREFORE, in consideration of the foregoing premises, the terms and conditions stated herein and other valuable consideration, the receipt and sufficiency of which are hereby acknowledged by the Borrowers and the Lenders, such parties hereby agree as follows:

CH1 3520229v.4

     1. Waiver. The Borrowers have informed the Lenders that Defaults or Unmatured Defaults have occurred and are continuing, or are about to occur, under Sections 7.1(A)(i)(a), 7.1(A)(ii), 7.1(A)(iii), 7.1(A)(iv), 8.1(B) and 8.1(C) of the Credit Agreement as a result of the Company’s failure to timely (a) file with the Commission its financial results and related documents for the third and fourth quarters of its 2005 fiscal year, for its 2005 fiscal year and for the first quarter of its 2006 fiscal year and (b) deliver to the Administrative Agent and the Lenders the financial reports (including without limitation the plan and forecast) and related documents required under the Credit Agreement for or during such periods (collectively, the “Specified Defaults”). In accordance with the provisions of Section 9.2(i) of the Credit Agreement, the Borrowers have requested that, subject to the terms hereof, the Required Lenders waive the Specified Defaults and waive the application of the default rate of interest provided under Section 2.10 of the Credit Agreement. The Required Lenders hereby agree to such limited waiver and furthermore agree that, solely during the period commencing on November 14, 2005 and ending at the end of the Waiver Period (as defined below) and notwithstanding anything contained in Sections 2.1(A), 2.2(A), 3.2, 3.4, 3.5(A) and other applicable Sections of the Credit Agreement to the contrary, (x) Section 5.3(B) of the Credit Agreement shall not be deemed to

apply to the representations and warranties contained in Sections 6.4 and 6.10 of the Credit Agreement insofar as such Sections relate to the Company’s internally prepared financial statements (and related statements, reports, certificates and documents) for its four fiscal quarter period ending December 31, 2005, which have been delivered to the Lenders in connection with the prior Waivers and the draft September 30, 2005 Form 10-Q and the draft December 31, 2005 Form 10-K which are being delivered to the Lenders in connection with this Waiver (collectively, the “Unaudited Statements”) and the financial information (and related statements, reports, certificates and documents) which the Company has delivered to the Lenders on or prior to December 31, 2005 and which the Company is currently in the process of investigating as disclosed to the Lenders, (y) the last sentence of Section 5.3 of the Credit Agreement shall not be applicable and (z) the Company and the Administrative Agent may agree to such modifications to the forms (as set forth in the applicable Exhibits to the Credit Agreement) of Borrowing/Election Notice, request for the issuance of a Letter of Credit and compliance certificate as are reasonably deemed appropriate by the Company and the Administrative Agent to give effect to the foregoing clauses (x) and (y); provided that this waiver shall (i) only remain in effect during the period (the “Waiver Period”) commencing on the date hereof and expiring on the earlier of (a) the occurrence of any Default or Unmatured Default other than one of the Specified Defaults and (b) the Waiver Expiration Date and (ii) be subject to the receipt by the Administrative Agent of evidence satisfactory to it that the requisite number of noteholders party to the Note Purchase Agreement have duly executed and delivered an agreement to substantially the same effect as this waiver agreement such that no default, event of default or unmatured default would exist under the Note Purchase Agreement during the Waiver Period. As used herein, “Waiver Expiration Date” means (a) September 30, 2006 with respect to the “plan and forecast” described in Section 7.1(A)(iv) of the Credit Agreement and (b) June 16, 2006 with respect to all other financial statements and reports required under the Credit Agreement. Furthermore, the parties hereto agree that from and after the date hereof until the earlier of the end of the Waiver Period and the date of delivery to the Administrative Agent and the Lenders of the financial statements which are the subject of the Specified Defaults, for purposes of calculating the Applicable Floating Rate Margin, Applicable Eurodollar Margin, Applicable L/C Fee Percentage and Applicable Commitment Fee Percentage under Section 2.14(D)(ii), the Leverage Ratio shall be determined based upon the Unaudited Statements.

