<PAGE>

                                                                   EXHIBIT 10.30
                                AMENDMENT NO. 2


     This Amendment No. 2 dated as of July 21, 1999 ("Agreement") is among
Cooper Cameron Corporation, a Delaware corporation ("Borrower"); Cooper Cameron
(U.K.) Limited, a company formed under the laws of the United Kingdom, Cameron
France, S.A., a societe anonyme formed under the laws of the Republic of France,
Cameron GmbH, a Gesellschaft mit beschrankter Haftung formed under the laws of
the Federal Republic of Germany, and Cooper Cameron (Singapore) Pte. Ltd., a
private limited company formed under the laws of the Republic of Singapore (the
"Borrowing Subsidiaries"); the Lenders (as defined below) executing this
Agreement; and The First National Bank of Chicago, as agent for the Lenders
("Agent").

                                 INTRODUCTION


     A.  The Borrower, the Borrowing Subsidiaries, the Lenders, the Co-Agents
(as defined therein), and the Agent are parties to the Amended and Restated
Credit Agreement dated as of March 20, 1997 and Amendment No. 1 to the Credit
Agreement dated as of July 11, 1997 (as so amended, the "Credit Agreement").

     B.  The Borrower, the Borrowing Subsidiaries, and the Lenders have agreed
to amend the Credit Agreement to (i) revise the definition of "EBITDA", (ii) add
the Euro as an available currency under the facility, and (iii) address the Year
2000 Problem (as defined below).

     THEREFORE, the Borrower, the Borrowing Subsidiaries, the Lenders, and the
Agent hereby agree as follows:

     Section 1.  Definitions; References.  Unless otherwise defined in this
Agreement, terms used in this Agreement which are defined in the Credit
Agreement shall have the meanings assigned to such terms in the Credit
Agreement.

     Section 2.  Amendments.

     (a) Article I of the Credit Agreement is amended as follows:

          (i) the following definition is amended in its entirety to read as
     follows:

          "EBITDA" means, for any applicable computation period, (a) the
     Borrower's and Subsidiaries' Net Income (excluding non-cash,  non-
     recurring, unusual charges) on a consolidated basis for such period plus
     (b) income and franchise taxes accrued during such period plus (c) Interest
     Expense accrued during such period plus (d) amortization and depreciation
     deducted in determining Net Income for such period.

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          (ii) the following new definition is added in alphabetical order with
     the existing definitions:

          "Euro" and/or "EUR" means the euro referred to in Council Regulation
     (EC) No. 1103/97 dated June 17, 1997 passed by the Council of the European
     Union, or, if different, the then lawful currency of the member states of
     the European Union that participate in the third stage of Economic and
     Monetary Union.

          (iii)  the definition of "Business Day" is amended to add the
     following passage in clause (a) after the words "carried on in the London
     interbank market":

     (and, if the Advances which are the subject of such borrowing, payment, or
     rate selection are denominated in Euros, a day upon which such clearing
     system as is determined by the Agent to be suitable for clearing or
     settlement of the Euro is open for business)

          (iv) the first sentence of the definition of "Eurocurrency Base Rate"
     is amended to replace the phrase "German marks, British pounds sterling, or
     Dollars" with the phrase "German marks, British pounds sterling, Euros, or
     Dollars".

          (v) the definition of "Restructuring Charges" is deleted in its
     entirety.

     (b) Section 2.16 of the Credit Agreement is amended to add the following
clause (c) after the existing clause (b):

          (c) If, after the making of any Advance in any currency other than
     Dollars, currency control or exchange regulations are imposed in the
     country which issues such currency with the result that the type of
     currency in which the Advance was made (the "Original Currency") no longer
     exists or the Borrower is not able to make payment to the Agent for the
     account of the Lenders in such Original Currency, then all payments to be
     made by the Borrower hereunder in such currency shall instead be made when
     due in Dollars in an amount equal to the Dollar Equivalent (as of the date
     of repayment) of such payment due, it being the intention of the parties
     hereto that the Borrower take all risks of the imposition of any such
     currency control or exchange regulations.

