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