Valve Station Research Articles

A Review of Residual Pressure Utilization of Natural Gas

Natural gas needs to be depressurized before wellhead to gas gathering station or long-distance pipeline to users. At present, choking technique is widely used at wellhead and pressure regulating station, which will cause a lot of energy loss. Considerable economic and social benefits will be generated, if these residual pressures can be recycled. In this article, the pressure energy contained in the natural gas wellhead and pressure regulating valve station will be calculated based on exergy analysis. The technology and present situation of residual pressure utilization of natural gas are summarized. The existing problems and future research directions in the process of residual pressure utilization are pointed out through cases. At present, there are many studies on the use of residual pressure in the pressure regulating station, but there are relatively few studies in the natural gas wellhead. Residual pressure utilization technology improves energy utilization efficiency and makes an important contribution to energy conservation and emission reduction.

Calculation of sealing pressures of shut-off valves

The proposed algorithm for calculating the sealing pressures of the shut-off valve allows one to take into account the structural features of its components and their elements that affect the amount of sealing pressures. These parts are divided into the mounting system and sealing system. Analytical dependencies for determining the forces acting in these systems allow us to determine the force values when tightening fasteners, during pressure buildup and release, and also when exposed to temperatures. When calculating the specific structure of the shut-off valve, it is shown that the forces in its sealing system and mounting system exceed the values determined by known methods of calculation, respectively, 1.4 and 1.2 times. The magnitude of these discrepancies for different structures of shut-off valves may differ from those indicated and depends on the number of components included in the stop valve station. In this regard, the proposed calculation method allows determining not only the forces in the shut-off valve, but also the optimal number of components and connections that will ensure safe operating conditions. It is shown that the method of calculating forces in the stop valve station used in practice is a special case in which the stiffness coefficient of the stop valve station α = 1. The proposed calculation method makes it possible to more accurately determine the forces acting in the shut-off valve, the sealing conditions and the stress-strain state of the components. The introduction of the developed calculation method is connected with the development of a regulatory document on its basis to replace the existing methods of calculating the stop valve station in shut-off valves.

Unforeseen Shock Hazards Resulting From Code Compliance: A Case Study at an Above-Ground Pipeline Valve Station

The Code of Federal Regulations (CFR) is a regulatory collection of general and permanent federal agency rules. This case study is specific to two sections pertaining to the control of corrosion and electrical protection of underground pipe lines and valve stations. The transportation of hazardous liquids is covered by 49 CFR 195 and the transportation of natural gasses by 49 CFR 192. Meeting compliance is obtained with the installation of devices and systems that electrically isolate a cathodically protected pipe line and valve stations from nearby grounded structures and equipment. This study focuses on a cathodically protected pipeline isolation system that exposed a worker to a higherthan- expected voltage level and unexpected hazard when work was performed at a valve station after the installation of a required isolation device.

Analysis of discharge process of oil pipeline with complex topography

During the commissioning process of ”first injection of crude oil after water injection”, due to the density difference between crude oil and water, the oil pressure on the left side of the ”U” section is less than the right hydraulic pressure, and the running process of the oil head is stagnated in a hilly oil pipeline with high elevation difference. Concerning this problem, solution of discharging pressure by using relief valve in valve station nearby oil–water interfacial point is proposed in this paper. According to the actual data, gas–liquid flow in a gas-cap empty process of a big drop and hilly oil pipeline was numerically investigated by dynamic multiphase simulation software OLGA. Simulation data in terms of flow rate, pressure and leakage were compared under different leaking apertures. The simulation results show that the general pressure variation tendencies at the vent, bottom point or top and low elbows show no connection with vent diameters but its final fluctuation that the smaller the diameter is, the more intensive the fluctuation gets.. And as for the emptying of a big drop and hilly pipeline, appropriate increase of leaking aperture can improve the drainage ratio (leakage/general capacity of the pipeline) and drainage rate, but excessive aperture will cause severe negative pressure and breakage cavity which foster the likelihood of close water-surge and damage to the pipe safety.