     (c) Clause (a) of Section 3.4 of the Credit Agreement is amended to read in
its entirety as follows:

          (a) deposits of a type, currency, and maturity appropriate to match
     fund Eurocurrency Advances are not available,

     (d) The following new Section 5.18 is added after Section 5.17 of the
Credit Agreement:

          5.18  Year 2000.  Except to the extent that a failure to do so could
     not

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     reasonably be expected to cause a Material Adverse Effect, the Borrower
     has (a) completed a review and assessment of all areas within its and each
     of its Subsidiaries' business and operations (including those affected by
     suppliers, vendors, and customers) that could be adversely affected by the
     "Year 2000 Problem" (that is, the risk that computer applications used by
     the Borrowers (or suppliers or vendors) may be unable to recognize and
     perform properly date-sensitive functions involving certain dates after
     December 31, 1999), (b) developed a plan and timeline for addressing on a
     timely basis, but in any event before September 30, 1999, the Year 2000
     Problem, and (c) to date, implemented that plan substantially in accordance
     with that timetable.  Based on the foregoing, the Borrower believes that
     all computer applications (including those of its suppliers and vendors)
     that are material to its or any of its Subsidiaries' business and
     operations are reasonably expected on a timely basis, but in any event
     before September 30, 1999, to address adequately the Year 2000 Problem
     (that is, be "Year 2000 Compliant"), except to the extent that a failure to
     do so could not reasonably be expected to cause a Material Adverse Effect.

     (e) Section 6.1 of the Credit Agreement is amended to add the following new
paragraph (j) after paragraph (i):

          (j) Prompt written notice in the event the Borrower discovers or
     determines that any computer application (including those of its suppliers,
     vendors, and customers) that is material to its or any of its Subsidiaries'
     business and operations will not be Year 2000 Compliant (as defined in
     Section 5.18), except to the extent that such failure could not reasonably
     be expected to cause a Material Adverse Effect.

     (f) Schedule 2.9 to the Credit Agreement is supplemented with the
information on Schedule 2.9 to this Agreement.

     Section 3.  Representations and Warranties.  The Borrowers represent and
warrant to the Agent and the Lenders that:

     (a) the representations and warranties set forth in the Credit Agreement
are true and correct in all material respects as of the date of this Agreement,
except to the extent any such representation or warranty is stated to relate
solely to an earlier date, in which case such representation or warranty was
true and correct in all material respects as of such earlier date;

     (b) (i) the execution, delivery, and performance of this Agreement have
been duly authorized by appropriate proceedings, and (ii) this Agreement
constitutes a legal, valid, and binding obligation of the Borrowers, enforceable
in accordance with its terms, except as limited by applicable bankruptcy,
insolvency, reorganization, moratorium, or similar laws affecting the rights of
creditors generally and general principles of equity; and

     (c) as of the effectiveness of this Agreement, no Default or Event of
Default has occurred and is continuing.

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     Section 4.  Effectiveness.  This Agreement shall become effective and the
Credit Agreement shall be amended as provided in this Agreement upon the
occurrence of the following conditions precedent:

     (a) the Borrowers, the Agent, and the Lenders shall have delivered duly and
validly executed originals of this Agreement to the Agent;

     (b) the representations and warranties in this Agreement shall be true and
correct in all material respects; and

     (c) the Borrower shall pay the following fees to each Lender which executes
this Agreement and delivers it to the Agent prior to 12:00 noon on July 21,
1999:

          (i)  a flat fee of $10,000 and

          (ii) .05% of such Lender's Revolving Credit Commitment.

     Section 5.  Effect on Loan Documents.

     (a) Except as amended herein, the Credit Agreement and the Loan Documents
remain in full force and effect as originally executed and amended heretofore.
Nothing herein shall act as a waiver of any of the Agent's or Lenders' rights
under the Loan Documents, as amended, including the waiver of any Default or
Unmatured Default, however denominated.

     (b) This Agreement is a Loan Document for the purposes of the provisions of
the other Loan Documents.  Without limiting the foregoing, any breach of
representations, warranties, and covenants under this Agreement may be a Default
or Unmatured Default under other Loan Documents.

     (c) The Borrower, as the Parent Guarantor, hereby reaffirms its obligations
under the Parent Guaranty and agrees that its obligations under the Parent
Guaranty are not affected by this Agreement and remain in full force.

