News & Insights from Dynaflow Research Group

Dynaflow ran a finite element analysis to ASME VIII Division 2 of a stainless steel SA240 316L support ring welded into a carbon steel Claus reactor. All primary stresses were within the allowable. At the head-to-ring connection, however, secondary stress reached 885 MPa (259 percent of the allowable), and fatigue

Two identical condensers cool sulphur gas to a temperature close to its dew point. The gas passes through 363 SA-179 tubes of 38.1 mm outside diameter and 8840 mm straight length, set on a 48 mm triangular pitch between two stationary tube sheets. On the shell side, water maintains a

New water hydrants were installed as part of an upgrade of the firewater system at a main degassing station. Each hydrant valve joins the steel hydrant part to the underground glass-reinforced epoxy (GRE) piping, and the GRE piping connects to steel piping coming from the above-ground equipment. The GRE is

Firing of three relief valves on a steam line operating at 225 °C and 9.5 barg was analysed in CAESAR II, with dynamic loads generated in BOSfluids. The spectrum analysis gave a combined dynamic and static stress of 128% of the occasional allowable stress and the time-history analysis including the

Condensation and Steam Hammer in a Cold Steam Line The analyses assumed steam at 380°C and 40 Barg entering a 36-inch high-pressure steam line with a pipe temperature of +5°C. Potential problems are anticipated at start-up because the steam condenses on entering the cold pipe. Steam remaining in the line

A BOSfluids surge analysis and slug impact calculation of a 12-inch steam start-up line gave maximum unbalanced forces of 1.32 kN, 1.3 kN and 3.2 kN for three surge scenarios, and 16.5 kN and 23 kN for 7 m and 10 m slug impacts on the pressure control valve. CAESAR

During re-alignment of the suction and discharge piping for sales gas compressors K2002A and K2002B, ready for connection to the compressor nozzles, the discharge line of K2002B could not be correctly aligned. The displacement at constant load hanger 04-SS-1017 (PS 1017) took the hanger out of its operating range. A

A CAESAR II stress analysis of a revised high-pressure blowdown line operating at 20.6 barg and 160 °C found that the system as proposed did not meet ASME B31.3 because of large thermal displacements of the DN600 header. If guide support S1 is replaced by a restraint in the z-direction

At a refinery, instrument air is supplied by three Atlas Copco compressors. Two are motor driven; the third is driven by a Coppus RHLA-24 steam turbine commissioned in 2008. Two months after start-up, a plain bearing malfunctioned. The turbine was overhauled and reassembled at site in August 2009, after which

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