Evaluation of the Construction and Investment Process of a High-Pressure Gas Pipeline with Use of the Trenchless Method and Open Excavation Method. Analytic Hierarchy Process (AHP)

The study presents the application of multi-criteria analysis, i.e., the Analytic HierarchyProcess (AHP), for the evaluation of investments related to the realisation of a high-pressure gaspipeline. The authors evaluated the realisation of the gas pipeline with the use of alternativemethods: the trenchless Horizontal Directional Drilling (HDD) method and the open excavationmethod, based on the example of the construction of a high-pressure gas pipeline DN1000. Sectionslocated in naturally valuable areas on the route of the pipeline Wierzchowice-Kiełczów (Poland)were analysed, on the section from the valve station in Czeszów to the Kiełczów node. The researchconsidered the following criteria: technical costs, economic costs, social costs, and environmentalcosts. The sum of these partial estimations is the “total cost” of the investment. Research revealedthat the technical costs of the open excavation method are in all cases higher than the technologicalcosts of the trenchless method during the realisation of a gas pipeline (in the AHP analysis, theyreceive an average score of −4 or −3, compared to a score of −2 for the HDD method). On the otherhand, the economic costs are comparable, with a slight advantage for the HDD method. The overallscore for the open excavation method obtained with use of the AHP multi-criteria evaluation is, fordifferent variants, approximately −19, while the evaluation of the realisation of a gas pipeline withuse of the Horizontal Directional Drilling method gives a score from −15 to −10, depending on thesection.

Proper Planning Minimizes Valve Operation Problems

Carefully choose key components and keep personnel in mind to optimize valve station performance.

Casino pipeline: novel pipeline integrity inspection

The Casino offshore pipeline required inspection to demonstrate the integrity of the pipeline and allow the operating life of the pipeline to be extended. There were numerous challenges in performing a conventional internal pipeline inspection which would have required diver operations to install and operate subsea pig launchers. Two alternative inspection methods were used to inspect the high priority sections of the pipeline, at the pipeline tees and in the horizontal directionally drilled (HDD) section of pipeline at the coastline crossing.The pipeline tees and well flowlines were inspected using an external magnetic flux inspection tool deployed by remotely operated vehicle (ROV), to test for top-of-line corrosion. Bi-directional pigging from the onshore valve station, offshore for 30 km using gas from the host gas plant and then return to the shore using gas from the offshore wells allowed for inspection of the HDD pipeline with a total of 10 bi-direction pig runs completed. The pig position was accurately predicted by monitoring the operating conditions of the pipeline and confirmed by displacement past the subsea well closest to shore (Casino 5). The novel pigging methods brought significant benefits for cost, schedule and reduced EHS exposure by avoiding diver operations. The cost of the overall inspection program was less than 25% of the conventional inspection methods and was achieved a year earlier than if a dive support vessel (DSV) had been mobilised. The bi-directional pigging campaign proved to be highly successful.

Seismic Isolation of Offshore Pipeline Block Valve Stations

As shown by the actual material analysis of offshore pipeline damage caused by strong earthquakes, the greatest damage is caused to complex assemblies such as branch connections, bends, and various joints .In the seismic resistance analysis of the offshore pipeline a fixed junction of an offshore pipeline section with a block valve station is modeled. To assess the connection assembly for seismic resistance, a number of accelerograms with descriptions of magnitude 8 and 9 earthquakes in the Black Sea region were considered. The calculations have revealed significant pipe wall stresses in the offshore pipeline/block valve station junction. The resulting conclusion is that offshore pipeline block valve.

SS16. Long-Term Results of Deep Vein Valve Reconstructions for Nonhealing C6 Venous Ulcers: An 18-Year Experience

In an era that has seen significant changes in the way we manage nonhealing venous leg ulceration, this study reports the rationale, results, and changing trends of an 18-year experience of deep vein valve reconstruction with evaluation of end points at 2, 5 and 10 years in the management of nonhealing venous leg ulcers in 228 patients. A total of 228 patients (302 limbs) undergoing deep vein reconstructions were followed up for 2 to 18 years (mean, 8 ± 2.3 years). All patients had nonhealing C6 venous leg ulcers of >3 months' duration and were offered deep venous reconstruction as a “last resort” treatment. End-points of the study were freedom from leg ulceration, vein valve patency, and competence assessed serially by physical examination and duplex scanning. Primary refluxive disease was present in 156 patients (209 limbs). External valvuloplasty was performed in 12 limbs (19 valves), and internal valvuloplasty was performed in 181 limbs (324 valves). External supports were used in 16 limbs (16 valves). Multilevel (≥2) reconstructions were performed in 126 limbs. Seventy-two patients had secondary valvular defects involving 93 limbs. Axillary-femoral vein valve transplant was performed for 49 patients (64 limbs) and Maleti Neovalve in five patients (five Limbs) respectively. Saphenofemoral venous transposition was performed in 7 patients (nine limbs), and femoral/popliteal vein ligation was carried out in 11 patients (15 limbs). At 10 years, external valvuloplasty showed ulcer healing in 16% of limbs, with maintenance of competency at only 15.7% of valve stations. Internal valvuloplasty was the most durable valve repair procedure, with actuarial leg ulcer healing rates of 67% and valve station competency of 79%. It was also noted that single-level repairs had significantly lower ulcer healing rates than multilevel repairs (P = .0018). For secondary incompetence, valve transplants had a gradual but increasing deterioration in valve patency and competency at 10 years: 46.8% and 38.3%, respectively, with 36.6% actuarial leg ulcer healing. Although the Maleti Neovalve in our hands performed well initially, all repairs thrombosed by 9 months. Even venous transpositions had no valve competency >2 years. Valvular reconstruction for refluxive disease is effective in healing venous ulcers that defy conservative management and superficial/perforator venous surgery out at 10 years. Furthermore, these procedures are useful for primary but not for secondary incompetence. Multilevel or multivalve reconstructions yield superior results to single-level repairs in medium-term follow-up. Open reconstructions for secondary incompetence may be a waste of time, with increased morbidity.