     Section 6.  Choice of Law.  This Agreement shall be governed by and
construed and enforced in accordance with the laws of the State of New York.

     Section 7.  Counterparts.  This Agreement may be signed in any number of
counterparts, each of which shall be an original.

     EXECUTED as of the date first above written.

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                                    COOPER CAMERON CORPORATION


                                    By:
                                       -----------------------------------
                                         Daniel P. Keenan
                                         Vice President & Treasurer


                                    COOPER CAMERON (U.K.) LIMITED
                                    CAMERON FRANCE, S.A.
                                    CAMERON GMBH
                                    COOPER CAMERON (SINGAPORE) PTE.
                                      LTD.


                                    By:
                                       -----------------------------------
                                         Daniel P. Keenan
                                         Attorney-in-fact


                                    THE FIRST NATIONAL BANK OF
                                      CHICAGO, individually and as Agent


                                    By:
                                       -----------------------------------
                                         Thomas E. Both
                                         First Vice President

                                    ABN AMRO BANK N.V., individually and as
                                    Co-Agent


                                    By:
                                       -----------------------------------
                                    Name:
                                         ---------------------------------
                                    Title:
                                          --------------------------------


                                    By:
                                       -----------------------------------
                                    Name:
                                         ---------------------------------
                                    Title:
                                          --------------------------------

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                                    THE BANK OF NOVA SCOTIA, individually
                                      and as Co-Agent


                                    By:
                                       -----------------------------------
                                    Name:
                                         ---------------------------------
                                    Title:
                                          --------------------------------


                                    THE CHASE MANHATTAN BANK,
                                      individually and as Co-Agent


                                    By:
                                       -----------------------------------
                                    Name:
                                         ---------------------------------
                                    Title:
                                          --------------------------------


                                    CREDIT LYONNAIS, NEW YORK BRANCH,
                                      individually and as Co-Agent


                                    By:
                                       -----------------------------------
                                    Name:
                                         ---------------------------------
                                    Title:
                                          --------------------------------


                                    PNC BANK, NATIONAL ASSOCIATION,
                                      individually and as Co-Agent


                                    By:
                                       -----------------------------------
                                    Name:
                                         ---------------------------------
                                    Title:
                                          --------------------------------


                                    ROYAL BANK OF CANADA, individually
                                      and as Co-Agent


                                    By:
                                       -----------------------------------
                                    Name:
                                         ---------------------------------
                                    Title:
                                          --------------------------------

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                                    SOCIETE GENERALE, SOUTHWEST
                                     AGENCY , individually and as Co-Agent


                                    By:
                                       -----------------------------------
                                    Name:
                                         ---------------------------------
                                    Title:
                                          --------------------------------

                                    AUSTRALIA AND NEW ZEALAND
                                    BANKING GROUP LIMITED


                                    By:
                                       -----------------------------------
                                    Name:
                                         ---------------------------------
                                    Title:
                                          --------------------------------

                                    COMMERZBANK AG, NEW YORK BRANCH


                                    By:
                                       -----------------------------------
                                    Name:
                                         ---------------------------------
                                    Title:
                                          --------------------------------

                                    By:
                                       -----------------------------------
                                    Name:
                                         ---------------------------------
                                    Title:
                                          --------------------------------

                                    NATIONAL WESTMINSTER BANK PLC


                                    By:
                                       -----------------------------------
                                    Name:
                                         ---------------------------------
                                    Title:
                                          --------------------------------

                                    By:
                                       -----------------------------------
                                    Name:
                                         ---------------------------------
                                    Title:
                                          --------------------------------

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                                    BANK OF AMERICA, N.A. (successor by
                                      merger to NationsBank of Texas, N.A.),
                                      individually and as Co-Agent


                                    By:
                                       -----------------------------------
                                    Name:
                                         ---------------------------------
                                    Title:
                                          --------------------------------



                                    BANK OF AMERICA NATIONAL TRUST
                                      AND SAVINGS ASSOCIATION (formerly
                                      Bank of America Illinois), individually
                                      and as Co-Agent


                                    By:
                                       -----------------------------------
                                    Name:
                                         ---------------------------------
                                    Title:
                                          --------------------------------

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