News & Insights from Dynaflow Research Group

A Branch Failure on a Methanol Plant Steam Header A methanol plant operating on a 3,000 tonnes per day basis suffered a piping failure on 19 May 2012. A ¾ inch branch broke off the medium-pressure (MP) steam header when the turbine driving the synthesis gas compressor tripped. In normal

A pulsation analysis to API 618 Design Approach 1 checked the proposed dampener bottles of onshore and offshore reciprocating compressors against a guideline of 70 percent of the allowable pulsation levels. All proposed bottles gave levels within the API 618 allowable. At the line connection nozzle, only the offshore discharge

Condensate Forwarding Duty at a Nigerian Gas Plant At a gas plant in Nigeria, four reciprocating pumps on an N+1 philosophy (three running, one spare) forward condensate from a storage and separation tank into a gas pipeline. A 12-inch suction header carries the condensate from the tank to the pumps,

Severe Vibration in Vaporiser Feed Pump Piping The suction and discharge piping connected to the quadruplex methanol vaporiser feed pumps was suffering from severe vibration. A pulsation analysis combined with a mechanical response analysis of the as-built piping was performed to establish the root cause. The analyses determined the stress

At the Utorogu Flow Station in Nigeria, vibration was observed in the suction header, the discharge header and the pump recirculation line. Dynaflow Research Group performed pulsation, mechanical response and static stress analyses to find the root cause, identify any other possible problems and recommend improvements. The station pumps crude

A third-party review of the HP discharge line at a gas compression station found that the designer’s stress report shows the discharge nozzle conforming to the vendor’s allowable values with the springs pinned, as API 686 requires. At the 7th April alignment check the flange separation exceeded the 4.5mm vendor

A new natural gas booster plant at Winksele, Belgium, was undergoing Site Approval Tests (SAT) after the end of construction. The SAT scope included a pipe vibration level assessment to verify that all vibration levels were within acceptable limits. This case study describes the measurement campaign and the VDI 3842

Compressor Suction Strainer and Its Fatigue Cracking The suction strainer of a centrifugal compressor developed fatigue cracks. The strainer is a perforated stainless steel truncated cone (Werkstoff 1.4571), 970 mm long, with an outside diameter of 160 mm at the upstream end and 420 mm at the downstream end. The

Operating Context and Damper Configuration Assumed At a plant in Qatar, a Dresser Roots compressor compresses seal gas in two stages. The client requested a simulation study, both acoustic and mechanical, of the compressor piping between the first-stage discharge and the second-stage suction. The second-stage bypass lines are included. The

Why Pulsation Risks Warranted Attention Before Operation The compression station was designed to increase and maintain operating pressure on a natural gas piping network, overcoming friction losses. It has four (3+1) two-stage centrifugal compressors with 19-blade impellers, running at a rated speed of 5750 RPM (95.8 Hz) within a range

A Commissioning Failure That Sent Debris Downstream During commissioning of a natural gas compressor station, pieces of fibreglass fabric, mineral wool and steel wire were found throughout the downstream system. A small amount of mineral wool was also found in the surge valve. Inspection showed that the mineral wool found

Compressor Piping Under Combined Marine and Process Loading The compressor module was located roughly halfway along the hull. Its connected piping had to accommodate thermal and pressure loads, wind loads, accelerations from wave-driven barge rocking and relative displacements from hull deformation. These loads could produce pipe deflection and bending and

Cyclic Thermal Duty in a Gas Treatment Air Cooler An air-cooled heat exchanger for a gas treatment plant is subjected to a varying inlet temperature. In the analysed winter case, which has the largest temperature variation, the fluid cycles between 7.5°C and 288°C during each 100-minute cycle. The first part

Consolidating Gas Flow onto a Single Metered Line A platform gas metering station has three parallel metering lines, two active and one spare. The modification replaces the orifice-type flow meter in the most eastern line with an ultrasonic (US) flow meter and directs the complete gas flow through that line.

Nitrogen Skid Stress Verification Requirement A manufacturer produces a nitrogen metering skid for a project. As a result of a client performance requirement, the existing design had to be verified by stress analysis. The skid is a straight pipe configuration with valves and flow meters, supported approximately 1000 mm above

An axisymmetric finite element analysis checked the flued flange expansion joint of a fixed-fixed tubesheet reboiler for low cycle fatigue, high cycle fatigue and primary stress to ASME Section VIII Division 2, at mean (26 mm) and minimum (22 mm) wall thickness. The largest low cycle fatigue stress range was

The station model of the Winksele Compressor Station, to be built in Belgium, was divided into two models with some mutual overlap, a compressor model and a filter model, each covered by a separate stress report. A third report covers the gas air coolers as model C, an add-on to

An additional separator was installed in Phase 2 of a cluster project and was to be connected to the existing lines through a modified above-ground (A/G) manifold. The manifold also connects to an existing buried (underground, or U/G) line. The analysis applied pressures of 100 / 225 Barg and temperature

A combined CAESAR II model of a gas metering skid and its structural steel frames was assessed against ASME B31.3 (2006). The piping stresses were below the allowables, the steel stresses were within the allowable limits for the sustained and expansion load cases, and several bolt shear loads exceeded the

Multi-Mode Metering Skid with Undefined Connecting Piping The unit assessed was a 24-inch, 300# ethane metering skid. Gas can be routed through a normal operating line (line 1), a testing and maintenance line (line 2), two flow control lines (lines 3 and 4) and a bypass. No more than one

CAESAR II stress analysis of 13 critical sections of a buried GRP fire water system, to ISO 14692, expected no problems for the underground piping under pressure and temperature loads. High stresses occurred in vertical above-ground GRP pipes where the pipe is vertically restrained; in section D, guide and rest