development of suction and discharge valves using non
Transcription
development of suction and discharge valves using non
Poster PO-17 DEVELOPMENT OF SUCTION AND DISCHARGE VALVES USING NON-METALLIC VALVE PLATES FOR BOG COMPRESSORS LE DEVELOPPEMENT DES SOUPAPES DE REFOULEMENT ET D’ASPIRATION EN UTILISANT LES PLAQUES PORTE SOUPAPE NON METALLIQUES FAITES EN RESINE POUR LES COMPRESSEURS BOG Katsumi ShinyaKoji Yoshida Toho Gas Co.,Ltd. 19-18 Sakurada-cho, Atsuta-ku Nagoya 456-8511, Japan Seiji Iwawaki Ishikawajima-Harima Heavy Industries Co., Ltd. 1,Shin-Nakahara-cho, Isogo-ku Yokohama 235-8501, Japan ABSTRACT BOG that evaporated in LNG tanks, are typically pressurized using reciprocating compressors and used as the energy source. Since BOG are low temperature, stainless steel materials are used for the suction and discharge valve plates in the reciprocating compressors, but since there is wear due to the contact between the valve plate and valve seat, valve plates must be replaced periodically, and inspection for the valve and adjustments are necessary. Since durability has been improved in recent years, resins have come into use for suction and discharge valve plates in reciprocating compressors in normal temperature ranges, but they have not been used at all in low temperature ranges because of the brittleness of resins. In this instance resin materials with cryogenic properties have been selected, the valve structure improved to alleviate impact forces, and suction and discharge valves made of resin valve plates at low temperatures developed for the first time. Therefore, valve plates with durability approximately twice that of conventional stainless steel valve plates have been realized. The resin valve plates have the following effects compared with conventional stainless steel valve; • inspection and maintenance cost reduction: approximately 30% with improvement in durability • power required by compressors reduction: approximately 2.4 % with improvement in sealing ability • lowering operating noise: approximately 4% by avoiding metal contact (contact metal and resin). The suction and discharge valves made of resin valve plates are new technology and can be used by factories with same kinds of facilities both domestically and overseas. PO-17.1 SESSIONS CONTENTS Poster PO-17 RESUME Les BOG évaporés dans les citernes GNL sont pressurisés typiquement, utilisant des compresseurs volumétriques à pistons, et utilisés comme source d’énergie. Les matériaux en acier inoxydable sont utilisés pour les plaques porte soupape de refoulement et d’aspiration dans les compresseurs volumétriques à piston, car les BOG ont températures basses. Comme suite à l’usure du contact entre la plaque porte soupape et le siège de soupape, les plaques porte soupape doivent être remplacées périodiquement et, les inspections des soupapes et les ajustements sont nécessaires. La durabilité s’est amélioré les dernières années et les résines sont utilisées pour les plaques porte soupape de refoulement et d’aspiration dans les compresseurs volumétriques à pistons pour domaines de températures normales. A cause de fragilité, les résines n’ont pas été utilisées du tout pour domaines de températures basses. En l’occurrence, des matériaux en résine avec propriétés cryogéniques ont été sélectionnés, la structure de la soupape améliorée afin d’atténuer les forces impulsives et, les soupapes de refoulement et d’aspiration faites de plaques porte soupape en résine à basses températures sont développées pour la première fois. Ainsi, sont réalisées des plaques porte soupape avec durabilité approximativement deux fois plus grande que celle des plaques porte soupape en acier inoxydable conventionnelles. Les plaques porte soupape en résine ont les effets suivants, par année, comparativement aux soupapes en acier inoxydable conventionnelles: • réduction des frais d’entretien et d’inspection: environ 30% avec amélioration de durabilité, • réduction du courant exigé par les compresseurs: environ 2,4% avec amélioration de capacité d’étanchement • abaissement du bruit de fonctionnement: environ 4%, évitant le contact métallique (contact métal- résine). Les soupapes de refoulement et d’aspiration faites de plaques porte soupape en résine, représentent une technologie nouvelle, et peuvent être utilisées en usines ayant le même genre d’installations, tant à l’intérieur du pays qu’à l’étranger. 1. OVERVIEW OF EQUIPMENT The BOG compressor taken up as the object of this testing and research is a two-stage compression reciprocating type (specifications: two-cylinder, two-stage, non-lubricated, 5600 m3N/h, 530 kW) in which BOG arising in LNG tanks are normally compressed and sent to caloric adjustment device. Fig. 1 shows a photograph of the main unit and a schematic diagram. PO-17.2 SESSIONS CONTENTS Poster PO-17 4 suction valves (-140ºC, 10kPa) 1st stage cylinder 4 suction valves (-40ºC, 0.35MPa) M BOG 2nd stage cylinder [Photograph of Main Unit] * St.1 St.2 * 4 discharge valves (30ºC , 1.1MPa) 4 discharge valves (-40ºC, 0.35MPa) suction valve 4 suction valves BOG Piston r e d n i l y C discharge valve [Photograph: Suction/Discharge Valves] 4 discharge valves 【Main Unit Schematic】 Fig. 1 Photograph of Main Unit and Schematic Each cylinder for 1st and 2nd stage equipped with four suction valves and four discharge valves, and they repeatedly open and close according to the reciprocation of the pistons at operating temperatures from the extremely low (-140°C) to normal temperatures (30°C). Fig. 2 shows a schematic diagram of the suction and discharge valves. It has been necessary to replace conventional stainless steel suction and discharge valve plates after 6,000 hours of use with valve plates for the normal temperature range and after 12,000 hours with valve plates for low temperature ranges because of decreases in strength and increases in internal leakage. 