     Pursuant to the provisions of Section 9.3 of the Credit Agreement, (a) no delay or omission of the Lenders or the Administrative Agent to exercise any right under the Loan Documents shall impair such right or be construed to be a waiver of any Default or Unmatured Default or an acquiescence therein, and the making of a Loan or the issuance of a Letter of Credit notwithstanding the existence of a Default or the inability of the Company or any other Borrower to satisfy the conditions precedent to such Loan or issuance of such Letter of Credit shall not constitute any waiver or acquiescence and (b) any single or partial exercise of any such right shall not preclude other or further exercise thereof or the exercise of any other right, and no waiver, amendment or other variation of the terms, conditions or provisions of the Loan Documents whatsoever shall be valid unless in writing signed by the requisite number of Lenders required pursuant to Section 9.2, and then only to the extent in such writing specifically set forth. All remedies contained in the Loan Documents or by law as a result of the Specified Defaults are hereby reserved on behalf of the Administrative Agent and the Lenders following the Waiver Period.

     2. Conditions of Effectiveness. This Waiver shall be deemed to have become effective as of the date hereof, but such effectiveness shall be subject to the following conditions: (a) the Administrative Agent shall have received (i) executed counterparts of this Waiver duly executed and delivered by the Company, the Subsidiary Borrowers and the Required Lenders and executed counterparts of the Reaffirmation attached hereto duly executed and delivered by the Subsidiary Guarantors and (ii) the Unaudited Statements and (b) the Company shall have paid to the Administrative Agent, for the benefit of each Lender which has delivered to the Administrative Agent or the Administrative Agent’s counsel its executed signature page hereto by such time as is required by the Administrative Agent, an amendment fee for each such consenting Lender.

     3. Representation and Warranties. Each Borrower hereby represents and warrants that, other than in connection with the Specified Defaults, (i) all of the representations and warranties contained in Article VI of the Credit Agreement are true and correct and (ii) no Default or Unmatured Default is in effect.

     5. No Implicit Waiver. Except as expressly set forth herein in connection with the Specified Defaults, (i) the execution, delivery and effectiveness of this Waiver shall neither operate as a waiver of any rights, power or remedy of the Administrative Agent or the Lenders under the Credit Agreement or any other documents executed in connection with the Credit Agreement, nor constitute a waiver of any provision of the Credit Agreement nor any other document executed in connection therewith and (ii) the Credit Agreement shall remain in full force and effect in accordance with their original terms.

     6. GOVERNING LAW. THE ADMINISTRATIVE AGENT ACCEPTS THIS WAIVER NO. 4, ON BEHALF OF ITSELF AND THE LENDERS, AT CHICAGO, ILLINOIS BY ACKNOWLEDGING AND AGREEING TO IT THERE. ANY DISPUTE BETWEEN ANY BORROWER AND THE ADMINISTRATIVE AGENT OR ANY LENDER ARISING OUT OF, CONNECTED WITH, RELATED TO, OR INCIDENTAL TO THE RELATIONSHIP ESTABLISHED BETWEEN THEM IN CONNECTION WITH, THIS WAIVER, THE CREDIT AGREEMENT OR ANY OF THE OTHER LOAN DOCUMENTS, AND WHETHER ARISING IN CONTRACT, TORT, EQUITY, OR OTHERWISE, SHALL BE RESOLVED IN ACCORDANCE WITH THE INTERNAL LAWS (INCLUDING §735 ILCS 105/5-1 ET SEQ. BUT OTHERWISE WITHOUT REGARD TO THE CONFLICTS OF LAWS PROVISIONS) OF THE STATE OF ILLINOIS.

[Signature Pages Follow]

     IN WITNESS WHEREOF, this Waiver No. 4 has been duly executed as of the day and year first above written.

Signature Page to Waiver No. 4 to
Chicago Bridge & Iron Company N.V. et al
Amended and Restated Credit Agreement dated as of May 12, 2005

Signature Page to Waiver No. 4 to
Chicago Bridge & Iron Company N.V. et al
Amended and Restated Credit Agreement dated as of May 12, 2005

Signature Page to Waiver No. 4 to
Chicago Bridge & Iron Company N.V. et al
Amended and Restated Credit Agreement dated as of May 12, 2005

Signature Page to Waiver No. 4 to
Chicago Bridge & Iron Company N.V. et al
Amended and Restated Credit Agreement dated as of May 12, 2005

Signature Page to Waiver No. 4 to
Chicago Bridge & Iron Company N.V. et al
Amended and Restated Credit Agreement dated as of May 12, 2005