Reduction internal valvuloplasty is a new technical improvement on plication internal valvuloplasty for primary deep vein valvular incompetence.

We describe a new technique of valve leaflet closure, reduction internal valvuloplasty (RIVAL), to treat primary deep vein valvular incompetence in patients with C6 venous disease. The RIVAL method involves excision of redundant valve and suturing of the freshened edge to the wall of the valve station instead of plication at the commissural junctions. Since January 2008, RIVAL has been successfully performed on 44 incompetent deep vein valves in 18 consecutive patients (25 limbs). All patients had C6 venous ulcers of a minimum 3months' duration. On mean follow-up of 1year (clinical assessment of venous ulcer healing and color-coded duplex scans at 1, 6, 12, 18, and 24months) of the 44 valves repaired by reduction valvuloplasty, all 44 valves (100%) maintained full patency. Forty-two valves (95.4%) were competent, achieving a valve closure time<1second with no reflux at thetarget valves on Valsalva maneuver in the reverse Trendelenburg and upright positions, and their intervalvular distances were reduced to >60% of preoperative levels. Eighty-eight percent of all ulcers (22 of 25) healed within 9weeks of surgery without any recurrence in the follow-up period. There was no valve thrombosis or resorption seen with this method. The RIVAL technique represents a significant advancement over the traditional existing valve plication techniques. It enables accurate anatomic fashioning and suturing of valve cusps and results in excellent competency and ulcer healing rates with fewer complications in our early experience. Further follow-up is anticipated to define its long-term role in the management of C6 venous disease.

Deep venous valve reconstruction for non-healing leg ulcers: techniques and results.

The purpose of the present paper was to report clinical and imaging results of a 5 year experience of deep venous valve surgery with evaluation of end-points at 2 year follow up for the management of non-healing venous leg ulcers in 137 patients. Between October 1994 and November 1999, 137 patients (169 limbs) underwent deep vein reconstructions for non-healing venous leg ulcers of clinical, etiological, anatomical, pathological classification (CEAP) C6 class, as a 'last resort' treatment. End-points of the study were post-valve reconstruction, freedom from leg ulceration, vein valve patency and competency at 2 years. Primary refluxive disease was present in 96 patients (118 limbs). External valvuloplasty was performed in 12 limbs (19 valves) and internal valvuloplasty was performed in 90 limbs (144 valves). External supports were used in 16 limbs (16 valves). Multilevel (2-3) reconstructions were performed in 37 limbs. Forty-one patients had secondary valvular defects involving 51 limbs. Axillary-femoral vein or saphenofemoral vein valve transplant was performed for 29 patients (35 limbs) and three patients (three limbs), respectively, saphenofemoral venous transposition was performed in three patients (four limbs), and femoral/popliteal vein ligation was carried out in six patients (nine limbs). Two year results of external valvuloplasty showed ulcer healing in 50% of limbs with maintenance of competency at only 31% of valve stations. Internal valvuloplasty was the most durable valve repair procedure with 2 year leg ulcer healing rates of 67% and valve station competency of 79%. For secondary incompetence, valve transplants had a significant deterioration in valve patency and competence at 2 years: 58% and 47%, respectively, with 55.3% leg ulcer healing. It was also noted that single-level repairs or single valve transplants had lower ulcer healing rates than multilevel repairs or valve transplants with multiple valve stations. In a 2 year follow up, valvular reconstruction for refluxive disease is effective in healing venous ulcers that defy conservative management and superficial/perforator venous surgery. Furthermore, these procedures appear more promising for primary than for secondary incompetence. Multilevel or multivalve reconstructions yield superior results to single-level repairs in medium-term follow up.