245 mm dia. (St. 1) 185 mm dia. (St. 2) BOG (from cylinder) Valve seat Discharge Valve plate Spring Suction (to cylinder) <Suction Valve> <Discharge Valve> <Valve Plate> Fig. 2 Suction and Discharge Valve Schematic Diagram PO-17.3 SESSIONS CONTENTS Poster PO-17 2. CONTENT OF STUDY 2.1 Testing of Materials Before carrying out verification tests in actual equipment, mechanical tests, such as tensile tests, were carried out on resin materials (PEEK materials: poly ether ether ketone resins with glass fibers added) for which there were records at normal temperatures under various temperature conditions from normal to -150°C. All permissible values were satisfied in each of the tests, and they were satisfactory with no remarkable reduction in performance at any temperature. The results of material testing are shown in Fig. 3. <Tensile test results> 160 Tensile Strength(%) 140 120 100 80 60 Tensile Strength 40 Permissible Tensile Value 20 0 -150 -100 -50 23 Test Temp.(℃) 120 120. 0 100 100. 0 80 80. 0 St r engt h of I mpact 60. 0 60 Per mi s s i bl e I mpact Val ue 40. 0 40 Hardness(%) Strength of Impact?%? Strength of Impact (%) <I mpact / Har dnes s t es t r es ul t s ? Har dnes s 20. 0 20 Per mi s s i bl e Har dnes s Val ue 0 - 150 0. 0 - 100 - 50 Tes t Temp. ? ? ? 23 Test Temp (ºC) Fig. 3 Results of Material Tests PO-17.4 SESSIONS CONTENTS Poster PO-17 2.2 Improvements in Valves Before carrying out verification tests of resin valve plates in the low temperature range, confirmatory tests were carried out with second stage discharge valves in the normal temperature range. As a result, a problem arose with partial damage to the outside of the valve plates at approximately 3,000 hours. As a result of actual measurements of the second stage valve chamber pulsation and valve plate behavior to clarify the reasons for this damage, problems, such as insufficient spring constant were discovered. The points improved for each problem are given in Table 1. Table 1: Problems and Improvements Problem Improvement Spring constant increased and force of Insufficient spring strength impact mitigated Valve plate thickness increased to Insufficient valve plate strength strengthen it Number of springs increased to make a Valve plate vibration uniform arrangement Teflon cushioning material (spring Valve plate wear button in the following) added between the valve plate and spring. 2.3 Verification Testing After improvements were made to the valves, verification tests started, continuing with second stage discharge valves in the normal temperature range (+30°C), and they gradually moved to the low temperature range. In addition, valve inspections were carried out every 2,000 hours, and the spring strength was reassessed, the spring button material changed, etc., such that the wear on the resin material was minimized to promote increased life. The schedule for each of the tests is given in Table 2. Table 2: Test Schedule Item 1996 1997 1998 1999 2000 2001 2002 Material tests Second stage discharge valve verification tests 21,000hours use Valve improvements First stage discharge valve verification tests Second stage suction valve verification tests First stage suction valve verification tests 18,000hours use 20,000hours use 14,000hours use PO-17.5 SESSIONS CONTENTS Poster PO-17 In order to confirm the state of deterioration of the second stage discharge valve plates and first stage discharge valve plates that completed the verification tests, material tests were carried out comparing them with new material. As a result, it was confirmed that there was no drop in the mechanical characteristics at any temperature from normal temperature to -150°C and the material strength of the new material was maintained. 3. EFFECTS There were effects on the following items when compared with conventional stainless steel valve plates. (1) Through improvements in the wear resistance, an increase in the period between breakdown inspections can be promoted, and a 30% reduction in inspection costs and valve equipment costs is possible. (2) Because of improvements in valve sealing, a reduction in internal valve leakage is promoted, and a 2.4% reduction in power consumption for compression is realized. (3) Since the metal contact between the valve plate and valve seat is eliminated, there is a 4% reduction in operating noise. A patent application covering the results of this development, including the structure of the suction and discharge valves has been filed jointly with Ishikawajima-Harima Heavy Industries, Co., Ltd. 4. CONCLUSION The effects of reducing the maintenance and inspection costs and improving performance for compressors were obtained by using a resin material in the suction and discharge valves of BOG compressors requiring low temperature characteristics. In particular, along with building up improvements to the valve structure in the verification test process, the important result of improving long-term durability was obtained. The suction and discharge valves developed this time making use of resin valve plates can be used by operators of low temperature gas compressors both domestically and overseas. PO-17.6 SESSIONS CONTENTS