DETAILED ACTION
Notice of Pre-AIA or AIA Status
The present application, filed on or after March 16, 2013, is being examined under the first inventor to file provisions of the AIA .
Continued Examination Under 37 CFR 1.114
A request for continued examination under 37 CFR 1.114, including the fee set forth in 37 CFR 1.17(e), was filed in this application after final rejection. Since this application is eligible for continued examination under 37 CFR 1.114, and the fee set forth in 37 CFR 1.17(e) has been timely paid, the finality of the previous Office action has been withdrawn pursuant to 37 CFR 1.114. Applicant's submission filed on 23 October 2025 has been entered.
Claim Rejections - 35 USC § 103
The following is a quotation of 35 U.S.C. 103 which forms the basis for all obviousness rejections set forth in this Office action:
A patent for a claimed invention may not be obtained, notwithstanding that the claimed invention is not identically disclosed as set forth in section 102, if the differences between the claimed invention and the prior art are such that the claimed invention as a whole would have been obvious before the effective filing date of the claimed invention to a person having ordinary skill in the art to which the claimed invention pertains. Patentability shall not be negated by the manner in which the invention was made.
Claim(s) 1, 2, 9-11, 14, and 15 is/are rejected under 35 U.S.C. 103 as being unpatentable over US Pre-Grant Publication 2021/0033095 to De Raeve et al. (De Raeve hereinafter) in view of US Pre-Grant Publication 2017/0306966 to Valland et al. (Valland).
Regarding claim 1, De Raeve teaches a pumping arrangement in Fig. 3, having a first multistage pump (1a) and a second multistage pump (1b), each having a housing (2) with a pump unit with an inlet (21), an outlet (22), and a plurality of impellers (31, 32 33) mounted in a torque proof manner on a pump shaft (5) having an upper drive end and a lower non-drive end, the pumps being arranged in series and having a first mechanical seal (50) with a process side facing the pump unit. De Raeve further teaches that the process side of the first mechanical seal (50) is downstream of the pump inlet of the first multistage pump to receive fluid therefrom. De Raeve does not teach pressure equivalence between the process side of the first seal and the suction pressure of the first multistage pump. Valland teaches another multistage pump generally, and particularly teaches that a pressure equalizing line (742) may be included to set the pressure at the process side of a mechanical seal (770) equal to process suction pressure (paragraph 42). Valland teaches that this “will provide a very stable barrier fluid pressure at the expense of slightly reduced efficiency” (paragraph 42). One of ordinary skill in the art would have found it obvious before the effective filing date of the application to provide a conduit as taught by Valland to the pump of De Raeve in order to provide stable barrier pressure therein. See below annotated versions of De Raeve Fig. 3 and Valland Fig. 7, with the De Raeve annotations showing a disposition of the pressure equalizing line of Valland in an analogous position. In this position, the claimed pressure equalization between the second multistage pump and suction side of the first multistage pump and fluid recirculation will occur according to the teachings of Valland and De Raeve due to the contiguous spaces defined by the balance and equalization lines in combination with the process side of the mechanical seal.
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Regarding claim 2, De Raeve teaches a balance drum (7) in each pump unit connected to the pump shaft (5) between the pump unit and the upper drive end of the shaft, the balance drums having a first side facing the pump unit and a back side.
Regarding claim 9, De Raeve teaches that each pump comprises a drive unit (4) and a drive shaft (not separately labeled) configured to drive the pump shaft via a coupling (8).
Regarding claim 10, De Raeve teaches that each first mechanical seal is arranged between the associated first balance drum and the drive unit.
Regarding claim 11, De Raeve teaches vertical pumps (paragraph 37).
Regarding claim 14, De Raeve teaches a pump configured for installation on a sea ground (paragraph 2).
Regarding claim 15, De Raeve teaches pumping compressible fluid in a dense state (see e.g. paragraph 8).
Claim(s) 3-6 and 16-17 is/are rejected under 35 U.S.C. 103 as being unpatentable over De Raeve in view of Valland and US Pre-Grant Publication 2020/0263680 to Bourne et al. (Bourne).