Five-Year Experience of Valvular Reconstructions for Nonhealing Leg Ulceration due to Deep Venous Reflux: Lessons Learned

Deep venous reflux is responsible for considerable morbidity in the form of venous leg ulceration and remains a significant health problem. Deep venous reconstructions have been looked upon as controversial in the past. To clarify the role of deep vein valve surgery in venous surgery, we report the lessons learned from clinical and imaging results of a 5-year experience of deep venous valve reconstructions. From 1994 to 1999, 137 patients (169 limbs) underwent deep vein reconstructions for nonhealing venous leg ulcers of CEAP C6 class, as a last resort treatment. End points of the study were leg ulcer healing, and vein valve station patency and competency. All end points were looked at on a follow-up of a minimal 2-year period following the valve reconstructions. External valvuloplasty showed ulcer healing in 50% of limbs with maintenance of competency at only 31% of valve stations. Internal valvuloplasty was the most durable valve repair procedure, with 2-year leg ulcer healing rates of 67% and valve station competency of 79%. For secondary incompetence, valve transplants showed a significant deterioration in valve patency (58%) and competence (47%) at 2 years, with 55.3% leg ulcer healing. Single-level repairs or single valve transplants had much lower ulcer healing rates than multiple-level repairs or valve transplants with multiple valve stations. Important lessons learned from this study are: 1) Valvular reconstruction for refluxive disease is effective in healing venous ulcers that defy conservative management and superficial/perforator venous surgery. 2) These procedures appear more promising for primary than for secondary incompetence. 3) Multiple-level or multiple-valve reconstructions yield superior results to single-level repairs, challenging the gatekeeper concept.

Venous Valve Station Changes in “Primary” and Postthrombotic Reflux: An Analysis of 149 Cases

The purpose of this study was to analyze valve station changes noted during venous valve reconstruction and the associated outcome. One hundred and forty-nine valve reconstructions were available for analysis at the time of surgical exploration; the venous valve was graded according to valve station changes (VS grades) from zero through six. Ascending venography was analyzed by a similar grading system and the two methods were compared. The results of this analysis showed that valve station wall changes are frequently present in patients with deep venous reflux and pose technical challenges during valve reconstruction; the outcome, however, appears unaffected. Grade 0 to 1 valve station changes are predominantly due to "primary" reflux, with an occasional instance of postthrombotic etiology. Grade 2 or 3 valve station changes are roughly evenly divided between phlebosclerosis of primary reflux and postthrombotic etiologies. The mechanism of onset of reflux with preservation of valve cusps in the latter group of postthrombotic cases is probably different from currently accepted theories of evolution of postthrombotic changes. Postthrombotic valve damage is variable, and the valve station anatomy may be sufficiently preserved in some patients to allow direct valve repair.

Determination of urinary 8-hydroxydeoxyguanosine by automated coupled-column high performance liquid chromatography: a powerful technique for assaying in vivo oxidative DNA damage in cancer patients

An automated analytical method has been developed for determination of the oxidative DNA adduct, 8-hydroxydeoxyguanosine (8OHdG) in human urine, based on coupled-column high performance liquid chromatography with electrochemical detection. Urine is concentrated on Bondelut CH by means of an automated sample processor, and the enriched sample injected on to a polymeric reversed phase column coupled in line with an electrochemical detector and a C 18 reversed phase column. By use of the electrochemical detector, a suitable retention time interval is set for collection of the fraction containing 8OHdG from the chromatography on the first column; this fraction is collected in a 2 mL loop and injected onto the C 18 column. The system is operated by an automatic valve station controlled by an integrator. The method has a large sample capacity and measures 31.1, 15.7, and 7.43 nmol 8OHdG/L urine with variation coefficients of 8, 8 and 24% within series and 8, 11 and 23% between series. Normal healthy individuals were found to excrete 14.9 ± 7.8 nmol 8OHdG/24 h, or 1.11 ± 0.62 μmol 8OHdG per mol creatinine, in their urine, whereas increased levels of 8OHdG were found in 24 h collections from a variety of cancer patients, both in samples taken before onset of oncological therapy (1.84 ± 1.12 μmol/mol creatinine, P < 0.01 versus healthy individuals) and after therapy onset (2.18 ± 1.44 μmol/mol creatinine, P < 0.001 versus healthy individuals). Moreover, mean values of 8OHdG in random urinary samples from cancer patients were significantly higher than from healthy individuals (2.42 ± 2.28 versus 1.19 ± 0.48 μmol/mol creatinine, P < 0.001), both in samples taken before therapy onset (1.91 ± 0.96, P < 0.001 versus healthy individuals) and after (2.57 ± 2.46, P < 0.001 versus healthy individuals). High levels of urinary 8OHdG were found in patients subjected to whole body irradiation, and in patients receiving chemotherapy with various cytostatic agents. The potential use of the method for detecting increased urinary 8OHdG excretion and conditions associated with increased oxidative DNA damage in humans is discussed.