News & Insights from Dynaflow Research Group

Weld 34 Crack and Dead-End Configuration The circulation system has two pumps, one operating and one spare. The operating pump feeds cooling water back into the Benson vessel at the top of the system. In the situation analysed, one pump had been taken out for revision. A blind valve was

Branch Failures in a Buried GRP Firewater Ring The firewater system is made from glass-reinforced plastic (GRP) pipe and is mainly underground. The main is a ring with large-bore branch connections, and smaller-bore branch connections feed the hydrants and monitors above ground. In early operation the system suffered a number

Slug Flow Operation and Two Elbow Fatigue Failures At a gas-to-liquids facility, the water feed line to an HCN/NH3 stripper (1C-1201) regularly operated in the slug flow regime. Slugs can generate large dynamic loads on the piping, which can eventually result in fatigue failures. Two leakage incidents occurred, each caused

Flange Leakage in 44-Inch Catalytic Oxidiser Piping The 44-inch top and bottom nozzles of a catalytic oxidiser are connected to the shell and tube sides of a recuperative heater by 44-inch piping. The hot design temperature is 527 °C. The required piping flexibility is provided by a number of expansion

Steam-Out Cycles of the Carbon Bed Vessels In the offgas cleaning system of an EBHP reaction section, vessels V105A to V105D absorb EB from the offgas on active carbon beds, because the EB has to be removed before flaring for environmental reasons. Once a bed is saturated, it is steamed

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