Regarding claim 3, De Raeve teaches the invention of claim 2 from which claim 3 depends, but does not teach a second balance drum. Bourne teaches another pump generally, and particularly teaches that a subsea pump may be provided with two balance drums so as to improve rotor dynamics and stability (paragraph 12). Bourne further teaches that the second balance drum (8) is fixedly connected to the pump shaft between a pump unit (3) and a non-drive end (52) and has front and back sides arranged as claimed, with a second relief passage (83) and a second stator (27). One of ordinary skill in the art would have found it obvious before the effective filing date of the application to provide a second balance drum as taught by Bourne to the pump of De Raeve in order to improve rotor dynamics and stability. Thus provided at the non-drive end of at least the second pump, the second balance drum would be in at least indirect fluid communication with the pump inlet of the first multistage pump.
Regarding claim 4, Bourne teaches that the balance line (9) is configured to connect the first back side of the second multistage pump with the second backside (82) of the second pump.
Regarding claim 5, Bourne teaches that the second drum front side is exposed to second pump inlet pressure (at 81).
Regarding claim 6, Bourne teaches a second mechanical seal (54) arranged as claimed.
Regarding claims 16 and 17, De Raeve as modified by Valland teaches a set of lines including the balance lines (9) of De Raeve and the pressure equalizing line (742) of Valland which combine (as shown in the annotated Fig. 7 of De Raeve above) to connect the process sides of the mechanical seals with the inlet of the first pump. Bourne teaches another balance line (9) arranged to connect a first back side (72) and a second back side (82) and wherein each back side is bounded by a drum (7/8) and a seal (531/541) as claimed herein. Bourne teaches that this enables the operation of the balance drums and the recirculation line at a desirable pressure (paragraph 71). One of ordinary skill in the art would have found it obvious before the effective filing date of the application to provide the balance lines of De Raeve in the same location relative to the balance drums of Bourne in order to allow their function at a desirable pressure in conjunction with the remaining elements of De Raeve.
Response to Arguments
Applicant's arguments filed 23 October 2025 have been fully considered but they are not persuasive.
With respect to the argument that none of the references disclose a two-part bypass, the examiner is not persuaded. As illustrated above, the proposed modification of De Raeve starts from a configuration in which the balance lines (9) are already present. As such, the first part of applicant’s “two-part” bypass is present in the base reference, namely the connection between the process side of the inlet side mechanical seal (at pressure P2 above) of De Raeve with the process side of the outlet side mechanical seal (at P3, i.e. the “back side” of balance drum 7). Valland teaches linking for pressure equalization the process side of the mechanical seal of the second pump (P2 above) and the inlet of the first pump (P1). Since the process side of the outlet side mechanical seal is linked by a balance line (9) to the chamber adjacent to the mechanical seal of the second pump (P2), the equalization line of Valland would be linked on one end to the inlet of the first pump (P1) and on the other end to the process side (P2) of the inlet side mechanical seal of the second pump, these pressures are equalized (P1 = P2). By the balance line (9) of the second pump of De Raeve, the pressure adjacent the lower mechanical seal is made equal to the pressure adjacent the upper mechanical seal (P2 = P3). Therefore, all three chambers would have at least approximately equal pressures subsequent to the combination in the same manner as the claimed invention.
The examiner further notes that the balance line of Bourne connects the back sides of the balance drums thereof, similarly to the applicant’s disclosed invention. While not necessary to establish the prima facie case of obviousness, this teaching of Bourne notably supports the examiner’s position regarding the spaces which could be connected to form applicant’s two-part bypass.
In view of the above, the examiner maintains that the claimed invention is obvious over the cited prior art.
Conclusion
Any inquiry concerning this communication or earlier communications from the examiner should be directed to PHILIP E STIMPERT whose telephone number is (571)270-1890. The examiner can normally be reached Monday-Friday, 8a-4p.
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/PHILIP E STIMPERT/Primary Examiner, Art Unit 3746 3 November 2025