Flowserve PHL API 610 OH2 Diffuser Process Pump

Flowserve PHL API 610 OH2 centerline-mounted diffuser pump

The Flowserve PHL is an ISO 13709/API 610 (OH2) overhung process pump, centerline mounted, in which the usual volute is replaced by a multi-channel diffuser. Flowserve describes it as a pump whose hydraulics can be tuned to the duty: more than 170 hydraulic configurations are supported by only four shaft designs and two bearing housing designs. Seven Star LLC supplies the PHL in Oman and the GCC as an independent supplier in Muscat. This page covers the PHL range as a series, so the exact size, materials and seal arrangement are confirmed against your duty data rather than a single ordering code.

An OH2 pump is a horizontal, single-stage, end-suction pump with a back pull-out rotor and a casing supported on the shaft centerline, which lets the casing grow with temperature without losing alignment. The PHL keeps these features but changes the way the fluid is collected after the impeller, and that change drives most of its claimed benefits: low radial load, low vibration and a wide operating window.

What the PHL name and API code tell you

PHL technical specifications

How the diffuser design works

In a volute pump the pressure around the impeller is only balanced at one flow point, so away from best efficiency the radial thrust on the shaft rises. A multi-channel diffuser guides the liquid through several symmetrical passages, so the radial load stays low at any flow. Flowserve states that this permits minimum continuous flow of 10 to 20 % of BEP, lowers shaft deflection and therefore improves mechanical seal life, and extends the L10 bearing life through lower vibration. The diffusers are replaceable, so the hydraulics can be re-tuned to a changed duty without replacing the casing.

PHL compared with other Flowserve API pumps

The brochure lists complementary designs for the same plant: the PVML vertical in-line OH5 diffuser pump, the PVXM OH3 vertical in-line diffuser pump, the HPX OH2 volute pump and the ERPN end-suction volute pump. The HPX, HPX-V, PVXM and HHPX pages are covered on separate pages of this site. Choose the PHL when the duty has a wide flow range, low NPSH available, high temperature or a need for very low vibration, and the HPX when a standard volute with a very wide size range is preferred.

Selection and ordering checklist for the PHL

• Normal, rated and minimum flow, with differential head and specific gravity.
• NPSH available at the pump suction and the suction nozzle orientation (end or top).
• Pumped liquid, temperature, vapour pressure and solids content; boron diffusion treatment where fines are present.
• Casing pressure rating, API 610 material class and flange class.
• Seal arrangement and flush plan per API 682 and API 610 piping plans.
• Bearing cooling: air fan or water jacket for temperatures above 200 °C.
• Driver type, speed and frequency (50 or 60 Hz).
• Testing and documentation requirements.

Installation, commissioning and maintenance

Centerline-mounted pumps are installed on a baseplate designed for API 610 loads; check the nozzle loads against the pipework and grout the baseplate properly. During commissioning, confirm rotation, check seal flush and cooling flows, and verify vibration at several flows because a diffuser pump should show low levels across the range. Regular maintenance covers the bearings and the mechanical seal; the back pull-out design allows the rotor to be removed without disturbing the casing and piping, and a spare rotor set shortens outages.

Typical applications of the PHL in Oman and the GCC

Flowserve lists oil production and transportation, hydrocarbon processing, petrochemical processing and general industry as the main applications. In Oman and the GCC this points to crude and condensate transfer, refinery and petrochemical process services, hot oil circuits, amine and reflux duties and seawater-related services where low NPSH and long seal life are valued. High ambient temperatures make bearing cooling and seal plan choices especially important.

Information to send with your PHL RFQ

• Liquid, temperature and specific gravity.
• Rated, minimum and maximum flow and the required head.
• Suction pressure and NPSH available.
• Material class, flange rating and seal plan requirements.
• Driver and frequency; site conditions and delivery location.
• Standards and test requirements.

Site conditions in Oman for the PHL

Pump selection in Oman has to account for the site, not only the duty point. Process liquids and cooling water can arrive warm in summer, which raises vapour pressure and reduces the available NPSH, so check the NPSH margin of the PHL at the highest expected liquid temperature. Motors on outdoor skids also work in high ambient air, and their rating, enclosure and cooling should match that environment.

For hygienic and process plants in the Gulf, plan the spare parts that wear first, such as seals, O-rings and bearings, and keep the material certificates with the plant records. Sharing the fluid, temperature, flow, head and cleaning regime with the supplier at RFQ stage makes it easier to confirm that the PHL is the right configuration before the order is placed.

Documents and quotation

A Flowserve PHL brochure is attached on this page. It gives the range chart and the operating parameters. Send your duty point and the PHL size you are considering, and we will confirm availability and lead time. Seven Star LLC is an independent supplier and does not claim any official status with the manufacturer.